help-with-hw-design

[marsh nest]

oooh, yeah, I'd like to control brightness

If it was GPIO I could use the MCP-whatevers. Already have one of them in the controller, works well (Except I can't have both it and the radio working at the same time on the M0, but that's a different problem)

[heavy jasper]

Adafruit has a dev kit for this chip: https://www.nxp.com/docs/en/data-sheet/PCA9685.pdf

Which can both directly act as a sinking input for common-anode LEDs if the current is in an acceptable range, or drive a PWM signal out for an external switch.

[marsh nest]

ooh, yeah, I've used that one for servos before

Would still leave the battery monitoring, though.

Which is, realistically, just an ADC of some sort

[heavy jasper]

Nothing wrong with having 2 chips

[marsh nest]

Nope, not at all

Just price, but a single chip that does everything would also be pricey

[distant raven]

Yeah

[marsh nest]

So, a PCA9685. I was thinking "Hey, this could be used for motor outputs as well, would just have to adapt a motor driver as well."

Turns out, the PCA9685 is what's used on the Stepper/DC Motor Featherwing.

[distant raven]

oh cool

[marsh nest]

So it's then a matter of adapting the featherwing to break out a few more pins.

[distant raven]

that ends up being pretty convenient

[marsh nest]

The PCA9685 has 16 outputs on the breakout. I really only need two dedicated motor drivers (Since the main motors are driven through a much beefier motor driver for obvious reasons)

Still ends up being 8 pins for motors and 8 pins for lights. And then there's the MCP3021 that's a nice, small little ADC. It doesn't have a CP library, but there is an Arduino one and it's very light. I'd just have to look at it and figure out how to translate it to CP

[marsh nest]

Yeah, it really is

[distant raven]

is it i2c compatible?

i haven't looked at the MCP3021 yet to know

[marsh nest]

Yeah, the MCP3021 is i2c

It has five pins: SCL, SDA, VSS, VDD, and AIN

Comes in a few varieties depending on what address you want

[distant raven]

that should be a really easy translation then

the hardest part is defining all the registers you need and making sure the helper methods read and write properly but overall not too bad

I used Adafruit's I2C circuitpython libraries as a reference

[marsh nest]

https://github.com/pilotak/MCP3X21
MCP3X21.cpp is 58 lines.... including a 24-line license, and MCP3X21.cpp is 78 lines, with the same license.

[distant raven]

seems like an easy transition then

[marsh nest]

Hopefully, except I know next to nothing about working with i2c

I'll figure it out though

[distant raven]

that's why it's great that adafruits libraries are open source

[marsh nest]

almost the entirety of what I do know I've learned from Adafruit's open source stuff

[distant raven]

they are a really helpful reference point

[marsh nest]

"Here, let me disassemble this and figure out how it works."

[distant raven]

and the fact that they take care of i2c for you

makes it that much easier

[marsh nest]

I seem to remember reading a few minutes ago that the MCP3021 doesn't have any registers to set

[distant raven]

so it's just a matter of reading then

[marsh nest]

You just poke it and it spits out numbers.

[distant raven]

which makes that easier

[marsh nest]

yep.

[distant raven]

actually

looks like there is a circuitpython library for MCP3xxx devices

in the adafruit circuitpython bundle

[marsh nest]

looking through that, it's an SPI driver for the 3004 and 3008

and 3002

[distant raven]

oh bummer

[marsh nest]

Yeah, but it's not like this is particularly complicated

[distant raven]

yeah

[marsh nest]

$10.35 for 5 of them and 5 SOT23 breakout boards. Shipping and sales tax brings the total to $15.97 from DigiKey. Not bad for some experimentation.

[distant raven]

Not bad at all

[elder peak]

Looks like a pretty good solution for some long SOT after parts.

[marsh nest]

Hah!

[sweet inlet]

where's a good place to get a pcb design reviewed before ordering? I think everything is right, but would be nice to have someone sanity check first

or maybe should yolo 🤔

[marsh nest]

What's the worry? Most places check for board errors - That is, if there's something that would prevent it from being made - but I don't know of anywhere that would check it for, say, making sure you actually have things connected

[sweet inlet]

mostly that I miswired something, or misrated a component

but given I'm assembling it myself and using mostly standard sizes, I guess I can always swap it out

[long wraith]

You could probably find someone here who would love to do it XD

[worldly schooner]

Yeah, if you're not ordering PCBA or production quantities, just go for it. You're probably only getting low-volume to start, so if there are errors you can have it redone later.

Also cut traces and bodge wires are a thing. If you're that worried, some of the guys around here can look at schematics and give feedback. Otherwise, have some faith in your designs, because even if they're not perfect, they'll be workable for sure.

[heavy jasper]

If you’re willing to post the design files here, I can try to take a look tonight.

[inland jungle]

@marsh nest you can get ~50 SOT23 breakout boards from Amazon for ~$8 or so

[marsh nest]

Yeah, but I don't need 50 (Realistically I'll probably only need one), and having them come from the same place is far handier

[long wraith]

Bodge is life

[upper elbow]

post to reddit /r/printedcircuitboard

(and/or here)

[sweet inlet]

Design files are in the zip a few messages down.

And here's the BOM / exact components

It's a microcontroller for a fancy keyboard (https://dygma.com/) I've already built a prototype using an stm32 blackpill, this is the nice looking version.

Concerns I have:

• Using copper pours for the voltage regulator and flash, wasn't sure if that's okay.
• The oscillator's have isolated grounds that I connected to the main ground using a via and a trace. In the app notes I've seen they connect it to the pin directly, but I wasn't sure how to route that without a trace.
• With the exposed pads I mostly don't know what I'm doing, put some vias under the mcu exposed pad but not sure how many or what arrangement they should be.
• Just in general if there are cleaner ways of routing, I'd love suggestions. Especially the i2c lines and number/placement of vias.
• Oh, and via size, I tried using big ones for power, medium for everything else.

and I just realized I have the wrong foot print on the LED 😄

[sweet inlet]

Fixed the footprint and i2c line issues I found

[heavy jasper]

From the schematic side, seems reasonable off the bat; I assume the using the type-C for USB is due to the thing you're interfacing with?

(it seems like an odd choice from a cabling perspective if no; having SDA and SCL wrapped together in the twisted pair will mean there's more coupling between them and potentially additional crosstalk, plus generally having 3 identical connectors on a board that do different things is a recipe for some sadness unless you're the only one assembling/using it.

I'm not sure how much kicad will like having two nets named the same thing (+3.3V and VBAT)

I'd just wire VBAT pin on STM32 also to +3.3V

I do think VCAP on the STM32 needs a 4.7uF decoupling cap?

You have I2C1_SCL/I2C1_SDA at 5V, but then your CAT24C512 is powered off +3.3V, I think you want to power the EEPROM off +5V as well

(it doesn't have overvoltage tolerant inputs)

Design style point: I generally prefer to keep my red LEDs reserved for indicating error conditions, not always-on to indicate that power is turned on.

(I'd swap to green, white, or some other color)

I do really like your use of the no-connect indicators; that's very good practice to indicate specifically "I intend to leave this pin unused" both to me as a reviewer, and to the tool's ERC.

Haven't looked at the layout in huge detail, but especially when your layout is vaguely rotationally symmetrical, I would definitely strongly advise adding big silkscreen messages about which connector does what.

(and especially having the USB-C headers labelled as USB2/USB3 despite now being used for I2C is to my view quite confusing)

I'd refactor the designators for all those connectors to be J1/J2/J3

and then add labels for (USB, I2C, I2C)

[distant raven]

Your input is always so spot on @heavy jasper 💪🏻

I’ve learned a lot just by reading your input on other people’s designs

[heavy jasper]

I've had probably hundreds of total years of engineering experience review my work in the past (among many engineers), happy to pass it along where I can.

[distant raven]

Your heavy hitting experience makes us all better so it’s always very appreciated

I’ll probably end up coming for feedback on a 6L board design one of these days. I’m working on a cape for a beaglebone black that uses a BGA EP2 FPGA from lattice to do some heavy lifting for a networking application

[heavy jasper]

For crystals: if you're replicating an existing design and their startup code/libraries, there's more value to consistency, but apart from that unless you're specifically trying to do a low-power RTC mode, you don't need both the HSE and the LSE; I'd probably keep just the HSE.

[distant raven]

I want to get it mostly right the first time since the EP2 is $32 a pop

I also picked up a NanoVNA so I can get better at RF design

[heavy jasper]

NanoVNAs are fun

I was doing some HF antenna tuning with one recently

[distant raven]

I wish I had the monies for the V2 since it gets high enough for 2.4GHz WiFi antenna

Though somehow when I was playing with the one I got, I managed to get it to do a 2GHz sweep

Lol

No idea how exactly because it said the max range was 1.5GHz

[sweet inlet]

Thanks for catching this!!

[sweet inlet]

Yep

[sweet inlet]

Is that the only thing an lse is used for? I wasn’t sure how to tell whether it’s used or not

[sweet inlet]

I put it in because my prototype uses an stm32 blackpill which has an lse

[heavy jasper]

The LSE can also be used as the main clock of the chip

(through some PLLs to up its frequency)

so unless you've gone through the startup / clock configuration code of the blackpill to make sure it only uses the HSE, probably best to just leave both.

[sweet inlet]

Thanks again!!!

[supple pollen]

This SparkFun article on getting PCBs working points out that you should cut, hack, bodge, whatever to get the first board working, then get another one made, don't just respin when you've fixed only the first thing. https://www.sparkfun.com/tutorials/109

[distant raven]

One of these days I need to get some enamel wire to do finer bodging

Lol

[marsh nest]

There's cases where it's easier to redo the PCB (Especially when you can get them for $5), but yeah. Better to bodge and check things than get twenty revisions of PCBs

[heavy jasper]

This is also why it's a good idea to order several of your first rev of board - when you're doing manual experimental bodge reworks to fix, you can hit the point of what me and some colleagues call 'critical jank'

where any change you're attempting to make has a 50/50 chance of causing more damage to the board just through the rework process, which causes all manner of confusion

and it can be helpful to take a mini-step of "okay, these are the reworks I know I need now at a base level, let me do those as cleanly as I can to a fresh board and then start over"

[supple pollen]

I usually use wire wrapping wire for bodging, it's a nice size (30ga) and easy to strip. Enamel insulated wire can be annoying to strip without damaging it, but then again, many people tack down PCB bodge wires (nail polish and hot glue are useful for this) so they won't flex and break.

[distant raven]

Nice

I’ll give it a look

[supple pollen]

Note that solderable insulation magnet wire does exist, I use it for things like winding transformers, but it takes a fair amount of heat to convert the insulation into flux so it can be soldered, and I'm reluctant to use that much heat on PCBs. http://www.allspectrum.com/store/magnet-wire-plain-enamel-pe-solderable-class-155-14-lb-spool-30-awg-p-2675.html?osCsid=0806e80237a331d7185be8bae45106cc

[long wraith]

How many boards should you order on your first run? 3? 5? 10?

