help-with-hw-design

[worldly schooner]

Doesn't the chip need 2.7V supply to run?

If your application is draining a coin cell to 2.5V after 10 mins, you probably need a different power supply.

Coin cells are typically used for very low-power applications, like RTC. If you're powering an LED with a coin cell, my guess is you're drawing way too much current to be relying on a coin cell for power.

[gaunt cedar]

dang. i probably should have done more power draw math.

It's a 2032 running a samd21e18 and a single neopixel

could the while true loop in python that listens for the gpio buttons add to the draw significantly?

[unreal flax]

It just means that the processor is fully active, the same as running any other code.

[gaunt cedar]

right, I suppose I should have made that question sound smarter. sleeping and looping to check if a pin is low shouldn't add a ton to the load you think or cycles are cycle and it would drive power down.

just experimented. removed the loop altogether and the ~10 minutes still occurs

[worldly schooner]

If you have a pulsed current draw without sufficient capacitors to smooth it, you could derate the battery capacity significantly.

On that note, are you using PWM dimming to control your LED?

[gaunt cedar]

no just the circuitpython implementation to control. setting brightness to .3

the pulsed current draw might be it? I have 2 test pads 3.3 and gnd. watching the voltmeter right now I can watch the voltage drop by .001 every 2 seconds

it seems to have stabalized now.

.001 every ~30 to 45 seconds

[supple pollen]

CircuitPython or no, that LED is likely being controlled by PWM, so is presenting a varying current draw

[worldly schooner]

I thought as much, but wanted to see the library source before confirming.

[supple pollen]

What kind of LED?

NeoPixels and DotStars use PWM

[gaunt cedar]

yeah its a neopixel 6812

[worldly schooner]

Yeah, 0.3 brightness is just the high-level simplification. The python libs are doing work behind the scenes to convert that brightness to a duty cycle for the chip to follow. If you have the traces and spare batteries to experiment with, I would put a nice big discharge capacitor across the neopixel V+/GND as close to the LED as possible, and see if your battery life improves at all.

It's an LED capable of 50mA drive current, and assuming your SAMD21 is drawing an average of 4mA, you LED running a single channel at max brightness should be able to get close to 4 hours of battery life. If the discharge capacitor is doing its job, you should be able to get at least close to that range.

[gaunt cedar]

thank you for this. I'll add a cap to the circuit and see how that goes

[tough matrix]

That's not quite accurate. For a neopixel, python libs (or C code in bootloader) produce a data signal which is sent to the pixel; the IC inside the NeoPixel reads the data and converts it to PWM duty cycle for each of the three color LEDs.

Of course, the end result is much the same: LED is powered using PWM signal, and yes, a capacitor is highly recommended to maintain voltage.

[worldly schooner]

Ah, I should have explained more clearly. Yes, a duty cycle VALUE to the Neopixel IC "chip". Thank you for the clarification.

[gaunt cedar]

what size cap do you recommend? closer to the power source or the led?

[supple pollen]

It's not critical: anywhere from 10µF - 1000µF is fine (you don't need a lot for a single LED). I might try 47µF or 100µF. Closer to the LED is best.

[distant raven]

100uF is pretty suitable for up to 50 Neopixel I’ve found. More than 50, you should at least add an additional 100uF+

[gaunt cedar]

if I wanted to get some more life out of this battery by lowering the clock to say ~8mhz. would I be making that change in the .bin that I flash or in the circuitpython uf2 build or both?

[supple pollen]

Depending on the clock source, you may also need a hardware modification to swap out the crystal.

[gaunt cedar]

clock source on this samd21 is internal. from what I gather there are a couple sources to choose from.
https://microchipdeveloper.com/32arm:samd21-clock-system-configuration

I know enough to be in the right area(ish) and I'll mess with the code to see if I can get the clock down. the reason I asked about where to make the change is because I thought I did it correct in the init_samd21.c file where it selected which clock source to use but when I'm in code I printed the microcontroller.cpu.frequency and its still 48mhz. I'll keep hacking away at it

I often find myself not knowing for sure if I'm going about it the right way and get a bit anxious I'm wasting my time 🙂

[supple pollen]

The microcontroller.cpu.frequency is probably just set in the code, not derived from the processor registers.

[gaunt cedar]

oof

ok

besides a scope or perhaps a usb power meter, any way I can verify?

[supple pollen]

You could send the clock signal to a GPIO pin, or write a timing loop (either toggling a pin or blinking an LED after a certain number of cycles).

[polar lantern]

Do you need hot air/a hot plate to use those SMD to breadboard things effectively?

And a stencil or whatever?

[supple pollen]

Not necessarily. I've soldered fine pitch SMD with thin wire solder and a (very) fine tipped iron. There are also "dragging" techniques. You can use solder paste without a stencil, you can apply it with a toothpick or something like an iExtruder. You can melt solder paste with an iron, but it's kind of awkward.

[polar lantern]

awesome, thanks!

I guess none of these questions are quite pcb design related, so apologies if there's a better place to ask, but I got some airtags and have been meaning to try and dump the firmware/get SWD access

does someone know what the right name for this kind of wire is?

and likewise, do you think this fellow used a fine tipped soldering iron? or something else?

[long wraith]

Looks like magnet wire/enable coated wire

Personally I'd use a fine tipped iron for that

Actually, it looks like the wires are going to the legs of ICs? so maybe a hot air station...

[polar lantern]

I think there are test pads for all the connections I need to make

In the video, the guy says he burnt a test pad off because he was impatient, and had to solder to the cap because of that

but I am also probably gonna get myself a hot air station as a birthday-gift-to-self

[gaunt cedar]

follow-up from earlier. I still haven't been able to verify if the clock speed is at 8mhz but that's what I set it to in the compile. I also changed the brown out fuse to a lot lower. it was tripping at anything under 3v. and lastly lowered the led power a bit more to .01 for this test and its been hanging out for over an hour now. still at ~2.6v

[worldly schooner]

Is 2.6V enough for SAMD21? Last I checked, it expects 2.7-3.6V...

[gaunt cedar]

datasheet says its happy down to 1.62v. My test board is currently at 2.56 and its cycling neopixel colors and a couple button inputs are still responding

[silk lark]

the flash chip needs 2.7V

on express boards

[supple pollen]

For that kind of work, I prefer a fine tipped iron to hot air, as I just want to heat a specific small area at a time. For a Hakko iron, I use the T18-I tip.

[tough matrix]

you need a really steady hand for using the iron, though

[rustic linden]

Bleh why do 2 versions of this chip come up as Basic and 2 as Extended when they're all pin compatible gah

[supple pollen]

Presumably the "basic" ones are fixed voltage and in stock, and the "extended" ones either need a voltage specified, or they're not stocked?

[rustic linden]

Nope, the basic ones are 5V and ADJ, and the extended are 12V and 3.3V

[supple pollen]

Presumably the "extended" ones are not in stock then, which is what I said.

[rustic linden]

the 12V one has 3500 in stock, while the 3.3V has 385

[worldly schooner]

If we're talking about JLCPCB, it's just a matter of how frequently each component is used. If it's common enough, they sit on their setup with the reel preassembled to their setup. The 12V is definitely not common, but idk about the 3v3...

[hollow swift]

Greetings. I am a beginner in IC design using Cadence Virtuoso. Are there any tutorial videos that you can recommend me?

I am actually trying to build the basic 6T SRAM and wish to know how to find properties like Average Area, Read/Write delay, SNM, WTV etc

[thick willow]

reinstalled circuitmaker... and still getting the bug about vias not connecting to planes :S. Oddly enough it works fine on my notebook...

[pearl tapir]

https://www.instructables.com/Build-Your-Own-DIY-3D-Printed-Soldering-Fume-Extra/

[distant raven]

Oh sweet

That’s pretty nifty @pearl tapir

The color scheme and shape of the enclosure is pretty retro feeling too

[pearl tapir]

@distant ravenThe only downside is the enclosure design requires that the pot be removed from the pcb and remotely located using 5 wires.
That needs to be redesigned.

[long wraith]

Looks like a TF2 prop, I love it!

[toxic patrol]

Well, I accidentally asked my question in general (#general-tech message)

But I guess the conversation should continue here

[unreal flax]

Unfortunately the consensus is usually that autorouters completely suck, if they converge at all, until you get into very high-end, very expensive specialized tools. Most people just suck it up and route boards manually.

[supple pollen]

You'll generally get better and more æsthetically appealing routing that way

[toxic patrol]

Do any of you have experience making PCBs in fusion 360?

[supple pollen]

I've made PCBs in Eagle, which is related...

[toxic patrol]

From what I can tell they're pretty close

Anyway

I have this part here:

The OLD part I was originally using looks like this instead:

When all 15 pins were on 1 side, it made the schematics easy to map out

But since the new piece splits them on 2 sides, I'd have to redo a bunch of my wiring

In the schematics editor (not in the layout designer or part itself) can I change the pins so they're on one side?

[supple pollen]

I don't think so, I think you have to do that in the part editor.

But then you can replace the part in the schematic and keep the connections if you like

[toxic patrol]

How?

Cause changing this doesn't seem fun:

[supple pollen]

Use the "replace part" function

[toxic patrol]

Wow

I'm amazed that worked so well and everything connected to the right spot despite being different parts

I guess it helps both were numbered 1-15

[supple pollen]

It does a decent job lining things up if the pins have compatible names

[toxic patrol]

Last thing and I should be done with questions

Should I replace something like this with 10 buses?

[supple pollen]

You can do that, or go to the trouble to line everything up

[toxic patrol]

I was nicely lined up lol. The auto replace kinda killed that

[supple pollen]

Or just use named signals. They're all valid, it's a matter of personal preference

[toxic patrol]

Well, I think the design is done

No clue if it'll work or not though

[supple pollen]

That reminds me a little of a board I'm working on.

[toxic patrol]

Huh. Cool

This one is (supposed) to switch between RPi cameras w/ the 3 signal pins there

Also, I'm pulling my power and ground from the camera connector of the pi, is that alright?

Actually nvm

It's only getting ground from the cameras

[supple pollen]

Mine involves cameras and relays, but in a completely different context: it triggers the camera focus signal, waits half a second for the camera to focus, triggers a flashbulb, waits 20-35ms for the flashbulb to come up to full brightness, then triggers the shutter. There's also an on-board charge pump to charge a capacitor to 27V so the flashbulb will trigger in a fast and reliable fashion.

[toxic patrol]

What do you use to make your PCBs? The one I've heard of is PCBway

[supple pollen]

I use several vendors, depending on my mood: OSHPark for the pretty purple and clear ones, PcbGoGo when I want a bunch of copies cheap, or JLCPCB for small quantities of inexpensive boards.

I've heard good things about PCBway and Seeedstudio, but I haven't tried their services (yet)

[toxic patrol]

Is JLCPCB what you'd do for a single board you're not even sure works?

[supple pollen]

Probably so. I've only just started using them, but they did a nice job knocking out these boards from an open source project for me

Generally the shipping costs more than the boards, but that's kinda what happens with really inexpensive stuff.

