#help-with-hw-design

heavy jasper Dec 18, 2021, 10:00 PM

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If you're going through a professional assembly house, or if you have a board prewarmer, this is slightly less of an issue

fervent lance Dec 19, 2021, 12:42 AM

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anyone have recommendations on free pcb design softwae?

cinder anchor Dec 19, 2021, 12:42 AM

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KiCad is pretty good.

spice turtle Dec 19, 2021, 3:27 AM

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Eagle cad too

cinder anchor Dec 19, 2021, 4:08 AM

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EAGLE isn't completely free, though, unless you're never going above whatever the layer-limit is.

limpid nest Dec 19, 2021, 4:10 AM

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It's 2.

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And 4 layer is a nice feature to have.

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Don't get me wrong, you can get a lot done in 2 layers (adafruit boards for example are nearly all 2 layer)

spice turtle Dec 19, 2021, 1:35 PM

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Is there anyway to set the via size in Eagle PCB for the auto router?

distant raven Dec 19, 2021, 1:38 PM

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change the minimum hole size

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then in the trace menu, set the hole size to that size you specified as the minimum

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should use that size after that

spice turtle Dec 19, 2021, 1:39 PM

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distant raven change the minimum hole size

under design rules?

distant raven Dec 19, 2021, 1:40 PM

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yeah

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the specific menu is sizes, then set minimum drill

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for me, a lot of places won't do smaller than 10mil so that's my minimum drill

spice turtle Dec 19, 2021, 1:42 PM

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jlpcb lists 0.2mm

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which is 7mils roughly

distant raven Dec 19, 2021, 1:43 PM

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sure, 10 mils is pretty safe size wise

limpid nest Dec 19, 2021, 11:43 PM

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I'm looking at trim pots. How are these wired? I have a circuit that needs a resistance between two points. Would I wire between those points 1 and 2, 2 and 3, or 1 and 3?

heavy jasper Dec 19, 2021, 11:51 PM

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You want to wire between either 1/2 or 2/3

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Essentially - there's a fixed resistance between 1-3 (that's the rated resistance of the potentiometer) and then the wiper is a contact that literally wipes along the length of that fixed resistor and taps onto a point on it.

limpid nest Dec 19, 2021, 11:58 PM

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heavy jasper Essentially - there's a fixed resistance between 1-3 (that's the rated resistanc...

ahh that makes sense thanks

elder peak Dec 20, 2021, 12:12 AM

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Remember that EagleCAD is free at the pleasure of Autodesk and they have decided to cut back on free options in the past, so if you are prepared to hitch yourself professionally to the train and pay down the road, cool... but a lot of folks were unpleasantly surprised when 360 started having stuff removed.

limpid nest Dec 20, 2021, 12:16 AM

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yeah, they are relatively cheap per seat though. Not actually cheap, mind, just relatively compared to other software. A seat of MATLAB is 1000s, for example.

spice turtle Dec 20, 2021, 12:54 AM

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Yea just like they used to do a once a year fee for hobbyist that was quite affordable but then they moved to the subscription model

limpid nest Dec 20, 2021, 12:55 AM

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everything is SaaS now

supple pollen Dec 20, 2021, 2:13 AM

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I'm still using my old fixed license, but will likely migrate to KiCAD at some point.

limpid nest Dec 20, 2021, 3:15 AM

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is it "wrong" to draw multiple polygons that intersect and have the same net name? I need to do kind of a convoluted shape and it's hard to do in one pass

unreal flax Dec 20, 2021, 3:21 AM

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That should be fairly legit, no worse than having a trace poke into a polygon to connect to it.

limpid nest Dec 20, 2021, 3:30 AM

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cool thanks

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I downloaded a footprint for a aluminum electrolytic cap. It had a giant tRestrict square over it. I tried just sizing it down but since it's tRestrict, I can't actually draw traces to the leads. See picture. Can anyone think of a reason why this part would have such a restrictive layer built into it?

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I'm planning on just deleting it since it makes it impossible to use the part except by drawing traces/polygons on the bottom. Unless that's the point?

unreal flax Dec 20, 2021, 4:07 AM

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If it's legitimate, the only thing I can think of is that the case perimeter of the capacitor is metal, so it would short against any trace that doesn't connect only through the vias. But I'd tend to think it's just a mistake by the footprint author, who wanted tKeepout instead or something.

limpid nest Dec 20, 2021, 4:09 AM

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yeah I agree. I think I'll write to them about it.

marble scaffold Dec 20, 2021, 8:45 AM

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is this my fault? or is the footprint just too cramped

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same here

bright thistle Dec 20, 2021, 10:01 AM

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Maybe the footprints clash with your min distances

marble scaffold Dec 20, 2021, 12:07 PM

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i'll just check w/ my pcb manufacturer

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aside from that though, here's the final pcb

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really proud of this one

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it's an improved version of this

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squeezing an infineon trust m into the same board footprint

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i was able to get the space by swapping out the LED for a smaller one and moving some things around

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just barely fit

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one thing that may be problematic is how thin the 3.3v bus is

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schematic

tough matrix Dec 20, 2021, 2:19 PM

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looks good overall
as for 3.3v bus, doesn't seem thin to me. What is the track width?

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one question: the bottom pads of U2, U5 are not connected to anything - is it how it should be? typically, exposed pad is connected to GND

distant raven Dec 20, 2021, 2:29 PM

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Yeah, need to connect that ground pad to ground

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A few via if you can for good thermal decoupling

tough matrix Dec 20, 2021, 2:29 PM

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one minor nitpick: for USB switch (U4), the traces going to bottom right and top left pads, instead of exiting the pad vertically, exit it sideways

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for no obvious reson

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doesn't affect the functionality, just looks weird

south gazelle Dec 20, 2021, 9:37 PM

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Hello! Does anybody know how to indicate V-CUTS in Kicad for a PCB panel (destined to JLCPCB) ? I was thinking of adding this in the User.Comments layer...

marble scaffold Dec 20, 2021, 11:08 PM

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tough matrix looks good overall as for 3.3v bus, doesn't seem thin to me. What is the track w...

25mil

tough matrix Dec 20, 2021, 11:09 PM

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should be more than enough

marble scaffold Dec 20, 2021, 11:09 PM

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alright, was just worried because the led might take up quite a bit of power

tough matrix Dec 20, 2021, 11:10 PM

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25 mil can easily take 1A

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and NeoPixel led at full brightness is 60mA max

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or are you using high-power led like they do in flashlights?

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anyway, your LDO can't produce more than an amp

marble scaffold Dec 20, 2021, 11:15 PM

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this is just a normal ol dotstar LED

tough matrix Dec 20, 2021, 11:19 PM

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then 25 mil is plenty

limpid nest Dec 21, 2021, 1:54 AM

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I'm trying to figure out how much power this board https://learn.adafruit.com/adafruit-i2s-stereo-decoder-uda1334a?view=all#circuitpython-wiring-test will take by looking at the chip's datasheet https://www.nxp.com/docs/en/data-sheet/UDA1334ATS.pdf. In the first table of interest, what are the parameters I need to be looking at?

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it doesn't seem like it uses much power at all

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18 mW/3.3V ~= 6mA?

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is 44.1 kHz a common frequency used in audio? I know not a thing about audio

supple pollen Dec 21, 2021, 2:03 AM

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If you're looking for the supply current, it's the digital supply current plus the analog supply current. Which does appear to add up to about 6mA, as you surmised. Yes, 44.1kHz is the sampling frequency for audio CDs, which makes it a popular rate that many devices support.

limpid nest Dec 21, 2021, 2:04 AM

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ah ok thanks

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what am I looking for when I'm trying to find Digikey's value added "we cut your female headers for you" service?

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because I'm not seeing it at all

supple pollen Dec 21, 2021, 2:41 AM

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It's not really a search term, but shows up in the item listings

limpid nest Dec 21, 2021, 2:44 AM

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Ahh ok

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What should I filter by to get stacking headers, should I want them?

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I see post length but there are a lot of post lengths

supple pollen Dec 21, 2021, 2:55 AM

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There are indeed, and a range of them could work as stacking headers, depending on your parameters.

limpid nest Dec 21, 2021, 2:56 AM

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hmmm. I just want to use stacking headers to plug something like this https://learn.adafruit.com/adafruit-i2s-stereo-decoder-uda1334a?view=all#circuitpython-wiring-test into a breadboard

supple pollen Dec 21, 2021, 2:59 AM

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I normally just use male headers for plugging breakout boards into breadboards. Granted, those square pins are a bit big for breadboards, but there are other options (like Fliptronics Flip-Pins).

limpid nest Dec 21, 2021, 3:55 AM

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I'm looking to decouple some 5V ICs, will these do, or do I need to spring for a more expensive variety?
https://www.digikey.com/en/products/detail/samsung-electro-mechanics/CL10B104KO8NNWC/3887597

CL10B104KO8NNWC Samsung Electro-Mechanics | Capacitors | DigiKey

Order today, ships today. CL10B104KO8NNWC – 0.1 µF ±10% 16V Ceramic Capacitor X7R 0603 (1608 Metric) from Samsung Electro-Mechanics. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

supple pollen Dec 21, 2021, 3:58 AM

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Those are just fine.

limpid nest Dec 21, 2021, 4:05 AM

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neat thx

limpid nest Dec 21, 2021, 4:20 AM

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Is there a difference between https://www.digikey.com/en/products/detail/onsemi/mc74hc595adr2g/919257
and
https://www.digikey.com/en/products/detail/texas-instruments/SN74HC595DT/1571266
?

supple pollen Dec 21, 2021, 4:40 AM

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Not a practical one.

limpid nest Dec 21, 2021, 4:40 AM

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Ok thanks.

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I realized on an old board I used the footprint for one and ordered the other.

limpid nest Dec 21, 2021, 5:04 AM

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what are the odds that the numbers on something like this https://www.amphenol-icc.com/media/wysiwyg/files/drawing/musbk152xx.pdf

are on any kind of standard? Like 1 is always 5V, 5 is always GND, etc?

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and what do folks reckon these are for? I see them cutout on the recommended PCB layout

unreal flax Dec 21, 2021, 5:21 AM

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Low odds of a standard pinout. Those would generally only happen when there's something like USB where you have standard cables and standard devices as part of a whole ecosystem, not just the connector itself.

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As for the cutouts, I expect those are just for mechanical mounting on the PCB.

limpid nest Dec 21, 2021, 5:22 AM

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This is USB though, right?

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Mechanical mounting how though? I don't see threads for screws

unreal flax Dec 21, 2021, 5:22 AM

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With 5 pins? I wouldn't have expected that to be USB.

limpid nest Dec 21, 2021, 5:23 AM

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Here's the part https://www.digikey.com/en/products/detail/amphenol-icc-(commercial-products)/MUSBK15230/3465047?utm_adgroup=Connectors and Interconnects&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Supplier_Amphenol Commercial_0664_Co-op&utm_term=&utm_content=Connectors and Interconnects&gclid=Cj0KCQiA8ICOBhDmARIsAEGI6o0D4Cli6fHayLAmlakf3KXb8ChpnMgBj1QHapFBbHNQXSt-M-fZmvwaAocXEALw_wcB

unreal flax Dec 21, 2021, 5:23 AM

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Just mounting with a big blob of solder for stability, heh heh.

limpid nest Dec 21, 2021, 5:23 AM

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lol

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This micro USB breakout has 5 pins though.. https://www.adafruit.com/product/1833

unreal flax Dec 21, 2021, 5:26 AM

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Ah, yeah, the fifth is the ID pin, which I think is only used for OTG masters.

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And yes, in that case the pin ordering should be very standard.

limpid nest Dec 21, 2021, 5:27 AM

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ok cool, so I just need to find a source of what 1-5 would be on the other end. Neat. Thanks

unreal flax Dec 21, 2021, 5:30 AM

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The easiest way is to find a connector pinout for the micro-AB port on the part, and assume that the pins connect straight back in the same order.

limpid nest Dec 21, 2021, 5:30 AM

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Like so? https://www.hobbytronics.co.uk/usb-connector-pinout

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so how is the 5th pin ever utilized if USBA Male/Female have only 4 pins?

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is it connected on the micro USB side of the connection and that allows whatever USB On the Go does do its thing?

unreal flax Dec 21, 2021, 5:32 AM

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With 4-pin connectors, the host and device is more or less fixed by A versus B ports. But the OTG allows the same connector to be used for both host and device, so the extra pin determines which is which.

limpid nest Dec 21, 2021, 5:32 AM

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interesting. I'll have to read more. Don't quite grok it.

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Does that hobbytronics source look reasonable?

unreal flax Dec 21, 2021, 5:34 AM

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Seems reasonable, yeah.

limpid nest Dec 21, 2021, 5:34 AM

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nice thx

tough matrix Dec 21, 2021, 7:07 PM

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OTG is used e. g. by cell phones. Normally a cell phone is the slave on USB connection (e. g. when you connect it to the computer). But sometimes you want it to act as a master, when you connect peripherals such as SD card reader to the phone

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so the same physical connector is used for both modes.

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The way the phone knows that it has to act as master is by using a special USB OTG cable, in which (iirc) ID pin is connected to ground. So when the phone detects such a cable being plugged in, it switches to master mode

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Not all cell phones support that but most modern ones do.

limpid nest Dec 21, 2021, 9:59 PM

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tough matrix OTG is used e. g. by cell phones. Normally a cell phone is the slave on USB conn...

Neat thx. So would you need a USBC->USBC or MicroB->MicroB cable to use that?

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I'm looking at the circuitbrains deluxe module. What are these pins used for? Programming it in languages other than circuitpython?

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unreal flax Dec 21, 2021, 10:04 PM

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Yes, those are SWD (Serial Wire Debug) pins. Similar to JTAG, it's a programming/debugging interface to the microcontroller.

limpid nest Dec 21, 2021, 10:04 PM

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ah OK so I should probably expose those

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Thx

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I need ground exposed as well on whatever interface I choose to use, correct?

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be it header pins or something else

unreal flax Dec 21, 2021, 10:04 PM

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Yep

tough matrix Dec 21, 2021, 10:05 PM

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I only know of using OTG with microusb cables. Here is a typical OTG cable: microusb to USB A female: https://www.amazon.com/dp/B00LN3LQKQ/ref=cm_sw_r_apan_glt_fabc_82X7ZVWYVSMQXTV6AQYW

UGREEN Micro USB 2.0 OTG Cable On The Go Adapter Male Micro USB to ...

Are you still bothered by the complicated traditional data transform methods? With this OTG cable,just connect your micro usb phone from male micro usb port and add the driver to female usb port,then you can send the files directly on your phone or tablets easily as a host. Allows you to connect ...

limpid nest Dec 21, 2021, 10:06 PM

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oh so it has 5 pins on the female port?

tough matrix Dec 21, 2021, 10:07 PM

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itshould have 5 pins on the microusb side, to signal to the cell phone that it must act as master

limpid nest Dec 21, 2021, 10:08 PM

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interesting

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Thanks!

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anyone ever solder a MicroSD card slot onto a board?

ember laurel Dec 22, 2021, 12:28 AM

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Darn, I just failed a radiated emissions test.

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limpid nest Dec 22, 2021, 12:30 AM

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😦

unreal flax Dec 22, 2021, 12:34 AM

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limpid nest anyone ever solder a MicroSD card slot onto a board?

Yes, they're usually more or less normal parts.

ember laurel Dec 22, 2021, 12:39 AM

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Really not sure what those peaks could be

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With motor off, it looks like this:

limpid nest Dec 22, 2021, 2:17 AM

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does anyone know how to export a library/part from an adafruit design in F360?