Unrelated, is it possible to order boards with serial numbers?

[distant raven]

I usually order 3

And then build up one to test against

[long wraith]

3 sounded like a good number in my head, lol

[bright thistle]

I think few fabs would offer it, and probably only for bigger batches.

Maybe you'd be better off with labels?
Perhaps with a tiny QR for authenticity purposes (I e.: encode the serial with a crypto key)

[long wraith]

Yeah, I could leave a place to stick a label. Not sure if I'll be doing anything at scale yet, not even ready for a first prototype, lol

[marsh nest]

PCBWay's minimum is 5. And while 5 and 10 are the same price, I rarely need 10 so I just stick with 5. I usually only use 2 or 3, though.

And yeah, even mass produced things have stickers for serial numbers.

[bright thistle]

Aisler fabs in the US as well and offer batches of 3 pieces like oshpark, but at a reduced cost, at least in my case.

Oshpark, ~€60
Aisler, ~€20

This only for the bare pcb, not including shipping

[marsh nest]

I use PCBWay because it's $5 for 5 pcbs, and shipping is another $20ish. And turn around time is quick too - I get them in less than a week. Bare boards, less than 100mm in any direction, but still great for prototyping or bare stuff

[bright thistle]

Fair :)

[long wraith]

When you say "5 and 10 are the same price", do you mean same price per board or total?

[marsh nest]

Total. 5 boards for $5, or 10 boards for $5.

There's restrictions on what other things you can get for that $5, but I have rarely needed any of them.

[long wraith]

Yeah, stickers are common, but I have seen them silkscreened on, seems like a lovely touch

[long wraith]

Ahh... I'd probably just get 10 then, extras can be coasters or art if not usable, lol

[bright thistle]

Silking a serial implies there's a frame for every board fabbed (plus a "common" one for all the other symbols), which really adds to the cost.

And since they'd be supposed to be used only once, it's also a waste

[marsh nest]

For me they just end up... accumulating

[bright thistle]

Unless there are methods that don't involve serigraphy?

Like laser etching, maybe?

[long wraith]

I thought they had the ability to stamp sequential numbers with a mechanical apparatus -- it's something you can do with rubber stampers on paper, I'd think the same can be done for silkscreen

[long wraith]

Lol, yeah, that sounds bad

[distant raven]

OshPark has slightly slower turn but in most cases comes out to the same. Benefits to their service is no international shipping. At least for me

I think they also have tighter tolerances on designs so I can get mask fill between 0.4mm pitch pads

I’ve done this and it works so that’s cool

[bright thistle]

Silkscreen is suitable for clone jobs, like the same drawings on multiple PCBs, or a bunch of t-shirts ;)

[long wraith]

Hmm...

[bright thistle]

Any variation you want to make, requires a dedicated screen, at least for that section

[long wraith]

Also, is this you @distant raven ? First result Googling "oshpark serial numbers", lol

[distant raven]

Lol weird hahaha

Yes that’s me hahaha

[long wraith]

Nice XD

[distant raven]

My journey started rough hahahaha

[bright thistle]

A compromise would be for you to prepare a writable area like this

And then rubber stamp the serial yourself

[long wraith]

Yeah, I could hand write them too XD personal touch

[bright thistle]

For small batches and if you have a good handwriting, sure

[long wraith]

Lol

[bright thistle]

In my case, I'd create some confusion
An example, my G looks like the logo from Inspector Gadget movie, and gets mistaken as a 4

[long wraith]

Lol, I didn't even know that was supposed to be a 4 as well as a G

Wait no brain fart

But I can kinda see a 4 since you mentioned it

[bright thistle]

See what I mean?

[long wraith]

Yeah

[bright thistle]

Also, you'd risk to lose track.
Just dedicate a serial stamp to that board, and leave it set to the last one you punched

Or keep a record somewhere if you want to reuse it for other projects

[long wraith]

Gotta have records XD actually, I could have a batch number and serial number, then if I'm doing batches of like 100 it could be batch X, sn 0-100

[long wraith]

Lol

[supple pollen]

I'll usually put a white area of silkscreen where I can write a serial number.

[bright thistle]

Or: how to use a smaller stamp twice instead of looking for a wider one :D

[long wraith]

Numbahs!

[bright thistle]

1up: go hex, auction DEADBEEF 😂

[long wraith]

lol

[bright thistle]

Or any other 1337 serials 😂

[long wraith]

Start with serial 1300 to be sure I get that, lol

[worldly schooner]

The fab houses I go to don’t even use stamps for some of our boards; when we up rev older pcbs with newer components, the fab house just sticks a label on for us, and it holds really nicely.

[long wraith]

Oh, if I can get serial stickers, that'd be swell!

I don't really care how it's on there, just want it there

[worldly schooner]

I can’t imagine that being too hard, nowadays label makers can print labels on the fly…

[long wraith]

Affixing them to the boards is the "hard" part

[worldly schooner]

Is it though?

[long wraith]

Yes, it's "harder" than printing them, lol

[worldly schooner]

Just lightly clean the area with alcohol before applying

It’s a bit more time consuming to do it yourself

But compared to handwriting… lel

[long wraith]

Yeah, not saying it's hard, lol

Bbl shower and haircut!

[bright thistle]

Aren't boards washed before shipping?
If so, just apply the label first thing they arrive

Or drop them in the dishwasher with liquid detergent 😜

[worldly schooner]

I personally don’t like to assume that everyone handles pcbs with latex gloves. Alcohol is just really easy to use if you have it on hand, you just dip a q tip and clean the application area…

You don’t need the whole board sanitized for a label haha

[bright thistle]

brushie brushie brushie

[worldly schooner]

If your application area is near the center of the board, less likely to have been touched. If you just stuck your serial in an empty corner like most people, an isopropyl or isopropanol dipped qtip goes a long way

[bright thistle]

wonders if you could dip a rubber stamp in some correction fluid instead of regular ink

[heavy jasper]

Laser etching is also done, as mentioned above. Generally the setup is a patch of soldermask above either copper or bare PCB, and then the soldermask is etched to reveal the copper/fiberglass underneath. From my experience this is more commonly done for machine-readable QR-type codes. (since by the time you're setting up laser-etching... you already have barcode scanners).

[sweet inlet]

you can get a laser etcher for pretty cheap nowadays

[kind pecan]

question (ping me if you reply cos i have the server muted), is it possibly to have the entire outer edge of a pcb be plated? it's not for electrical reasons, it's for use as a panel and the aesthetic would be cool and also fully lock in the fr4 with metal so no chance of tiny splinters

[tough matrix]

anyone has a favorite constant-current LED driver IC you could recommend?
I need 8 channels (each up to 20mA current), and I do not even need individual control - being able to turn them all on/off together is good enough.

Of course, I can search on Digikey, but it gives so many hits that I do not know where to start

[distant raven]

I have one, I don’t think it’s 8 channel but I think it’s rated for 500mA drive

[heavy jasper]

@kind pecan Yes, it’s possible, but it’ll be extra $$ and generally something you’ll need to ask your fab house for specifically. Sometimes with the web-based fabs, edge plating will be a listed as an option in the huge list of options.

[supple pollen]

Which one? 500mA is useful for my application (I only need a few channels) but I would want variable drive.

[distant raven]

Opp sorry it’s 350mA

AL5801W6-7

Comes in a sot26 package

https://www.digikey.com/product-detail/en/AL5801W6Q-7/AL5801W6Q-7DICT-ND/5223231

[kind pecan]

ah ok thanks

[supple pollen]

350mA may be plenty (I'm looking to illuminate some indicators in a costume and I want them to be visible in sunlight), thanks for the pointer!

[distant raven]

🙂

[marsh nest]

OK KiCad users. I managed to hit a key and.... now things are funky. In PCBNew, usually it'd change what layer was viewed depending on the selection in the right-hand panel. If it were, say, F.Cu, it'd show all the red stuff and everything else would be behind it.

Now it's showing all the layers with varying layers of transparency. Which is fine, I might even prefer it this way, except

I can't select anything. Or move it, for that matter. I previously was able to, say, click a footprint and drag it around. Now I can't do that at all. Nothing highlights when I click it, and the "Clarify selection" dialog rarely appears - and when it does, whatever I select isn't highlighted.

any clues as to how to reverse this?

Hm

It would appear that I had somehow switched to the legacy toolset

[tough matrix]

@distant raventhanks, but I do need to power 8 LEDs and would like to avoid using 8 ICs. I coudl connect the LEDs in series, but since supply voltage is 5V, I can't connect more than 2 in series.

[distant raven]

Makes sense

[distant raven]

There are these ones: I found this part with the Digi-Key mobile app. https://www.digikey.com/product-detail/en/A8508GLPTR-T/620-1679-1-ND/5014045

Obsolete but they have a few thousand so you could snatch some up before they’re gone

[bright thistle]

Doubt.
Is it legit to sip power straight from USB, without any id resistor, considering I'll be drawing relatively little current?

[marsh nest]

You can but some devices (Battery packs, especially) will cut off power after a short period if there's no ID detected and/or there's no significant current detected

[bright thistle]

Nah, it'll powered by the Pi port, or a branched cable to a wall wart, no batteries involved :)

[long wraith]

Should be good then

[bright thistle]

Uh. Making comparison between components shops, digikey had me fill an US purpose declaration, while mouser didn't, for the same articles

Albeit both ship from US

(also, I thought such big shops would have at least an EU depot?)

[long wraith]

I'd have thought so too

[worldly schooner]

They might, but stock varies between warehouses, so most components from a US-based distributor will still ship from its US warehouses.

I don't recall ever seeing Digikey or Mouser list where they stock parts, so it might all ship from the US. I do know bigger distributors like Avnet and Arrow have separate stocks by region, though.

[bright thistle]

In other news, my PCBs are delayed, but not for a lack of silicon, rather for a lack of 0.1" 3pin headers

[distant raven]

Awwww yissss I got some PCB in the mail! 🙂

[rustic linden]

I usually get mine in bulk and cut them to size

[supple pollen]

I wanted some odd-size sockets and found DigiKey is willing to cut them down for me, the order still shipped fast, it didn't cost much, and the sockets looked really nice with smooth ends, unlike the ones I had chopped off myself previously.

[heavy jasper]

Digikey value-add services are pretty great. They also sell a bunch of pre-crimped wires from various connector families, which is really handy when you need to build a harness but don’t want to buy the $$$ correct crimper or mess with generic crimpers (which can be of very dubious crimp quality).

[bright thistle]

Good to know, I'll be needing some Molex SL cables :)

Wonder if they make SL-to-dupont as well 🤔

[elder peak]

Yeah but they don't sell the crimped connectors that I want. 😦

[forest tiger]

Whats the best way of telling kicad/fab house that i don't care about NPTH holes overlapping?

[unreal flax]

It's possible that the fab house would care even if you don't, since the drill bit might react weirdly to the adjacent hole.

[forest tiger]

I thought that was more if it was less than a radius away from the other hole.