[toxic patrol]

Ok. I think I'm gonna order it, but do you mind checking it over in case I messed anything up?

[supple pollen]

I can have a look, but I could miss stuff too (I often do)

[toxic patrol]

The only thing I'm worried about is some vias under some components

[supple pollen]

Those vias should be fine, if they're "tented" (have soldermask)

If you like to make your vias double as test points, then have them untented and out where you can get at them.

Trying to figure out the relay connections, they seem odd.

[toxic patrol]

What seems off about them?

[supple pollen]

They appear to be wired in series?

Also those traces seem really narrow (but maybe none of them are carrying anything high frequency or high current)

[toxic patrol]

It's all running at 3.3v at 250mA roughly

Unless the camera data lines are high frequency, I think nothing is

https://www.arducam.com/raspberry-pi-camera-pinout/

The idea behind the wiring of the relays is that you enter a 3bit binary signal on the 3 pins (at 3.3v) which allows power to get to only 1 of the cameras

It all works in my head and from what I can think of, but I may be wrong here

[supple pollen]

Okay, they are in series, as a 1 of 8 decoder, got it

Those MIPI signals can range from 80MHz to much higher, you might want to think about at least a ground plane

[toxic patrol]

How would I add that?

[supple pollen]

Scroll down to "Finishing Touches", "Adding Copper Pours" https://learn.sparkfun.com/tutorials/using-eagle-board-layout

[toxic patrol]

Shoud I pour then do the auto trace?

Or auto first?

[supple pollen]

Make backups first! I usually do the pour first then route, but you can try it the other way too (which sometimes ends up being multiple pours you have to stitch together somehow).

[toxic patrol]

Ok, V2 here we go

[supple pollen]

That seems more likely to work nicely to me. Make sure you run ERC and DRC too.

[toxic patrol]

The ERC warnings I'm getting are all "wires close but not connected" because of this mess from the auto replace

DRC is giving me actual errors tho... Apparently it left some airwires

[supple pollen]

You'll want to address those before getting a board fabbed. I got burned by that once with a short between a 3.3V power supply and ground, in an internal board layer (the board had multiple power domains and I goofed)

[toxic patrol]

I'm stupid... The airwires are between all the grounds that are connected with the polygon...

I spent the past while trying to find why they didn't connect

Wait, nvm

There is an actual issue

Can I just stick vias in random places?

I think I may have it fixed?

Gimme a sec

[supple pollen]

Yes, that's what I was getting at when I mentioned you could get multiple pours and you'd have to stitch them together. Doing so with a lot of vias is known as "via stitching".

You can see some via stitching here at the bottom around the WiFi antenna, at the top, under the WiFi module, and to the right, at a voltage regulator. It's popular when you need good high frequency or high current performance.

[toxic patrol]

Alright, all airwires have been connected

I did have to move some wires around tho, and now parts of it look stupid

There wouldn't happen to be any sort of way to "optimize" the lines, would there?

[short zodiac]

it's been a while since i did PCB stuff, but i seem to remember that certain angles are sub optimal

acute angles may be high on that list

[supple pollen]

I usually limit the angles, enable "snap to grid" and drag them individually. It's slow, but I have full control on how they end up.

[toxic patrol]

It was really weird about legging me drag stuff for some reason though

[supple pollen]

Yeah, acute angles can act as "acid traps", have some inductance, and are rarely the optimal routing. With modern PCB manufacturing techniques, acid traps are less of a bugaboo than they used to be.

[toxic patrol]

I know the pic is a mess, and not what it should look like, but it doesn't wanna let me put traces where they should go

[supple pollen]

Eagle (and every other PCB design program in existence) is quirky and you may need to tweak some settings to drag things the way you want to.

[toxic patrol]

Ok, V3

Well, assuming it's good, I'm gonna place the order

[supple pollen]

@rustic linden You were looking for some surface mount diodes? https://www.adafruit.com/product/5099

[elder peak]

No more SOD stories about not being able to find one

[long wraith]

Lol

[tender cedar]

Is there any guidance for footprint cutout geometry for surface mounting a QTPy RP2040? I made a janky guesstimate footprint in KiCad by measuring the QTPy fab print but am wondering if there is a published reference footprint for the cutout anywhere? 🙂

[twilit mango]

@tender cedar Like the PCB file for the actual board? They're EagleCAD, so I don't know how KiCad handles those, but would that help? They're on GitHub. Not sure if that's what you already used.

[tender cedar]

More specifically the cut out I would need to make to accommodate the bottom-side components if I want to use the castellated pads to solder the QT Py onto a custom pcb design. I am not sure whether there’s a recommended size for it or if I need to ensure some specific minimum clearance from the under side components. I am pretty new to pcb design so maybe I’m just overthinking it!

[twilit mango]

Oh! I don't think I fully registered what you were asking. I was thinking QT Py standard, forgot about the RP2040's underside. I'm new to it as well, so I'm not much help (ergo the pretty useless answer 😄 ). Someone else might have a better idea.

[tender cedar]

I literally received and soldered my first ever custom pcb design today, so.. very new!

[twilit mango]

Congrats!

[untold seal]

Nice. This is very special. Basically Adafruit that taught me how to do it. The people from here.

[tender cedar]

😊 the design is a digital potentiometer breakout which is very obviously inspired by the Adafruit stemma qt breakout format. Adafruit is for sure the reason I was able to even get this far!

[tough matrix]

there are actually quite a few components on the bottom - not only RP2040 but also smaller comppnents, capacitors, etc, so you would need a large cutout

an easier option might be using regular male headers which you solder to both boards so that the plastic spacer is between them

providing 2.5mm clearance, which should be enough for all components. This way, no cutouts are needed

[tender cedar]

That’s probably the better solution. Not as cute though!

[tough matrix]

true

would look like this

(this is before trimming the pins)

[tender cedar]

I will probably just do that

[floral karma]

designed this stm32g491 feather form factor pcb the other day. ordered with the wrong thickness for the pcb usb c tho 🤦‍♂️

[distant raven]

😅

[silk lark]

@floral karma in my experience both 0.6 and 0.8mm work

@floral karma you can still test it by whittling down one side

[floral karma]

yeah i’ve reordered with 0.8mm. that was the plan always, i’m just a moron who can’t fill out forms

speaking of actually 😅

[silk lark]

good!

but if you reordered it already, it doesn't save you a prototype

at least you will know earlier

[floral karma]

i had to cut thru a bunch of important vias so this ain’t working. idm tho

love how well it works mechanically. a handy tip for saving bom cost, especially in these shortage times

i'm actually proper proud of this design. the feather shoould be able to be a dual role port- so it can sink up to 20v to power stuff (the freebie pin is vbus) or source 5v like a power bank

[tough matrix]

I am pretty sure that everyone here made equally stupid mistakes more than once.
On my most recent PCB, I forgot to connect negative terminal of the battery which is supposed to power the whole thing to the ground pour...

[floral karma]

woof. at least that's bodge wireable

[tough matrix]

yeah.. using a 22awg bodge wire 🙂

[rustic linden]

I actually really like how you're using the PCB as the connector for the USB-C port!

[languid light]

Hello, this is my first time designing a PCB, and I have a few questions about my current design. First of all, if I have a 170v line (2.5mA). Is it ok to have my GND copper pour on this layer of the board? I cannot really set the amount of margin to give the power line in the software. Also, (not entirely related to the pcb specifically) what would be recommended for the Ohms of the pull-up resistor for the Feather Huzzah32 (the learn guide recommended one.) I currently have a 4.7k marked there, but it can be changed easily.

(Feel free to @ me)

[tough matrix]

pullup resistors for I2C lines?
any value between 2-10K should work
choose larger value (10K) if you are trying to conserve energy and get as much time as possible from a battery, choose lower values for better performance over long distances.
4,7K should work just fine.

but what is confusing me are resistors R1 and R2. They seem to be placed in series between SCL/SDA pins of the MCU and SCL/SDA pins of a connector... why?

@languid light

[lime thunder]

you seem to short SCL and SDA together as well

[distant raven]

Hurray! I got more boards in 🙂

24x PixelLeaf Matrix to stock more on my tindie shop

[long wraith]

Yeet!

[distant raven]

I think I have enough to build 10 to stock

Need to order another reel

1500 didn’t last as long as I though 😅

[long wraith]

XD

I assume you're talking about the NeoPixels... Yeah, goes fast when you do 24 at a time, lol

That's only like 62.5 boards per reel for 1500

[lime thunder]

amazing how fast parts go

[long wraith]

Stocks be like... nyoom!

[distant raven]

Well, 24 boards would use 1200 Neopixel

You’d get 30 boards total using 50x per boards

[lime thunder]

I am not sure if that many parts would drive me crazy or be super zen

[long wraith]

Ohhhhh

My brain blorped, I thought you meant 24 NeoPixels per board, durr

[lime thunder]

(I did actually find it super zen placing the 224 (dumb) LEDs per panel on one of my products)

[distant raven]

It’s super repetitive so it’s kind of zen placing 50 neopixel at a time

[long wraith]

Both XD

[lime thunder]

except when I flicked tiny little grains of light-up rice all over the place because bad tape holder

[distant raven]

I can see why Ladyada loves making boards that use neopixel and all the other neopixel projects she makes and sells

[long wraith]

I find zen in repetition -- one time I had to sort about 20k pieces of colored paper

That was calming and satisfying

[distant raven]

Super relaxing and satisfying to place tons of neopixel and then they just work

[long wraith]

light-up rice XD

[distant raven]

Lol

I kind of want to make the PixelWing on a flex PCB to see how it works

Seems like it would be really fun to do

It might not be as flexible as I would hope since it has huge power pours on it

[lime thunder]

really want to play with flex one of these days too

[distant raven]

PixelLeaf would also be fun to do flex. It’s be easier than the PixelWing since it doesn’t have USB connector or a ESP32-S2 or other things on it

One day I need to trademark my product names

Or the ones I can anyway

[lime thunder]

I really should trademark the logo I'm using

esp before I start putting out Open source hardware

[distant raven]

I need to clean up some schematics and start submitting to OSHW

[lime thunder]

but I also need people to actually buy up some of my stock first >_>

[distant raven]

Yeah same

[lime thunder]

buy my stuff so I can get money so I can make more stuff

[distant raven]

My RGB boards and LiPo power pack sell pretty well

But I’m not selling many CP Saplings

[long wraith]

What has?

[distant raven]

And I can’t ship to the EU right now because CE certification being more enforced right now

And the UK also has its own certification process now after leaving the EU so i have to figure all that out

Also VAT stuff for the EU but couriers can deal with that but

Bit *

[lime thunder]

https://affsnake.us/s (mostly that absolutely tiny and slim breadboard indicator)

[I like snakes, and I picked an arbitrary adjective >_>]

[long wraith]

https://tenor.com/view/stevenuniverse-star-gif-4782048

[lime thunder]

[ I'm also trying to offload some components I got and didn't use through Tindie's Flea Market to no success but shrug ]

[long wraith]

How many of those indicator boards do you have?

