help-with-hw-design

[tough matrix]

what current do you need?

[limpid nest]

~8-15 mA

Really not much

[tough matrix]

This would work: https://www.digikey.com/en/products/detail/microchip-technology/TN2106N3-G/4902377

or this
https://www.digikey.com/en/products/detail/microchip-technology/TN0606N3-G/4902373

[limpid nest]

Neat thanks! I'll have to pay for rapid shipping TT

[limpid nest]

I use rosin core leaded solder. When I'm done soldering I use a sprayer of isopropyl alcohol into a bucket (no sink at work, it's a thing) along with a toothbrush to get the Flux off. When I'm done, is the toothbrush contaminated with lead?

[steel valve]

I assume this is where I would ask; what is the difference between the NRF52842, NRF51822, and NRF52840

Pretty much, I am making a miniature PCB that wants to be as small as possible while having an analog multiplexer connecting sensors to the nrf module

It'll also have charging capabilities

[unique patio]

do you mean nrf52832?

[steel valve]

yeah

typo

[unique patio]

nrf51822 is an older smaller chip, nrf52840 has native USB, nrf52832 does not. Tile and AirTag use nrF52832 I blieve

[steel valve]

So the NRF52840 can be programmed by USB, while the others can't, ok

Is there any diff in power consumption?

[unique patio]

they are all very low

[steel valve]

So basically not enough to matter

[unique patio]

nrf52840 can be a USB device, the others don't have native USB, not a big deal for what you want, maybe

[steel valve]

Right now I utilize the Sparkfun Artemis Nano but its charging speed is way too fast so I am making my own pcb.

Pretty much, it just needs to be programmable via usb, connect to a lipo battery (and charge the lipo too), have usb c, and not use a lot of power.

[unique patio]

my brother noted the following article just yesterday, which might be an interesting overview. It's about modules,and is a couple of years old, but has some itneresting observations: https://predictabledesigns.com/review-of-bluetooth-low-energy-ble-solutions/

[steel valve]

When you mean a USB device, as in connect to the PC via usb for programming? Or do you mean something different

[unique patio]

I mean it can be a USB drive, an HID device, etc. General USB device. We use those features for CircuitPython

[steel valve]

Ah, yeah not intending to use that

Just intending for it to be programmable via Arduino or Segger.

So in that case, I assume the NRF52842 is the best option

Since I don't need to use it for CircuitPython and it has the faster processor, and if I remember right the NRF51822 is BLE 4.0 and the other two are 5.0

[unique patio]

yes, I think the '832 is the best choice for this.

we sell '832 dev boards, or you could use the official ones

[limpid nest]

I'm curious why adafruit went with the pinout they did with the AW9523 board. Bread boarding with it is definitely interesting.

It's not hard but I feel like it could possibly have been easier.

[unique patio]

it is meant to be compact. I think you might want to put upward facing pins or jacks on the VIN row

[limpid nest]

Ah I see

Upward facing pins?

My use case is a bit odd, I can't source enough current for the LEDs out of the 3v3 rail on my board so I'm going with a separate PSU

[steel valve]

Where are official ones obtained?

[unique patio]

https://www.digikey.com/en/products/detail/nordic-semiconductor-asa/NRF52-DK/5773879 for example

[steel valve]

Oh you mean the development kits

Yeah I currently have that

And am moving to the smaller stuff

[unique patio]

note that the bar chips are in high demand. I only see one version in stock at digikey

https://www.digikey.com/en/products/filter/rf-transceiver-ics/879?s=N4IgTCBcDaIHYCcBmBWMAOAzBAugXyA

[steel valve]

Yeah

That's my main issue RN is stock issues

Like for example, the 822 is way more available than the 832 and 840

Like mouser has 900 or so of the 822, and then like 4 of the other two

But I don't know how much processing speed I really need for my project since it is pretty simple

Try to send the sensor values as fast as possible

With ~8MS latency as the goal

Oh nice digikey has a crap ton of the 4077 module

(In the case that its a better idea to use the 832)

[marble scaffold]

just finished this schematic

this is a pi hat that takes in a 7.4v battery

uses it to power the raspberry pi through a buck regulator, a microcontroller through the pi's 3.3v line, and 2 motor drivers

anything i should revise here?

microcontroller is responsible for giving PWM to the motors

and reading the battery voltage

slightly updated version

[marble scaffold]

got a weird issue

everything that's supposed to be ground

is mapping to BATT+

are the nets accidentally connected somehow?