[forest tiger]

I'll turn it into a slot with board outline.

[bright thistle]

d'oh, they don't make SL cables at all :/

oh, they do.
they're filed under "positive lock $numbers" 🤦‍♂️

[bright thistle]

great, nobody seems to be stocking Molex 1719760104 :/

[elder peak]

Would you say that you need a hookup hookup?

[bright thistle]

ಠ_ಠ

[bright thistle]

If it doesn't return available in a decent time, guess I'll go with the version with mounting pegs/studs and file them if needed

[tough matrix]

quick question about boost converters
I am looking at constant current LED driver/boost converter, CAT4238: https://datasheet.lcsc.com/lcsc/1809272038_ON-Semiconductor-CAT4238TD-GT3_C145527.pdf
(BTW, if anyone can comment on whether it is a good choice to drive 8 IR LEDs in series, I'd appreciate it).
The schematics in the datasheet calls for 0.22uF capacitor on output:

Am I correct that I can replace it by 1uF cap?

[distant raven]

It looks like 10 on that design

So probably within reason to run 8

[unreal flax]

Yeah, I expect the reference value would be a minimum, but it should be fine to increase the capacitance.

[distant raven]

And @unreal flax is right, it probably wouldn’t hurt to have more

[tough matrix]

I thought so but wanted to double-check

thanks!

[distant raven]

Just not too much more because the value the picked is probably based on transients of that particular circuit

0.47uF-1uF is definitely within reason

[tough matrix]

I am using 1uF elsewhere in the design and wanted to minimize the number of different components

[distant raven]

Sure, it should be fine and probably won’t have a huge affect on performance

[forest tiger]

i2c doesn't really ever pass 8Mhz yes?

[distant raven]

3.4MHz is the fastest it goes I believe

[unreal flax]

Yeah. The passive pull-ups generally limit the bus speed to below that of actively-driven things like SPI.

400kHz is considered "fast mode".

[elder peak]

@tough matrix Do pay attention to the PWM rate tho

So, if you are using it as an IR illuminator, cool, bt if you were using for communication it'll be not so helpful

[tough matrix]

no, the IR led is part of reflectance sensor, and it is not modulated, so PWM is not an issue

[bright thistle]

uh... is it ok to talk (not requesting support) about sparkfun stuff, or would I risk summary justice?

[ornate glen]

https://tenor.com/view/of-to-gulag-gif-19230867

[bright thistle]

oh look, it's Peppone!

[tough matrix]

@bright thistle sure you can talk about sparkfun products here - or products of any other company

[long wraith]

Adafruit is open to all!

[bright thistle]

@tough matrix @long wraith you never know, I've seen communities whose fanatism was... Nope. 😅

Well, I've received this capacitive buttons and they really are smol :3

(only reason I got them from SF is because of the SMD pads for the connector, I want them flush behind a perspex panel)

[distant raven]

Neat

[bright thistle]

Got five of them: ⏪⏯️⏩🔀🔁

And that's why I was looking for SL SMD connectors, but at this point I might just go with kk254

[distant raven]

I love the microchip capacitive touch chips

I made a breakout for the 7 channel one

[bright thistle]

cute :3

[distant raven]

On the topic of NeoPixel

I was reading that the application schematic in the data sheet for the ws2812 and sk6812 chips is assuming you’re making strip lighting which is the usual application

This is because the strip PCB used in led strip lighting has poor capacitance, so they add 0.1uF caps to help increase capacitance on the power paths

On regular PCB it isn’t as necessary, especially using ground and power pours. So you can just throw a larger bull capacitance in the Vdd and VSS pins

[bright thistle]

good to know 🙂

now I'm thinking of using a NePx ring for displaying a track's moodbar, thank you! XD

[bright thistle]

aaaand, it appears to be a hard mess to attempt to do it, welp, nevermind 😛

[bright thistle]

prepping a v2 of my board, swapped SOT223 to TO252-2 so to take advantage of that sweet sweet copper pour in the back

and switched from SL connectors to KK254 (easier to source)

[long wraith]

Lol, yeah

[dreamy saffron]

Got a weird power issue. I have a PCB with an RP2040 on it. When I power it by USB, everything works as expected. I've got a second board with another MCU. If I power it via USB, works as expected

The two connect via a 20 pin connector that shares a number of buttons, as well as power and GND. If I hook up the non-rp board to USB with the two plugged together, it bricks.

If they're both attached to USB at the same time, everything works fine.

Any clue what I might have done? Could the draw from the rp2040 board cause issues?

[distant raven]

Do you have a picture of your setup @dreamy saffron ?

🧐

[dreamy saffron]

... did my reply actually do anything there or is discord just angry at me? haha

[distant raven]

Probably used terms or phrasing that the moderation bot didn’t like

[dreamy saffron]

of course I did. here we go again:

short version, there are a bunch of buttons there that are routed to both pins on the Pico and pins on a 20pin header. the 20pin header also has vcc/gnd. it attaches to this guy: https://www.brookaccessory.com/detail/53169470/

if I hook up all 18 pins other than the two vccs, it the other board works great. receives the key presses and all. if I hook up usb to both, they both receive the key presses and all of that.

if I hook up vcc and only have the zero pi board plugged in, it immediately disconnects. both still show voltage, roughly same current, yada yada. but they're very sad.

[distant raven]

Hmmm that is strange

Can you show me your physical setup?

[dreamy saffron]

I think I actually just figured it out. skerr, you get 300% of the credit for being the best rubber duck of all time.

short version, you hold a few buttons to put the brook board into dfu mode to flash it. I finally had the thought to see what windows says when it goes away, and it was still showing up, just not as a game controller any more. even verified the flash software could see it. after forcing it to restart (without unplugging anything), works like a champ. so off to figure out why the dumb thing thinks buttons are being pressed.

[distant raven]

Haha good deal

[crystal lava]

Hi sorry if this is not the correct place to ask. On the adafruit feather 32u4 le is it possible to connect a battery to the BAT and Gnd pins for charging instead of the connector? I want to take the connector of the board and relocate it on my pcb for compactness. I checked with a multimeter and these pins are connected to the battery header.

[silk lark]

yes

that's exactly what the bat pin is for

[bright thistle]

if it looks like a duck, smells like a duck, HONKs like a duck, make an impression of Al Bano like a duck, ducks like a duck...

[silk lark]

are you going with this somewhere?

[long wraith]

it is a duck

[distant raven]

I was going to say a bread convention

[long wraith]

Lol

[tough matrix]

If we have bat pins, we should have duck pins, too

[distant raven]

Lol

[distant raven]

I thought this channel was deleted 😳

Then realized it was renamed lol

[long wraith]

It was? o.o

[distant raven]

It was #pcb-design and now it’s #help-with-hw-design

[long wraith]

Oh, I didn't notice XD

Oh, @distant raven , is your Bread board open source?

[distant raven]

It will be

I try to open source most of my designs

[marsh nest]

Open source is great

[rustic linden]

I should do more PCB designs, I have the drive for it rn

[mystic crypt]

I have a project, you have the drive... Wanna team up? lol

[rustic linden]

I mean, depends on the project, but... not entirely opposed

[mystic crypt]

I guess the fewest component project is a simple picoammeter

A trasimpediance op amp and a gain op amp

Or making a sigma Delta picoammeter with IVC102 (small current integrator), a monostable oscillator, and an atmega328pb

[sweet inlet]

Heyo!

[rustic linden]

Howdy

[hot otter]

@velvet patio so if i were to wire up IRLZ44N to the LED and sensor, would this be correct?

based off this

or this but i can only get these to work with 2 power supplies

i think that may just be a software fault

as is G is getting power from sensor, D is connected to ground on all lights, VCC is directly into LED input

[unborn basin]

does anyone know if there's a pcb drawing for this?
https://www.adafruit.com/product/4892

[supple pollen]

The data sheet gives the footprint

[unborn basin]

thanks

[vapid grove]

What is that led part number btw?

[distant raven]

Sk6812-EC3210F

[warped atlas]

y'all have any good resources for learning pcb design? All the online tutorials I can find don't go into much detail

More specifically: I know how to make basic schematics & make a basic 2-layer layout, but things like BOMs or getting my design pick&placed are pretty foreign to me

[supple pollen]

SparkFun has a nice series of Eagle tutorials that includes some design for manufacturing ones: https://learn.sparkfun.com/tutorials/tags/eagle?sort_by=title

[warped atlas]

this is perfect, thanks!

[smoky mica]

for using a USB-C 3.0 plug with the 2.0 standard, what should I do with all the extra pins?

Should I leave them unconnected or connect them to ground

[cerulean crest]

Everything but all grounds, VBUS, D+, D-, CC1, CC2 should be left unconnected

[smoky mica]

ty

the shell should be grounded too right

[cerulean crest]

Yes the shield should be grounded

[bright thistle]

Amphenol appears to have 2.0 type C connectors

[distant raven]

I use 2.0 type C connectors

I read that you either leave 3.0 pins unconnected or tied to ground

[supple pollen]

The shield is normally grounded through a static discharge network, but you can often get away with connecting it directly to ground.

[smoky mica]

So what ended up happening was that the cheapest type c connector with just 2.0 data pins was unavailable, but the next one with the 3.0 pins was available and a few cents extra

[sweet inlet]

Going to be a fun weekend! First time doing this, any tips?

[heavy jasper]

Are you hand-soldering or doing paste?

[sweet inlet]

Paste

I need to taste it to make sure it’s fresh right?

[heavy jasper]

That's between you and your local ER

[sweet inlet]

Mostly I’m worried that I breath wrong and send components flying

[heavy jasper]

Main advice: stock up on some thin solder wick and a tube of flux

It's easy to over-paste on first boards and bridge contacts

[sweet inlet]

😮

[heavy jasper]

and trying to pull the solder off without wick (or w/o flux) is kind of miserable

[sweet inlet]

I got wick and flux!

My soldering iron is crap, I can just reheat on a plate to reflow right?

[heavy jasper]

should work ok

[sweet inlet]

Thank you!!

[heavy jasper]

and if you have to do any rework with the wick: wick and iron should come off together, not the iron first then the wick

Odds of pad-delaminating go up when they're not all plated through holes

[rain solstice]

Hello everyone. I have a project, where I have LiPo with charger and power switching. My main project project components, in total, are consuming as low as 0.5uA in sleep mode. I just want to make sure that the LiPo Charging and the Switcher units are not consuming and current.

While reading the datasheet of MCP73831 (https://ww1.microchip.com/downloads/en/DeviceDoc/MCP73831-Family-Data-Sheet-DS20001984H.pdf), I found this section:

I was wondering when The usb is not plugged in, does the battery charger and the switcher units combined, drains very very tiny amount of current from the battery? How to prevent that in that case?

[heavy jasper]

The lipo charger looks like it will draw ~2uA, and the switching circuit draws (leakage of cap, probably quite low) + (leakage through schottky diode, which at most is ~250nA at 25C given the possible reverse voltage)

[rain solstice]

@heavy jasper if VDD is floating...