[lime thunder]

120 ready

[long wraith]

Hmmmmm

[lime thunder]

a bunch more if I sit down with some wire strippers

[long wraith]

So I see there's a kit and fully assembled options, is that just adding pins?

For the kit?

[lime thunder]

you've gotta solder in the pins and a single wire (both are included)

[long wraith]

Ahh, I see what I'm guessing is the ground wire on the back

[lime thunder]

I'm trying to not assume where you are picking up the ground from

and yeah I have it running along the back

[long wraith]

How come when you have all 8 lit, half are brighter than the others?

[lime thunder]

that's in the description which might not be clear enough

[long wraith]

Or is that PWM flicker?

[lime thunder]

I'm showing the brightness from both 3.3V and 5V power

[long wraith]

Ohhh

Yeah, I read that and misunderstood XD

[languid light]

Oh, perhaps I do not understand how the pull up resistor works. Would you mind explaining the proper way to connect the resistors? I will head to my computer later on and try.

[languid light]

Where do you see this?

[lime thunder]

looking again I believe I was mistaken

[languid light]

Ok!

[long wraith]

@lime thunder Oh,something I noticed -- the 3D printed version of your NeoKey plate seems to pull the switches together and cause the whole thing to bed. Not a lot, but some

[lime thunder]

yeah I think it needs to be thinner

but it might be too flexible then?

[long wraith]

Maybe?

I'mma order one of your PCB ones :D

[lime thunder]

\o

[long wraith]

o/

[languid light]

Oop, just realized I forgot to connect 3.3v to the line 😉

Thanks for the help!

[long wraith]

@lime thunder have you considered different colors for that baby indicator board?

Also, does USPS really not consider that a "tiny item"? XD

[lime thunder]

I wish I could hide those names

and Tindie's shipping rate system is... annoying

tiny item basically means "I can shove 1000 of these in an envelope and it will still weigh .001 gram"

[long wraith]

Ahh... Yeah, that's a dumb name. Those boards are tiny

[lime thunder]

oh actually no it should be a "tiny item"?

[rustic linden]

I assume one of the pins would be a common?

[long wraith]

I think they're trying to rip me off XD

[lime thunder]

the common pin is separate

on a wire

[rustic linden]

Hmm?

Oh

[lime thunder]

@long wraith I can check the rates when I get home to make sure it's not doing something silly

[long wraith]

Ohh, wait, I realized there's Priority Mail tiny and First Class tiny, it must be using First Class... but First Class costs less to start, and it might upgrade to Priority Mail... so basically I'm dumb and can't read XD

[lime thunder]

ah yeah

basically if someone actually buys 100 of them

it will cost more than $3.whatever to ship

so I had to do a bunch of math and try to make the rate match as best as possible to my actual cost (because Tindie)

[long wraith]

Maths!

[tough matrix]

@languid lightit woudl be easier to discuss if you also provided schematics

[rustic linden]

I'm unsurprised I can't get these shipped to me

[tough matrix]

@rustic linden you are in Australia, right?

[lime thunder]

@rustic linden I can check international rates, but it'll be ow

[tough matrix]

@lime thunder I am using PirateShip to ship my items from Tindie; they have a very convenient rate called "Simple Export Rate"

[lime thunder]

and I probably need to verify the international shipping rules

[tough matrix]

https://www.pirateship.com/usps/simple-export-rate

[rustic linden]

Yeah, Australia

[long wraith]

Pirates :O

[tough matrix]

Yarrr

[long wraith]

lol

[tough matrix]

basically any country in the world - same rate
$10 for small package

[lime thunder]

actually for some reason I have a rate set up, but that board was deselected

check now?

[lime thunder]

mine said $12 when I calculated it but same idea

[rustic linden]

For a board where I don't want to introduce much more draw on data lines for LEDs, should I use transistors to power them?

[tough matrix]

you are talking about usual - "dumb" - LEDs, not neopixels?

[lime thunder]

yeah, "dumb" LEDs

[tough matrix]

then yes, transistor or MOSFET is the way to do it

[rustic linden]

Even at only 3.3V or so?

With a MOSFET

(usually only see them in higher power stuff)

[tough matrix]

yes

[rustic linden]

Australia shipping shows up for $12

[tough matrix]

in fact most adafruit boards use a MOSFET to automatically swithc power between USB and LiPo battery connector

[lime thunder]

yes alas 😦

[rustic linden]

Oh, I know, I've used one for that purpose on a board i used

[tough matrix]

so there are plenty of MOSFETs which are fully on with V_gs = 3.3V

[rustic linden]

Any recommendations for transistors/mosfets that trigger at about 3.3V?

[supple pollen]

I looked one up about a year ago, it's lost in the scroll now

[tough matrix]

I recently used this one:
https://lcsc.com/product-detail/MOSFETs_Vishay-Intertech-SI2301CDS-T1-GE3_C10487.html
just because it is on "basic parts" list of JLCPCB

[lime thunder]

if I do a second version of that I should really try to experiment with the very low current LEDs that are still reasonably bright

[supple pollen]

Ah, found it: STP160N3LL

[tough matrix]

@supple pollenwow... 3.2mOhm RDS_on !!

and 120A

might be an overkill for most of my purposes

[elder peak]

Either way, you should be FETed for your discovery.

[lime thunder]

A N-FET would not really work for my board. I only have a common cathode version right now. Alas.

[languid light]

Ok, you would like a screenshot of the schematic or is there a way to send the file…

[lime thunder]

so I do see the pullups ( R7 and R8 ) but I also see R1 and R2 inline in the SDA and SCL lines -- what are you trying to do with those?

[languid light]

Those are the ones which I forgot to add 3.3 v to

[lime thunder]

you should only need 1 set of pullups on the bus

[languid light]

because on the PCB, the cable runs the whole board, I figured I might as well have one on each end

I suppose that there is no harm in having it just in case

Unless there is?

[lime thunder]

the resistors will be effectively in parallel

so you have 2.4kOhm of pullup

instead of 4.7k

[distant raven]

I don’t see a need for them. I have this board here that has I2c and I’m only including 4.7k pull ups. Adding additional resistance might have negative affects as you add additional devices

[languid light]

Ok, sounds good!

Which end would you recommend I keep the pull-up resistors?

[distant raven]

Usually you put them close to the MCU or the connector for your i2c device

A lot of breakouts have pull ups on them too

[languid light]

Ok, so closer to the MCP23017

(GPIO extender)

[distant raven]

Yeah that would be a good place

[languid light]

Ok

Thank you for helping me out, @lime thunder , @distant raven !

[distant raven]

Best of luck in your design endeavors 🙂

It’s a lot of fun to get a board designed and working

[languid light]

🙂 I will probably post it in #show-and-tell when I get it working! Good luck to you too!

[rustic linden]

THANK YOU basic parts are always helpful for me!!

[lime thunder]

also oo yay there's my email from OSHpark saying they got the panel my board is on

[lyric nymph]

Can anyone tell me what package of ATSAMD21 is used by the Adafruit QT-Py?

[unreal flax]

It looks like a QFN-32, but there are two variants of that, with and without wettable flanks, and I'm not sure which is used. I'd assume without, as that seems to be the more common version.

[lyric nymph]

Thank you! 🙂

[lyric nymph]

I was thinking it might be QFP-32, but that package is much larger.. I measured the chip on the board and it's only 5mm across, which matches QFN32, so I think you're right there, @unreal flax !

[distant raven]

Yeah it is QFN-32 🙂

I use a similar chip on a samd21 board I develop and sell

[silk lark]

ATSAMD21E18

[lyric nymph]

Ok, looks like I get to keep the board moving here! 😄 I bought some APA102's in 2020 size (http://adafru.it/3341) ... I'm trying to build the pattern for these in DipTrace, but the PDF Documentation does not show a clear mechanical drawing... Anyone have a better lead on that?

Here's a screen-grab of the mechanical drawing. It's pretty unreadable at least to my eyes..

[worldly schooner]

Well, looking at similar LEDs from the original manufacturer, this should be more than close enough for your purposes.

[lyric nymph]

Beautiful! Thank you!

[tough matrix]

@lyric nymph@worldly schoonerare you guys related?

[lyric nymph]

Heheheh. Not as far as I know, but as big as the internet is these days, it wouldn't surprise me too much either!

[worldly schooner]

I would assume no, Hem is taken from my first name haha

[keen jungle]

Is there a simulation software? Or something that would allow me to swap components and make sure the system still runs? Or is this a built in thing in most software now?

[heavy jasper]

That's. a very broad question, and it really depends on what you're trying to do, and what you mean by "runs."

e.g. ltspice is very good at simulating analog circuits (though it takes some work to get used to it) and I'd trust it if I'm e.g. swapping out op-amps in a filter circuit and want to verify that my filter performance is still what I want.

For a digital circuit (e.g. I want to swap out a flash chip and see if the MCU can still read it properly) there isn't so much a simulation tool that will work, and you'll need to do it by comparing datasheets.

[worldly schooner]

Background: I have a schematic for a Pi Pico - Capacitive touch display interface, but I'm struggling on the backlight power supply circuitry. I was initially planning to use an MC33063 (because JLCPCB) to boost the 5v input to a ~20V output, but I have little clue what I'm doing when it comes to selection of inductors or zener diodes.
Question: how do I determine Vsat or Vf? I have no idea what my output switch or output rectifier is.
Also, does anyone have any advice regarding boost converter circuit design and component selection? I considered copying one of Adafruit's circuits, but I was hoping to use JLCPCB/EasyEDA to accelerate the design process...
Datasheet: https://datasheet.lcsc.com/lcsc/1809171620_ON-Semiconductor-MC34063ADR2G_C32078.pdf

[distant raven]

Has anyone worked with 8051 based microcontrollers at all?

Particularly the ones like SiLabs makes

[unreal flax]

I did a small project with one years ago. I found them surprisingly easy to program, compared to, say, more complex STM32 peripherals.

[distant raven]

Any recommendations for programming them? I’m seeing the have a 2 wire type interface.

I want to make a small board to fiddle around with one both hardware wise and learning assembly for them

I found some good assembly references for them

[unreal flax]

I just bought whatever the little USB programming dongle was that SiLabs suggested, but I'm not sure what other options are available.

[distant raven]

Did you use an eval board?

Or make your own?

[unreal flax]

I think I started with an eval board to test things out, but I did make my own too.

[distant raven]

Ah okay cool. I’ve got a bunch of 150mA 3.3V LDO, that should be enough to evaluate them at least I think.

[unreal flax]

Yep, they're pretty low-power.

Although I'm not sure that I would be designing with one today. At the time I was driven to them because of the capacitive-touch sensors that weren't readily available on other chip families, but today it would probably be a hard sell versus an M0.