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I know how to do it in EAGLE but not in F360

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Trying to make sure I understand this circuit. When the jumpers aren't soldered, A0 and A1 are pulled down. What happens, electrically, when the jumpers are soldered? A short between VCC and A0/A1 it seems? Is that pulling the value up?

elder peak Dec 22, 2021, 2:44 AM

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So, there's a 10k resistor pulling them down.

limpid nest Dec 22, 2021, 2:45 AM

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when the jumpers aren't shorted, but when the jumpers are shorted, it changes things, no? You get a short between A0/1 and VCC

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Would current flow into A0/1?

elder peak Dec 22, 2021, 2:46 AM

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So if you short the jumpers, it'll pull A0 or A1 up and a tiny amount of current will flow through the 10k resistor to ground.

limpid nest Dec 22, 2021, 2:47 AM

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that's what I was thinking, but why doesn't current flow into A0/1?

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They must be inputs, no?

elder peak Dec 22, 2021, 2:47 AM

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Probably

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Like, most microcontrollers have multi-purpose pins.

limpid nest Dec 22, 2021, 2:47 AM

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some sort of high impedance input. Let me check the datasheet.

elder peak Dec 22, 2021, 2:48 AM

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Yah, basically if you try to use A0 or A1 as an output, bad things might occur.

limpid nest Dec 22, 2021, 2:49 AM

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Here's the part in question https://cdn-shop.adafruit.com/product-files/4886/AW9523+English+Datasheet.pdf

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Hmmm, for this part could I power it with 3v3 but sink LEDs that are lit with 5V?

unreal flax Dec 22, 2021, 2:55 AM

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No, I think it wouldn't necessarily like that. Though it looks like you could power the chip and the LEDs with 5V but still use 3.3V on the I2C pins okay.

limpid nest Dec 22, 2021, 2:56 AM

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mk, I was thinking of using mosfets to level shift the signals so that I don't need to worry about 3v3 vs 5V

unreal flax Dec 22, 2021, 2:57 AM

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This seems to have a purposefully low threshold voltage so it's happy interfacing with even 1.8V logic.

limpid nest Dec 22, 2021, 2:58 AM

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interesting well that would make the BOM just a bit smaller which is always nice

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I see in one of the tables
I2C interface device address，connect to VBAT or GND，and control the default state of output pin (refer to table 1). But I don't see anything in the tables above the one that text is from, and none are labelled as Table 1

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That's for pin A0/1

unreal flax Dec 22, 2021, 3:04 AM

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Ah, I couldn't spot it either at first glance. Table 1 is hidden at the bottom of page 10 and the top of page 11.

limpid nest Dec 22, 2021, 3:05 AM

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Ahhh

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Thanks

limpid nest Dec 22, 2021, 3:12 AM

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unreal flax Ah, I couldn't spot it either at first glance. Table 1 is hidden at the bottom o...

Do you think I need to worry about the default GPIO state if I'm not using this to expand GPIOs?

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I see that if I want to use 2-4 of these, some of my ports will be default Hi Z. Does that interfere with the ability to sink current?

unreal flax Dec 22, 2021, 3:14 AM

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Well, the default state would also control whether the LEDs are on or off, if you care about that. I think you can override the default state via I2C, though, so it shouldn't interfere with the chip capabilities.

limpid nest Dec 22, 2021, 3:14 AM

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ahh of course. It would just be the default state of the LEDs before I start running code. It's fine if some of them are on briefly before the code runs.

sinful depot Dec 22, 2021, 3:20 AM

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@limpid nest the A0 and A1 pins are only used to set the I2C address and don't effect any of the functions of the expander chip.

limpid nest Dec 22, 2021, 3:21 AM

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They affect the default state of the pins but that can be overridden

sinful depot Dec 22, 2021, 3:21 AM

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Not according to the Adafruit documentation

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https://learn.adafruit.com/adafruit-aw9523-gpio-expander-and-led-driver/pinouts

Adafruit Learning System

Adafruit AW9523 GPIO Expander and LED Driver

A cute and powerful I2C expander with a lot of tricks up it's sleeve!

limpid nest Dec 22, 2021, 3:22 AM

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hm check the datasheet.

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Let me get the link

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https://cdn-shop.adafruit.com/product-files/4886/AW9523+English+Datasheet.pdf

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now the question of the century. Adafruit uses pull downs to ground for their board, but the datasheet shows just straight connections to VBAT or GND.

sinful depot Dec 22, 2021, 3:26 AM

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P0, P1 and so on effect the state of the IO. A0, A1 only effects i2c address (4 possible i2c address)

limpid nest Dec 22, 2021, 3:26 AM

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hm

sinful depot Dec 22, 2021, 3:27 AM

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It shows that at the bottom of page 10 of the chip datasheet

limpid nest Dec 22, 2021, 3:27 AM

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that's what my screenshot is of.

sinful depot Dec 22, 2021, 3:27 AM

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Read the paragraph above the chart

limpid nest Dec 22, 2021, 3:28 AM

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"After power on, all the 16 I/O ports are configured as GPIO output as default, which default
states are set according to the I2C slave address selection inputs, AD0 and AD1, refer to table 1
for detail."

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I think we might be miscommunicating or just saying the same thing in different ways.

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I'm saying that, per the datasheet, when I power on my system it will be configured as GPIO outputs, with some ports as High impedance, but that I can override that quickly, so it isn't an issue.

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hmm let me make sure this is the right datasheet actually. There's a trailing letter on the part designation. Hopefully it's the right one. AW9523B vs AW9523

sinful depot Dec 22, 2021, 3:32 AM

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Only the P0s and P1s effect the high and lows.

limpid nest Dec 22, 2021, 3:32 AM

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Looks like adafruit is using the AW9523B but are just calling it AW9523

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confusion cleared

sinful depot Dec 22, 2021, 3:35 AM

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The datasheet you linked to is for the AW9523B

limpid nest Dec 22, 2021, 3:35 AM

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I can't even find references on the internet to just AW9523 so it must just be a weird naming convention adafruit used.

limpid nest Dec 22, 2021, 3:35 AM

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sinful depot The datasheet you linked to is for the AW9523B

Indeed. But the chip in the product picture for adafruit's board is the AW9523B.

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No idea why they called it just plain AW9523

sinful depot Dec 22, 2021, 3:36 AM

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Simpler to name I would imagen.

limpid nest Dec 22, 2021, 3:36 AM

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Yeah

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Plus I got paid money to be confused by this naming convention so it's all good

sinful depot Dec 22, 2021, 3:37 AM

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lol

limpid nest Dec 22, 2021, 3:46 AM

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Any fellow travelers in Fusion360: I exported an adafruit board's libraries using explib, which put microbuilder.lbr in my project folder (see below). However, this did not make the microbuilder library available to me to use in projects. Does anyone know what the next step is? Double clicking the microbuilder.lbr file in F360 just opens a firefox window to autodesk.

limpid nest Dec 22, 2021, 4:11 AM

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I went through the library manager > Add From Team and it doesn't show up there either

supple pollen Dec 22, 2021, 4:15 AM

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I normally just copy it into the lbr directory where Eagle is installed.

limpid nest Dec 22, 2021, 4:16 AM

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yeah Fusion360's worst feature is the cloud aspect of it. It really obfuscates where files are. You can get to them from within F360 but finding your project files in the huge nest of nonsense that is the F360 filesystem is nigh on impossible.

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oh boy this is the workaround of all workarounds, but it works. Open the schematic in Eagle, File>Export>Libraries. Open F360, CTRL+O>Open library>Save

supple pollen Dec 22, 2021, 4:34 AM

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I'm using an old version of Eagle that doesn't have that.

limpid nest Dec 22, 2021, 4:36 AM

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it's a nice feature

supple pollen Dec 22, 2021, 1:24 PM

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Not having that? I'd agree.

fervent lance Dec 22, 2021, 2:36 PM

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after doing a bunch of research I still couldn't find a clear answer on what are the best ways to get 5V at 2.5A from a USB-C port. Some people on the digikey forum claim just using two 5.1k resistors at the CC pins gives up to 3A. Adafruit (which uses this method) says on their product page it can give out 1.5A max. So which one is true? Also heard the TUSB321 would be ideal for getting 5A at up to 3A, but from what I was reading that chip doesn't just give 5V 3A, but needs to connector to another microcontroller? So in the end... is the only good choice to use the IP2721 ?

distant raven Dec 22, 2021, 3:02 PM

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fervent lance after doing a bunch of research I still couldn't find a clear answer on what are...

USB standard is up to 3A with 5.1K resistors. There is a caveat, you have to have a USB Type C PSU that is able to use the 5.1K resistors to set up power delivery for 3A. Otherwise it’s 1.5A max

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But it’s generally more complicated than that too. TI has a good primer on the topic: https://www.ti.com/lit/wp/slyy109a/slyy109a.pdf?ts=1640123852019&ref_url=https%253A%252F%252Fwww.google.com%252F

fervent lance Dec 22, 2021, 3:59 PM

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so much about USB-C being simple...

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hehe

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by the way - what is likely to happen if WLED on an ESP32 tries to get 2.5A for both the ESP and LEDs combined - and USB-C only allows 1.5A? microcontroller / software crashing? or just dimmer lights? (WS2812B)

distant raven Dec 22, 2021, 4:19 PM

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Dimmer lights I’d guess. Or the USB supply simply might not deliver power due to being over drawn

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Computers with USB C for instance would just turn off power delivery if too much power is drawn

limpid nest Dec 22, 2021, 10:45 PM

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For a D-Sub meant to send 26 two wire signals (so 52 total) from a board, do I want a female socket on the board side?

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I think I do

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wow the 52 position ones are crazy expensive. May have to do 2 x 26

limpid nest Dec 22, 2021, 11:16 PM

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It seems the raspberry pi has 1.8k pullups on the SDA/SCL lines. For making a hat for the pi, would I be well suited to add some 4.7k or even 10k pullups to my I2C lines?

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I guess any resistors I add will only lower the bus resistance, won't they...

tough matrix Dec 23, 2021, 12:04 AM

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if existing resistors are 1.8k, I don't think it should be necessary to more pullups

limpid nest Dec 23, 2021, 12:09 AM

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That's my read as well, thanks

proper anvil Dec 23, 2021, 12:20 AM

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I'm converting a 555 timer circuit that I've made to a PCB, and im wondering what kind of diodes im meant to use. Additionally, I have flyback diodes for DC motors, what kind would I use there? On my breadboard I'm just using diodes I had on hand that came with some kit, im not sure what kind they are (but they work).

limpid nest Dec 23, 2021, 12:21 AM

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proper anvil I'm converting a 555 timer circuit that I've made to a PCB, and im wondering wha...

I think you can just use what are commonly referred to as "signal diodes". Couldn't spec a particular part for you though

proper anvil Dec 23, 2021, 12:23 AM

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limpid nest I think you can just use what are commonly referred to as "signal diodes". Could...

Would that fall under 'general purpose' diodes?

limpid nest Dec 23, 2021, 12:23 AM

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I would assume so, but I also might wait for someone with more knowledge to chime in.

proper anvil Dec 23, 2021, 12:25 AM

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Okay thank you

limpid nest Dec 23, 2021, 12:57 AM

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For a supply like this (https://www.mornsun-power.com/html/pdf/LM25-23B05.html) does VO- sit at earth ground or does it float somewhere above that with VO+ = VO- + 5V ?

heavy jasper Dec 23, 2021, 1:49 AM

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It floats - see the isolation and insulation resistance specs.

distant raven Dec 23, 2021, 2:02 AM

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proper anvil I'm converting a 555 timer circuit that I've made to a PCB, and im wondering wha...

Something like a 1N4148

limpid nest Dec 23, 2021, 2:08 AM

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heavy jasper It floats - see the isolation and insulation resistance specs.

Ahh thanks, missed that

proper anvil Dec 23, 2021, 2:29 AM

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distant raven Something like a 1N4148

Okay thanks

limpid nest Dec 23, 2021, 2:36 AM

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What about the isolation and insulation resistance clues me that it's floating?

heavy jasper Dec 23, 2021, 2:48 AM

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They specify a minimum 100Mohm resistance from output to ground

limpid nest Dec 23, 2021, 2:49 AM

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ahhh duh that makes sense

heavy jasper Dec 23, 2021, 2:49 AM

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and that you can put 1250VAC from output to ground for 1 minute with a max leakage current of <10mA

limpid nest Dec 23, 2021, 2:49 AM

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so if it were 0 Ohms, I'd know they are connected. I'm just thinking about safety procedures for the device this will power. First among them is always unplug the device!

heavy jasper Dec 23, 2021, 2:50 AM

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They likely just wouldn't spec it if it's a non-isolated supply.

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since it wouldn't be a parameter of note

limpid nest Dec 23, 2021, 2:51 AM

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makes sense. What's the benefit of having VO- and + float like that?

heavy jasper Dec 23, 2021, 2:54 AM

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Some things have safety requirements and isolated supplies are good ways of saying "mains AC voltage will not appear on the output"

limpid nest Dec 23, 2021, 2:54 AM

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ah ok

heavy jasper Dec 23, 2021, 2:54 AM

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or you just don't want ground loops, or want to have a voltage at some offset (e.g. say you have two of these supplies, there's nothing preventing you from connecting Vo+ of one to Vo- of another to have a bipolar power supply)

limpid nest Dec 23, 2021, 2:55 AM

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if they weren't isolated could you not connect them that way?

heavy jasper Dec 23, 2021, 2:56 AM

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With both Vo- tied to earth ground - you'd be shorting one supply

limpid nest Dec 23, 2021, 2:57 AM

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huh, I'll have to think about that

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Can't quite picture it.

heavy jasper Dec 23, 2021, 3:38 AM

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MSPaint - the best CAD tool

limpid nest Dec 23, 2021, 3:40 AM

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ahhhhh I see

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I like the !s

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Reminds me of metal gear solid

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I even heard the sound effect

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Is the same true if you wire them in parallel?

supple pollen Dec 23, 2021, 4:17 AM

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Then you'd short them to each other, probably not what you want.

limpid nest Dec 23, 2021, 4:21 AM

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Like so?

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I'm making a board to split this PSU into two channels. Am I well advised to put decoupling mechanisms on that board? I don't see an application circuit in the datasheet but I do see a maximum ripple of 100 mV which is not nothing.

heavy jasper Dec 23, 2021, 5:09 AM

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If you're putting them in parallel - in all likelihood you should just buy a power supply with the same voltage but a higher current rating.

limpid nest Dec 23, 2021, 5:23 AM

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Ah I'm not actually doing this, I was just curious

limpid nest Dec 23, 2021, 5:24 AM

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limpid nest I'm making a board to split this PSU into two channels. Am I well advised to put...

I realize the two sets of questions were confusing as they seem related, this question is unrelated to the PSU parallel vs series issue.

heavy jasper Dec 23, 2021, 5:25 AM

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Yeah, I was just doing some digging: https://www.mornsun-power.com/public/uploads/enfiles/mornsun_enclosed_&_din-rail_acdc_converters_application_guide_(2020).pdf shows a bit more about their circuits under test. But from the main datasheet, it seems like they use at least a 47uF electrolytic and 0.1uF ceramic capacitor as filtering

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And for the LM25-23B05 specifically, don't put more than 4000uF of cap on the output (if you were going to)

limpid nest Dec 23, 2021, 5:28 AM

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4k uF is a bunch lol, I wouldn't have considered that. But a 47 and a .1 doesn't seem out of order. Thanks! What did you search to find that?