[heavy jasper]

VDD?

oh, of the charger

So, yes, in the unplugged state

If you need to cut that 2uA, you should probably just switch to a different battery charger with a smaller leakage spec

e.g. the STBC15 seems to spec <250nA when the input power source is removed

and 10nA in a dedicated "shelf mode"

[rain solstice]

Thank you, Let me have a look

[heavy jasper]

I have no experience with the STBC15 in particular, it's just what popped up when I googled "ultra low leakage battery charger"

[rain solstice]

This does look promising but the charging current is super low, 40mA). Where as, in MCP, the lowest is 100mA . My battery src is of capacity 120 mAh.

[heavy jasper]

This is now essentially just a shopping exercise.

Hopefully they spec discharge current as a parameter on digikey.

[rain solstice]

🤓

[rain solstice]

Also found this: https://www.ti.com/lit/ds/symlink/bq25306.pdf?ts=1630046006438&ref_url=https%253A%252F%252Fwww.mouser.com%252F

[bright thistle]

I don't have a soldering iron yet, let alone spare tips for SMD 😂

[sweet inlet]

lolol

[bright thistle]

PCB looks cool, tho, good job and good luck with soldering! 👍

[sweet inlet]

thanks!

[fervent lance]

Is PCB trace length matching required for routing SPI and I2C signals?

[tough matrix]

for i2c it is certainly not necessary

[unreal flax]

As a rule of thumb, the speed of light is about 1 foot per nanosecond, so compare that to your bus clock rate to determine what timing shifts you care about.

[crystal lava]

My feather 32u4 le now has a solid red light and is not functional after attempting to connect a battery. Anyone know what this means? Is the board dead?

[smoky mica]

so, circling back on that: could I get away with no ESD protection on USB-C?

Assuming I can't,

whats the simplest way I could get ESD protection on a simple USB-C port

[silk lark]

@smoky mica in what context? are you trying to get CE/FCC certification?

I think usually you just add two zener diodes on the data lines

the datasheet should have an example

[supple pollen]

It depends on what code the board is running. For some boards, red means "USB enumeration failed", which could be the case if you're running it from a battery.

[twilit aurora]

ESD Protection is optional. It will work without, but I would recommend including it. There are ics doing that job, I recommend TPD2EUSB30 for USB 2 / two data line D+ and D- and TPD4EUSB30 for SSRX+- and SSTX+- of USB 3. If you do not have equipment for SMD soldering or you are not creating a custom pcb, then don't waste too much time on that.

[twilit aurora]

You need one diode from gnd to data, one diode from data to either VCC or leave it floating and you need a combined zener diode between gnd and VCC/floating for all data lines. I do not recommend using discrete components. Use ics - there is a reason why they exist

[thick willow]

I'm having trouble with using a second pcb on a circuitmaker project. when i build gerber second board doesnt appear. Im also not sure how to tell the pcb from what schematic file to import components

[heavy jasper]

I don’t think that circuitmaker does multi-PCB projects, that’s a big-AD feature. If you need multiple PCBs, you should just make separate projects.

[thick willow]

it does support having multiple PCBs though on a single project...

but maybe unintendedly?

I guess I'll just separate it...

[heavy jasper]

You can have multiple boards in a project, but in both cases it assumes all schematic files are intended for both boards (e.g. 2 different form-factors of the same design). And I'm not sure how well the Circuitmaker-specific implementations of manufacturing output tools handle having 2 boards there. (big-AD lets you choose which PCB you want to generate the outputs from, not sure if circuitmaker does the same)

[thick willow]

Yeh I notice that it assumed that... I neded loading that pcb into a differnt project by loading the cached file.... at this point I'm starting to get a bit disappointed of circuitmaker, some features are nice but it has some serious inconveniences... I guess I'll give fusion 360 a try (if I manage to get the startup version of it)

[thick willow]

Thanks for the help harry

[heavy jasper]

I think that restriction is going to be the same across most CAD tools.

[distant raven]

I believe you are right

I’m Eagle/fusion360 you can only have one schematic and associated board file open at any given time

I have projects with multiple schematics/board files and have never been able to use more than one at a time

[feral night]

Hi, I'm looking for a pcb for an ortholinear keyboard. But I want each key to send it's unique code like with the pico keypad (1, 2, 4, 8 for the first row, 16,32,64,128 for the second row). It's really hard to find, because i'm probably using the wrong search terms. I only get premade keyboards. I have about 50 rgb mx rgb switches. I'll probably order some more though. But the pcb should have a place for smd rgb leds. I have no clue about designing one, but if someone knows a place and software to get started, that would be great. It's going to be part of my multi sensor keyboard 😄 So i might use a raspberry pico or something similar to control everything.

[silk lark]

I don't think the code you send for each key depends on the PCB

[supple pollen]

This might be a start, has keys set up as a (row/column) matrix and NeoPixels for lighting: they can be snapped apart and combined for various shapes, and the code that controls it would control what codes the keys send. https://www.adafruit.com/product/5157

[feral night]

That's a really good start indeed. But it's a grid layout and as far as I know this can't register some buttons pressed at once (0,0) + (0,1) + (1,0) will give some problems I think.
That's what I liked about the pimoroni rgb keypad. It returns a sum of all buttons pressed. Like the first three buttons will be 7 (1 +2+4) or the first and the fourth 9 (1 + 8) and so on. I guess I'll need some kind of chip for the logic. Or connect the keys trough i2c somehow.

https://www.adafruit.com/product/4980

[supple pollen]

Yes, for multiple key detection, it would need isolation diodes. What it returns is more a matter of software than the key circuitry.

Ah, those boards do have isolation diodes, and can correctly register multiple keys pressed at once.

[feral night]

Mental note to self: isolation diodes. (I have no clue how they work yet lol)

My guess would be that you limit the current (hope it is the right term) for different keys differently and calculate based on that what was pressed

resistance maybe.

[supple pollen]

Diodes allow electricity to flow one way, but not the other. This is used in matrix keyboards to avoid "sneak paths" where the power flows through a series of closed switches to produce a misleading reading.

[feral night]

Do the diodes work as a resistor too?

[supple pollen]

Ah, you're thinking of an analog keyboard. While those exist, they normally are only used for a few keys. For larger numbers of keys, resistance encoding is problematic.

[feral night]

Problemetic idea = now scrapped

[silk lark]

if you google for "keyboard matrix", there are some articles that explain it in detail, with images

http://blog.komar.be/how-to-make-a-keyboard-the-matrix/

for example this

[feral night]

Yeah, I've read some examples, but I have some gaps in knowledge that make them hard to understand. But all matrix keyboards have a rollover I believe. I want all buttons to be able to be registered at once.

[silk lark]

that's not true, if there is a diode on every switch, there is no rollover

[feral night]

Or in several usb hid reports, since you can only send 6 keys + modifiers I think

[worldly schooner]

The rollover is defined by limitations in the USB communication protocol these days, not the matrix format.

[silk lark]

there may be rollover introduced by the default USB HID protocol, but there are also ways around that

circuitpython now supports NKRO keyboards, by using a bitmap HID device

[worldly schooner]

Matrix keyboards are the standard setup for pretty much all top-shelf mechanical keyboards on the consumer market today.

As well as all of the lower-end ones LOL

[feral night]

I know matrix is the standard. That's why I want to build my non standard one 🙂 The article @silk lark sent mentioned what I want is NKRO. It also provides an example I don't understand yet haha.

[silk lark]

this is what I did for my keyboard to get NKRO working: https://hackaday.io/project/174095-dorsch-40k-keyboard/log/195783-shiny-new-code

[supple pollen]

There are several non-standard approaches. You can have a signal for each key, you can use resistance encoding, you can use self-encoded keys (several methods), you can use physical mapping (several methods), and probably a few I haven't thought of.

[feral night]

@silk lark that keyboard makes me drool

I hope it's waterproof

[silk lark]

thanks

[feral night]

I think I'll have to wire up each key to a gpio expander in a worst case scenario lmao. That's gonna be a lot of wires.

[silk lark]

there is nothing wrong in using a matrix and scanning it

as long as you have the diodes, you can press as many keys at once as you want

it's then a question of the software to encode it to correct USB reports

[worldly schooner]

Be careful with GPIO expanders, they can hurt your poll rate quite a bit.

[silk lark]

out of curiosity, what are you building? a chording keyboard? a stenotype? a piano?

[feral night]

The article http://blog.komar.be/how-to-make-a-keyboard-the-matrix/ mentions "the ultimate solution". But if i read that schematic, I can't see how to differentiate between r1 and r2 in the first column if they're both being held.

[worldly schooner]

What size keyboard are you trying to build? Do you already have an MCU?

[supple pollen]

That's the "signal for each key" method I referred to.

[worldly schooner]

Oh.

[silk lark]

@feral night you only enable one column at a time, and then read the rows, and then switch to the next column, and read the rows, etc.

[feral night]

I'm trying to build ... the ultimate keyboard. No, just for fun, because I can keyboard. With temperature sensors, mems sensor, joysticks, touch pads, rotary encoders. I want to create a monster.

[silk lark]

the remaining columns are disconnected, floating (the pins are switched to inputs)

[supple pollen]

It sounds like you're trying to build the ultimate keyboard, but not using a usual approach. This is completely valid, but can be frustrating but you'll end up learning a lot.

[feral night]

Now the term "scanning" makes total sense!

[silk lark]

doesn't it?

[feral night]

I get it now, this helped enourmously!

[silk lark]

CircuitPython has now a built-in module keypad that does the scanning for you in the background

you just tell it which pins are rows and which are columns, and it gives you key-up and key-down events

so that part became much easier

[feral night]

@supple pollen It's for fun and learning indeed. And then I'll pick some useful stuff to make a real application for some funny thing I came up with.

[silk lark]

building an ultimate keyboard can be very frustrating and expensive experience, I highly recommend starting with a small macropad first, to learn the ropes

[worldly schooner]

Ahhh, gotcha. So you're going to need a lot of inputs... I don't think the typical budget MCUs are going to cut it, you'll probably need some heft to handle it all.

[silk lark]

stuff like https://hackaday.io/project/175326-keeblet

[feral night]

Good to know, about the keypad module. But I think I'll write my own one which will also keep track of other stats like "last_pressed" and "release_time". It would be a waste of resources to loop trough everything twice.

@worldly schooner hem I don't mind if I end up having to use a gaming PC to handle all inputs. I'm starting small, but in the end I might even add facial recognition lmao.

[silk lark]

the keyboard switches are expensive, and smaller PCBs are also cheaper...

[feral night]

So being able to expand on it is fun.

[worldly schooner]

No, not the PC, the microcontroller that controls the keyboard. You're going to need an MCU on the keyboard itself to translate your keys to USB data.

[feral night]

I have 50 cherry mx rgb compatible brown switches laying around now.

[silk lark]

a regular keyboard has 101 keys

a tenkeyless has 60-70

you could go for 40%

[feral night]

I think 101 will be overkill as I'll be using sensors to switch modes and stuff.