[distant raven]

It’s mostly for fun

Plus $0.98 or less depending on the one you use, there isn’t much to lose to learn at least

[unreal flax]

Gotcha. Yep, should be fun. I was pleasantly surprised at the learning curve, anyway.

[heavy jasper]

For the boost: MC33063 is a very, very old part, and probably more flexible than you need. I'd probably go with a more modern FET-based one (and it looks like the cheapest one on LCSC, https://lcsc.com/product-detail/DC-DC-Converters_SHOUDING-SDB628_C77805.html, is actually a decent choice)

This set of calculations from TI is a good choice: https://www.ti.com/lit/an/slva372c/slva372c.pdf?ts=1627486566148&ref_url=https%253A%252F%252Fwww.google.com%252F

[worldly schooner]

Thank you very much for this! I actually found and started reading through the ti literature earlier, and it definitely helped a lot!

[heavy jasper]

(but also just for your info, Vsat is the "Saturation Voltage" on that datasheet, and then for Vf it's somewhat a matter of just picking a diode with enough current limit (your output current) and going with it; 0.5-0.8V is a reasonable first estimate

[worldly schooner]

Oh, I missed that Vsat. Thank you!

[heavy jasper]

for what it's worth, specifically for LT (now Analog) products, this is actually the sort of thing where ltspice can help tremendously.

They have fully modeled components for many of their switching regulators, and a bunch of other components (Diodes, MOSFETs) modeled as well, so you can draw up a schematic and then simulate it. But that's going to be somewhat more annoying / impossible to do completely for a non-LT/Analog part (it requires the other company to have an unencrypted SPICE model, which is fairly rare).

and LT/Analog parts (while very very nice) tend to be quite expensive as well.

[supple pollen]

I've become quite fond of their LT107x and LT117x switchers.

Even this nutty bodge to (ab)use a CCFL inverter to make a kilovolt regulated power supply using an LT1172 worked nicely.

http://www.vitriol.com/images/tech/scope103.png

[distant raven]

I’m a little surprised that the ESP32-C3 mini module requires so many external bits to function compared to the WROOM

[distant raven]

The ESP32-C3-WROOM peripheral schematic is also interesting

It lists an external 32.768kHz crystal but labels the connections as NC (no component). I can’t tell if that’s because it’s optional or they don’t want you to use it. It’s kind of unclear.

Actually both the mini and the WROOM modules have the same NC on the external crystal

[tough matrix]

isn't the crystal on IO0 and IO1? they seem to be connected, no NC there

[distant raven]

Look closely

Both crystals and components for the crystals have NC and they are grayed out

This is true on both peripheral schematics

[tough matrix]

indeed

i guess it means it is optional...

[distant raven]

That’s all the I can gather. I wonder what cases they would suggest where you might use it rather than leave it off

[worldly schooner]

As far as I know, 32.768kHz oscillators are usually only used as a tuning fork for RTC or other precise-time applications. System clocks usually use MHz-range oscillators instead.

[distant raven]

I imagine if you used the it in a situation where you were not connected to the internet consistently it would be better for timing as you suggest

[worldly schooner]

Even if you were assuming a constant connection, having a precise frequency that can be easily divided into exact seconds can significantly reduce drift between time queries, so you can stay in sync with other services with far less power.

Alternatively, you could also use that as a way to query time far less frequently.

Wait, that's kinda the same point.

Anyways, it's better for precisely-synchronized operation in every metric except cost. Power consumption comes down with less wireless transmission, processor load comes down with simpler clock dividers, and accuracy is improved with drift-free seconds counting.

Relatively, anyways.

Even simple data-logging applications benefit from it being there. Cost-wise, it's not a huge impact, but function-wise, it's pretty much a net positive.

[distant raven]

Does this seem like a suitable replacement to the DMG3415U-7? I’m not familiar with the brand but the specs seem similar enough.

https://lcsc.com/mobile/product-detail/MOSFETs_UMW-Youtai-Semiconductor-Co-Ltd-AO3415A_C347479.html

Footprints match

[supple pollen]

A fair number of modern MCUs use a 32kHz crystal and PLL to get very high clock frequencies.

[distant raven]

Right, it’s a great crystal for that. I was just intrigued by the fact it was on the peripheral schematic but listed as no component.

[elder peak]

Maybe it's just there.... vibing.

[lyric nymph]

I bought some WS2812 LEDs in 3535 size.. The spec sheet is here: https://cdn-shop.adafruit.com/product-files/2686/SK6812MINI_REV.01-1-2.pdf ... but it doesn't mention a recommended pad layout, and the pads are unusually shaped. Any recommendations on how to create a pattern for this part?

[distant raven]

Those are the SK6812mini which are different from the WS2812B

The pins are rotated 90° counter clockwise

[lyric nymph]

Agreed that the pin layout is different -- but the Adafruit Neopixel driver will run them the same as WS2812B's.. Anyrate, my question is about what pad pattern I should use. 🙂

[supple pollen]

I guess you could look at the files for an AdaFruit board that uses it

[distant raven]

Sparkfun library has them

You just need to adjust to 3.5mm x 3.5mm footprint

[lyric nymph]

But the pads on the 3535 look drastically different than the 5050. Here's the 3535..

So I don't have a clue how I would set up a pattern like that in the EDA software I'm using. Plus, there's really not much mechanical data on that drawing..

[distant raven]

This is how my pads are setup

[lyric nymph]

Any chance you've got that in DipTrace? 🙂

[unreal flax]

Ouch. On the EDA side, sometimes people make a polygon for the pad and overlap a small SMD rectangular pad on top of it for the signal connection.

[distant raven]

I’m not familiar with DipTrace 😅

[lyric nymph]

It's not quite as popular as say, Eagle, but I definitely prefer it over Eagle. Eagle just hasn't felt natural to me somehow.

[distant raven]

Yeah, I run in eagle. But overall it wouldn’t be too hard

Do you know how to make footprints in diptrace?

[lyric nymph]

Absolutely.

Just don't have the mechanical drawing enough to convert the mfr's "Back Pad Size" to a layout.

[distant raven]

Draw a 3.5mm square and place four 1mm square pads on two parallel sides

Set the center spacing between the two at 2mm

[lyric nymph]

Cool, I'll give that a whirl.

[distant raven]

So the distance from the center of one pad to the center of the next pad on the same size is 2mm

Then center those pads on the edge of each side

[lyric nymph]

And each pad is 1x1mm?

[distant raven]

Yeah

And the center to center spacing is 1.75mm not 2mm

Had to open my footprint to double check

[lyric nymph]

Disregard pin numbers; haven't set those yet.. But are these measurements what you're describing?

(I'm OK with them being off by a thousandath of a millimeter. 😆 )

[distant raven]

So you only need 1.75mm between 1&2 and 3&4

The distance between centers for 1&4 and 2&3 should be 3.5mm

[lyric nymph]

If it's a "3535" package, shouldn't the distance between 1&2 be the same as between 1&4?

Ah, disregard. I see what's up there.

[distant raven]

Yeah, it leaves enough under and some on the outside for soldering

[lyric nymph]

Sweet. Many thanks for the help!

[distant raven]

🙂

[silk lark]

I wonder, does anybody have experience with soldering double-row pin headers on the edge of a PCB to pads on both sides? Something like this:

it seems reasonably solid, but I wonder if I'm missing something

[distant raven]

Seems reasonable

[worldly schooner]

That's an interesting idea. I imagine this would only work with 1.27mm on 1.2mm pcb, or 2mm on 2mm pcb, though.

I don't think you could get a 2.5mm pcb from most places?

[silk lark]

it's close enough on a 1.6mm PCB to work

[worldly schooner]

Pins are usually something like 0.4x0.6mm?

[silk lark]

on the female header, the pins are bendy enough, and on the male one you just use more solder

[supple pollen]

"the bigger the glob, the better the job!"

[worldly schooner]

I mean, you'll probably have to solder it by hand, which affects scalability, but otherwise the only other issue I foresee is potential flexing of the board-header connection

The geometry should be okay, but I worry about the durability of the pins and potential stress on a right angle connection, unless you have other ideas for mechanical support.

[silk lark]

https://www.sunrom.com/img/p/958/958_1_800.jpg

looks like I'm not the first one with this idea

[worldly schooner]

Oh wow, is that a plastic piece on the back side extra support?

[silk lark]

I think it's to plug into the case

I think it's not plastic, it's foam

[onyx kernel]

I've made a little macro keyboard with an display, nRF24L01 module and a integrated Arduino Leonardo. but since its my first PCB project want to make sure, that it works. Thx to everyone who looks at it 😄 and sorry for the messy wiring

[heavy jasper]

Okay, so, step 1: Let's clear up this ratsnest of wiring, it makes it essentially impossible to review. A note: you already have GND and +5V power symbols on your project. Instead of having all the GND be physically wired out from there, you can just put a GND/power symbol wherever you need it, and they'll connect to each other.

even as I'm going through to try to remap some stuff as an example, it looks like you e.g. have the same net named both +5V and VCC, which hopefully is generating an error somewhere.

If you can get the drawing cleaned up a bit (w/ power nets used locally for voltages instead of having everything drawn across the screen) I can take a deeper look.

[onyx kernel]

ty ill clean it up tomorrow

[broken zenith]

Truer words have never been spoken

[onyx kernel]

That should be better 🙂

[broken zenith]

Just a question: I know the basic workflow of KiCad, but is EasyEDA better for simple PCBs? I've heard mixed opinions and I can't really afford a paid option

[onyx kernel]

ice never heard of KiCad but i like EasyEda its pretty simple

[heavy jasper]

IMO if you've already started using KiCad and understand it, you might as well keep using it.

[broken zenith]

I have plenty of time on my hands to learn new software so if you think it's worth it, I might give it a shot.

[broken zenith]

KiCad is this pretty cool(imo) open-source pcb design software that runs locally, not in the web

[heavy jasper]

Okay, this is much easier to read! Some notes:

The upper-right switch has a GND port that's not connected

I don't see that you have a way to flash the bootloader onto the atmega32u4, are you getting them pre-programmed?

I'm super happy to see the type-C connector, but you'll need 2x 5.1K resistors from CC1 to GND and CC2 to GND to indicate to the upstream device that there's actually something plugged in (a true type-C port, if you have a C-C cable, doesn't supply VBUS until it sees something on the CC1/CC2 lines).

[onyx kernel]

Jeah that's a thing I haven't implemented jet I think I'll just take the pinns of the nRF24L01

[onyx kernel]

Oh that's good to knew

[heavy jasper]

I would recommend adding some additional decoupling at the AVCC/VCC pins (probably 0.1uF - 1uF per pin, since they're spaced fairly far apart on the chip).

And probably some local decoupling capacitors near the keyswitch LEDs and the OLED connector.