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I tried LM25-23B05 application circuit and didn't get anything

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and any reason not to use ceramics for both capacitors? I was going to for the 0.1 uF but I don't know about the 47

heavy jasper Dec 23, 2021, 5:30 AM

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Yes - 47uF ceramic at enough voltage will be kind of annoyingly large and expensive, and could induce some instability from being so much low-ESR cap

limpid nest Dec 23, 2021, 5:30 AM

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interesting. I would have thought low-ESR is better.

heavy jasper Dec 23, 2021, 5:31 AM

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From the datasheet you linked they make a reference to "please refer to Enclosed Switching Power Supply Application Notes for specific information"

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I couldn't find anything named exactly that, but found the page on mornsun's website where they have all of their application notes, and just clicked through ones that seemed promising until I found the right one

limpid nest Dec 23, 2021, 5:31 AM

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ahhhh nice sleuthing. Thanks for taking the time.

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Read the Darn Manual strikes again

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where did the very common value of 47 uF come from for bulk capacitance? If it came from anywhere.

heavy jasper Dec 23, 2021, 5:33 AM

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Cargo-cult design, generally

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plus it's a common enough value for the engineer doing the validation to have just grabbed one from a bin, said "this looks roughly right" and called it a day

limpid nest Dec 23, 2021, 5:34 AM

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interesting

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Is it best practice to have your ground symbols actually pointing down? I can save some whitespace on my schematic and hopefully make it fit into a Letter Frame if I make 2 ground symbols point sideways. It feels icky though

heavy jasper Dec 23, 2021, 5:37 AM

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Sideways is marginally acceptable, facing upwards is unacceptable, facing downwards is best (IMO)

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Do you expect to actually be printing your schematics?

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I always draw my schematics on huge frames

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because I only ever view them in at most a PDF viewer

limpid nest Dec 23, 2021, 5:37 AM

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Possibly. I work sometimes with a guy who's very old school and likes to print stuff out

heavy jasper Dec 23, 2021, 5:37 AM

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Do you have access to a plotter

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or fedex shop

limpid nest Dec 23, 2021, 5:37 AM

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no to the first one, yes to the second.

heavy jasper Dec 23, 2021, 5:38 AM

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IMO if you're cramped enough that you're having to worry about drawing symbols sideways - your design should be bigger to begin with

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either split across multiple letter-size pages

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or on a bigger page

limpid nest Dec 23, 2021, 5:38 AM

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Ooh splitting it is a good idea. Although I like the flow it has now.

heavy jasper Dec 23, 2021, 5:39 AM

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If you're using a tool with hierarchical design - try to find some blocks that can be easily split on their own and represented as a single smaller block on the top page

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voltage regulators are classics for this

limpid nest Dec 23, 2021, 5:39 AM

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Hard to decide. I just put down an 8.5 x 11 explicit frame and it's actually bigger than the frame I'm currently using (A4L-Loc) which is weird, I thought A4 was 11 x 17

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I'm using fusion 360, which I'm pretty sure is hierarchical

heavy jasper Dec 23, 2021, 5:40 AM

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I think you're thinking legal?.

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(hm that's 8.5 x 14)

limpid nest Dec 23, 2021, 5:40 AM

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let me check the web again

heavy jasper Dec 23, 2021, 5:40 AM

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A4 is 8.25 x 11.75

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A3 is 11.75 x 16.5

limpid nest Dec 23, 2021, 5:40 AM

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Yeah

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hmmm I got it mixed up I guess let me look at the US letter size frame again and see if the size difference is that dramatic

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Yeah it's a pretty good difference, looks like more than an inch on either side. I wonder if the L in A4L means anything relevant

ember laurel Dec 23, 2021, 7:43 PM

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Yay, my unit passed all (medical) electrical safety testing.

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It failed EMI though - so I will need a re-test on that one with an adapted unit.

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Does anyone have any good tips on how to measure EMI at home?

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right now I've hooked up an inductor to the tip of a scope probe, and move that inductor close to various radiating sources.

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It seems to work rather well - I can pick up everything like this

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I've also ordered some EMI nearfield probes.

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But this is all qualitative - I cannot get any absolute references like this.

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I don't have any spectrum analyzer, except for the FFT built into my scope

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(Keysight DSOX1102G)

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I may look at getting a spectrum analyzer as well - I can get a really good deal on the Rigol DSA-815-TG

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Is there some other reasonably priced SA that I should look at?

heavy jasper Dec 23, 2021, 7:55 PM

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You might also look to see if there’s an equipment rental shop near you.

ember laurel Dec 23, 2021, 7:56 PM

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yeah that could be an idea - but do they usually have stuff to do proper EMI testing?

heavy jasper Dec 23, 2021, 7:56 PM

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I’m assuming you got the results, so you know the frequencies where you failed and how far over the line you were - so you can at least try to correlate with the equipment you have.

ember laurel Dec 23, 2021, 7:57 PM

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when motor is off, I am very good

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With motor on, it's not as nice

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heavy jasper Dec 23, 2021, 7:58 PM

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They should have gear to do at least decent pre-compliance testing, and your thing is small enough that you could even potentially get an anechoic shielded box if you’re having trouble resolving vs. the noise floor of your area.

ember laurel Dec 23, 2021, 7:59 PM

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this is what I measured at the motor, using my improvised inductor probe

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(inductor to probe, ground floating)

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after lowering the gate currents, I got this:

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which looks a lot better

heavy jasper Dec 23, 2021, 8:01 PM

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That was going to be my first suggestion - and definitely looks cleaner.

ember laurel Dec 23, 2021, 8:01 PM

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FFT said this:

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vs

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I think I may have some more room for going lower on current even

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right now I'm at 10mA source, 20mA sink for the upper and lower gates

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FFT on my scope is really rudimentary though

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not to mention my highly improvised probe 🙂

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now that's a quality probe for ya

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seems to pickup the important stuff though.... But the cheapo probe set from Amazon should be here in a few days

heavy jasper Dec 23, 2021, 8:11 PM

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You might just try directly probing the drive signals as well, since they’ll be your antennas primarily.

ember laurel Dec 23, 2021, 8:13 PM

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yes, they look very similar.

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I've been probing them through some pF capacitors

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since the device is already with the testing lab, I may just send them a firmware update (I can do OTA updates), and re-test with the 10mA/20mA drive currents

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but may have to add additional current limiting resistors

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I'm using the DRV8323S chip, which allows adjusting gate drive current over SPI

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Can get expensive with re-tests though

limpid nest Dec 23, 2021, 11:05 PM

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Hmm electronic_harry mentioned this product note (https://www.mornsun-power.com/public/uploads/enfiles/mornsun_enclosed_&_din-rail_acdc_converters_application_guide_(2020).pdf) using 0.1 uF and 47 uF capacitors but I don't see those specific values. I only see caps for the multi-output devices (see picture)

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and the typical application circuit just has a load on the output, no filtering

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I see them call out a 1uF ceramic cap for C2/C4 but for C1/C3 they just call out an electrolytic cap

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I must be missing something

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I'm trying to locate the technical manual they mention but having no luck

heavy jasper Dec 24, 2021, 12:35 AM

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The 47uF/0.1uF pairing was from the datasheet (it was the setup used for taking the noise measurements)

limpid nest Dec 24, 2021, 12:39 AM

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ooohhhh

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ok may as well just do that (more cargo cult design). I can't see how it would hurt

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I really should have ordered some BSS138W mosfets weeks ago. Can't seem to find them now. Shucks

limpid nest Dec 24, 2021, 2:55 AM

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heavy jasper The 47uF/0.1uF pairing was from the datasheet (it was the setup used for taking ...

Sorry to bug you about this PSU again, but I can't find that in the datasheet either. Is this the sheet? https://www.mornsun-power.com/html/pdf/LM25-23B05.html

heavy jasper Dec 24, 2021, 2:55 AM

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limpid nest Dec 24, 2021, 2:56 AM

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ahhhhh

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thank you

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I'll have to see if I can find Enclosed Switching Power Supply Application Notes

heavy jasper Dec 24, 2021, 2:57 AM

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That's the one I found and linked above

limpid nest Dec 24, 2021, 2:57 AM

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oh interesting ok

heavy jasper Dec 24, 2021, 2:58 AM

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It has more information about the ripple test measurement setup, but not really about the decoupling caps or similar

limpid nest Dec 24, 2021, 2:59 AM

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yeah I don't recall info about decoupling caps. I guess I'll just add the two from the datasheet and move on to other tasks. Thanks again.

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Do aluminum electrolytic capacitors not have a temp co-efficient?

distant raven Dec 24, 2021, 3:07 AM

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limpid nest Do aluminum electrolytic capacitors not have a temp co-efficient?

Fairly robust but do have specific operating ranges

heavy jasper Dec 24, 2021, 3:07 AM

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And they'll spec it as a separate ppm/deg C, instead of it being baked into the dielectric information like ceramics are.

limpid nest Dec 24, 2021, 3:08 AM

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Interesting. I'm just getting in the habit of adding more Attributes to my schematics and didn't see anything like X7R for example

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In digikey

distant raven Dec 24, 2021, 3:10 AM

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Yeah, X*R is important for noise filtering and defines how consistent the cap is across it’s designated range

limpid nest Dec 24, 2021, 3:10 AM

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Yeah

distant raven Dec 24, 2021, 3:10 AM

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Not so important on electrolytic

heavy jasper Dec 24, 2021, 3:10 AM

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The 3-character setup (X7R, Y5V, etc) is just for ceramic caps

limpid nest Dec 24, 2021, 3:10 AM

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That makes sense, thanks both

limpid nest Dec 24, 2021, 5:33 AM

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Does anyone know how to turn this text https://raw.githubusercontent.com/JLCPCBofficial/jlcpcb-eagle/master/cam/jlcpcb_2_layer_v9.cam into a cam job in F360?

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JLC just says to "download the cam job" but their darn link just leads to a text file

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looks like JSON but I don't know for sure the format

unreal flax Dec 24, 2021, 5:44 AM

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Eagle, and by extension F360, mostly uses text formats for its files, so if you save this as a .CAM extension, F360 should be able to use it.

limpid nest Dec 24, 2021, 5:47 AM

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Ahh ok just copy/paste into a text editor and save as? That's easy. I retract my annoyance.

unreal flax Dec 24, 2021, 5:51 AM

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Or just save from the browser window, yeah.

limpid nest Dec 24, 2021, 5:53 AM

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ah even better

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I was a fool

ember laurel Dec 24, 2021, 12:13 PM

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@heavy jasper I tried probing directly on the mosfets with the change of gate current

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Before (333mA limit):

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After (10mA limit):

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so yes, it charges noticably slower, but I cannot see any ringing directly on the mosfet here

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but it is a marked clear difference in the radiated EMI

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I'd like to round off that top a bit as well

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perhaps it is just a function of the square wave giving a lot of harmonics

proper anvil Dec 24, 2021, 4:48 PM

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Hello, I'm looking for an idiot-check.. this is a PCB that i've put together to control 12 servos off an ESP32, with voltage divider for reading the battery voltage, the battery wires are to be soldered onto the large rectangular pads (+ on top, - on bottom). Not so much expecting an in-dept functionality report but more of a 'Well there's a glaring issue here..' sort of check before I order as im still new to this 😬 on stall current could be up to 20A for a few seconds, on average im expecting <10A.

distant raven Dec 24, 2021, 4:52 PM

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Can you also share your schematic in a pdf form?

unreal flax Dec 24, 2021, 5:48 PM

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proper anvil Hello, I'm looking for an idiot-check.. this is a PCB that i've put together to ...

The main "hang on a sec..." thing that pops out at me is that you've got a lot of copper fill under the ESP32's antenna. So if you intend to use the wireless on it, you might be in trouble there.

proper anvil Dec 24, 2021, 6:28 PM

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unreal flax The main "hang on a sec..." thing that pops out at me is that you've got a lot o...

Didn't think about that! I'll move the divider and remove the copper from underneath. Thanks

proper anvil Dec 24, 2021, 6:35 PM

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distant raven Can you also share your schematic in a pdf form?

Sorry I didn't think to do that and now I'm out, should be able to in an hour or so if you care to see..

ember laurel Dec 24, 2021, 6:48 PM

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Remove the plane fills on both sides of that antennae. Just cut out a whole portion of the PcB fill

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Otherwise your precious signal will partly go to eddy currents in the copper fills, creating heat rather than good connection.

thick willow Dec 24, 2021, 6:53 PM

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I want to use a Cortex A to run some computational/memory expensive operations. I've seen that soem Cortex-A MPUs also include a Cortex-M, what can the Cortex-M do that the Cortex-A can't?

proper anvil Dec 24, 2021, 6:53 PM

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distant raven Can you also share your schematic in a pdf form?

📎 Schematic_robotdog_2021-12-24.pdf

unique patio Dec 24, 2021, 7:03 PM

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thick willow I want to use a Cortex A to run some computational/memory expensive operations. ...

Cortex-M is not as fancy, has fewer memory management options, etc. I think the main idea is to use the Cortex-M as a real-time co-processor, when the A is running something like Linux.

thick willow Dec 24, 2021, 7:03 PM

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What if I run freertos on an A?

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Isn't it possible to set linux as RTOS?

unique patio Dec 24, 2021, 7:21 PM

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thick willow Isn't it possible to set linux as RTOS?

@thick willow you could do both of those things, but for close-to-the-metal programming, the M would be helpful, so that you can, say, read or write pins very fast, without going through the Linux drivers

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FreeRTOS on the A would be fine. We are developing a version of CircuitPython that runs on the RPI Broadcom chips, without an OS, just like regular CircuitPython.

thick willow Dec 24, 2021, 7:58 PM

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I suppose freertos on A would make it harder to use stuff like TCP/IP

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or other high level stuff

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I want to design a MPU board so I'm trying to figure a few things out... one is to decide what MPU to use...

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One interesting MPU is the STM32MP1 series, those include cortex-m4, so I was wondering how usefull that would be. I'm also wondering how the integrated solutions compare to discrete MPU and MCU

distant raven Dec 24, 2021, 8:23 PM

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proper anvil

I have the same suggestion as @ember laurel about the antenna. Remove the copper pour from under it otherwise you’ll have bad performance.

As for your power traces, how thick are those?

proper anvil Dec 24, 2021, 9:14 PM

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distant raven I have the same suggestion as <@728007183673065614> about the antenna. Remove th...

The thick one is 4mm the thinner ones are 2.54mm

distant raven Dec 24, 2021, 10:33 PM

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Okay seems good enough

supple pollen Dec 24, 2021, 10:45 PM

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One trick is to omit soldermask on high current traces and glob solder on them to let them carry more current.

proper anvil Dec 24, 2021, 11:01 PM

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supple pollen One trick is to omit soldermask on high current traces and glob solder on them t...

Yeah I thought about that, I'd want to get some liquid soldermask to insulate it

distant raven Dec 25, 2021, 1:03 AM

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supple pollen One trick is to omit soldermask on high current traces and glob solder on them t...

Yeah, I’ve seen this. Cool work around to trace size limitations

ember laurel Dec 25, 2021, 1:54 AM

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Why do you need so much current?

heavy jasper Dec 25, 2021, 2:06 AM

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And if you're going to do something like that, unless you are super, super, super cost-conscious (read: making a single-layer board in quantity millions) it's much cleaner to just pay for heavier copper in your stackup - then you don't need to worry about QCing your soldering blobs, you get all the benefits of soldermask out of the factory, etc.

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But if this is the design above - I don't see anything there that seems like it would warrant needing such measures - normal PCBs will be totally fine (but if you're already doing different pours on top and bottom - you may as well just go all-out and do a full V+ pour on top layer and V- pour on bottom layer around your headers

worldly schooner Dec 25, 2021, 3:54 AM

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I don’t think the l7805 can drive that much current in the first place. You’ll probably get some large voltage dips long before your motors draw more than 2A…

heavy jasper Dec 25, 2021, 4:04 AM

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I think the 7805 is just for powering the MCU board, right?