And other inputs. I think 40 will be the minimum and 50 adds some nice flexibility.

[silk lark]

are you going to use stabilizers, or are all keys going to be 1U?

[worldly schooner]

Standard TKL goes up to 87 keys for the most traditional typing numpad-less experience

Usually varies between 70-87 keys?

60% keyboards are popular amongst mechanical keyboard enthusiasts though

[silk lark]

by the way, I like to use http://www.keyboard-layout-editor.com/ to plan my keyboard layout, it's pretty convenient

[feral night]

Forget about standard 😛 I think I'll use a touchpad for numeric keys. Or some other input.

[silk lark]

something like JD40 in the presets there could work for you, but it requires stabilizers

Planck is another popular 40% layout, and it only needs a stabilizer on the space, but it's orthonormal

and you can go full ergonomic with something like the Atreus

[feral night]

I don't think I'll use stabalizers.

And I'll probably make the case from wood myself.

[silk lark]

a version of Atreus with double keys in the middle (instead of the longer keys there) won't require stabilizers at all

https://cdn.shopify.com/s/files/1/0920/0728/files/P1010289-Edit_720x.jpg?v=1609980474

like this

[feral night]

I'll create a grid, so I can always change the location of the spacebar if I want to. And I'll second that a spacebar doesn't have to be bigger indeed. If I look at the wear and tear at my Keyboard, the spacebars wear is like 1 key wide on two places

Anyway, thanks for all the advice. I think I might go with scanning indeed, since the usb protocol doesn't allow for an lot of keys at once anyway (unless you register it as two keyboards etc.) It will be a 4x12 grid with a row of elevated touch buttons on top.

[silk lark]

oh, by the way, you don't necessarily need a pcb

https://cdn.hackaday.io/images/8888401450821121594.jpg

this is the first keyboard I made from scratch

the case is laser-cut, generated with http://builder.swillkb.com/

[feral night]

Oh, nice, the main reason I want a pcb is to hold the rgb smd leds in place.

Otherwise manual soldering would be fine.

glue comes to mind now.

I gotta go. A family member needs medical attention xD i'll be back

[royal cypress]

@feral night It looks like you picked up some good knowledge in this conversation, but here's a video that I really liked for demonstrating how isolation diodes allow for more detected key presses. Ben Eater is doing a whole series on USB protocol and keyboards. It's deeper knowledge than you'll need with modern microcontrollers and keyboard libraries, but sometimes it helps to have a fuzzy but deep understanding of a topic. https://www.youtube.com/watch?v=2lPzTU-3ONI

[feral night]

Thanks, the diodes make even more sense now. Also interesting at the end how he explained the usage pages. It gives me a good idea how I can send the data for nkro. Kind of how I imagined it how the keys would be added to one bit. I remember watching one of his videos thinking: here I am watching a video from some dude explaining how the usb protocol works... what would other people do if they can't sleep.

[royal cypress]

Haha I love his videos. They wouldn't help me sleep, as gentle as his speaking voice is, though! Too much information to try and not pay attention to.

[hushed lily]

Those videos always put me to sleep. I have to watch a few times. It’s the only way I can get to sleep now.

[sweet inlet]

like a good steak

I forgot to take my chipquik out of the fridge

can I just blow on it with a warm breath to heat it up?

or should I wait for tomorrow

[worldly schooner]

I’d wait until tomorrow if it’s not urgent

But if you really must, take a fresh ziploc bag, seal it in well with most of the air removed, and submerge in a bath of warm water

Be careful not to let the syringe poke a hole in the bag though

[sweet inlet]

completely unopened, fresh, tasty, newage, shiny chipquik

[long wraith]

Please do not consume the ChipQuik.

[rustic linden]

What's ChipQuik?

[tough matrix]

a brand of solder paste

[rustic linden]

huh

[long wraith]

Not edible solder paste

[worldly schooner]

They are best known for solder paste and solder removal

So most people who deal with PCB reworking regularly will at least know of the name

https://www.chipquik.com/store/index.php?cPath=400&osCsid=9cckmdpcas9d8nc2ojb09r93f1

[tough matrix]

is there any other kind?

if so, I'd like to get some!!!

[long wraith]

Saying ChipQuik is "tasty" would indicate someone thinks there's edible versions XD

[tough matrix]

"all mushrooms can be eaten, but some, only once in your life"

[bright thistle]

Sounds like a digestive version of
"Speed alone doesn't kill. Getting suddenly stationary, now that's what gets you."

[long wraith]

Or "falling from great heights won't kill you. It's the sudden stop at the end that gets you."

[long wraith]

?

[cerulean crest]

Well, there are cases where you can die before you hit the ground if you go high enough, I would much prefer that. Lack of oxygen and our bodies are weird flimsy things. However there are multiple cases through history where people have survived falling out of an airplane so I guess if you like lottery numbers you'll love falling

[long wraith]

Ah XD Yeah, always fringe cases

[brisk hearth]

No, cringe cases

XD

[sweet inlet]

so I'm trying to solder 0402 smd capacitors for the first time

I can't tell what's the top and what's the bottom

[unreal flax]

They don't really have a top and bottom. No markings, and the shape should be symmetric.

[sweet inlet]

do they have sides?

[unreal flax]

Yes, they will be flatter in one dimensions and wider in another.

Usually, anyway. Depending on the thickness, some might actually be square-shaped in cross-section.

[sweet inlet]

this reminds me why I switched from electrical engineering to software 😄

I am just a mere mortal

thank you!

[unreal flax]

Actually, I see some that are even thicker than they are wide. Guess that's a compromise to get high capacitance in the same 0402 footprint.

[sweet inlet]

I feel like I'm counting grains of sand

😄

[unreal flax]

I feel ya. 0603 is my personal sweet spot.

[heavy jasper]

0402 is around where steady magnification (e.g. a microscope) becomes super, super useful.

It’s totally possible to do it without, but after your hand-eye coordination retrains to working under magnification 0402s become pretty straightforward.

[hushed lily]

Any recommendations for USB microscopes? Everything I’ve seen comes with mixed reviews so it’s not super clear.

[heavy jasper]

I've used one that looks a lot like this: https://www.amazon.com/Microscope-Magnification-Handheld-Inspection-Endoscope/dp/B08D73XS81/ref=sr_1_28?dchild=1&keywords=USB+microscope&qid=1630651983&s=electronics&sr=1-28 and it's okay for taking photos of static boards e.g. for documentation.

I have not used any USB microscope with low enough latency to make it workable for tasks requiring hand-eye coordination.

[hushed lily]

I've got one of those ring light magnifying glasses that works for that. TY for the recommendation.

[ember laurel]

I've got the Andonstar AD407

it's pretty alright

very sharp

https://www.amazon.com/Andonstar-Microscope-Adjustable-Repairing-Soldering/dp/B07VK52X9C

I like that it includes the display

[distant raven]

I’m doing 0201 on a design I’m starting. By hand prototype will be hard 😳

[tough matrix]

That's brave

[long wraith]

Or is it crazy?

[silk lark]

should be fine as long as you don't sneeze

[long wraith]

lol

[dreamy saffron]

had a board get rejected for fab and I could use some brain power on how to fix it.

short version, I have an rp2040 using the kicad lib provided with the official example board. the spacing between the pads is 0.2mm. the fab house needs that to be 0.22mm or for me to not have solder mask between the pads. that second one seems uh, bad, but I can't understand how i can tell kicad to increase the space between the pads. or if that's even possible, since that means shrinking the pads right?

[silk lark]

use a different fab

that's the easiest solution

you can also tell kicad what the "margin" should be around the pads without the solder mask — if you make that overlap, there won't be solder mask between pads

[supple pollen]

Or just accept not having soldermask ("copper defined pads")

[warped atlas]

Honestly, I always found 0201 hand-soldering to be therapeutic. If you're not under a time crunch & losing a resistor or two isn't catastrophic, it's nice to just listen to music and solder SMDs.

[sweet inlet]

can I rework smd components without hot air? I used the hot plate method to get it on, but used too much solder

I got an iron and a wick

this doesn't look photoshopped at all

[hushed lily]

not an expert, but whatever you can do to get heat where you want it and not where you don't should be fine. i think hot air is attractive because you can heat multiple pins simultaneously and also get under components you wouldn't be able to with an iron.

[sweet inlet]

I got a hot plate, so I could rewarm the whole thing too, mostly I made a ton of bridges on my stm32 qfn mcu

[forest tiger]

I'm looking for constructive criticism on my layout/routing. If anyone has the time to check out my kicad project: https://github.com/frakturedev/Yokai

[silk lark]

@forest tiger I can't see the pcb, since I don't have whatever program you used to make it, but I can provide some feedback on the layout, based on a series of low-profile orthogonal one-piece split keyboards that I made for myself.

[forest tiger]

Please, all feedback is helpful. So far I'm hearing the pinky stagger should be greater.

[silk lark]

I wouldn't know about that, mine is not staggered at all, you might want to print the layout and try it with your hands.

What am worried about in this layout is the sifting of the digit keys by one, the moving of the + and " keys, and tab, esc and backspace being hard to reach

also not sure what the */ key is?

[forest tiger]

I feel like moving the digit keys wont be too bad, coming from a traditional keyboard 1 is usually just past Q horizontally and I type up to 6 with my left hand. You might be right about Tab and Escape though. The */ is just an attempt at putting math operation keys closer together so I have multiplication, division, addition and subtraction all next to each other.

[silk lark]

if it helps, this is the layout I eventually settled on for myself

the moved esc and tab took about three days to get used to, otherwise it's mostly fine

braces are of course weird, but you use them very rarely

a nice thing here is that all keys are 1U, so you don't need stabilizers

[rustic linden]

Why not switch the Esc and Tab

[silk lark]

sure, whatever works for you

[long wraith]

No left space shudders

[ornate glen]

Split keyboard shudders

[rustic linden]

It's weird, I usually type space with my left hand

[silk lark]

then just swap them, it's just an example

what works for me doesn't have to work for you

and it's split, but it's one piece, so you can still press the key with the other hand easily

[cursive steeple]

What is a easy way to find the Eagle files for the Proximity Trinkey ? I am a newby at searching git.

[distant raven]

Primary learn guide

But it doesn’t appear to be up yet

[tough matrix]

if it were available, it would show up here: https://github.com/orgs/adafruit/repositories?q=trinkey

[dusty rampart]

Hi...can someone help educate me..whats the purpose of a resistor in boost converter ic..the resistor is in series from battery+ to VIN pin of the boost converter ic...how do I choose the value?

[silk lark]

it tells you the value right there, 400Ω

[supple pollen]

The purpose is to provide a little filtering between the input voltage to the circuit (which will be very electrically noisy in a switching power supply like this), and the supply voltage to the chip. The resistor and capacitor form a low-pass filter that attenuates the higher frequency noise, to provide a smoother voltage to power the chip.

[distant raven]

Wouldn’t that be a pi filter? CRC pi filter?