[onyx kernel]

Well thank you very much. I'll have to go off now but I'll read your messages tomorrow (if you have any more)

[heavy jasper]

It looks like the OLED display needs I2C; and at the moment the pins you have wired to it are just normal GPIOs so you'd need to use a GPIO-implemented I2C library, which is a bit annoying. It looks like the actual I2C pins (PD0/PD1) are just being used for button-press sensing right now, so it should be pretty easy to swap those around and have a true I2C hardware peripheral driving the display

I also don't know if that OLED has its own pull-ups on the I2C lines, but it'd be good to add in a pair of ~4.7K pull-up resistors to the I2C lines.

As a more general style point, I generally like any net that actually runs somewhere important to be named ; it makes the purpose a lot easier to understand.

[long wraith]

Usually I2C peripherals don't have pull-ups built in, but it should warn you if you're trying to use I2C without them

[heavy jasper]

Sure, but at that point the only options for adding pull-ups becomes either A) rework the board to hack them in or B) rely on the very weak internal GPIO pullups on the atmega, which could limit bus speed pretty severely.

vs. just adding them to the PCB design to start with, and you can always depop later.

• D1 is an RF PIN diode, which means it's probably more expensive than it needs to be, and its abs-max max forward current is 50mA, which seems low for all the LEDs you have running here. I'd recommend replacing it with either a low-voltage-drop standard diode, or even more so, a schottky.

[long wraith]

Ahh, you're talking about designing a board for the OLED? I popped in during and thought you were talking about doing the MCU side

[heavy jasper]

This is the MCU side, and the OLED is on some unknown carrier board

so I'm not going to necessarily trust they put pull-up resistors on.

[long wraith]

Ohh... I'd expect the OLED not to, and would put them on the MCU

[heavy jasper]

Yeah it can be a mix. And resistors are cheap, so may as well add them to the MCU board for safety.

[long wraith]

Mhmm

[heavy jasper]

(it's a lot better than having to hack them on later)

[long wraith]

Or having to go external [or have your customer use external if it's a product]

[heavy jasper]

• A small reset switch would also be a nice addition so you don't have to keep unplugging/replugging to reset your board when programming.

• I did check the nRF24L01 and the atmega32u4; initially I was concerned about overdriving the 3.3V-powered 24L01 inputs, or the 24L01 not having enough voltage to drive the 32u4 inputs sufficiently 'high'. In this case (somewhat rarely!) it's actually OK: the nRF24L01 has 5V-tolerant inputs, and the ViH of the atmega32u4 is 0.2*VCC+0.9V, or 1.9V which is easily satisfied by the 3.3V out from the 24L01.

• Unless otherwise specified, I'm assuming you're going to be using the internal pull-up resistors on the GPIOs to drive all your switches. A lot of what I do tends to be in a fairly wide operational environment and with a lot of noise nearby, so I tend to prefer having at least pads for discrete pull-up resistors so I can make the line a bit more noise-immune by increasing the pull-up strength, but you'll probably be OK here.

• In general, the USB-C will only be giving you 5V, so trying to LDO to 5V isn't going to go super well. I'd probably just entirely remove U4 and let the bulk of the board be supplied by the USB raw voltage.

• C5 appears to currently be specified as a tantalum cap (though with no specific BOM callout yet so it may just be a placeholder. In general, it's best to avoid tantalums wherever humanly possible; for small high-capacitance applications ceramics have gotten quite good, for larger SMT bulk capacitances polymer caps are also pretty decent. Pure-tantalum has a nasty habit of catching fire if you mistreat it. It's also a conflict mineral so especially if you're not getting a name-brand capacitor from a known-trusted source, the odds of the supply chain incurring some strong negative externalities goes way up. For your application here, any electrolytic cap would likely serve you perfectly well.

[distant raven]

Wow didn’t know tantalum capacitors were potentially conflict mineral dependent

[heavy jasper]

Tantalum itself is a conflict mineral (and so are many other things we use, but this one is a lot easier for most folks to design out)

[distant raven]

I usually buy tantalum caps from DigiKey so I think they probably try to avoid conflict sourced tantalum capacitors?

I should say I always buy them from Digi-Key

[heavy jasper]

Hopefully yes, though it's worth checking with the brands you're actually buying to see what guarantees they make.

Digikey gives you a pretty good guarantee that you're actually buying the brand you think you're buying.

[distant raven]

I use them on my led boards since they are low profile

[heavy jasper]

For what value/size?

[distant raven]

100uF 1206

6.3V 20% variance

It’s hard to find high value ceramic caps

And they can be prohibitive cost wise

[heavy jasper]

Yeah, that's generally where I'm going to be branching into polymer

[distant raven]

Tantalum polymer?

Or another kind?

[heavy jasper]

or aluminum-polymer

[distant raven]

Oh gotcha

How do aluminum polymer compare price wise?

[heavy jasper]

But I believe tantalum-polymer is better than pure tantalum, at least from a safety perspective.

Generally the aluminum-polymer tends to be more of the can type, unfortunately

[distant raven]

Yeah

100uF is just to provide some bulk capacitance to the sk6812mini

It’s not perfect because the surge current on the ones I’m using is small compared to the max you would expect for 50 sk6812mini

But the thought was they are pretty bright at even 10% brightness so one one should ideally be turning them on at full brightness with all three colors on

[heavy jasper]

TBH in your situation I'd probably just parallel a couple smaller ceramics

22uF or so becomes a lot more available

if you primarily care about height, not x/y

[distant raven]

Probably better

I can buy 1000 for 4-5¢ a piece

And 5 of 22uF in parallel is more than 100uF of a single and only $0.25 compared to $0.40+ at volume

Plus tantalum caps are starting to get hand to come by

[vapid grove]

Simple, but powerful, I managed to route a 4 layer board there

[onyx kernel]

Here is version 2.0 🙂 i've added all recommendations (i understood). And thanks again for all the hints yesterday

[gleaming thistle]

Came across this today, Honeywell Hall Effect Sensor, I suspect the one on the right as counterfeit. Contacting the vendor now (I won't name until I can confirm).

[bright thistle]

Uhmmm... Is it feasible to solder 1210 and 1206 SMD by hand?🤔

[marsh nest]

Absolutely! When I use SMD resistors/capacitors, I typically do 0805 and they're easy enough to do by hand. The 1210 and 1206 are both a little bigger. You'll need a nice set of tweezers (I love some angled ones for this), but it's not too tricky

I have soldered smaller, but I really don't want to solder smaller.

[bright thistle]

@marsh nest thank you!
I've sent my first PCB to fab, remembered I've put 3 SMD (2 caps, 1 regulator) and went "Wait. Do I know how to solder those with a pencil iron?!" 😬😅

As for tweezers, would "reverse" ones be ok? :)

[marsh nest]

Reverse ones should be fine.

The way I've done them in the past (To be fair, it has been a while) was to put solder on one pad, then get the SMD item right next to it, heat up the solder, and move the one pad into it. Remove the iron, let it cool, then solder the other pad.

Also I'm just going to put a reminder out there to double check all your measurements when making a new footprint.

Because a 1.25mm peg does not fit into a 0.75mm hole...

[bright thistle]

I'm using the ones provided with kicad 😅

[marsh nest]

There's quite a lot, and I'm really liking how they have things set up

Having independent symbols and footprints really gives a lot of flexibility

[bright thistle]

The only footprint I've ever made is a silkscreen to put as a thank you to fab :)

[marsh nest]

The program I used previously was footprint AND symbol as one "item"

Which has some perks but, flexibility wise? KiCad's method wins.

[bright thistle]

Yep, I see many people being turned down by "too much flexibility", even in other fields, but at the end it boils down to mental flexibility, not the tools

[marsh nest]

Too much flexibility can be a thing, especially if it's flexibility that's not needed or is forced - IE, you have to click through a menu that most people never need

But I haven't seen that in KiCad.

[bright thistle]

Sounds more like a UI problem.
I don't think there's ever gonna be an "overload" if you stash less common options and keep stuff well separated (again, kicad is brilliant in this)
As long one knows that something is doable and knows how to reach it, you just need not to clutter

Ok, the biggest one here is a 0603, I'm going to be fine 😅😂

Smallest is a 008004 😱

[marsh nest]

I don't ever want to solder those.

[lime thunder]

I'm pretty sure that 008004 is just a grain of salt

[lime thunder]

how are those made?

[bright thistle]

By casting a hex at the magic smoke, I guess

[worldly schooner]

Same way they make any ic, plant little silicon wafers and watch them grow

[marble scaffold]

just finished my first schematic

i'm aware this is pretty messy, can clean it up later
this is for a hardware password manager that you can plug in like a usb thumb drive
(think: yubikey but password decryption instead of 2fa)
for the experts out there: is there anything i'm missing, or ways i could improve?

edkeyes mentioned adding decoupling capacitors

[glass fox]

Question: I got a senor based project in mind: an environmental sensor suite: temperature, humidity, air quality, water level, ekg, etc. I want to make my own pcb instead of using a prefab board. How do I best determine what I use for the MCU and every other components that accompany it, and is that part typically in the datasheet? I already have all the sensors I want to use planned out, thinking about using i2c or spi for communication between them. Please @ me Ill forget to check otherwise.

I got Eagle and Fusion360, and have been going through the tutorials lately too.

[supple pollen]

@marble scaffold You'll need to use the AdaFruit bootloader if you're going to omit the crystal. I'm still a little boggled at USB support without a crystal.

@glass fox MCU choice is, in my opinion, determined somewhat by circuit requirements and largely by personal preference. Factors I usually consider are software support (are there libraries available for the sensors I want to use), USB support, 3V vs 5V signalling, number of I/O pins and interfaces (UART, I2C, SPI, etc.), packaging (DIP vs surface mount), programming support (ISP), performance (8/16/32 bit, clock speed), support requirements (power supply, crystal, filtering, etc.), and built-in peripherals (PWM, ADC, DAC, EEPROM, etc.).

[distant raven]

It sets an internal oscillator which I found out by looking at the SAM-BA bootloader in atmel studio that there are a number of internal oscillator options. It then uses the timing signal from USB to tune the internal oscillator

It’s interesting

If I remember correctly there are two or three internal oscillators on the samd21

Internal 32.768kHz, 1MHz, and an 8MHz

The internal 32.768kHz is for low power timing

[supple pollen]

I can understand all that, but I'm still a little surprised it works well, given the tight timing requirements of modern USB implementations.

[distant raven]

Yeah, internal oscillators are notoriously unstable

But they appear to compensate for drift pretty well

Crystals are also ridiculously cheap anymore so unless you’re just going for a super compact design, it makes no sense to leave it off

[supple pollen]

I keep seeing clever ways to basically replace hardware with software, and am repeatedly impressed with the kinds of things that can be done with sophisticated enough algorithms.

[distant raven]

Lattice semi has one of the best internal oscillators on their ICE40 fpga

They clock 48MHz and up without external components

[supple pollen]

That chip comes close to "replace arbitrary circuitry with this"

[distant raven]

And they just tune the PLL with a SPI clk signal when flash is programmed

Since the SPI clk should always be active due to the parallel usb to serial, you always have a tuning source

[supple pollen]

It's the same kind of thinking that let inkjet manufacturers replace expensive stepper motors with cheap DC motors, optical encoders, and carefully designed firmware to build ever-cheaper printers and maintain 4800dpi resolution.