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It looks like its input is on the V+ side

worldly schooner Dec 25, 2021, 4:27 AM

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Oh, I see it now. Right, vcc is input, not output…

proper anvil Dec 25, 2021, 4:48 AM

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Yep the 7805 is just for the MCU and maybe a few sensors in the future, the servos are to be powered off a lipo (but for now a 360W bench PSU)

proper anvil Dec 25, 2021, 4:49 AM

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heavy jasper And if you're going to do something like that, unless you are super, super, supe...

Yeah it's a one-off board really just for a personal project, so nothing particularly cost concious. Pretty cool that PCBs are that cheap to manufacture that it's possible to do something like this.

proper anvil Dec 25, 2021, 4:50 AM

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ember laurel Why do you need so much current?

12 mg995 servos that can draw something like 1.5A stall current

distant raven Dec 25, 2021, 4:57 AM

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proper anvil Yep the 7805 is just for the MCU and maybe a few sensors in the future, the serv...

What’s your input voltage?

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12V?

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Ah 7.2V

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Probably make sure you have some sort of heat sink on the 7805

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7.2-5V isn’t a big drop but 2V @ 500mA is still 1W dissipated.

ember laurel Dec 25, 2021, 9:47 AM

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You have a 7.2V 150W Power Supply?

fervent lance Dec 25, 2021, 10:46 AM

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'borrowing you' to bookmark near the beginning of this channel. ;) sorry for the ping.

worldly schooner Dec 25, 2021, 3:47 PM

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For future reference, there is an option to turn ping off when you reply to messages.

fervent lance Dec 25, 2021, 3:48 PM

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worldly schooner For future reference, there is an option to turn ping off when you reply to mess...

Oh that's a nice feature! Thanks!

compact portal Dec 25, 2021, 10:42 PM

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Hey guys, does anyone know any good and comprehensive tutorials on high speed interface (USB, HDMI) pcb design? Thanks in advance

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or resources of any kind

heavy jasper Dec 25, 2021, 10:45 PM

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If you want "comprehensive" this is pretty much the book: https://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241

High Speed Digital Design: A Handbook of Black Magic

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For a more straightforward simple set of guidelines: https://www.ti.com/lit/an/scaa082a/scaa082a.pdf

compact portal Dec 25, 2021, 10:47 PM

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thanks a lot!

limpid nest Dec 25, 2021, 11:42 PM

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For a USB connection I need to do in the future between an RP2040 stamp and a micro USB port, it's very important that the D+/D- lines be equal length, right?

supple pollen Dec 25, 2021, 11:49 PM

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It depends on what speed USB you plan to support, the faster speeds are more critical.

limpid nest Dec 25, 2021, 11:57 PM

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Whatever circuitpython requires

supple pollen Dec 26, 2021, 12:09 AM

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I think the RP2040 supports up to "full speed", which is 12MB/s, not terribly demanding. The hardware design manual gives more details as to what's required. https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf

distant raven Dec 26, 2021, 12:57 AM

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Good ole USB 1.1 PHY spec

limpid nest Dec 26, 2021, 1:01 AM

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Interesting. Wonder why they have those 27.4 Ohm resistors in there.

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I've never seen that value before

modest grail Dec 26, 2021, 1:44 AM

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how do you export gerber files in kicad?

unreal flax Dec 26, 2021, 1:58 AM

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modest grail how do you export gerber files in kicad?

I think you're looking for the "File -> Plot" menu command.

supple pollen Dec 26, 2021, 2:32 AM

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limpid nest Interesting. Wonder why they have those 27.4 Ohm resistors in there.

The "USB" section of that document explains it, they serve a couple of purposes. One is to (along with the circuitry on the chip) meet the correct impedance for the data lines. Another is to absorb reflections that occur when signals bounce off discontinuities.

limpid nest Dec 26, 2021, 2:32 AM

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Interesting

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I'm watching TV with a friend so I didn't get that far.

proper anvil Dec 26, 2021, 3:38 AM

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distant raven What’s your input voltage?

I'll consider it, maybe expose the ground plane and add some thermal paste? kinda dirty?

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eh, i've got lots of little heatsinks anyway. may as well do it right I suppose

modest grail Dec 26, 2021, 3:17 PM

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how do you add an immage in kicad?

fervent lance Dec 27, 2021, 1:27 AM

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anyone have recommendations on how i would go about commissions someone to do PCB design and assembly of a flexible board with a bunch of neopixels on it?

limpid nest Dec 27, 2021, 1:29 AM

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adafruit jobs board isn't a bad idea

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many PCB services will do assembly for you.

unreal flax Dec 27, 2021, 2:42 AM

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Although note that flex PCBs tend to be more expensive than standard ones. This is all possible, but just bear in mind that a custom-designed, custom-fabricated, custom-assembled board is not going be be a $20 sort of project. 😉

limpid nest Dec 27, 2021, 3:09 AM

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What's the best way to get my PCB's schematic out of F360 and into a PDF?

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nevermind, I found it. There's a print button in the Document section

limpid nest Dec 27, 2021, 3:56 AM

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what size heat shrink should I use for these? They are going to 28 AWG wire (https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/160597-4/2284582?s=N4IgjCBcoOwBxVAYygMwIYBsDOBTANCAPZQDa4AbAAwCscMIAuoQA4AuUIAymwE4CWAOwDmIAL6EwVACwNoIFJAw4CxMiBoAmMDSasOkbnyGiJ4GQnmLleQiUjkpVOFT0h2nHgJHjJATjg-RAU0LFs1BxBXZncDI29TQgBaTWDFPgBXVXtyXUYxM1TI7BZ0ABNcAAIkIkFBXCQ2Il5sJjEgA)

Additionally, anyone know of the proper crimp tool for these?

supple pollen Dec 27, 2021, 2:05 PM

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limpid nest what size heat shrink should I use for these? They are going to 28 AWG wire (<ht...

Did you want to shrink the entire terminal (they're 3mm wide, so 1/8" tubing would suit), or just the wire end, in which case 1/16" is probably a reasonable choice)?

compact portal Dec 27, 2021, 7:06 PM

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hey, i don't have a lot of experience with pcb design

i'm trying to program the attiny24a using an arduino as ISP, but it's giving me all sorts of errors, and the errors are quite inconsistent. sometimes it fails to verify the flashed fuse, sometimes it doesn't even read the device fingerprint. could this be a result of the pcb layout and routing of the signals? or is it with the programmer/configs/software?

to program the attiny, i'm using ATtinyCore and the arduino ide, for the fuses i used avrdude and its configs provided by the arduino ide via a terminal

limpid nest Dec 27, 2021, 7:38 PM

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supple pollen Did you want to shrink the entire terminal (they're 3mm wide, so 1/8" tubing wou...

The whole terminal, thanks

boreal bobcat Dec 27, 2021, 8:53 PM

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I am a noob when it comes to electronics. This is my first PCB. I have a ESP32 based board that I needed to power with a battery and charge it. This is my first attempt at it. Can you please share your feedback on this board?

https://oshwlab.com/vagmi/upsboard

upsboard - EasyEDA open source hardware lab

In EasyEDA open source hardware lab, open source square pools all kinds of electrical design engineerings together to realize resource sharing easily.

limpid nest Dec 27, 2021, 10:29 PM

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why the heck does fusion360 say that the frame I'm using is 8.5" x 11", yet when I go to print to PDF it wants to print on 6 pages to fit it all?

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I just want a nice schematic!

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Here's what the menu says

supple pollen Dec 27, 2021, 10:31 PM

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compact portal hey, i don't have a lot of experience with pcb design i'm trying to program the...

The routing looks fine to me, so I'd suspect a clock/power problem.

compact portal Dec 27, 2021, 10:32 PM

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could you please elaborate on what you mean by a clock problem?

supple pollen Dec 27, 2021, 10:36 PM

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The ATtiny has a variety of possible clock sources it can use, an on-board oscillator, a couple of crystal/resonator options, or an external clock. Before the fuses are programmed, it will use whatever its default clock source is. If that's (say) a crystal, and no crystal is present, it will oscillate at random frequencies (if at all), causing all sorts of problems.

compact portal Dec 27, 2021, 10:37 PM

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oh i see

limpid nest Dec 27, 2021, 10:37 PM

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limpid nest Here's what the menu says

I kind of figured it out. I needed to change the size of the paper I was "printing" to. Even then the frame was off the page but scaling it down worked OK. Super weird

supple pollen Dec 27, 2021, 10:38 PM

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The fancy STK500 programmer provides an external clock for reliable programming in such situations, since it's designed to be able to program chips in a variety of situations.

compact portal Dec 27, 2021, 10:38 PM

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occasionally the attiny will read the fuse bits and the factory setting seems to be internal 8mhz oscillator with CLKDIV8 (so essentially 1 mhz internal clock)

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i have to look into the avrdude configs i guess

supple pollen Dec 27, 2021, 10:39 PM

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Ah, that should be okay, which leaves power issues, signal interference of some sort, or an issue with the programming setup (which is what you're looking at, so you're doing what I would do in this case)

compact portal Dec 27, 2021, 10:39 PM

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makes sense

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thanks a lot!

limpid nest Dec 27, 2021, 10:48 PM

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in F360, how can I get the value of a part to display? In this case a capacitor. Do I need to edit the library?

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The value shows up in the symbol so I'd expect it to show in my schematic

unreal flax Dec 27, 2021, 11:02 PM

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limpid nest The value shows up in the symbol so I'd expect it to show in my schematic

It may be case-sensitive... I've always seen >NAME and >VALUE. But if the library part is correct, the value will be substituted for whatever you set in the schematic with the value tool, like "1uF".

limpid nest Dec 27, 2021, 11:02 PM

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ahhhh didn't even notice that. Let me try again

compact portal Dec 27, 2021, 11:19 PM

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boreal bobcat I am a noob when it comes to electronics. This is my first PCB. I have a ESP32 b...

hey, first thing i noticed is, that you have put what looks like a 1k ohm resistor on the PROG pin of the charger chip, which according to the charge current formula from its datasheet would give you 1A of charge current. the max charging current of the chip however, seems to be 500 mA, which means, that you should have at least a 2k ohm resistor on the PROG pin

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i mean the R2 resistor

limpid nest Dec 27, 2021, 11:27 PM

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unreal flax It may be case-sensitive... I've always seen `>NAME` and `>VALUE`. But if the li...

Tried switching those to upper case, no dice. Thanks though, it was a good idea.

boreal bobcat Dec 27, 2021, 11:33 PM

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@compact portal - thanks. I missed that. It should be 2K. I've fixed that now. 👍

compact portal Dec 27, 2021, 11:33 PM

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and I also recommend you use ground planes to attach your grounds

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in easyeda it's copper area in pcb tools

limpid nest Dec 27, 2021, 11:56 PM

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just watch out for ground loops

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hmm I found a forum post that discusses "radio buttons" that need to be engaged in order to see the value. It was an EAGLE forum though so I don't know how relevant it is to F360

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AH!

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I found it!

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It's at the bottom of the Devices menu

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oops, nevermind that didn't solve the issue

limpid nest Dec 28, 2021, 12:31 AM

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oh my gosh. I figured out how to get the value to show (reposition attributes) but now the text doesn't have anchors so I can't move it around!!

modest grail Dec 28, 2021, 4:53 PM

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so i an designing a custom connector and need to know how to do contact fingers in eagle

modest grail Dec 28, 2021, 5:28 PM

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nvr mnd. figured something out. now then, how do you add images to eagle

compact portal Dec 28, 2021, 8:11 PM

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supple pollen Ah, that should be okay, which leaves power issues, signal interference of some ...

update: it finally works! switched from using an arduino as isp to a raspberry pi 4b and works like a charm

#

the solution could've been either switching from an arduino to a raspberry pi or switching to 3.3V logic (which i've read somewhere that it should be more stable)

ember laurel Dec 28, 2021, 9:25 PM

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does anyone have a good resource for ferrite core selections?

supple pollen Dec 28, 2021, 10:49 PM

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There's the Würth Elektronik book on inductors, and various vendors' sites (Amidon, Ferroxcube, Micrometals, Acalbfi, Dexter Magnetics, Torelco, etc.)

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There are also some rules of thumb based on frequency and usage

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Nice brief writeup here: https://www.vkham.com/Info/ferro/tut_2a.html

ember laurel Dec 28, 2021, 11:07 PM

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Fair Rite has a decent amount of material as well

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Right now I’m using this one: https://www.farnell.com/datasheets/1685831.pdf

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But I didn’t have any wraps - wires just go straight through

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I measured with one or two wraps as well, and the 30Mhz noise is heavily lowered

#

#

That’s with no wraps around the ferrite core

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Here with two wraps:

supple pollen Dec 28, 2021, 11:24 PM

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Ah, you're looking for something like EMI filtering

ember laurel Dec 28, 2021, 11:29 PM

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Yes

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I’ve already tuned down my mosfet gate switch current as far as I can go

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All in all I think I’m good now, but since I don’t have an EMI lab, I’ll have to send out the device for testing.

supple pollen Dec 29, 2021, 12:09 AM

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I'll usually use something like a slew rate limiter for tasks like that.

limpid nest Dec 29, 2021, 3:10 AM

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What are the PP_N parts in this schematic?

#

And is the X in MF-MSMF250/X a placeholder?

unreal flax Dec 29, 2021, 3:19 AM

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PP probably stands for "probe point", i.e. a test pad.

limpid nest Dec 29, 2021, 3:20 AM

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ah OK, I don't need to probe anything, I don't think. I just checked over a pi and I see what I would have assumed were probe points labelled with PPN

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Is the box around the circuit with the mosfet on top an IC?

#

I'm trying to power a pi through the 5V header, but I want to add the protection circuitry into my design

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If my barrel jack is far from the actual 5V pins, should I put the power protection circuitry close to the barrel jack or close to the 5V pins?

neon slate Dec 29, 2021, 5:38 AM

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Hey how long does it usually take for a pcb to be delivered from jlcpcb?

limpid nest Dec 29, 2021, 5:38 AM

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sometimes it's like 5 days, sometimes it's 8 or 9. Super depends on your shipping choice.

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if you went with DHL, I'd expect it in 5 days, 7 at the outside

neon slate Dec 29, 2021, 5:41 AM

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Bro I’ve been waiting 35 days!!

limpid nest Dec 29, 2021, 5:41 AM

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why might a mosfet have 4 drain pins?

limpid nest Dec 29, 2021, 5:42 AM

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neon slate Bro I’ve been waiting 35 days!!

What part of the world do you live in?

neon slate Dec 29, 2021, 5:42 AM

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USA

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I live in Texas

limpid nest Dec 29, 2021, 5:42 AM

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that's....highly abnormal.

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I would contact them

#

Sounds like someone messed up pretty badly.

neon slate Dec 29, 2021, 5:42 AM

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Ok

limpid nest Dec 29, 2021, 5:42 AM

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limpid nest why might a mosfet have 4 `drain` pins?

supple pollen Dec 29, 2021, 5:42 AM

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The little SO8 packaged MOSFETs?

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Oh, that's different: probably for heatsinking

limpid nest Dec 29, 2021, 5:43 AM

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hmmm

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interesting

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@neon slate FYI they have full tracking of your board's progress on their site.

supple pollen Dec 29, 2021, 5:44 AM

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Those small packages have poor heat dissipation capabilities, so they leverage the PCB traces to draw away heat. The drain pins are probably on the die carrier and have the lowest thermal resistance.

neon slate Dec 29, 2021, 5:44 AM

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limpid nest <@!746533006872674485> FYI they have full tracking of your board's progress on t...

Ok

supple pollen Dec 29, 2021, 5:44 AM

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If you choose the cheapest shipping, it can be around 40 days and there's no tracking (they generally mark that shipping as "not recommended")

neon slate Dec 29, 2021, 5:45 AM

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supple pollen If you choose the cheapest shipping, it can be around 40 days and there's no tra...