You would then also have high pass filtering as well

[supple pollen]

It could be viewed as a pi filter, but I don't see high pass anywhere.

[distant raven]

Nvm the high pass filter, too early for me to look at schematics lol

[tough matrix]

what is pi filter?

[heavy jasper]

This isn't quite a pi filter (which would be an inductor) but it's close enough for common usage: bidirectional low-pass filter

(so the input ripples are isolated from the DC-DC, and the DC-DC's own ripples are isolated from the outside world)

See CBat and Cin on each side, and Rs in the middle.

[supple pollen]

It is a π configuration (two parallel elements and one series), but CRC instead of CLC.

[distant raven]

Pi Filters can be CRC or CLC

[heavy jasper]

It is definitely pi-topology, this may be a regional/certain textbooks difference.

I don't think I've ever seen a CRC called a "pi filter" in any of the textbooks, but also by the time it's being introduced and named as such mostly they're being used for impedance matching, or the higher-order filter effects are desired so they just don't bother going back to talk about resistors again.

[distant raven]

It depends on the context it’s implemented

Or this is what I read this morning

Say post power rectification filter vs antenna filter

On Semi references an RC “pi filter” in this documentation

https://www.onsemi.com/pub/collateral/and8200-d.pdf

[heavy jasper]

They seem to be very much leaning into using it as specifically a topology term, given that they also refer to a "bidirectional pi filter using uniderectional zener diodes"

[distant raven]

Sure, they mention the zener function as capacitors in that context as well

[supple pollen]

I hadn't seen zeners used as varactors before, but it's valid

[heavy jasper]

I guess I'll then walk back my earlier statements, but with the "when you hear hoofbeats, think horses, not zebras" caveat that generally when folks say "pi filter" they're expecting CLC

[distant raven]

I think it’s probably fair to use pi filter to describe the topology

[distant raven]

Just say RC Pi Filter or LC Pi filter lol

Duck*

Darn it

Then Duck for cover

Fat fingered the keyboard and typed a bad word. Whoops

I think I’ll keep that on semi article book marked for the future though because there is some really good info in it

[silk lark]

another one

[cerulean crest]

Do you have docs on your project somewhere?

I really like that layout

I spilled cranberry juice in my keyboard and honestly thats the most appealing board Ive seen to replace

[silk lark]

the layout is Atreus with extra columns and low-profile switches

[cerulean crest]

Do you have the project files open source and posted somewhere?

[silk lark]

not for this one, I still need to post them, but the Flatreus is at https://hackaday.io/project/175043-flatreus-keyboard

[cerulean crest]

Thank you, I will be watching closely

[silk lark]

I will describe the wider one tomorrow

@cerulean crest by the way, the layout looks like this: http://www.keyboard-layout-editor.com/#/gists/0e39f605adf20c633a847a47daad1550

[cerulean crest]

Thanks, I like that it accounts for finger length

[worldly schooner]

Digging the psp joystick on that flattens though. Is that designed for mouse control, or some other control?

[silk lark]

yes, mouse

[fervent lance]

(asking here due to strong electronics theory expertise):

Want to know what's an appropriate value of an electrolytic capacitor to directly connect across a 'beefy' power supply.

Not really sure (yet) what purpose that'd serve; just riffing on the NeoPixel Uber Guide idea for this.

I have a Korad KD3005D linear power supply 0-30 VDC @ 0-5 Amperes.

https://www.digikey.com/short/2d9hr1r5
New, made 2020 (August) according to two references (one is the serial number!)

Near as I can ascertain, this PSU has no switching PSU type circuitry what-so-ever. ;)

Digitally controlled - using a PIC micro of all things. Regulated for both voltage and current (beyond my understanding just how).

🔹

[worldly schooner]

The amount of capacitance needed for a power supply depends on the max amount of current you plan on switching at any given time, and the max speed you plan on switching it. The job of the big capacitor is to provide extra current to the circuit in the event of a sudden increase in current draw, until the 'beefy' power supply catches up with your load. The larger the capacitor, the more current it can provide in that instant. The aspect of greater importance here is not how large the power supply is, but rather how much and how quickly the current demand changes, as well as how fast your power supply can adjust its output to meet said demand.

Tl;dr Depends more on the load than it does the supply.

[fervent lance]

I think the changes are measured near 100 milliseconds (probably no AC power, switch on, to full DC power).

I had a specific question in mind when I formed that question about the capacitor, but didn't write it down. ;)

Not quite sure just what I had in mind - why use one at all.

But the slew rate for changing demands was on my mind, maybe.

Specifically, a user in another discord suggested a (specific) value for a capacitor, and I was wondering why that value.

[distant raven]

Depends on the needs of the circuit. Some people just use common values like 100uF because it can provide enough additional current on say Neopixel strips (0.25A+) over that build up time.

I’d say most people select known values of what other people used

[fervent lance]

I found it.

We were tallking about overcurrent protection and trying to diagnose. Someone suggested 2200 uF to ameliorate (perhaps) current inrush to the DUT.

[worldly schooner]

I don't know too many people who think too hard about capacitor sizing these days. Most people will just follow general application guidelines from datasheets or commonly selected components from similar circuits.

[distant raven]

For instance, on the neopixel matrix boards I make, I use 100uF caps for power on inrush. It doesn’t provide a lot, but 0.25A for a few seconds let’s things power on more cleanly.

[fervent lance]

During power-on sequence; the OCP protected supply refused to start. Turned out to be operator error. ;)

[distant raven]

Usually the more capacitance the better

[fervent lance]

I was thinking of attaching a big electrolytic semi-permanently across this PSU's output.

[distant raven]

Only issue with larger caps is they tend to have lower voltage ratings, and the higher voltage rated large caps are expensive

A few $$ a piece

[fervent lance]

It's a 30 Volt supply.

So 75 Volts should be enough overhead.

[worldly schooner]

I mean, AFAIK electrolytic caps still go up to 600V

[distant raven]

So you want a 50V+ 2200uF

If you were to choose 2200uF that is

[distant raven]

They do, they just cost a few dollars

[worldly schooner]

I would hope nobody needs more than one or two of those...

[fervent lance]

I guess what I'm worried about is the effect on the power supply itself when you put an electrolytic across its output.

[worldly schooner]

Most of those 600V devices are industrial machines that cost $$$ anyways

[fervent lance]

I'm assuming the input circuit it feeds (the DUT) would never operate incorrectly no matter what value that capacitor was (within reason).

[distant raven]

You can convert it to its impedance value and calculate the effects

1/jwC

Some imaginary number in Ohms

[fervent lance]

Yeah, I like that idea.

[distant raven]

w is omega, I imagine the 30V supply is from 60Hz circuit

[fervent lance]

Not that I'd understand it, initially. But I relate very well to resistance in Ohms in such circumstances.

These supplies have a reputation for a nasty spike when they're powered on or off.

[distant raven]

Wait that was correct, Hz to radians

[fervent lance]

Like double the set-point value (in Volts) if I understood EEVblog #315 (minute 21) properly.

[distant raven]

1Hz is roughly 6.28 radians

[fervent lance]

https://youtu.be/Fya-4mjV4N4?t=1251

Well I know that lightning is affected by the impedance of the conducting path.

But DC is 'zero hertz' or something.

"a capacitor blocks DC and passes AC; an inductor blocks AC and passes DC" is the (primitive) rule of thumb.

I guess my question boils down to 'is there a capacity, in microfarads, beyond which your electrolytic should not be specified when connecting it 'dumbly' across a power supply' (basically for superstitious reasons)

[distant raven]

I imagine there is a “using a dump truck when a wheelbarrow Would do” scenario

[worldly schooner]

No. The only undesirable effect to having a capacitor too large is slower charging speeds, which would likely be a scale of seconds vs milliseconds.

Nothing will blow up or stop functioning, but if it's too large, your supply might take a minute to charge it.

[fervent lance]

So if you want responsiveness, pre-charge that capacitor (by unspecified means) or live with a long RC time constant.

[worldly schooner]

And during that charging time, you might give your circuit less voltage than you would like.

[fervent lance]

Okay that sounds understandable. ;)

[distant raven]

Are you using long Neopixel strips?

[fervent lance]

I was trying to theorize how a linear supply (digitally regulated for both voltage and current) gets that power-on spike in the first place.

@distant raven The two test cases I have in mind are a CB radio transmitter (solid state 4 Watts) and the RPi4 plus connected equipment (peak 1.2 Amps at 5 VDC and 900 mA constant draw).

[worldly schooner]

Generally, the spike comes from the switching on of the system. Has nothing to do with linear or switching.

You might be getting inrush mixed up with ripple.

[fervent lance]

So how does a good power supply reduce that spike?

I'm not conflating inrush with ripple - I'm ignoring ripple as a solved problem. ;)

EEVblog author (I'm not a regular viewer) seemed very surprised at the spike generated by this power supply (in 2012 when he did the review).

[worldly schooner]

Either filter it with a capacitor internally, or start with a high impedance on the line side and adjust said impedance until the load side is at its desired state.

[distant raven]

Cascading power on sequencing lol

[fervent lance]

Hmm there's an idea!

If I lean on the PSU chassis I don't hear much when I throw the AC power switch on it.

But if I don't lean on it - a good sized TCHUNK sound as that power hits the windings of the xformer.

(I'm guessing my body weight dampens the vibration)

The claim is that connected equipment might be damaged by that spike.

[worldly schooner]

It does. Though my guess for the TCHUNK would be a relay coil energizing. Transformers alone don't usually make very percussive noises from my experience.

[supple pollen]

Sort of: the electrolytic process doesn't really work well above 450V or so. Most of the higher voltage electrolytic capacitors are really two in series.

[distant raven]

Unless they explode lol

[fervent lance]

I have been using DPST switch to interrupt both positive and negative lead paths, to prevent that spike from getting into the DUT during AC power up.

I have two switches inline; one is SPST and the other DPST - on the notion the spike could propagate on the negative lead of the PSU even without a complete path/circuit. /superstition

Yeah I could totally see it: a series of SPST toggles, left to right on a front panel, to be thrown in sequence.

On the notion the electrical changes happen at a much more rapid time evolution than the time it takes to move your hand from one toggle switch to the one on it's right.

[supple pollen]

Old style. That works. Or you could use a cam switch.

[fervent lance]

Never heard of a cam switch! Sounds nice.

So you would have for example:

120 VAC on the first toggle, which (if not thrown) prevents any power from reaching the equipment (the power supply's internals, including it's step-down power transformer).

The last toggle would be the one that enables normal operation, perhaps by completing the final path to the output binding posts.

Intermediate toggles go wherever it makes sense, to reduce the current inrush related harmful 'signals'.

Maybe one of them completes the path for an 'extra' capacitor in parallel not really required, but helpful.

(optional use cases when you can in fact tolerate a full sixty second delay in system start-up)

[covert blaze]

It looks pretty

Is it necesary to have thicker routes for +5 volt?