[distant raven]

Yeah

It’s amazing what you can do these days with even just an Arduino

Like an atmega328p

I see the 328p/pb used a lot in smaller industrial controllers

[supple pollen]

I've designed those into a bunch of projects.

[distant raven]

Which is kind of funny considering it’s clout as a hobbyist chip

Are you using optocouplers for power switching?

[supple pollen]

I started in the PIC world, but ended up deciding it was worth paying a few cents more per chip for the more convenient architecture and better documented programming interfaces of the AVR line.

The board runs a pair of the 4-tube nixie boards: the optocouplers serve to switch the 180V anode supply, they do the level shifting and soft switching intrinsically, making a simple, low component count design.

Here's the breadboard version

[distant raven]

Nice, that’s a pretty cool application of the octocoupler

[supple pollen]

It's a somewhat odd use case, but works nicely

[distant raven]

Nice

I’ve always wanted to do stuff with tubes to make a present or something for my dad

He used to scavenge through junk yards for good tubes when he was a kid to fix radios and whatnot

[supple pollen]

People tend to think of tubes as fragile and short-lived, but they're surprisingly reliable. I still repair tube gear, and the tubes are rarely the problem.

[distant raven]

Yeah, I just think it’s be cool to make him a custom tube radio or something

[supple pollen]

That would rock. There are some nice designs out there, from simple 1-tube regenerative sets to fancy multiple conversion superheterodynes.

While you probably don't want a kit, there are a few good ones available, and they can be a great source of design ideas.

[marble scaffold]

just finished routing my PCB

ik it's really messy

but this is the first time i've done something like this

and there's a lot going on

kicad screenshot with all layers

[supple pollen]

Not bad, it's æsthetically appealing, which isn't technically required, but something I aim for

[marble scaffold]

3d model

probably messed up somewhere

i can almost guarantee that i'm going to fry my first board

[supple pollen]

It looks like several JTAG pins aren't connected. I do like having the switch out where it's easy to get to.

[marble scaffold]

forgot to connect ground to jtag

there we go

it's fine to leave vref unconnected, right?

[supple pollen]

I'd have to crack a manual, I don't remember. You can connect the USB connector mounting pins to ground via a high resistance to give some static protection. Speaking of which, I don't see the traces to the USB protection chip.

[marble scaffold]

i ended up removing the usb protection chip

could probably re-add it though

have more than enough room

[supple pollen]

It reduces the chance of zapping your MPU, especially if your board is going to be riding around in your pocket without an enclosure or things like that

[marble scaffold]

re-added the usb protection

[supple pollen]

That's shaping up nicely!

[marble scaffold]

yeah

surprised how much i was able to get done in just 3 days

is there anything else i should add here?

[supple pollen]

I'm not sure enough of myself to say you "should" do anything, but I'll give you a few thoughts: a couple of test points might come in handy, I'd probably add a static electricity drain to the USB shield connection, you might consider adding antireflection resistors to the USB leads, maybe nudge your components a little farther apart if you're considering hand-soldering them, a mounting hole or two?

[marble scaffold]

thank you for the advice

im asking because this is my first time doing pcb design and I feel like I'm missing something

just a couple questions though, how would I do a static electricity drain? just a trace from the shield to ground?

or is it more than that

[worldly schooner]

Resistor to ground

[marble scaffold]

what value?

[worldly schooner]

Actually, ignore that, I was thinking earth ground.

You just just tie it directly.

[marble scaffold]

https://electronics.stackexchange.com/questions/4515/how-to-connect-usb-connector-shield

yeah just found this post

[supple pollen]

I usually use a 1 megohm resistor

[distant raven]

I had seen some older design guides suggesting a ferrite bead for USB static electricity dissipation but then recently some hardware researchers found that ferrite beads can actually introduce some not so good noise into your design

[supple pollen]

I haven't seen ferrite beads used for static suppression, they're normally used for noise reduction. They're basically a small, lossy inductance.

[distant raven]

It was in a TI design guide from like 2008 that I found like over a year ago

It was like a filter, it wasn’t just a ferrite bead either so I guess I should have clarified that 😅

[supple pollen]

I've seen some cute little modules used in rows to protect signals going offboard, each one with a capacitor and a pair of ferrite beads.

[heavy jasper]

There are also these (feedthrough filters):

most commonly used for sending signals through EMI chamber walls or through completely sealed metal shielding boxes

[neon slate]

Hey, I want to design a pcb that uses a ir remote to control a stepper motor. I made it with and arduino but I want to make it smaller. How would I do that?

I’m a noob to pcb design btw

[unreal flax]

You'd use a tool like Kicad, to create a schematic and then a board layout. It generates files you send to a fabrication house to make the PCBs, and you can either solder parts yourself or have them do it for you.

[neon slate]

Ok

Thanks

[unreal flax]

Often you can find existing designs for some boards, like Arduinos or Adafruit boards, either as CAD files or as just PDF schematics, but either way they'll be good references for how to design your own.

[neon slate]

Ok, got it

[supple pollen]

Even using chonky through-hole components, it's not hard to squeeze an Arduino into a small space. The left hand 14mm or so of this board is basically an Arduino

[ornate glen]

👍

[neon slate]

Anyone know how to design a macropad pcb?

[tough matrix]

easiest way would be by copying Adafruit files
https://github.com/adafruit/Adafruit-MacroPad-RP2040-PCB

[neon slate]

Thanks!

[tender cedar]

Blinka-themed Stemma QT-compatible adaptor. I needed a adaptor with holes to loop the wires through for mechanical stability. It kind of looked like a python face, so I leaned into it.

[distant raven]

On nice

[rocky quest]

anyone mind looking at my samd21 dev board

[tough matrix]

some comments:

• there should be bypass caps on all vdd pins - check the datasheet
• it is suggested to add a cap and resistor to reset pin - again, check the datasheet
• ii seems that you broke SWDIO and SWDCLK to a 2-pin header. Normally for SWD programming you use a 5pin header (with 3.3v, reset, and gnd)

[rocky quest]

ok I see

[rocky quest]

I used the schem from adafruit feather m0

[tough matrix]

I didn't check it, but I am sure they also included bypass caps

anyway, you can find the datasheet here: https://www.microchip.com/en-us/product/ATsamd21g18
It is over a thousand pages, but in particular, here is the relevant recommended schematics for power connections:

(in section 45, schematics checklist)
Same section also shows suggested cap/resistor for nRESET pin

and this: "Note that a pull-up resistor on the SWCLK pin is critical for reliable operations. Refer to related link for more
information." (45.7)

Quite possibly you can skip some of these pullups/bypass caps and it will still work. But I wouldn't recommend it

Finally, note that the traces between D-/D+ and USB connector must have impedance specified in USB specs - which means you need to pay attention to spacing between them and trace width. But I am not an expert there - probably others can say more. (I was not aware of it myself when designing my own breakout, and it still worked...)

[worldly schooner]

The effects of impedance is dependent on frequency. USB gets a bit finicky at high speeds, but for simple low speed applications, usb devices are actually fairly tolerant of impedance variations.

Once you get to high speed data, usb has an impedance spec to ensure your data doesn’t get deformed by unintended capacitance or inductance.

In other high speed data applications with multiple lines, signal timing also becomes an important factor. HDMI and LVDS not only have an impedance spec, but they also need trace length matching, as a mismatched trace length or cable length can cause two signals to not line up properly…

But you probably don’t need to worry about that.

[distant raven]

Yeah, samd21 don’t really require much in terms of impedance matching, especially for short runs.

Some other considerations with the samd21 is there are different scenarios where you might want to consider bypass caps and a ferrite bead on power but the average application doesn’t need those things and they describe a minimum implementation in the data sheet as well

If you’re using a LDO and are not doing critical analog data processing, you can ditch the ferrite bead and go with the minimum bypass configuration which is 3x 1uF caps on power pins.

@tough matrix’s application was dealing with stepper driver and other potentially high noise operations so a ferrite bead/inductor on the power input would have been valuable.

Switch mode or DCDC power supplies also require additional bypass and inductive elements on the power rails because of introduced noise.

But honestly all these possibilities is what makes the samd21 a great MCU.

[supple pollen]

Adding antireflection resistors (low value, 22Ω or 33Ω) in the USB data lines can help with impedance issues as well.

[distant raven]

Yeah, and the random designs that have 27ohm ones

[supple pollen]

I hadn't seen that yet but I expect anything in that range would be fine.

[distant raven]

The RP2040 has it in their hardware design guide

[spice crater]

this has likely been covered before, but is there an updated Adafruit Eagle Library? The one on GitHub hasn't been updated in 6 years and their downloadable schematics reference parts not available in the GitHub version....

[velvet patio]

I've never had to take RF propagation into account before when doing a board but starting on one with an esp-01 and qwiic as a cheap $2-3 general sensor-to-mqtt controller. I presume hanging the esp's antenna off the edge of the board is the best way to proceed since that's the way I've seen other dev boards do it, but are there any basics for laying out the rest of the board (big ground plane or is that going to give weird reflections on the wifi?)? Sorry if its a stupid question but my radio-fu is weak.

[distant raven]

You can hang it over the edge or just leave an empty PCB below it, or recess the edge so it seems more continuous

[supple pollen]

Even if it's not updated, you can grab parts from the downloadable schematics (I do this a lot). You can either use File->Export->Libraries, or use exp-lbrs.ulp directly.

[spice crater]

Thanks

[distant raven]

Fun fact: there is PDIP package QSPI NOR FLASH

4MB (32Mb) that can be clocked at 133MHz

Just look up W25Q32JVDAIQ on Digi-Key

[sweet inlet]

What do folks here do for manufacturing small batch pcbs cheaply? I have a design for an stm32 based board, and on jlcpcb the min amount is 5 and it comes out to $135 in total or so.

If I just want 1 to make sure the design works, what’s my cheapest option?

[distant raven]

Order a stencil with your pcb and all the parts and place with tweezers

[sweet inlet]

And using a soldering iron? You don’t need a reflow oven?

[bright thistle]

Either you go with an iron and no stencil (steady hand and loupe suggested), or stencil, solder paste and at the very least a heat gun

[worldly schooner]

Depends what parts you're soldering.

[bright thistle]

Btw, oshpark and aisler have min batch of 3

[worldly schooner]

If everything has exposed pins, an iron will suffice.

[sweet inlet]

I’d want to solder 0402 size components

I think there’s an exposed pad on the mcu though

[worldly schooner]

0402 is probably as low as I would attempt with a fine point iron

[bright thistle]

If you go a bit up in chat, you'll find a video of somebody hand soldering 0603→008004

Whoops, my bad, they're only the pictures, but I can find the link to the video easily if you want

[worldly schooner]

If you have a lot of components needing reflow, a hot plate is really good for it. https://www.sparkfun.com/tutorials/59

[sweet inlet]

Can I do this if I need to solder an exposed pad?