I think I paid extra for it to get here within 10 days

supple pollen Dec 29, 2021, 5:45 AM

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I can see the appeal of the cheap shipping, as their boards are so inexpensive, it kinda rankles me to pay $16 to ship $3 worth of boards.

#

I'd suggest going to their site and checking the progress of your order. If it hasn't shipped, there may be a delay (sometimes they'll have questions on your board, and if their note goes in your spam folder, you can miss it). If it has shipped, there should be a tracking number available.

neon slate Dec 29, 2021, 5:48 AM

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supple pollen Dec 29, 2021, 5:55 AM

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Hmm, looks like a handoff from one transit company to another didn't go well.

ember laurel Dec 29, 2021, 10:09 AM

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@supple pollen I have already tuned my slew rate of the mosfets

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I have very fast Mosfets... CSD88539

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https://www.ti.com/product/CSD88539ND

CSD88539ND data sheet, product information and support | TI.com

TI’s CSD88539ND is a 60-V, N channel NexFET™ power MOSFET, dual SO-8, 28 mOhm. Find parameters, ordering and quality information

#

They have a Qgd of 1.1nC

#

There is absolutely no measurable ringing at all on the mosfet outputs

#

where I can measure a ringing - is next to the BLDC motor itself

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right now, it looks like I have an issue around 8.7MHz

#

I don't think it is an issue with my measurement setup, since I also measure an existing, competing product

#

it has a different commutation scheme, but lacks this 8.7MHz peak

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Mine

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Competing product:

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Zooming in on that overshoot in the top part of graph, on mine:

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Again, nothing of this is measurable on the mosfet output, or BLDC motor terminals on the controller board

#

it is only measurable using an inductor (antenna) by the motor itself

ember laurel Dec 29, 2021, 11:31 AM

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Ok - using a 1nF cap on the motor wire outputs to gnd does the trick

#

quasi flare Dec 29, 2021, 6:37 PM

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does anyone know the specs on the ferrite beads on the MAX98357 breakout? I'm trying to incorporate that circuit into a custom board, and having trouble figuring out what ferrite to use.

unique patio Dec 29, 2021, 6:42 PM

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quasi flare does anyone know the specs on the ferrite beads on the MAX98357 breakout? I'm tr...

They are TDK MPZ2012S221A

quasi flare Dec 29, 2021, 6:42 PM

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tyvm!

oak bough Dec 29, 2021, 8:19 PM

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Howdy. Is there a better channel to discuss PCB etching?

distant raven Dec 29, 2021, 9:06 PM

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oak bough Howdy. Is there a better channel to discuss PCB etching?

This is perfect

latent plinth Dec 30, 2021, 10:55 AM

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What circuit design and simulation software do you guys use/recommend? I used to work with Multisim, but I don't have the license any more and its reputation doesn't seem to be too good.

distant raven Dec 30, 2021, 4:11 PM

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EDAPlayground

spice turtle Dec 30, 2021, 5:48 PM

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TINA TI

heavy jasper Dec 30, 2021, 6:22 PM

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LTSpice is my go-to usually (the solver is very well-written and fast, they have a native Mac version, and it runs just fine under WINE to my recollection); the TI equivalent is fine and maybe preferred if you’re using a bunch of TI parts, want to use their built-in models, and can’t get unencrypted spice models from them.

distant raven Dec 30, 2021, 7:35 PM

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You can also make transistor and semiconductor models in magic VLSI to import into LT Spice I believe

heavy jasper Dec 30, 2021, 8:57 PM

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I think that’s just everything spice-based anyway, though maybe they have some layer that easily translates some graphics as well.

ember laurel Dec 30, 2021, 9:15 PM

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One more vote for LT Spice here

limpid nest Dec 30, 2021, 9:39 PM

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Learned a smidgen of LT Spice in college. Just enough to see how cool and powerful it is.

silver marsh Dec 30, 2021, 9:50 PM

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👍 for LT Spice and KiCAD’s (somewhat more difficult-to-use) cousin.

fiery parcel Dec 31, 2021, 10:02 PM

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Hey all, I'm currently prototyping a design with a CLUE board and using Circuitpython, but eventually I want to design a custom PCB. Is there an open source circuitpython-compatible board that I can reference when I get around to designing custom PCB's?

limpid nest Dec 31, 2021, 10:03 PM

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The CLUE is OSHW is it not?

worldly schooner Dec 31, 2021, 10:09 PM

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fiery parcel Hey all, I'm currently prototyping a design with a CLUE board and using Circuitp...

All of adafruit-made boards these days have schematics available, the bigger question is usually component availability. All of the samd chips are really short in supply, but things like esp32-s2 modules might still be available.

fiery parcel Dec 31, 2021, 10:41 PM

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Interesting

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So if I were to get say, 5 or 6 of these custom boards made, do I need to figure out things with the bootloader and whatnot?

worldly schooner Dec 31, 2021, 11:26 PM

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Depends on the chip. Rp2040 is really easy to use with its rom boot loader iirc

distant raven Jan 1, 2022, 12:49 AM

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worldly schooner Depends on the chip. Rp2040 is really easy to use with its rom boot loader iirc

The RP2040 and ESP32-S2/S3 are definitely this way

#

The C3 has BLE Circuitpython support in the works

thick willow Jan 1, 2022, 8:45 PM

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How dififcult is it to design a PCIe interface and drivers compared to say USB3 and gigabit ethernet?

distant raven Jan 1, 2022, 9:15 PM

#

The PCIe hardware interface isn’t hard

#

The driver is where you might have some issues

heavy jasper Jan 2, 2022, 1:01 AM

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And “isn’t hard” is a bit relative - it depends a lot on what you mean by “design the interface.” Are you going to use some off-the-shelf interface chip and just need to know how hard it is to plumb it on a PCB? That’s a different story from “I want to implement the verilog of a PCIe controller on an FPGA.” PCIe has a lot more to get wrong, and a lot less visibility when you do (and visibility is a lot more expensive - PCIe protocol analyzers ain’t cheap).

#

And it’s somewhat harder to do the “I’ll make the simple version and then build up from there” strategy that can be more easily done with e.g. a USB3 to parallel bridge chip and an associated FPGA that only needs to send parallel.

#

Plus also - USB3 and Gigabit are natively something that’s easy to hot-plug - PCIe is not necessarily so (unless you’re using a fairly recent computer platform and know you have support for it in the BIOS, or a thunderbolt adapter), which means if you need to make edits to your FPGA code and relaunch, you can get into a situation where each code change needs a computer reboot, which is a huge pain.

round stump Jan 2, 2022, 1:24 AM

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I found it some time ago but lost it - does anyone have a link to the tutorial, or a tutorial, for doing PCB artwork with traces, silkscreens, etc.?

limpid nest Jan 2, 2022, 1:55 AM

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Hmmm no tutorial but SVGtoEagle is a very helpful tool.

tough matrix Jan 2, 2022, 3:28 AM

#

here is one resource:
https://www.youtube.com/watch?v=EI2CLwQi6N0

YouTube

The Accumulator

Bringing Vector Artwork into Autodesk Eagle

Import sophisticated vector artwork from Adobe Illustrator into Autodesk Eagle and use it on your PCBs without rasterizing! Enjoy!

Hit me up on Twitter : @TallDarknWeirdo

▶ Play video

tough matrix Jan 2, 2022, 3:44 PM

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Hi all:
I decided to try and create a curated list of "commonly used components" - both for myself, so I can keep track of what I commonly use for ease of reordering, and for others - to answer common questions "help me choose among 10 million diodes available on Digikey for my project".

Of course, each component on Digikey is useful for some project, so it is not easy to make selection. The goal is to have no more than 5-10 items in each category (say, P-Mosfets) which should be enough to cover most of typical use cases.

I created a template (at the moment, as google sheet) and will slowly work on adding to it; once I believe it is worth sharing I will announce it.

If anyone here wants to help, I'd be happy to add you as collaborator in google drive.

I wish I could do it in github so people could do PR, but it doesn't work for spreadsheets...

#

Anyway here is the link to (almost empty) template: https://docs.google.com/spreadsheets/d/1DtasBIGTwcviqOkmKRJ8JbwxWOKteo67BdFHE-8p2e0/edit?usp=sharing

supple pollen Jan 2, 2022, 6:56 PM

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You could use this as a starting point (it's pretty solid, but hasn't been updated for a while): http://www.ladyada.net/wiki/partfinder

limpid nest Jan 2, 2022, 7:52 PM

#

I'm trying to use this protection circuit in a design (see pic) but Q3 is unavailable. Is this a workable replacement?
https://www.digikey.com/en/products/detail/diodes-incorporated/DMP2033UVT-7/7725073?

unreal flax Jan 2, 2022, 8:15 PM

#

limpid nest I'm trying to use this protection circuit in a design (see pic) but Q3 is unavai...

The closest I can find with a quick Digi-Key search is the DMP2045U: https://www.digikey.com/en/products/detail/diodes-incorporated/DMP2045U-7/8275356

DMP2045U-7 Diodes Incorporated | Discrete Semiconductor Products | ...

Order today, ships today. DMP2045U-7 – P-Channel 20 V 4.3A (Ta) 800mW (Ta) Surface Mount SOT-23-3 from Diodes Incorporated. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

limpid nest Jan 2, 2022, 8:16 PM

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I found the one I found by picking parameters I thought were relevant and narrowing down that way. How did you? And is the one you found "close enough"?

unreal flax Jan 2, 2022, 8:20 PM

#

Yep, same procedure. Sorry, I missed that you had linked to a potential replacement already. I think yours would also work, it's just in a different package instead of a drop-in for the original, if that's important.

limpid nest Jan 2, 2022, 8:23 PM

#

Drop in isn't that important. Just something that will work. Thanks!

#

How would you pick between mine and yours?

unreal flax Jan 2, 2022, 8:27 PM

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"Six of one, half a dozen of the other"... they're very similar, and I expect either will work. Yours has a little higher power dissipation, mine has a little lower resistance, for example.

limpid nest Jan 2, 2022, 8:30 PM

#

Interesting ok. I'm still trying to grok that circuit so knowing that either will work helps. Thanks

ember laurel Jan 2, 2022, 8:44 PM

#

@limpid nest polarity reversal protection?

limpid nest Jan 2, 2022, 8:44 PM

#

I guess? It's from the raspberry pi schematic

#

I think the TVS diode is somehow for over voltage protection but I'm still puzzling out how. I've just heard that's what they're for

ember laurel Jan 2, 2022, 8:45 PM

#

the SMBJ?

limpid nest Jan 2, 2022, 8:45 PM

#

Indeed

ember laurel Jan 2, 2022, 8:46 PM

#

mhm

limpid nest Jan 2, 2022, 8:46 PM

#

I just don't see how it would protect from over voltages since there's still a near 0 ohm path past it

ember laurel Jan 2, 2022, 8:46 PM

#

overvoltage from whatever is before it

limpid nest Jan 2, 2022, 8:46 PM

#

Hm

ember laurel Jan 2, 2022, 8:46 PM

#

I'd somehow expect a TVS on the input there

limpid nest Jan 2, 2022, 8:47 PM

#

But can't whatever is before it just go right past the TVS thru a trace?

ember laurel Jan 2, 2022, 8:47 PM

#

it would lead any overvoltage down to ground

#

usually you have a TVS on the input, for ESD purposes

#

in this configuration, I expect ESD would be risky for the mosfet and trannies

limpid nest Jan 2, 2022, 8:48 PM

#

So does its impedance drop a ton when the voltage spikes?

ember laurel Jan 2, 2022, 8:49 PM

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https://www.littelfuse.com/media?resourcetype=datasheets&itemid=fc83cff9-7655-4e4e-b1dc-e1b436c0b632&filename=littelfuse-tvs-diode-smbj-datasheet

#

between 6.4V and 7V it will breakdown and start conducting

limpid nest Jan 2, 2022, 8:50 PM

#

Hmm link won't open

#

Ahh ok so then it provides a lower impedance path to ground for high voltages than the traces in that case?

ember laurel Jan 2, 2022, 8:52 PM

#

yes the idea of the TVS is that it should eat any transient high voltages

limpid nest Jan 2, 2022, 8:52 PM

#

I see thanks!

#

I ran into them in another design and was mildly confused. Are they a kind of zener diode?

ember laurel Jan 2, 2022, 8:54 PM

#

well, sort of, except normal operation for a zener would be to use them in reverse

#

and a TVS would be used as a regular diode

limpid nest Jan 2, 2022, 8:57 PM

#

Ah ok

#

Thx!

ember laurel Jan 2, 2022, 9:04 PM

#

I mean... you wouldn't really use one instead of a regular diode

tough matrix Jan 2, 2022, 9:04 PM

#

sorry, I got confused... isn't TVS normally also used in reverse, I. e. so that under normal circumstances there is no current through it?

ember laurel Jan 2, 2022, 9:04 PM

#

just use it for what it is there for 🙂

#

well, it will just block current like any diode.

#

zeners are usually operating normally in reverse, that's what I meant

tough matrix Jan 2, 2022, 9:05 PM

#

yes, that's what I mean

#

oh, got it

ember laurel Jan 2, 2022, 9:05 PM

#

while the TVS is normally blocking something

#

anyway 🙂

#

I'm tearing my hair a bit about some EMI stuff here

#

Does anyone have any good thoughts on a reasonable bench setup for reliably investigating this stuff?

#

right now I'm using some probe set from Amazon together with the spectrum analyzer on my scope

#

I'm not very certain about the origins of my EMI issues - it could be either motor mosfets or buck.

#

I'm running a Synchronous buck at 950kHz switching freq..

#

and yeah, there is quite a bit of noise around the buck, but I don't see much anywhere else on the board

#

I have a peak somewhere around 35MHz, which I'm not sure whether it is from some resonance in my measurement setup, or from a resonance on the board itself

#

I cannot really relate any voltage probing to these frequencies

#

I'll perhaps give it another go and see if there is some harmonic that falls right on there from the buck converter, and try setting up a snubber for it

tough matrix Jan 2, 2022, 10:27 PM

#

I am afraid I am not much help there

thick willow Jan 3, 2022, 3:38 AM

#

@heavy jasper Thanks for the response. I was wondering what's the simplest way, in terms of time required to develop the hardware and software required to implement a fat data pipe to a PC. It appears that USB is quite complex to implement at the software level. So unless there are some readily available solutions I would think that gigabit UDP package transmission might be the easiest way to transfer data fast

heavy jasper Jan 3, 2022, 3:38 AM

#

Yeah Ethernet is my go-to for stuff like that until something drives me away.

#

I’m also a sucker for packet-switched networks in general (easy to add on more switches, adapters, etc)

#

For Azeteg - are you able to correlate your local probing with the results from the EMI chamber at all? Especially since you now have 2 data points (the two different speeds). Multi-megahertz noise (if actually from a buck) doubly screams fast edges exciting the self-resonant frequency of the inductor and being shot straight through to the output. These would most commonly be seen as the same type of ringing you already solved on the motor drive (just much faster) and with the same types of fixes. If your buck is monolithic and doesn’t give you the same edge rate control, a quick thing I’ve done in the past is to add a bit of series resistance to the gate bootstrap capacitor.

limpid nest Jan 3, 2022, 4:15 AM

#

Has anyone ever gone from a Fusion 360 part drawing and transported it into F360 EDA as a board outline?