[distant raven]

Depends on the current requirements

And copper weight

[covert blaze]

Well, not much at all

Well I think sp

[distant raven]

https://www.pcbcart.com/article/content/copper-trace-and-capacity-relationship.html

[covert blaze]

The circuit takes a voltage pair on CN2 and a another on CN3 measures it using instrumentation amplifier setup

And outputs to CN4

[distant raven]

Standard outer copper is 1oz, inner copper is often 0.5oz

That matrix gives a pretty good idea of what you can expect I think

[covert blaze]

Wonder if I can easily determine current usage of my circuit

[distant raven]

I’d go off what the data sheets give for I max

since most components are in parallel, you should just be able to add the max current for each device together

In many cases, you are regulated by the power supply element like a DC-DC converter or a LDO

Common LDO have ratings at 5V for about 500mA up to 1A

[covert blaze]

Thanks for the help I'll get an estimate on power consumption. Then use that matrix

[distant raven]

👍🏻

[covert blaze]

Oh boy I forgot LEDs

Most important part

[distant raven]

Whoops lol

[covert blaze]

Should I only do copper fill on one side of a 2 layer pcb?

[supple pollen]

You can do both sides, I often do. It's basically free shielding.

[covert blaze]

Yeah that is what I was thinking

Well there it is, no idea if it'l work yet. But hey that is half the fun

[worldly schooner]

What's the vertically-mounted guy over there?

[covert blaze]

L7905

[worldly schooner]

He seems like he might need some heatsinking.

[covert blaze]

Unfortunately can't find him in surface mount

He probably will yeah, hence why he is on the edge. Planning on making aluminium case so will mount him to it

[supple pollen]

I suspect your circuitry doesn't draw enough current to require heatsinking with that TO-220 package. There are surface mount versions available, but you'd probably have to add some copper area and thermal vias for heatsinking.

[worldly schooner]

Yeah, there should be a DPAK form factor for it, if that's your preference.

[covert blaze]

I already have many ideas for a V2, but first got to see if this one works

[worldly schooner]

If you plan to mount it to chassis, I'd nudge that footprint closer to the edge of the board a bit. I don't know if you can get it perfectly flush, but you probably have some room to get closer.

[covert blaze]

Yeah I see now there is quite a gap, I'll move it a bit

[supple pollen]

If your current draw is low, you could use a "rail splitter" type IC like TLE2426 and a single 9V battery to get plus and minus 4.5 volt rails.

[covert blaze]

I was looking at premade solutions for the negative rail

Most were stepdown converters

And I can be wrong but they can be noisy

[supple pollen]

Yes, there are various switching converters available too. The "rail splitter" notion is an analogue solution which involves deriving a voltage midway between the input voltage positive and negative. Then you define that midway voltage as your zero volt reference, so 9V becomes +4.5V and -4.5V.

[covert blaze]

yeah I totally missed the one you sent now

I will have a look at it for V2

[heavy jasper]

There are also negative-voltage LDOs, so if you need a low-noise solution for a negative voltage from a non-battery-powered source, you can do a switching regulator to get the negative voltage, then post-regulate it with a negative-output LDO.

[covert blaze]

Was considering it, but didn't know if switching regulator + LDO would be still more efficient than just a LDO.

Ti has a switching regulator that can make +15 and -15 rail so I can then regulate with ghe LDO.

[supple pollen]

Generally yes: a linear regulator (including LDOs) dissipate the current through them times the voltage drop. So a 5V linear regulator running from a 9V source would dissipate the current through it times 4 (volts).

[covert blaze]

Well in reality I think the circuit is really only going to draw a few mA, think a pair of 9Vs are going to last a very long time

[covert blaze]

Anyone that can maybe shoot a quick look at my schematic to see if anything is terribly wrong before I order it from China

Positive and negative LDO to make +-5V rails, and then basically 2 instrument amps with a 2.5 voltage reference for offfset

[rapid slate]

Hey there PCB design channel.

I'm looking for a textbook or a website, or even the proper language (search words) for getting started with this.

I made a pcb with Eagle to act as a flight computer, but it was just putting traces onto a pcb and through holes that we soldered premade breakboards into. Boards like a Teensy 4.0 and a BNO055. This was fun and I learned a lot doing it, but I want to try something a bit harder with more components so I'd like to learn how a microcontroller board like the Teensy, can be made. Do you have starting suggestions? Right now I'm watching videos from Predictable Designs.

I'm also reading an instructables and making notes about different components that need to support the MCU.

[worldly schooner]

If you want a real-world example, the RP2040 hardware design guide goes into the design process of the Raspberry Pi Pico. It's by no means a Teensy, but it gives you an idea of the concepts and thought process that goes into designing an MCU.
https://datasheets.raspberrypi.org/rp2040/hardware-design-with-rp2040.pdf

[rapid slate]

Thank you kindly.

[covert blaze]

The RP2040 has a glorious design manual

Next project will be to make a custom RP2040 breakout board for myself

[worldly schooner]

From there, you can consider your own applications and decide on your own core, peripherals, and supplementary circuitry to match your needs.

[rapid slate]

Oh cool, so the off the shelf MCUs have Low dropout voltage regulators to reduce the current. So if I want my pins to be able to output at a higher voltage to run larger servo motors to operate valves or control stabilizers, I can have the overall board have a larger power supply with the dropout regulator.

[worldly schooner]

Well, it's not always that simple. You also have to make sure that the chip itself is capable of the current you want to use, or add extra circuitry to separate chip logic from your power.

[tough matrix]

It is a worthy goal, but of course you know that there are already quite a few RP2040 breakout boards - from established companies like Adafruit or Sparkfun, and from many makers - like arturo182 (aka solderparty) and our own @distant raven

[worldly schooner]

Is fritzing not free...?

Official download is asking for 8 euro

[twilit mango]

There are older versions of it on GitHub, available, compiled. But the latest version is not free, no.

[radiant wolf]

You can also compile from source

[covert blaze]

Well it's just practice. The idea is to build familiarity with the chip and its design constraints. And then to use that knowledge in purpose built PCBs.

[merry narwhal]

Anyone know what these pinouts are

and if possible a circuit diagram for this d flip flop

[heavy jasper]

What's the context of this schematic? Is it possible this sub-block is being defined elsewhere (given that e.g. it doesn't list pin numbers for an IC).

(and can you zoom out a bit so I can see what's connected to those inputs, which may give more of a hint)

With a bit of google-fu, it looks like this is part of a counter IC:

So it may or may not be available at this level of abstraction directly as a chip.

[silk lark]

@worldly schooner fritzing is still free and open source, if you log in on the forum you have an option to download it free

[merry narwhal]

yeah its apart of a 4516b counter

i like the design since it includes parallel loading and im just comfortable with that design

@heavy jasper Also thank you for taking the time to help me i greatly appreciate it

[heavy jasper]

You can probably make one of these elements for yourself with something like a 74HC112 (JK flip-flop with asynchronous set and reset)

plus some glue logic to turn preset enable and parallel in into said set/reset lines

[merry narwhal]

And it would probably work on that diagram above?

[heavy jasper]

Timing issues aside, theoretically yes if it has the same truth table.

[merry narwhal]

yeah

well if anything you got any other parallel load 4bit bin counters?

[heavy jasper]

At least a more modern one, by the looks of it: https://www.onsemi.com/pdf/datasheet/mc14516b-d.pdf

If you're looking for DIP packages... availability will be generally limited

[merry narwhal]

nah im not looking for an ic to buy

looking for a diagram to make up

seems like a weird request lol

ahahah im back to this again. Whats the diagram for the flip flop

[heavy jasper]

That sounds like an exercise left to the reader, to me.

(See if you can figure out a way to do it, build just one, and see if it matches the truth table, iterate if no)

[merry narwhal]

hmm yeah i will have to look into it

not too comfortable with making flip flops with presets

but anyway thanks for the help

[worldly schooner]

Has anyone used JLCPCB for component sourcing? I was wondering if I could get a bag of resistors and capacitors through them from LCSC with a PCB order, while sourcing my other ICs from Digikey...

[covert blaze]

I ordered few days ago

Waiting on delivery

Prices were significantly better than Mouser. So I hope it works out

[lament vapor]

atmega32u4's datasheet asks for a pair of 22ohm resistors in series with the D+/- pins. but apparently I only have 20ohm resistors on hand. how critical is the resistor value in this case?

[worldly schooner]

2 ohms difference isn't going to prevent it from functioning, and I wouldn't worry about it breaking anything. If your device has some behavior that might indicate unstable signal, it's not too late to replace it then.

Does anyone have any experience with USB-C termination? I want to build a keyboard that can draw USB3-level currents to power a bus-powered hub, but I'm not sure how to best terminate the CC pins...

[distant raven]

Using pull down resistors on CC sets the current.

Usually 5.1k are used but let me find the table that describes the values and with they set for PID control

https://microchipdeveloper.com/usb:tc-pins

5.1K will allow you to draw a lot of current on USB 3 compatible ports

10k is good for 3A, 20k for 1.5A, etc..

[tough matrix]

do they do that?
I mean, you can order PCBs from JLCPCB and components from LCSC, but these will be two different orders, shipped separately

[distant raven]

Obviously the combo of PU and PD on the entire connection will be the ultimate determination of current capacity on a USB bus

[distant raven]

Also, this might be helpful https://forum.digikey.com/t/simple-way-to-use-usb-type-c-to-get-5v-at-up-to-3a-15w/7016

[covert blaze]

They do combined stuff now, can order parts along with your PCB

I got the option of doing it when I ordered

[tough matrix]

interesting. I didn't see it with my latest order - where do they show this option?

[brisk hearth]

Is Kicad or EAGLE easier to learn?

[silk lark]

yes

[rocky quest]

https://www.digikey.com/en/products/detail/chip-quik-inc/SMD291AX50T3/5130159?s=N4IgTCBcDaIMoFkAiYCcBGAggDQKwAYAVAZhAF0BfIA

is this good solder paste

[toxic patrol]

I'm designing a PCB and found a chip I need from TI. It uses an nFBGA 36 pin ZEC package, and I've never soldered BGA before...

Since I'm the one making the PCB, I figured maybe I could put a small hole under each of the 36 pins (like you'd see in through-hole soldering) so I could essentially fill each hole with solder from the back to attach it, would this work?

Only issue I can see is it would be hard to get the traces out from the center pins w/ the holes there

[worldly schooner]

Looks fine, it is leaded so make sure to use a fume extractor and/or proper ventilation.

[worldly schooner]

The size of those pins make for really small holes that I'm doubtful you'll get solder through. That technique is suited to soldering ground pads for something like QFN, not BGA pins. I would just invest in a cheap reflow setup instead, if you can't get away from BGA.

Use solder paste and a stencil to solder all the tricky QFN/BGA chips on one side, and take a hotplate to solder them all down. Then, you can freely hand-solder all the passives on the back as needed.

[toxic patrol]

I'm looking at the TMUX646 from TI. It's only offered in that package, and there's currently 10 in stock (I'm ordering 7). I'm sitting here in the cart really debating it...