[bright thistle]

https://youtu.be/P72U2yHWKSk

[worldly schooner]

An exposed pad?

[sweet inlet]

On the mcu, under the middle is a grounding pad

[worldly schooner]

Yeah, the hot plate method is probably the best way to reflow solder paste under a chip without entering professional equipment territory.

[distant raven]

Yeah

I use a hot plate for basically everything

Hot plate + hot air for two sides boards

[unreal flax]

You can also do exposed pads with an iron if you modify the footprint to have a large via in the middle. That lets you melt the pad from the opposite side. A little janky but can work for a prototype.

[sweet inlet]

Thank you all! Time to buy things 😄

Last question, looks like the mcu I’m using is out of stock until next year at digikey, arrow, mouser, any other sources of parts I might not be looking at?

[distant raven]

What do you need?

STM32f401?

I’d say find another alternative. STM32 are essentially impossible to find.

Well, honestly most MCU are hard to come by

[tough matrix]

BTW, what hotplate are you using?

[distant raven]

LED Microcomputer Electric Hot Plate Preheat Soldering Preheating Station Welder Hot Plate Rework Heater Lab 110V 800W 200X200mm Plate https://www.amazon.com/dp/B07921YZDK/ref=cm_sw_r_cp_api_glt_fabc_PZR61QCPKDG8G54DWKRV?_encoding=UTF8&psc=1

It’s not terribly great but it’ll do up to 300°C decently well

I mostly use it less than 175°C

[kind pecan]

anyone know of linear control vca chips? it's intended for a non-audio control voltage

or a chip that can be biased to either mode

ping me if you reply

[sweet inlet]

STM32F411CEU6

[distant raven]

Ah yeah.. good luck finding that one any time soon. This chip shortage has been bad

[sweet inlet]

ooph -- jlcpb had more last time I checked, now they have 8

I do have some extra blackpills with the same chip, probably not worth trying to salvage them from there

looks like there's some on aliexpress though

[distant raven]

Don’t chance Aliexpress

If you want the STM32 either harvest chips off other boards or pay for the minimum order on JLC.

Harvesting isn’t hard if you have a good hot air gun and are patient with it

[marsh nest]

In most cases, AliExpress is fine. Specifically for chips during the chip shortage? I wouldn't risk it.

[sweet inlet]

https://giphy.com/gifs/knowledge-TI32JwHmWQEi4

appreciate you both!

[sweet inlet]

Is LCSC generally trustworthy for parts? They have stock. I imagine so, they're the same company as jlcpcb right?

[marsh nest]

I'm not familiar with either, unfortunately

[sweet inlet]

👍

[distant raven]

I buy from them occasionally

I don’t necessarily trust microcontrollers from there but common components have been safe

[marsh nest]

....Writing up some initial software for the tankbot and using my PCB schematics for referencing pins and I realize I forgot to connect one (1) thing in the schematic. Was a little worried I'd have to run some long bodge wires, but turns out. Nah. Only a few mm.

I forgot to connect from the feather header to the input of the level shifter. But the output of the level shifter is connected just fine, and the level shifter is tucked directly underneath the feather on the opposite side of the board.

The bodge I'll have to make (On the PCBs arriving tomorrow)

[supple pollen]

@kind pecan The ancient CA3060, the newer CA3280, and the more or less unobtainable CEM3381 come to mind, but they're all old technology, it would seem likely there's something more modern available other than just using a four-quadrant multiplier.

Oh, I know that feel with the bodge wires. Hence my username.

[marsh nest]

Heh, yeah

I was just worried I'd have to bodge from the feather to the input, and from the output to the header this is connected to. Which is... pretty far away

[supple pollen]

That one came from my home-rolled footprint generator that got the pin numbering backwards on one edge. Fortunately, I was only using a few pins on that side of the SIM808 module.

[marsh nest]

The ones coming tomorrow are the third version of this PCB, but the fourth effective version.

First version worked pretty well, but I hadn't taken into account the need for level shifting for the LED transistors. And because these transistors were inverted (One of the LEDs is common-cathode), that meant that I couldn't quite turn them off.

[supple pollen]

Ouch.

[marsh nest]

So I grabbed another one, cut some traces, and grabbed some level shifter breakouts I had lying around. And some bodge wires.

That was effectively a V2.

I did some updates and tweaks in V3, including a multiplexer so I can have multiple cameras and switch between which one is getting routed to the transmitter

[supple pollen]

That's starting to sound like a journey

[marsh nest]

The only reason there's a V4 is because I screwed up measurements on some other PCBs. This one I could have made work (It was about a mm off size-wise), but if I was ordering other PCBs, may as well re-order this one. I also added a header to connect a little DVR unit, too, which is cool!

And that's the line that I didn't have connected.

[marsh nest]

Oh yes

I mis-measured or typed the wrong thing or reverted to defaults, so my 1.25mm post switches wouldn't fit into the 0.75mm holes on two of the four PCBs I had ordered. This PCB was number 3 out of the 4. Plus side, PCB number 4 was perfect

[supple pollen]

We had a last-minute requirement to make it thinner, and ended up putting cutouts in the bottom panel for the thicker components

[marsh nest]

Hey, it works!

Thankfully, this work is just a personal project of mine. A little RC tankbot that I've envisioned for something like. ten years or so. I got a version of it working last year, but having a servo for the elevation on the turret ended up being kinda jerky due to how the commands were being sent.

So because I was swapping out that motor, I.... rebuilt the entire turret.

[supple pollen]

As one does.

The ceramic house didn't want to put wraparound contacts on this module, so I ended up installing it upside down and hoping capillary attraction, flux, and wishful thinking would get good solder joints.

[marsh nest]

Did it, though?

[supple pollen]

Happily, yes

[marsh nest]

Going from "Will this work? I have NO IDEA!" to "Hooray, it worked!" is always a good feeling

[supple pollen]

Truly.

[kind pecan]

yeah i found an old one when looking, but also figured out that there’s a way to use two exponential ones (or logarithmic i can never remember which) and some opamps to get a linear or in-between response

[bright thistle]

what's considered as a "standard height" for 2.54mm headers?

I'll be using it for selecting voltages with a jumper cap

[worldly schooner]

I think it's about 6mm of pin length? The headers I typically see are 8 or 9 mm from board surface, including the 2mm plastic base and and extra mm for SMD.

[bright thistle]

thought so, went with it in the BOM 🙂

and the asiler BOM-i-nator is a breeze to use 😄

2 caps, a voltage regulator, a USB plug, 7 Molex-SL connectors and a 3-pin header, total ~€11 (for a single board), plus service and VAT

[slow oyster]

Does anyone know what this type of UCB-C female connector is called?
https://www.adafruit.com/product/4396

Trying to source the same part from Digikey/Mouser/etc and having a hard time finding it

considering Inline isn't an option

or even this style:

though that may just be a vertical through-hole connector with the PCB sandwiched between it?

[long wraith]

Inline USB C socket

or Inline USB Type C socket

"inline" meaning it's in line with the plane of the PCB, rather than sitting on top

The PCB doesn't actually go into the socket -- you can see the soldered connection from the back view

[slow oyster]

Right, but inline isn't an actual mounting option on mouser/digikey, so I can't seem to find it

and typing inline usb-c doesn't bring it up

Must be under a different name?

[long wraith]

Hmm.... Possibly

Lemme see

[slow oyster]

Digikey does have Freehanging (Inline) but that is plugs only and more for cabling because they include metal housings

[unreal flax]

Looks like "board edge straddle mount" is what they call it.

[slow oyster]

I looked at that too, but it's all plugs no sockets

Maybe it's in another category, I've been looking in USB, DVI, HDMI Connectors - Adapters

[long wraith]

Ok, I did a search for "USB C socket", then go to "USB, DVI, HDMI connectors", select "USB-C (USB TYPE-C)", and "Board Edge, Cutout; Surface Mount; Through Hole, Right Angle"

Got 2 results

[slow oyster]

Ok I'll try that thanks

[long wraith]

np

[slow oyster]

Ah nah those aren't the same thing

I need a socket that is about the same length as the plug past the board edge

I just can't seem to find the connector itself, only breakout PCBs

99% of all USBC sockets only stick out past the board edge by a few mm

I bet that second one I linked is just a vertical THT connector turned sideways

I only need the USB-C connector for power, and the case walls are kind of thick so a regular one isn't long enough, I need one with bare connector like the two examples above. Or I need to find one of those breakouts with actual mounting holes

Found similar ones to the one Adafruit sells maybe I'll just message them lol

https://www.aliexpress.com/item/32951195698.html

[fervent lance]

Not sure if the right channel but there is something I never understood about PCB. The end result of a project is a PCB right and maybe checking if some peoples would be willing to pay to have you make the same thing for them. Do you need to include an arduino in the PCB ? Can you convert fritzing circuits to PCB ? Actual example: One if my arduino is busy forever sampling humidity and temperature from 4 0.50$ TM temperature/humidity sensors so I know what it is inside. I can't make that into PCB because 1 simple SMD chip that costs 3$ is 10x time more accurate than a single TM. So If I was going to use it I would have to make it a PCB from the start
So it seems PCB and arduino are two completely different fields?

I mean if I had used the SMD chip from the start it would be a completly different circuit but I don't even have the equipment to solder SMD chips so I have no idea how you prototype an SMD

[slow oyster]

SMD can be done with a regular soldering iron (in most cases) but I prefer using a stencil, solder paste, and a $40 hot air gun

You can probably find a breakout board for your SMD chip as well if you don't want to make a PCB for it

there are breakout boards for all types of SMD component chips, you just need to know what kind of package it is

You could also make a standalone PCB that you connect to an arduino via wires, you could make a HAT board for your arduino that plugs into the GPIO pin headers, or you can incorporate an ATMEGA chip directly on your PCB and basically have the arduino integrated in your design.

[fervent lance]

It's 8-VFDFN Exposed Pad 8-DFN (2.5x2.5)

One of sensirion AG SHT chip

[slow oyster]

and what is the sensor itself? If it is popular at all there are probably already breakout boards for it

if not you can get a generic breakout board for that package and solder the chip on

[fervent lance]

so if I understand correctly there are 3 main options: 1) Have a PCB made to expose the connections myself 2) Buy a generic breakout board for that type of package 3) Check if the usual suspects near me have made a board for it (adafruit, spark, cana, digikey etc in my case) ??

But I still have to prototype it on an arduino before I PCB the final thing

[slow oyster]

For prototyping breakout boards are usually best

is it a SHT20?