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I feel like it's gotta be possible

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The two programs are like....right next to each other. And you can go the other way

thick willow Jan 3, 2022, 4:17 AM

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What conenctor is mor physically robust, type B or C? Can't find a comparison between them. I suspect its B, but would ike to confirm.

limpid nest Jan 3, 2022, 4:24 AM

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My instinct says B as well but I have a glimmering of something I read saying C is more. I think my C ports have been longer lasting than B ports

thick willow Jan 3, 2022, 4:38 AM

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Yeah to be honest the C looks kinda fragile because of size, still maybe I should just use C, it will look more modern at least

limpid nest Jan 3, 2022, 4:40 AM

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Isn't C bigger than B physically?

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I think B is tricking us because it's trapezoidal instead of slot shaped

thick willow Jan 3, 2022, 4:47 AM

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No C is the tiny one

limpid nest Jan 3, 2022, 4:47 AM

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Hmm I'm mostly out of B cables but I'll trust you

thick willow Jan 3, 2022, 4:48 AM

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Thts the C, is kinda new

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can be plugged in any direction

limpid nest Jan 3, 2022, 4:49 AM

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Yeah I basically only have C except a few B down in my workbench area. But I'm cozied up with the dog so not going to investigate

thick willow Jan 3, 2022, 4:51 AM

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I still have lots of micro

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most of the devboards that i own are micro

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I suppose they will slowly begin to dissapear and get replaced by C

limpid nest Jan 3, 2022, 4:52 AM

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It's pretty common for MCU boards

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Yeah I agree.

thick willow Jan 3, 2022, 4:52 AM

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yeah

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i have only on1 MCU board with C

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its a cypress

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posc6

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everything else ismini

limpid nest Jan 3, 2022, 4:53 AM

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I think adafruit is slowly transitioning that way but I have no insider knowledge

thick willow Jan 3, 2022, 4:54 AM

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I've had a few mini break because they were smd

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smd connectors are a pretty bad idea

heavy jasper Jan 3, 2022, 8:01 AM

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My view: By default choose type-C unless you’re building into an existing ecosystem of specific cabling (e.g. synthesizer stuff) or are hand-soldering and can’t find a good type-c option that works for you. Anywhere you would use micro-B or mini-B in particular are prime candidates for replacing with type-C. Select a type-C connector with through-hole shielding/retention features (nearly all do).

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Especially as more laptops start going primarily type-C, adapter cables for C-to-mini or C-to-micro are annoying, vs a C-to-C that’s become ubiquitous (at least if you only care about usb 2.0 and power - don’t get me started on the fragmentation of higher-speed USB3/USB4/Thunderbolt cables)

ember laurel Jan 3, 2022, 9:38 AM

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Measured on my buck switching node

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I cannot really find any of the 35-ish MHz noise probing voltages

ember laurel Jan 3, 2022, 10:05 AM

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heavy jasper Yeah Ethernet is my go-to for stuff like that until something drives me away.

Using the conducted emissions probe, I can clearly see a peak around 37-ish MHz

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This would be straight above the buck inductor

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The peaks are multiples of the buck frequency, 960-ish kHz

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Somehow whatever I get close to seems to have that same peak though

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So I’m considering this to be from measurement

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(also other devices....)

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Here is the failed EMI test

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that's with motor ON

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With motor OFF it looks a bit better

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I suppose all of the radiation actually comes from the motor cable, which is 1.5m, running out of the box through a ferrite core

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I didn't do any windings on this ferrite core though - something which would probably have helped a lot.

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I am quite tight on space - which is why I didn't do any windings.

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the noise that is there seems to be amplified when motor is on, especially that peak around 72-ish Mhz.

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when motor is OFF there isn't much coming out that cable - it is just 3 motor wires connected to mosfets that are off, and also two LED wires, connected to mosfets that are off.

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This is the ferrite I am using:
https://www.farnell.com/datasheets/1685831.pdf

supple pollen Jan 3, 2022, 1:28 PM

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limpid nest Isn't C bigger than B physically?

It depends on which B you mean. The original B was pretty chonky, then there was mini-B then micro-B (which is what many people think of as "B").

thick willow Jan 3, 2022, 1:51 PM

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I ment type-b, the micro-b and mini-b are usually just called micro and mini. I still have to see an miniA and microA

tough matrix Jan 3, 2022, 3:26 PM

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Usb-C is certainly smaller than type B

limpid nest Jan 3, 2022, 7:31 PM

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supple pollen It depends on which B you mean. The original B was pretty chonky, then there wa...

Good pt I was thinking of micro B because it's what C immediately replaced

limpid nest Jan 3, 2022, 9:20 PM

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Are the highlighted connections here the shield?

limpid nest Jan 3, 2022, 9:41 PM

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I'm also definitely still suffering from sick brain, I was asking myself why there were two 6s. But one of them is a 9 lol.

ember laurel Jan 3, 2022, 10:16 PM

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Yes, they would be the shield. They also function as the sturdy physical solder joints, that keeps your connector in place

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(because who doesn't like usb connectors that come loose)

limpid nest Jan 3, 2022, 10:26 PM

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Oh I see now there are actual pins there. The colors of the pins and the traces being so similar threw me

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Does this mosfet https://www.diodes.com/assets/Datasheets/DMP2045U.pdf actually have the two diodes pictured in the datasheet? Or are those a recommended part?

elder peak Jan 3, 2022, 10:53 PM

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In that case, there is a gate protection diode that is present and the other diode is a reminder that there's a body diode in the MOSFET.

ember laurel Jan 3, 2022, 10:55 PM

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It does say ESD protected gate in the datasheet...

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it doesn't specify any HBM or so though

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I guess it's protected from some random unspecified ESD 🙂

fervent lance Jan 3, 2022, 11:03 PM

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Hello guys, I'm interested in this adafruit connector because of the good size (https://www.adafruit.com/product/4048). The problem is that I can't find the footprint/CAD model anywhere, even in the official website of adafruit. Could someone help me?

limpid nest Jan 3, 2022, 11:08 PM

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ember laurel

Interesting. That's probably a good feature

ember laurel Jan 3, 2022, 11:08 PM

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can help you to spare easily killed mosfets

limpid nest Jan 3, 2022, 11:09 PM

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In fusion360, I need to make my design on multiple schematic pages, but I can't cut/paste because that ruins my PCB. Does anyone know if it's possible to move portions of a design to a new schematic page without the PCB losing its mind? Or do I need to do a complete respin?

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I guess I could do a workaround and only do the part that isn't fitting on the schematic on a new page. That's kind of ugly though. I'd rather to Power/Data Inputs | ICs | Outputs on 3 pages

twilit mango Jan 3, 2022, 11:11 PM

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limpid nest In fusion360, I need to make my design on multiple schematic pages, but I can't ...

I remember looking this up a while ago, and I don't remember what I found. I do know I ended up not bothering, so I feel like maybe it turned out to not be reasonable. This is not entirely helpful though.

limpid nest Jan 3, 2022, 11:12 PM

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Not to worry, it's a data point. Thanks. I think I'll just do my workaround

limpid nest Jan 3, 2022, 11:53 PM

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Why might this footprint from the manufacturer have a huge tRestrict box around it? It's preventing traces from reaching the pads, as far as I can tell.

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it's a P Channel MOSFET

unique patio Jan 4, 2022, 12:06 AM

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limpid nest In fusion360, I need to make my design on multiple schematic pages, but I can't ...

maybe this would help?https://forums.autodesk.com/t5/eagle-forum/moving-schematic-sections-from-one-sheet-to-another-possible/td-p/8295627

Moving schematic sections from one sheet to another possible?

I have a schematic and board layout where I have deleted many sections of the original schematic. The original schematic was from a more complex design, and the current project was to simplify it. What is left is a technically functional schematic but it is spread over numerous sheets now. If I co...

limpid nest Jan 4, 2022, 12:07 AM

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Oooh forgot to check for eagle specific questions. I was getting nothing relevant search Fusion 360

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Thanks

unreal flax Jan 4, 2022, 12:09 AM

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limpid nest Why might this footprint from the manufacturer have a huge `tRestrict` box aroun...

Looks just like a crappy footprint, judging by the name/value labels.

limpid nest Jan 4, 2022, 12:09 AM

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Mk thanks

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I agree. Too many footprints put the name/value in a crummy place

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I have a number of overlapping polygons. There's no way to select a polygon by clicking the body of it right?

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I guess I could do show <signal>

limpid nest Jan 4, 2022, 2:50 AM

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Hmm has anyone run into the value of a schematic part in EAGLE/F360 not being movable? I can't click on the origin shown here.

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I've tried smash

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as well as reposition attributes

unreal flax Jan 4, 2022, 2:53 AM

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There is a "lock" command, so maybe the component is locked down?

limpid nest Jan 4, 2022, 2:54 AM

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oooh let me try unlock

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nope not recognized. Hm

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Hmmm, EAGLE forums are talking about a "lock button" but I def don't see one

limpid nest Jan 4, 2022, 8:34 PM

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I'm doing a multi-page schematic. What does /3.2D signify, exactly? I'm assuming that the 3 refers to page 3 (as that's where this signal leads) but what about the .2D? It's SignalName/3.2D.

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in Fusion360

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Only thing I can think of is that it refers to the X/Y portion of the frame that the part is within. But that seems wrong

unreal flax Jan 4, 2022, 8:47 PM

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limpid nest Only thing I can think of is that it refers to the X/Y portion of the frame that...

Yes, I think that's correct. So it'd be page 3, and then "2" and "D" for the frame row and column.

limpid nest Jan 4, 2022, 8:48 PM

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Interesting

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That's neat that the program can figure that out. I guess it was worth my 500 heckin' dollars

limpid nest Jan 4, 2022, 10:20 PM

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What would be the best way to go about soldering a TQFN4X4-24L package chip? Can I use low temp solder paste and a hot plate?

tough matrix Jan 4, 2022, 10:22 PM

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yes
but a stencil is highly recommended

limpid nest Jan 4, 2022, 10:23 PM

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And then squeegee/roller?

twilit mango Jan 4, 2022, 10:23 PM

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tough matrix yes but a stencil is highly recommended

How hard is it to get stencils?

limpid nest Jan 4, 2022, 10:23 PM

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Not hard

tough matrix Jan 4, 2022, 10:24 PM

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$7 at jlcpcb

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plus shipping

twilit mango Jan 4, 2022, 10:24 PM

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Oh huh.

limpid nest Jan 4, 2022, 10:24 PM

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can you exclude thru hole parts from your stencil?

twilit mango Jan 4, 2022, 10:24 PM

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I sort of figured they were pricy and difficult to get.

tough matrix Jan 4, 2022, 10:24 PM

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that was 10 years ago

twilit mango Jan 4, 2022, 10:24 PM

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Never looked into it because of that. (Not that I even have a board to stencil, but I had ideas...)

limpid nest Jan 4, 2022, 10:24 PM

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nah they do em with a laser, so initial equipment cost is high, but price per unit is real low.

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So they don't charge a ton.

twilit mango Jan 4, 2022, 10:25 PM

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Good to know.

tough matrix Jan 4, 2022, 10:25 PM

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through hole parts are excluded by default

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stencil is determined by solder paste layer in your gerbers

twilit mango Jan 4, 2022, 10:26 PM

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(Gerbers is a great word.)

limpid nest Jan 4, 2022, 10:26 PM

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Ahhhh nice

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Ok, so I'll need to apply tCream to my library parts then?

tough matrix Jan 4, 2022, 10:27 PM

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one non-obvious tip when ordering from JLCPCB: make sure to select custom stencil size - if you are not doing a full panel, you can just get a 120mmx120mm stencil

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makes shipping much cheaper

limpid nest Jan 4, 2022, 10:27 PM

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nice

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Thanks

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So the solder paste layer, how does one ensure that only some SMD parts have solder paste? Or can one?

tough matrix Jan 4, 2022, 10:29 PM

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in eagle, every footprint normally includes solder paste layer, and it is exported to gerbers by default, so you do not have to do any extra work

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unless you got some crappy library that you need to manually fix

limpid nest Jan 4, 2022, 10:30 PM

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Ah ok thanks. Yeah this TQFN4X4-24L is probably the only one that "needs" to be hot plated, so I was just going to manually solder everything else since I'm more familiar there.

tough matrix Jan 4, 2022, 10:34 PM

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@distant raven has lots of experience using hotplate for QFN

limpid nest Jan 4, 2022, 11:06 PM

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Hey folks, separate issue that came up in #help-with-circuitpython. I'm looking at using two of these (https://cdn-shop.adafruit.com/product-files/4886/AW9523+English+Datasheet.pdf) to drive some SSRs, but I'm concerned about the fact that the address jumpers determine the default state of the device. There's no state (refer to table 1) where I'm comfortable "pushing" a voltage against that state by default. E.G when both are pulled low, the all 16 pins are in a Output state with a Low value. I would hope that since this thing advertises that it can sink current for LEDs that I'm just over-reacting and it's fine to have them be briefly in a non-LED state?

elder peak Jan 4, 2022, 11:25 PM

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twilit mango (Gerbers is a great word.)

One of the guys I used to ride the train with forced me to pronounce Gerber properly.

limpid nest Jan 4, 2022, 11:25 PM

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Is it "Jerber" or something?

unreal flax Jan 4, 2022, 11:29 PM

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I've always heard it with a hard "g".

limpid nest Jan 4, 2022, 11:29 PM

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Does a hard G mean like in "gift"?

unreal flax Jan 4, 2022, 11:30 PM

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Yes, that's what I meant, sorry.

limpid nest Jan 4, 2022, 11:30 PM

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No worries, just wanted to be sure.

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Hmmmm, maybe this chip won't actually work for me. The datasheet claims that when using two, you need separate SDA lines. I've never seen that in a chip before.

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I'm using a pi to talk to this chip and afaik its other SCL/SDA lines are taken up by the EEPROM

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What's weird is that the adafruit breakout is in the stemma QT format and re-uses SDA. Would this be a good topic for support@adafruit.com ?

unreal flax Jan 4, 2022, 11:43 PM

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limpid nest Hmmmm, maybe this chip won't actually work for me. The datasheet claims that whe...

That would be very unusual for an I2C device. Can you point me to what page of the data sheet says that?

limpid nest Jan 4, 2022, 11:44 PM

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I thought it was very odd too. https://cdn-shop.adafruit.com/product-files/4886/AW9523+English+Datasheet.pdf page 4 note 2.

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I'm just assuming since adafruit put this on their stemmaQT platform, that they are right and the datasheet is wrong

unreal flax Jan 4, 2022, 11:45 PM

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Oh, that example is showing two chips set to the same address, in which case you would need separate SDA in order to send data to one or the other of them. But if they have different addresses, it shouldn't be necessary.

limpid nest Jan 4, 2022, 11:45 PM

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ohhhh

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ok that makes so much sense.

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Phew, this chip is perfect for my needs so I'd hate to not be able to use it.

twilit mango Jan 4, 2022, 11:47 PM

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elder peak One of the guys I used to ride the train with forced me to pronounce Gerber prop...

Oi, is there a wrong pronunciation? I only know what I've heard, heh.

limpid nest Jan 4, 2022, 11:47 PM

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Does adafruit use pull downs on their address pins so that if you jumper the pad with solder you aren't creating a short to ground?

unreal flax Jan 4, 2022, 11:50 PM

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For things like address pins, it's usually safe to tie them directly to VCC or ground, since the chip is always using them only as high-impedance inputs.

limpid nest Jan 4, 2022, 11:51 PM

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Here though, if you didn't have the 10ks, once you bridge the jumper, you'd have a 0 ohm path to ground, no?

unreal flax Jan 4, 2022, 11:52 PM

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You're correct, sorry, I was assuming that there would be a jumper on both sides, but a jumper-plus-resistor is indeed valid.

limpid nest Jan 4, 2022, 11:52 PM

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I'm planning on just shorting to VCC/GND since I don't need to change the addesses.

limpid nest Jan 4, 2022, 11:52 PM

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unreal flax You're correct, sorry, I was assuming that there would be a jumper on both sides...