I'd have to get that equipment you just mentioned as well

[worldly schooner]

Solder paste is cheap, and you can get a taping knife to spread it from your local hardware store pretty easily. Stencils are offered by every PCB manufacturer you're likely to order them from, so the only difficult equipment would be the hot plate.

Actually, hot air is an option too, now that I think about it.

[toxic patrol]

I have access to a heat gun

[supple pollen]

It's T3, which is fairly coarse grained. It should work okay with stencils, but would be difficult to use with (say) a syringe

[toxic patrol]

It has been ordered

[worldly schooner]

Oh solder paste isn't even needed

The balls in the ball grid are solder

http://www.electronicsandyou.com/blog/bga-ball-grid-array-repairing-and-soldering-bga.html

Flux paste...

Crud

Well, it's certainly doable with hot air though

Paste does help make the temperature curve less strict, but flux looks like a must-have

And preferably one that isn't straight liquid.

https://www.eevblog.com/forum/projects/bga-for-hobbyists-is-it-even-possible/

Does anyone have experience with any of the ~$50 hot air stations on Amazon? I thought a hot air station designed for soldering would be more expensive than that...

[supple pollen]

I regard the amazon stuff as particularly sketchy, even if someone else bought an "identical" item and had a good experience with it, their "equivalent merchandise" policy means you could get a completely different one.

[toxic patrol]

shoot

this thing is 2.45mm x 2.45mm x 1mm

uuuhhhhhhh

Shoud I try to cancel the order??????

[worldly schooner]

The chip?

[toxic patrol]

yes

I'm pretty sure the chip

[worldly schooner]

I mean, depends on your confidence.

[toxic patrol]

Ball diameter is 0.25mm

As someone who has only soldered through-hole, do you think I can pull this off?

[worldly schooner]

The smaller the chip, the easier it is to heat.

As long as you have the flux and a properly designed pcb...?

Wait you've never done SMD before?

[toxic patrol]

I mean, I guess you're right

There'll be SMD on this thing I'm doing

It's time to leard all the solders!

woo!

cries

[worldly schooner]

At that point, you might also consider paying for PCBA

If you can get a fabhouse to put the hard one on for you, you can probably handle passives on the back?

[toxic patrol]

I used JLCPCB for my latest (and first) PCB, and was thinking of using them again. I don't think they offer that

This chip is just 6x6 balls in a straight grid, not sure about passives or anything

[worldly schooner]

They do, but you're restricted to their supply.

[toxic patrol]

And they don't offer BGA I don't think

[worldly schooner]

Passives refers to all the resistors and capacitors, etc.

[toxic patrol]

ah

I thought this chip would maybe be 1 in x 1 in lmao

[worldly schooner]

Hence why the through hole method you tried to suggest would've been a catastrophe LOL

[toxic patrol]

yeah...

[worldly schooner]

It's fine, you should decide for yourself if the risk here is worth taking or not.

To my knowledge, the harder part isn't the actual assembly, but the design and layout.

6x6 shouldn't be too bad, but if you're not confident, I'd look for a different chip for now.

[toxic patrol]

Well, I gtg for now... I'll return in a few hours to keep working on this

If I did order from a site with assembly, I'd still have to cancel my order, right?

[worldly schooner]

Probably? I'd recommend it

[toxic patrol]

So... in your opinion, what would you do in my situation...

[worldly schooner]

Cancel, get a PCBA quote, and decide from there

[toxic patrol]

k

[worldly schooner]

What kind of chip are you trying to use, anyways? I find it strange that a particular chip with less than 50 pins isn't available in alternate packaging...

Especially from a manufacturer as large as TI.

[toxic patrol]

MIPI multiplexer

[toxic patrol]

Also, TI said they couldn't cancel it

Which is annoying seen as I ordered it like an hour before I tried to cancel

Oh well, good luck to me I guess!

I'll figure it out

[supple pollen]

We all seem to accumulate a stash of chips we'll never/can't use...

[sweet inlet]

@unreal flax @supple pollen @heavy jasper thank you all for helping me with my pcb design / soldering! Got t fully functional yesterday:

[distant raven]

Very nicely done

[sweet inlet]

@distant raven thank you too! IIRC you recommended components to me, ended up using your recommendations!

[distant raven]

🙂

That’s a very smart looking design too 🙂

Did JLC assemble that?

[sweet inlet]

The shape was copied from the one that came with the keyboard 🙂 lots of fun laying out traces

I assembled it, took 2-3 fixes to get it working.

[distant raven]

Oh wow, nice job!

[sweet inlet]

too much paste at first, accidentally rotated a couple resistors 😄

thanks!

[distant raven]

0402 or 0201?

Those components look absolutely tiny

[toxic patrol]

I'm back again with the camera switcher nonsense I'm sure you're tired of hearing about. Is there a downside of leaching the 3.3v and ground for the multiplexers from the cameras, as opposed to a dedicated power and ground input?

[worldly schooner]

Would depend on the design of the source you're trying to pull from and the sensitivity of the chips you're trying to power, but if it's insufficient you may get intermittent voltage dips.

Are you trying to make a Raspberry Pi camera switch?

Power for the Pi cameras come from the RPi, not the camera module. The regulators on the Pi camera handle conversion to 2.8v, 1.8v, and 1.2v.

[toxic patrol]

The RPi cameras run on 15 pin ribbon cables. 1 of the pins us 3.3v power from the Pi to the cameras. Another 4 pins or so are all ground. My options are
A) Hook multiplexer power up to that 3.3v line for power
B) Use a dedicated terminal block for the 3.3v power and ground

The pinout for the cameras is on Arducam's website

I used the power leeching design in V1 (I've posted the schematics for that one before if you search from:Zman has:file)

[worldly schooner]

I would expect the Pi's 3v3 is pretty stable, though I'm not sure how much current is being pulled into your chip compared to how much the ribbon cable can carry. Do you know how much your multiplexer chip pulls?

[toxic patrol]

I'd be using the Pi's 3v3 anyways, its just a question of pulling from the camera cable vs the GPIO pin (although I'm fairly certain they're the same but idrk).

Here's what I got current-wise

(there's 7 muxes, model: TI TMUX646)

[supple pollen]

so 30 * 7 = 210µA? That doesn't seem like it would be a problem.

[limpid nest]

I need to transmit ~15 mA @ 5V over a distance of up to 15 feet in order to toggle a relay on/off. I need connectors (and cables) to connect the 5V and GND from my main enclosure to a number of sub enclosures. They need to be (relatively) inexpensive and water/dust resistant. Would IP rated barrel jacks/plugs be an out of line choice?

oh and also not require an expensive crimp tool

[distant raven]

Why not use an ESP32?

[limpid nest]

wifi?

[distant raven]

FeatherS2 from Unexpected Maker can do battery power, Wifi, etc..

It’s a great option without 15ft of wire

[limpid nest]

ah interesting, let me give some background. I'm currently retrofitting/refurbishing a university team's capstone project. In this iteration of the project I'm a bit limited to just getting what they did working again, as it has to be done fast. Later on I'll be doing my own design and I can do some groovy stuff. What I'm working on is a "brain" box to send the control signals to the 12 sub boxes. I'd need 13 feathers in that case right?

[distant raven]

Well, featheS2 is one example, but they have cheap ESP01 modules which could do that cheaper if you need a lot

[limpid nest]

another constraint is it needs to be easy to debug and repair without me around. The company this is for will have lots of folks with electrical experience, but almost none if not no people who can program or debug wifi issues

But I do love the idea of no wires

[distant raven]

Okay, so picking something that can do circuitpython might be a really great option

https://www.wemos.cc/en/latest/s2/s2_mini.html

[limpid nest]

yeah, right now we're working with a pi 3 A+ since we need to play music. It's overkill to the extreme for what we need but I want to find a way to use the hdmi out

[distant raven]

~$4

There is a circuitpython build for it. If you need batter, Adafruit sells a battery backpack that could probably power that

[limpid nest]

oh we're switching AC power, so power isn't a problem. I kept the pi as the board for this since I knew I could do circuitpython with it

[distant raven]

Okay, yeah just one of those Wemos S2 mini

[limpid nest]

as the control unit?

[distant raven]

Yeah

It can be easily programmed with circuitpython

[limpid nest]

I'm relatively comfortable with upython as well

[distant raven]

And debugging is visual through repl so easy for future maintainers

[limpid nest]

I'll definitely include wifi as an option in my presentation for future versions of the product!

[distant raven]

Plus Wifi so you could set it up to log to Adafruit IO or something like an mqtt server

[limpid nest]

Any thoughts on IP rated barrel jacks for now? Seems like a cheap way to route two signals

[distant raven]

I’ve never seen barrel jacks used for data before, but they have where you can use power outlets for data so probably possible

[limpid nest]

hmm I'll keep looking, keep that in my back pocket

[supple pollen]

I normally use automotive connectors for things like that. They often seal nicely when mated.

[limpid nest]

do you need special crimp tools?

[supple pollen]

It depends on the connector. Some work fine with generic crimp tools.

[limpid nest]

would I search automotive connectors on digikey?

It would be nice to be able to mount them in my plastic enclosure

[supple pollen]

DigiKey should carry stuff like that. The pictured ones are just the ones I happened to find an image of, but those are MX80 connectors, which use a thousand dollar crimper, so they're not the specific ones you're looking for.

[limpid nest]

ahh ok, any idea on search terms? Coming up slightly dry

Ah I found it It hink

[supple pollen]

Connectors, Interconnects -> Rectangular Connectors - Housings, then under features, select all the "waterproof" and "weatherproof" options.

[limpid nest]

noice!

thx

how does one tell if a connector requires expensive tools if it isn't called out in the datasheet?

contact the supplier?

[supple pollen]

It can be tricky. Some contacts work fine with a generic tool, some don't.

[limpid nest]

shucks

[heavy jasper]

These folks tend to have a decent variety of stuff, and frequently make their connectors with solder cups instead of crimped connectors, which can be easier to assemble w/o nice tooling: https://www.switchcraft.com

In general, for any crimp you might do, order extras, then clamp the contact to a table and try to pull the wire out to see how much force it takes. Usually smaller connectors are a bit easier to get right with generic tooling; the biggest problem for fancier connectors is not accidentally deforming any geometry that the housing relies on. For anything larger (~14-16 awg is my rough limit), having the correct tooling or at least tooling with appropriate leverage (think foot-long handle ratcheting crimpers) becomes a big deal.

[tough matrix]

I've finally found a system of storing loose SMD components I am happy with: modular boxes + 3d printed trays: https://www.thingiverse.com/thing:4965344

[empty hollow]

What would you recommend for bypassing capacitors for a simple pcb with a couple of sensor chips and serial-ttl chip. I am making a hat pcb for pi zero to be put inside a neopixel lamp.

[mystic crypt]

That's my method and besides being a little janky it is nice since it can handle many values with a small footprint

[fervent lance]

Looking at the datasheet for the MCP23008 I2C I/O expander, pins A0-A2 , RESET and INT are unused but need to be biased externally. How do I do this?