[fervent lance]

Been a long time ago so I don't remember exactly, I think it was SHT-X not SHT-XX but if the only thing available is SHT-20 I guess I'll take that

[slow oyster]

Typically you can find a breakout board with that chip already on it if it is popular, i.e. this
https://www.amazon.com/GY-213V-SHT20-Temperature-Humidity-Transducers-Electronic/dp/B07RZF6FXM

You can probably find that cheaper off of Amazon mind you

Otherwise get a generic breakout and solder it yourself, i.e. https://www.icbreakout.com/products/dfn-8-breakout-board-3x3-mm-0-65-mm

[fervent lance]

In an ideal world I'd like to have a bunch of breakout boards and be able to buy any chip off digikey and that chinese suppliers you guys keep talking about 😄

[slow oyster]

If you want to do SMD stuff though a hot air rework gun goes a looong way

https://www.amazon.com/Tek-Motion-Display-Soldering-Station/dp/B01MR2IWBN

[fervent lance]

I mean sometimes I see very nice SMD chip for 1-2$ with much more performance than anything DIP and I'd sure like to try them

what about fumes/smoke alarm in a small apartment ?

[marsh nest]

There's also hot plates which are really nice, although I've yet to try any

[marsh nest]

Fumes and smoke are minimal. And you can get an extractor, too

[fervent lance]

There's a fab lab near my home who have CNC/laser etching/large 3d printing/SMD stations/PCB fabs so I'll ask them about it as well plus they give free courses

[slow oyster]

You get more smoke when hand soldering with an iron imo

[fervent lance]

and it's like 5 minutes from my home by bus

[slow oyster]

Yeah definitely try them out

Makerspaces are great when first getting started

[fervent lance]

I'm going to a basic soldering course next weekend with them

Haven't done electronics since like 2 years because I didn't have projects and the DFN problems so I'm asking you guys couple of question so I can ask them good questions

[bright thistle]

ping boards manufactured, tests done

Oh, nice, lemme check

Errors!

Wut?

[fervent lance]

What about dconverting fritzing schematcis ? My understanding is that arduino is open-source so they have to incorporate a bit of the arduino and the microcontroller when printing your PCB right ?

[bright thistle]

So much noise for nothing, they're intended to be open

[slow oyster]

Never used Fritzing personally so no idea there

[slow oyster]

Incidentally I did find some of those USB connectors on AliExpress (and ONLY AliExpress...)

https://www.aliexpress.com/item/32896785322.html

So it'll take a month but at least I found em

[worldly schooner]

I wish there was a breakout board for TQFP-100, but it's way too obscure...

[bright thistle]

https://www.silicon-ark.co.uk/tqfp100-breakout-board-by-ett

[worldly schooner]

Oooo, but it's out of stock.

[slow oyster]

Different places sell similar boards

[inland jungle]

https://www.digikey.com/en/products/detail/chip-quik-inc/PA0223/5014873?s=N4IgjCBcoBw1oDGUBmBDANgZwKYBoQB7KAbRADYB2AJkoBYQBdAgBwBcoQBlNgJwEsAdgHMQAXwJgArNQAMCEMkjps%2BIqRB1pdSlKasOkbnyGix5oA

proto-advantage has them too

[slow oyster]

Yeah and there's also this style which can do multiple sizes

https://www.amazon.com/Breakout-Board-QFP-Chips-0-5mm/dp/B002USY09W

$20 is a bit silly for that though

and the breakout pins look like a pain to deal with

Good starter project if you want to start making PCBs lol

Get your own made for like $3 for 10

[worldly schooner]

I mean, yeah, but I'm not paying 20 bucks for 1 board. At that point I'd have my own made for less than that...

[slow oyster]

Yep

[worldly schooner]

I just haven't committed to it because I haven't the time to actually learn to program it afterwards haha

[slow oyster]

Anything PCB related off Amazon is way overpriced heh

But its quick!

😛

[worldly schooner]

The exact opposite of me ordering random stuff from China and waiting for a large freight container, and yet I'm still stuck with more mcus than I know what to do with....

[slow oyster]

I know the feeling

[long wraith]

Sell for a profit!

[marsh nest]

Drat!

So I had thought I had a connected net that I didn't have to bodge.

I was wrong.

Not a big deal, it's not terribly difficult, just annoying

[long wraith]

Do trace lengths and widths matter for the RP2040?

[distant raven]

Depends

If it’s USB, they generally want fat traces between USB port and the line resistor

[worldly schooner]

Depends what you’re doing with it? Usually that only matters when you’re working with ghz frequency applications where timing is super critical

[distant raven]

But if it’s like <1cm probably not a bit deal

[distant raven]

RP2040 can’t do that fast lol it’s only PHY 1.0

Lol

12Mbps 😀

Woo

[worldly schooner]

Well, I’m trying not to assume anything since I was considering overclocking a pico for display output

And at that range, the pio lines do start to matter

Even if it’s not hdmi or Ethernet level strict

Rp2040 is only usb 1.0? I thought it was 2.0 capable…

[distant raven]

Nope lol data sheet says PHY 1.0 controller

I was shocked myself

[worldly schooner]

Ah, 1.1, you’re right

Wait

Huh

Whatever

[distant raven]

Anyway lol

[long wraith]

Yeah, not doing anything speedy, lol. Just programming and CP stuff

[bright thistle]

what I linked was double sided: front 0.5mm, back 0.4mm pitch 😉

uhmmm... in my pcb I left AZ1117 pin2 floating, since I'm sipping Vout from the tab... hopefully I haven't done a mistake!

[fervent lance]

you are in the Canadas ?

[slow oyster]

No, U.S.

[worldly schooner]

There's always bodge wires...

[bright thistle]

ಠ_ಠ

[bright thistle]

ok, made a further inspection of all the datasheets and of my routing, there should be no issue.

first two entries are related to the USB port's shileding contacts, that act as anchor points as well (but since I'm only sipping power, it needs no data lines, nor shielding)

third entry is AZ1117 pin2, but since it's internally connected to the tab... ¯_(ツ)_/¯

[sweet inlet]

I'm looking for a voltage regulator to go from 5v to 3.3v for an stm32.

The 5v is coming from usb, and I have a few questions:

1. Nominally USB is 5v, does this mean I can use a regulator that's rated for 5.5v or 6v max input? Or do I need to give it some extra headroom?
2. Can I use a dc-dc switching regulator, or could I run into problems with that? I saw something about noise but wasn't sure.

[unreal flax]

Yes, USB 5.0V should be pretty precise, so it's safe to have a max rating of 5.5V or so. And yes, you can use a switching regulator unless you are doing some precision analog stuff where a little power-supply ripple would affect those circuits.

[distant raven]

How much current do you want?

Usually 500-600mA is enough

[bright thistle]

@sweet inlet the one I'm using accepts up to 18V max, outputs up to 1.35A, and has versions with fixed outputs available

https://www.diodes.com/assets/Datasheets/AZ1117I.pdf

[distant raven]

I’d you only want to handle usb voltages down to 3.3V and are okay with tiny packages, this is a good one. https://www.digikey.com/product-detail/en/NCV8177AMX330TCG/NCV8177AMX330TCGOSTR-ND/6166740

[sweet inlet]

Thanks!

[sweet inlet]

I measured my breadboard prototype at around 200ma, my designer requires ~160ma, I've heard I should budget here too

[sweet inlet]

Thanks!

[distant raven]

If you want a nice easy to use LDO with a solid 500mA in a SOT-23-5 package, the TLV75533 is a great option

It’s my go to LDO

Super stable, super low I_q

Only place that has them currently is LCSC from what I can tell

Granted 2x normal price

$0.66 a piece

[sweet inlet]

ah -- the smaller package looks similar to what you linked, too https://www.digikey.com/en/products/detail/texas-instruments/TLV75533PDQNR/9356536

[sweet inlet]

Is it a good idea to put a fuse on this board just in case?

[distant raven]

A fuse isn’t a bad idea

A Schottky diode would work just as well

Except it only blows once 😀

The MBR0540 or MBR0530 is a good option

I personally use the MBR0520 in the SOD-123 package

It has a 500mA rating and only about a 0.6V drop across the diode

So it makes my 5V lines around 4.95V on average

[sweet inlet]

thank you!!

[bright thistle]

@distant raven wouldn't a PPTC be good as well?

[distant raven]

Sure

PTC fuses have their place

Particularly in places where the input voltage and potential for surge current isn’t well known

Like if you power over USB from a wall WART

[haughty wolf]

with emphasis on the wart lol

[bright thistle]

extreme emphasys and prejudice

[elder peak]

Other than the voltage drop, you don't hear any SOD stories about putting an extra diode in.

[marsh nest]

I'm looking to make a proper interface board for the hull parts of my tankbot. Currently it has a feather motorwing running all four motors (Left tread, right tread, turret traverse, and turret elevation), and that's probably going to stay because it's pretty convenient. I might strip it down and integrate it into the board, but that doesn't change things.

The other thing I have is for controlling the hull lights and monitoring the battery. There's two headlights, and I plan on adding two tail lights at some point, largely because I can. I'm wondering what the most reasonable method to accomplish this goal is. I'm currently using a SeeSaw, whish is all great and all but I look warily at the chip shortage eating all of those chips up and making the SeeSaw unable for people to get. So I'm looking for alternatives.

I see there's the LC709203F for battery monitoring, but that's single-celled (And I have a 3S battery)

[distant raven]

You can find a chip that has alternative programmable GPIO

The ADS7138 (possible 7318) is an ADC that can have its 8 input pins used as GPIO. It configures over I2C

[marsh nest]

Another caveat is that... I am not up to figuring out a complex library for things. Even if I hadn't been neglectful of my various electronics stuff for.... too long, that's not a skill level I've been at. So things with CircuitPython libraries would be excellent

[marsh nest]

Ooh, I'll take a look

Looks like 7138 is the right number. DigiKey has WQFN packages, which... hmm. Not sure I've ever dealt with those before

[heavy jasper]

Do you have a 3S battery with fully complete internal protection for balancing and such? (Which is to say, you can just look at the output voltage and trust it’s balanced internally?)

[distant raven]

I have written a partial library for the ADS7138 for circuitpython

[marsh nest]

https://smile.amazon.com/gp/product/B06XNQGZY6 This is the one I purchased.

[distant raven]

https://github.com/skerr92/adc7138-python/blob/main/odt_ads7138.py

It’s for a board I’m making but haven’t exactly launched yet

[marsh nest]

Makes sense that you knew it right off hand then.

[distant raven]

I need to finish it out and get it published to pipy

[heavy jasper]

It’s a bit unclear, though really it primarily matters on charging (that’s where the dangerous situation actually manifests - cells out of balance far enough to make a reasonable output voltage while one cell is over-discharged, then charging that configuration), and I assume you’re not charging on this machine or running for spectacularly longer periods than the RC drones it was designed for. So probably fine to just monitor bus voltage.

[marsh nest]

The whole tankbot is something I've built largely from the ground up. I bought a chassis that had motors and treads and have built everything else. But yeah, I use an external charger and monitor the voltage, cutting things off when it gets too low.

Neat thing is that this battery has a little connector that breaks out each individual cell, which is what's used for charging.

[heavy jasper]

One note for the ads7138 is that it has gpio, but no pwm output, so if you want to do brightness control on your tail lights, for instance, might have some trouble.