Neat thanks

elder peak Jan 5, 2022, 4:09 AM

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twilit mango Oi, is there a wrong pronunciation? I only know what I've heard, heh.

Hard G not a soft G. So, in IPA, a ɡ not a dʒ. Like "golf" not like "gym"

elder peak Jan 5, 2022, 4:10 AM

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twilit mango Oi, is there a wrong pronunciation? I only know what I've heard, heh.

I was pronouncing it with a soft g and he's like "No, I remember using an original Gerber machine, it's pronounced like..."

elder peak Jan 5, 2022, 4:10 AM

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limpid nest I'm planning on just shorting to VCC/GND since I don't need to change the addess...

Making short work of it, so to speak.

cinder anchor Jan 5, 2022, 4:11 AM

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is Gerber of Germanic origin, etymology-wise?

elder peak Jan 5, 2022, 4:14 AM

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Wikipedia says Austrian-born.

cinder anchor Jan 5, 2022, 4:15 AM

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So a Germanic word, I am guessing. Yeah, then it's definitely a hard G.

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Like. Gangsta.

elder peak Jan 5, 2022, 4:16 AM

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Yeah, I asked a Berliner about the intricacies of Germanic vs Teutonic vs other things and got a long complicated answer.

cinder anchor Jan 5, 2022, 4:18 AM

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Might as well have asked French people why they refuse to speak English in France, but they expect everyone to speak English to them when they're not at home. 😄 We used to drive them mad back home. They'd ask us something in French, or English, and we'd just respond in Swedish.

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We had a lot of European tourists around where I grew up. Beautiful lakes, so there were a bunch of time shares.

elder peak Jan 5, 2022, 4:19 AM

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Yah, that was frustrating because I had to take a language, in spite of being really really bad with languages, so I picked French. And no Parisian would ever denigrate their language by letting me speak it in their presence, so it was a giant waste, really.

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Conversely, if I went to Wallonia and stayed, I'd probably be able to figure it out because they'd actually work with me on it. I couldn't use numbers over eighty but whatevers.

cinder anchor Jan 5, 2022, 4:24 AM

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Yeah, they're super picky, and kind of not nice about it. Especially in Paris.

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Anyway, I hear it's gotten better since I was there last, so maybe they've given up on being a world power... 😄

elder peak Jan 5, 2022, 4:25 AM

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My friend's trick is to say "Hey, I don't speak any French, do you speak Polish?" and of course they don't, but then it also places him in a slightly higher bucket than being American and monolingual.

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When he ran into Polish speaking folks, they thought it was funny, too.

cinder anchor Jan 5, 2022, 4:26 AM

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Ha! Yeah, my wife usually tells people she's Canadian.

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😄

elder peak Jan 5, 2022, 4:26 AM

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I manage to confuse the Parisians as not-American somehow.

cinder anchor Jan 5, 2022, 4:26 AM

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(it can be way safer that way, especially in places where Americans are not popular)

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anyway, this is pretty #general-chat for the PCB channel

elder peak Jan 5, 2022, 4:26 AM

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Oh ya.

cinder anchor Jan 5, 2022, 4:27 AM

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Sorry.

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I should have mentioned you in the #general-chat channel. I am still learning the magics of Discord.

elder peak Jan 5, 2022, 4:33 AM

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....is it causing great Discord amongst the populace?

cinder anchor Jan 5, 2022, 4:34 AM

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Yes, one could say that.

tough matrix Jan 5, 2022, 4:25 PM

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can anyone suggest what is a good crystal to use with RP2040?
Official "Minimal design guide" suggests ABLS-12.000MHZ-B4-T, which is a rather large one. I was looking for a smaller one, but not sure which one to use: there are plenty of 12MHz ones, but their ESR is usually more than 50 Ohm. Not sure if it matters.
I tried looking at Adafruit designs, but this time, they are not helpful: the schematics just says "12Mhz crystal" without giving the part number. @twilit mango , is it intentional?

unique patio Jan 5, 2022, 4:50 PM

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tough matrix can anyone suggest what is a good crystal to use with RP2040? Official "Minimal ...

we have tried several different ones, and would recommend you pick your own. Try to match the example specs.

tough matrix Jan 5, 2022, 4:51 PM

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the one spec I have difficulty matching is ESR - I can't find a 50 Ohm ESR small crystal.

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the smallest I can find is 80 Ohm

unique patio Jan 5, 2022, 4:53 PM

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tough matrix the one spec I have difficulty matching is ESR - I can't find a 50 Ohm ESR small...

https://forums.raspberrypi.com/viewtopic.php?t=314935

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The chosen crystal for this design is an ABLS-12.000MHZ-B4-T (Y1 in Figure 8). This is a commonly available 12MHz
crystal with a 30ppm tolerance, which should be good enough for most applications. This device also has a maximum
ESR of 50Ω, and a load capacitance of 18pF, both of which have a bearing on the choice of accompanying components

tough matrix Jan 5, 2022, 4:55 PM

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I saw that thread, and RPi engineer wrote there:

ESR is important (it should be max 50R) and allowed crystal drive level (as long as it can tolerate max 200uW you should be fine). Otherwise you risk overdriving your crystal (which can cause it to fail).

unique patio Jan 5, 2022, 4:55 PM

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you may not be able to find a smaller crystal that matches the specs

tough matrix Jan 5, 2022, 4:55 PM

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yeah.. will have to experiment with 80 Ohm

unique patio Jan 5, 2022, 4:58 PM

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we have had trouble with the XOSC taking longer to start than expected, which is why we added https://github.com/raspberrypi/pico-sdk/pull/457, PICO_XOSC_STARTUP_DELAY_MULTIPLIER. We originally though this was due to our choice of crystal (which was different than theirs), but further experimentation showed that the problem occurs with different parts and different capacitor values.

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the crystal we use does have a higher ESR than 50 ohms

thick willow Jan 5, 2022, 5:30 PM

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Have anyoen had trobule with DRC violations while routing in Kicad6? It appears to be a bug as if I disable the check and then manually perform a DRC no error is found

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I also noticed that sometimes the router can find a path from pad A to pad B, but not from pad B to pad A

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I don't remember having any of those issueswith Kicad5

distant raven Jan 5, 2022, 5:45 PM

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@tough matrix

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Sorry pressed enter too soon

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ESR is cumulative in the return line so 1050ohm total ESR should mean you can use (1050-80)ohm resistor

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For instance, I use a 953ohm resister with my 100ohm ESR crystal

tough matrix Jan 5, 2022, 5:48 PM

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do you remember exact part number you used?

distant raven Jan 5, 2022, 5:49 PM

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Yeah, let me grab it

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I found this part with the Digi-Key mobile app. https://www.digikey.com/product-detail/en/ECS-120-18-33-JGN-TR/XC2300CT-ND/6821668

still sphinx Jan 5, 2022, 5:55 PM

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what are the light gray smt devices? they look like a small resistor or capacitor but light gray instead of brown/black

supple pollen Jan 5, 2022, 6:24 PM

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still sphinx what are the light gray smt devices? they look like a small resistor or capacito...

On a particular board, or in general?

still sphinx Jan 5, 2022, 6:57 PM

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supple pollen On a particular board, or in general?

on a psu board (i discharged the caps dont worry)

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im recreating the schematic from the pcb just to learn i suppose

limpid nest Jan 5, 2022, 9:14 PM

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I have a 2 layer board that I want to make 4 layer. What sounds more practical?

Starting from scratch and just copying every component layout/ most of the inter-IC traces
Converting the existing board to 4 layer and redoing the ground and power pours as well as traces/vias to them
?

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I was thinking it would be:
signal

power

GND

signal

limpid nest Jan 5, 2022, 10:00 PM

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Another issue. I'm trying to copy my design so I can try one of my 2 options. When I copy the Electronics Design, Schematic, and Circuit Board and rename them, everything looks to be working fine. However, when I go to open the "new" electronics design I get the message
"The linked file is used by this electronics design:
myolddesign
Do you want to close it and open the new one?"

Anyone know if I can copy a design and sever the link between the copied design and what it was copied from?

thick willow Jan 6, 2022, 3:26 AM

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What track clearance standards do yo use when working with mains voltages?

tough matrix Jan 6, 2022, 3:42 AM

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limpid nest I have a 2 layer board that I want to make 4 layer. What sounds more practical? ...

I would choose option 2.
As for stackup, I believe more common is
signal
GND
power
signal

limpid nest Jan 6, 2022, 3:46 AM

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Interesting. Any idea why?

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I swear I learned the other way but I could be wrong.

tough matrix Jan 6, 2022, 4:21 AM

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i couldbe wrong too - i am no expert.

limpid nest Jan 6, 2022, 4:22 AM

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I have no confidence in my memory

tough matrix Jan 6, 2022, 4:23 AM

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my understanding is that if you hsve some high-frequency signals in top layer, signal integrity is improved by having gnd layer being close

limpid nest Jan 6, 2022, 4:23 AM

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Interesting.

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I don't so it probably doesn't matter. Well I think it's a fast frequency but it's not in the grand scheme of things

tough matrix Jan 6, 2022, 4:27 AM

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if you only work with pwm, i2c, and USB, you should be ok with any stackup

limpid nest Jan 6, 2022, 4:28 AM

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SPI too I would think, in the slower speed versions at least

thick willow Jan 6, 2022, 4:46 AM

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oats there are many ways to actually build the stackup... stuff like if you are doing RF may play an important factor

#

for instance

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or high frequency... for instance a USB track

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when you need controlled impedance you really want ground next to signal

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now the stackup can also add a distributed element capacitor, in some cases you may want to take that into account

limpid nest Jan 6, 2022, 4:50 AM

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usually the cap is in the low low picofarads range, that's not enough to mess with anything I do

thick willow Jan 6, 2022, 4:50 AM

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The amount of copper at each layer may also be important... for instance jlcpcb controlled impedance stackups have half the amount of copper in the inenr layers

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sure, it always depends on the application

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There are no hard rules

thick willow Jan 6, 2022, 5:30 AM

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wow kicad6 is nice but full of bugs...

supple pollen Jan 6, 2022, 1:37 PM

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It's open source, you can fix the bugs yourself (theoretically anyway)

still sphinx Jan 6, 2022, 1:42 PM

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thick willow wow kicad6 is nice but full of bugs...

updating kicad is like switching software, just keep the same distribution. no more functionality, all just rearangement

supple pollen Jan 6, 2022, 1:45 PM

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thick willow What track clearance standards do yo use when working with mains voltages?

There are several existing standards, but the absolute values depend on the mains voltage, the "comparative tracking index" of your PCB material, and how clean it is ("degree of pollution"). There are several standards governing this. Searches for the above terms, as well as the spacing words used ("clearance" and "creepage") will yield lots of advice. One reasonably compact and informative writeup is here: https://minntronix.com/wp-content/uploads/2019/11/CreepageandClearance.pdf

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There is also a handy calculator here: https://pcbdesign.smps.us/creepage.html

PCB Creepage Calculator

Calculation and measurement of creepage distance based on UL60950-1 2nd Edition.

still sphinx Jan 6, 2022, 2:30 PM

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do the safety spark gap pads on pcbs create parasitic capacitance (i assume they do, just wondering if it's enough to need to be taken into account)

tough matrix Jan 6, 2022, 3:17 PM

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thick willow wow kicad6 is nice but full of bugs...

so far I was mostly happy using it, haven't encountered any bugs. (I have been using nightly builds since August)

limpid nest Jan 6, 2022, 6:44 PM

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still sphinx do the safety spark gap pads on pcbs create parasitic capacitance (i assume they...

Do you mean between layers? They do but it's usually very small and not relevant unless you're doing high speed/RF stuff

still sphinx Jan 6, 2022, 7:04 PM

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limpid nest Do you mean between layers? They do but it's usually very small and not relevant...

limpid nest Jan 6, 2022, 7:11 PM

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Oh yeah I guess technically yeah they do. But I would think parallel plate capacitance eqs would be relevant. That's a small area, very small

unique patio Jan 6, 2022, 7:12 PM

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@bright sparrow You asked elsewhere:

Not sure where this question would go but trying to figure out what CAD model would be close to what the SCD-40/SCD-41 (CO2 sensor) is based on .. seems like a common sensor board base which is perfectly square PCB. Trying to bring in the various components into my 3d modeling to work out design

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Here is a video about creating CAD models using our board designs: https://youtu.be/S8U09Pj1m6M

YouTube

Adafruit Industries

Fusion 360 Tutorial – Using Library IO & Eagle

In this video I walk through the workflow of turning an adafruit board into a detailed 3D model. I use Autodesk Library IO to generate custom components to populate PCBs.

Adafruit CAP1188 Breakout
https://www.adafruit.com/product/1602

Adafruit CAD Parts on Github
https://github.com/adafruit/Adafruit_CAD_Parts

EagleCAD Download
https://www.au...

▶ Play video

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no written guide yet

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PCB files for SCD-4x here: https://github.com/adafruit/Adafruit-SCD-4x-PCB

limpid nest Jan 7, 2022, 12:31 AM

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I'm looking at a design using the AW9523B, and I'm trying to figure out if it's safe for my micro to power the AW9523B at 5 V, but not level shift the SDA/SCL lines. Anyone know off the top of their head if this is going to cause me issues? It's not difficult to level shift those lines, for me.

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let me find the datasheet

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Had it up earlier

supple pollen Jan 7, 2022, 12:46 AM

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SDA/SCL should run fine with 3.3V pull-ups on SDA and SCL, the input high voltage is a minimum of 1.4V. The reset pin, however, could be problematic.

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Thinking it over, reset should be fine too.

heavy jasper Jan 7, 2022, 12:57 AM

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Make sure the VoL of the AW9523B is low enough to register as a ViL low on the MCU as well (for SDA)

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It might not pull it low too aggressively if it assumes it’s driving for a 5V-signaled ViL (which will be a chunk higher).

limpid nest Jan 7, 2022, 1:06 AM

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I was told elsewhere that the leakage back into the micro could be a big issue. I have a ton of board space so I may as well just level shift the i2c so I don't have to worry about it.

supple pollen Jan 7, 2022, 1:07 AM

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I wouldn't expect that over I2C lines, which should only be pulled down.

limpid nest Jan 7, 2022, 1:16 AM

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Hm? Do you mean internally? I've only ever seen i2c pulled up

heavy jasper Jan 7, 2022, 1:18 AM

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So - we were assuming the pull-up resistors on the I2C lines would be to the MCU IO voltage of 3.3V

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The folks advising you about leakage may have assumed you were going to wire the pull-up resistors to 5V, which could indeed cause leakage if the MCU isn’t designed with overvoltage tolerant inputs.

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madbodger was saying that assuming you tie the pull-up resistors to 3.3V, the AW9523 isn’t going to pull the lines up to 5V itself (it won’t drive the lines high, only drive them low).

limpid nest Jan 7, 2022, 1:28 AM

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ahhh I see

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Ok I think I'm still going to use level shifting so I can just not worry about it. Why does anyone level shift if it's safe to just pull the bus up to the lower voltage?

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I guess not all chips can trigger on 3v3

heavy jasper Jan 7, 2022, 1:38 AM

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Or if you need your 5V rail to turn on later than your 3.3V rail and you’re careful about power startup leakages.

limpid nest Jan 7, 2022, 1:39 AM

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Ahhh

heavy jasper Jan 7, 2022, 1:39 AM

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Proper level shifting provides some decent guarantees about each side not interfering with the other when unpowered.

limpid nest Jan 7, 2022, 2:16 AM

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How could they interfere with each other when they are unpowered? Or did you mean when one side is powered and another is not?

tough matrix Jan 7, 2022, 2:35 AM

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What is everyone's favorite P- and N-channel MOSFET for switching currents of 1-10 A (voltages up to 30v, Vgsth low enough for the mosfet to be fully on using 3.3v)?
Ideally in SOT23 or SOIC8 packages

I was using AO3400, AO3401, but they seem to be at end of life

bright sparrow Jan 7, 2022, 3:10 AM

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unique patio <@422953155039330305> You asked elsewhere: > Not sure where this question would ...

This is great.. thanks Danh

ember laurel Jan 7, 2022, 11:51 AM

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@tough matrix A&O recommends AOSS32334C

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as replacement

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I'm shipping a modified unit to EMI testing today. Crossing my finger.

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Changes:

Ferrite beads (420ohm@100MHz) on all wires going out the motor (3xphases, 2xLED)
Larger ferrite core with 2 wraps (used to be small core with no wraps)
1nF capacitors from each cable terminal to GND.
Slowed down mosfet switching by changing gate current to 20mA (source), 60mA (sink) (used to be 333mA source, 1A sink)
Changed to newer buck converter - from SY8303A to SY21153AAIC

I can measure a slight improvement using near field probes. I definitely should invest in some more equipment to measure this stuff better, however.

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had to put those beads inline with wires, using shrink wrap. New board will of course be done incorporating the beads.

ivory jasper Jan 8, 2022, 1:03 AM

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Anyone have a kicad footprint for the Adafruit KB2040 Kee Boar? Just want the symbol for the pins and a footprint for the pinout (to make a board that uses it)

worldly schooner Jan 8, 2022, 2:30 PM

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ivory jasper Anyone have a kicad footprint for the Adafruit KB2040 Kee Boar? Just want the s...

The footprint should be pretty close to that of an elite c? If you can’t find that, you could use a pro micro and tweak it to add the d+/d- pins.

ivory jasper Jan 8, 2022, 2:31 PM

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worldly schooner The footprint should be pretty close to that of an elite c? If you can’t find th...

Yeah that's exactly what I was planning if I couldn't find a repo with the footprint in question

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I'm making a tutorial and wanted to be able to point users to an existing repo but I'm not against making my own if necessary

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I've decided not to use the Kee Boar anyway... The RP2040 just doesn't have enough analog pins for a normal-sized analog keyboard (what the tutorial is about). At this point I'm figuring that a Black Pill would be better... Even though it's a bit more complicated to use

worldly schooner Jan 8, 2022, 2:32 PM

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I’m also wondering why it doesn’t seem to exist, but it seemed like it was more intended as a pro micro substitute that I guess I never questioned it aloud.

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How many analog pins do you need?

ivory jasper Jan 8, 2022, 2:35 PM

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worldly schooner How many analog pins do you need?

Well, the design uses 74HC4067 analog multiplexers which have 16 pins each. This allows you to turn a single MCU analog pin into 16 analog inputs. So the RP2040 is limited to 64 inputs using this method. That means the biggest keyboard you could make would be something like a 60%

worldly schooner Jan 8, 2022, 2:36 PM

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Oh, so ideal would be like 7 pins for 112 keys…

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Hm.

ivory jasper Jan 8, 2022, 2:36 PM

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The Black Pill has 10 analog pins (and they're all 5V tolerant which is great for beginners). That means it can support 160 analog key switches (Void Switches!). Or you could mix in some analog hall effect rotary encoders which use 2-3 hall effect sensors each

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My latest analog rotary encoder design actually uses five sensors which might be going a bit overboard. The extra two sensors are to enable absolute positioning. So if you reboot your PC it'll "know" that you left that knob turned 90° 👍

worldly schooner Jan 8, 2022, 2:38 PM

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Is it necessary to have simultaneous reads? Esp32 s2 has two adc channels but it’s accessible on 10 pins each

ivory jasper Jan 8, 2022, 2:38 PM

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Th 5th sensor (or the 3rd in the "don't care about absolute positioning" style) is for adding pushbutton functionality. This gif should explain how that works: https://gfycat.com/fabulouscostlyblackrhino

Gfycat

PXL 20210922 134146451

▶ Play video

ivory jasper Jan 8, 2022, 2:39 PM

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worldly schooner Is it necessary to have simultaneous reads? Esp32 s2 has two adc channels but it...

All that matters is the number of analog pins. Not the number of ACDs inside the MCU

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The Black Pill only has two internal ADCs but 10 pins (strangely, only two go to ADC0)

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The rotary encoder design is pretty nice: It's 3D printable and entirely contactless just like my Void Switches. You can lift it off along with the rest of the top plate (i.e. to go clean it in the sink): https://gfycat.com/enchantedmeageranteater

Gfycat

Hand-wired analog macro pad has hot swap top plate

▶ Play video

worldly schooner Jan 8, 2022, 2:40 PM

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Oooooooo

ivory jasper Jan 8, 2022, 2:41 PM

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I'm using the Black Pill on that macro pad. It's all hand-wired! https://gfycat.com/delectableeverydoe

Gfycat

The world's first hand-wired analog keyboard

▶ Play video

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I released the Void Switch design files the other day (https://github.com/riskable/void_switch) so now I'm working on a board design tutorial. I really love the RP2040 because it's so simple to work with (any pin can do any function and PIO is awesome) but the limitation of only 4 analog pins is too much.

GitHub

GitHub - riskable/void_switch: 3D printable magnetic separation con...

3D printable magnetic separation contactless key switch and stabilizers (OpenSCAD files) - GitHub - riskable/void_switch: 3D printable magnetic separation contactless key switch and stabilizers (Op...

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The PCB footprints and symbols for Void Switches are here: https://github.com/riskable/void_switch_kicad

GitHub

GitHub - riskable/void_switch_kicad: Kicad files for making an anal...

Kicad files for making an analog hall effect keyboard using 3D printed Void Switches - GitHub - riskable/void_switch_kicad: Kicad files for making an analog hall effect keyboard using 3D printed Vo...

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It's really nice: If you set your "User grid" to 4.7625mm you can just drag & drop your keyboard layout around the PCB and everything will line up real easy

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(4.7625 being 19.05/4)

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(19.05mm being the standard "key unit" spacing)

proper anvil Jan 8, 2022, 2:48 PM

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Im creating an arduino uno clone (with some additional features) and i am trying to find what value the associated capacitors should be for the crystal I've selected, according to this guide (https://rheingoldheavy.com/arduino-from-scratch-part-9-16mhz-crystal-oscillator/) it should be specified in the datasheet. Is it the 'shunt capacitance' referred to in the datasheet?

#

#

trying to find appropriate values for C7, C8, which are 22pF on the official schematic but according to the guide it varies by crystal.

tough matrix Jan 8, 2022, 2:50 PM

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you need "load capacitance"

#

that is, you need

load_capacitance = C/2 +parasitic_capacitance

where C is the value of C7, C8 and parasitic capacitnace is capacitance of traces

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see e.g. https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf

proper anvil Jan 8, 2022, 2:52 PM

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Okay, if I make the traces very short can I ignore parasitic capacitance?

tough matrix Jan 8, 2022, 2:53 PM

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Or you can just pretend it is 5pF, as the RP2040 doc suggests

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AFAIK, couple of pF one way or another won't make much difference

ivory jasper Jan 8, 2022, 2:54 PM

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Yeah I totally blew it on one of my boards once and added 22pF when it should've been 4pF. It still worked fine 😄

proper anvil Jan 8, 2022, 2:54 PM

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Oh okay, yes the link you gave is very clear. Thank you!

proper anvil Jan 8, 2022, 4:17 PM

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My intention is to integrate a motor controller IC on the arduino uno, in testing I found that having the IC connected straight to the digital pin all the time made it unreliable for purposes other than controlling the motor controller (I don't remember specifically, but I believe it was pulled high or low unintentionally). At the time I separated the motor controller with latching push switches, so it could be physically disconnected when not in use. But now im thinking could I instead use a voltage follower on each pin, exactly how the arduino controls the inbuilt LED?

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the goal being that you can easily use the motor controller with pre-assigned pins, but if you don't need the motor controller, you can still use those pins as normal digital pins.

queen skiff Jan 8, 2022, 7:07 PM

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anyone know what DC-DC converter I can use to do the 5-9-12-15-20V DC to DC conversion from a 4S battery pack?

unreal flax Jan 8, 2022, 7:40 PM

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queen skiff anyone know what DC-DC converter I can use to do the 5-9-12-15-20V DC to DC conv...

You'd generally want a buck-boost converter with selectable output via an I2C interface or similar. Maybe something like this? https://www.ti.com/product/TPS55288

queen skiff Jan 8, 2022, 7:44 PM

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that looks really good, thanks!

ember laurel Jan 9, 2022, 9:02 AM

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Good luck getting hold of one 🙂

fervent lance Jan 9, 2022, 6:43 PM

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I am working on a PCB design, based on the HUZZAH32 ESP32 board. Any suggestion what components I need to get 5V from a connected battery? (lipo or 18650) Should I just take the schematic from the https://github.com/adafruit/Adafruit-PowerBoost-1000C board and try to figure out how to connect it my schematic design?

GitHub

GitHub - adafruit/Adafruit-PowerBoost-1000C: PCB files for Adafruit...

PCB files for Adafruit PowerBoost 1000C. Contribute to adafruit/Adafruit-PowerBoost-1000C development by creating an account on GitHub.

unreal flax Jan 9, 2022, 8:20 PM

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fervent lance I am working on a PCB design, based on the HUZZAH32 ESP32 board. Any suggestion ...

Yes, that's probably a good approach, since you need a boost converter to do that, and the PowerBoost ought to be a reasonable design for that kind of circuit. You can also pick out a boost converter chip you like (TI has a good portfolio, for example) and based your PCB on the reference design in its datasheet.

limpid nest Jan 9, 2022, 10:41 PM

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In Fusion360, does anyone know how to set the location of a pin name in a symbol? You can see pin 1 on the left and 16 on the right, but together it looks like 116

cinder anchor Jan 9, 2022, 10:52 PM

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limpid nest In Fusion360, does anyone know how to set the location of a pin name in a symbol...

there's no way to align them?

limpid nest Jan 9, 2022, 10:53 PM

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no way to touch them

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I need to just learn kicad

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I ended up having to do this

cinder anchor Jan 9, 2022, 10:54 PM

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are you sure there's no way to change the position?

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I distinctly remember messing with that and figuring it out, but it was months ago, lemme see if I can install Fusion 360.

limpid nest Jan 9, 2022, 10:55 PM

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I did a bunch of googling. According to the forums, there isn't a way as of 2017. It's possible it got added in the last 5 years but I don't see a way

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wow 2017 was 5 years ago. Time flies

cinder anchor Jan 9, 2022, 11:00 PM

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huh

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why don't they have a Linux version?

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firing up Windows VM

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also, my gaming rig updated to Windows 11... I don't remember having a choice... ick

limpid nest Jan 9, 2022, 11:21 PM

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cinder anchor why don't they have a Linux version?

Market share, I would suspect.

unreal flax Jan 10, 2022, 12:17 AM

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You can turn off the pin-number display, but I don't think there's a way to relocate the label.

limpid nest Jan 10, 2022, 12:21 AM

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That's what I'm finding as well. Very frustrating

tough matrix Jan 10, 2022, 1:10 AM

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fervent lance I am working on a PCB design, based on the HUZZAH32 ESP32 board. Any suggestion ...

May I ask why do you need 5V? ESP32 by itself only needs 3.3V...

thick willow Jan 10, 2022, 3:35 AM

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I made a 3D model of a component in solidworks but when I try to render on Kicad it looks OK with OpenGL, but bad when Raytraced

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Opengl VS Raytracing

supple pollen Jan 10, 2022, 3:36 AM

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Looks like polygon orientation isn't correct.

thick willow Jan 10, 2022, 3:36 AM

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I looks liek if either some polys were flipped or 2 polies were zfighting

supple pollen Jan 10, 2022, 3:37 AM

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I like the shadows on the raytraced version

thick willow Jan 10, 2022, 3:37 AM

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yeah but if its an orientation issue, why would it render jsut fine on GPU? I would expect GPU to actually care about orientation and raytracing not much

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what shadows?

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When I open the file with fusion360 it renders just fine, I also tried to export it from fusion just in case it would fix it but no luck

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any idea on how I could correct it?

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for instance poly orientation (if thats actually the case)

supple pollen Jan 10, 2022, 4:07 AM

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GPU may not be doing orientation backfacing (this would make sense to me)

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Look at the upper part of the curved metal bits in the lower cavities: in the raytraced one, their tops are dark.

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I have no idea how to fix it in Solidworks, I'll admit my usual approach is to export it, then write a quick utility to go through it and clean it up.

thick willow Jan 10, 2022, 5:35 AM

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What about fusion? do they get exported fine?

fervent lance Jan 10, 2022, 8:27 AM

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tough matrix May I ask why do you need 5V? ESP32 by itself only needs 3.3V...

To power WS2812B LED strips

thick willow Jan 10, 2022, 11:56 AM

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Those leds require a crapload of power

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so unless you are using just a few and lightly, you wont get much batt life

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the ESP32 by itself consumes quite a bit of power too

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But assuming you already have all of that considered, you may want to use a DC/DC converter to get 5V and a level shifter

dry jetty Jan 10, 2022, 1:24 PM

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I am integrating several mcu's on small motherboards, including Feather M4 and Trinket M0. I would like to supply them all from a 3.3V regulator supplied from a LiFePo4 battery (3.2V). The Feather seems to take either 5V USB or through its charger circuit to 3.7V battery. Does that mean that I have to give it 5V to the USB pin, or is there a neater way? I do not think the Feather 'understands' a LiFePo4 battery, but for safety reason that is chemistry I would like to use.

inland hollow Jan 10, 2022, 5:14 PM

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On a board like the Adafruit QT Py ESP32-S2, can it accept 3.3V input on the BAT/GND pads? I wasn't sure if the voltage regulator would handle equal input as output.

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I'd just like to solder a LiPo connector on for input.

unique patio Jan 10, 2022, 6:02 PM

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inland hollow On a board like the Adafruit QT Py ESP32-S2, can it accept 3.3V input on the BAT...

Our boards almost always use a low-dropout regulator (LDO), so that should be no problem. That board uses an AP2112K-3.3, which is typical. It will not cut off below 3.3V: https://www.diodes.com/assets/Datasheets/AP2112.pdf

inland hollow Jan 10, 2022, 6:18 PM

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@unique patio Thanks! I appreciate it!

opal timber Jan 10, 2022, 7:26 PM

#

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I'm stumped as heck... is this a dupont cable?

tough matrix Jan 10, 2022, 7:38 PM

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no, certainly not
Doesn't look like any JST connector I know either
Maybe some Molex?

opal timber Jan 10, 2022, 7:49 PM

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Extensive online search for both are coming up dry. This is definitely a common part I've seen before, but don't know the name of it to save the life of me.

tough matrix Jan 10, 2022, 7:57 PM

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what is the pitch?

ember laurel Jan 10, 2022, 8:28 PM

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does anyone have a good recommendation on a reasonably priced linear regulator with good PSRR around 1MHz?

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with 500mA+ current

limpid nest Jan 10, 2022, 10:06 PM

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Anyone know if a right angle jst should (stemma qt) port will fit in the footprint of a flat one?

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Digikey just sold out of the flat one

twilit mango Jan 10, 2022, 10:08 PM

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limpid nest Anyone know if a right angle jst should (stemma qt) port will fit in the footpri...

Does Adafruit make boards with both versions? Can check the board files. Not sure what you mean by "flat" versus right angle though...

limpid nest Jan 10, 2022, 10:18 PM

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I meant right angle. Sorry I forgot words. I just ordered from adafruit since I needed a stemma cable from you folks anyway

I was thinking it would be: signal

power

GND

I was thinking it would be:
signal