[ember laurel]

I guess so

that doesn't look great 🙂

same for both of your motor drivers

[marble scaffold]

yep thats the problem

accidentally shorted together

[ember laurel]

or an intentional resistive heater, relying on a very long trace for resistance

[marble scaffold]

also got my 3.3v and 5v swapped

😛

[ember laurel]

oh indeed

[marble scaffold]

now the last issue is that the pin header starts numbering from the right side

[ember laurel]

I guess that's just what your footprint is like

[tough matrix]

Shouldn't D1 be Schottky, not Zener? we had talked about it.
Also, I am curious: you connect Pi to samd09 by both i2c and rx/tx. Which of them do you plan to use?

as for numbering of pins in footprint, KiCad has a number of different footprints with different numbering of pins - see if you like any of them better

BTW, do you have a stock of DRV8871? last time I checked, they were out of stock everywhere...

I am doing my own version of 2-channel motor controller right now, but using different driver IC, TLE9201

and last suggestion: do you want to add indicator LED to show power on?

[ember laurel]

https://lcsc.com/product-detail/DC-DC-Converters_Silergy-Corp-SY8303AAIC_C2937216.html - a bit pricey right now, but still in stock. Small, very efficient.

[twilit mango]

Bah. Why would EagleCAD not mirror three of the layers when I did select all / mirror group?

(╯°□°）╯︵ ┻━┻

Ends up looking like this instead of everything being mirrored.

Or however many layers it's skipping anyway.

[limpid nest]

Looks kinda like a screen glitch. I've done stuff like that before

[twilit mango]

I've tried repeatedly, same issue.

Let me quit and reopen I guess?

Highlight all doesn't seem to be.... highlighting all.

The bits that aren't getting mirrored stay dark when I do CMD+A or use the "group" tool to highlight the whole board.

[limpid nest]

EAGLE/Fusion have some glaring issues

Makes me wonder why I paid 500 bones for it sometimes

[twilit mango]

I'm one of Adafruit's seats. But yeah understandable.

[limpid nest]

It's "worth" it but it's annoying. If KiCad had some kind of killer 3d modeling integration I'd go for it

[twilit mango]

Sigh. I'll have to ping Limor. I need to flip this board to do the Fritzing object.

Thanks though!

Wait maybe not. Only need to flip the STEMMA connectors...

No, whole board, and then reflip STEMMA connectors. Bleh.

WAIT. I remember a possible reason. Something about locked layers. Hopefully I have notes.

Yes!

Flipped!

There's a lock icon, and if you click it, the top bar has an "unlock all" icon which I clicked. Then when I highlighted all, everything was bright, and everything flipped.

🤦🏻‍♀️ Was the wrong rev anyway. But hey, at least I remembered the issue.

[limpid nest]

Wooooo glad you solved it

[ember laurel]

@limpid nest what kind of 3d modeling do you need integrated?

[limpid nest]

Mostly 1) STEP quality models of my board and 2) drawing a 2D shape in 3D CAD and making a board profile out of it

The importing of your 3D PCB in Fusion360 parametric is pretty good

[ember laurel]

hmmm I see

[limpid nest]

What were you thinking?

[marble scaffold]

yeah this was updated in the schematic, photo i posted was before that

[marble scaffold]

i made a copy of the footprint that had pin ordering mirrored, it's all sorted out

[marble scaffold]

https://www.aliexpress.com/item/1005002141174726.html the wonders of aliexpress

[marble scaffold]

good idea, i'lll add that

update since last i talked here: finished the pcb layout

[ember laurel]

@marble scaffold now just hope it is not some chinese copy

[marble scaffold]

yeah

[ember laurel]

delivery times from aliexpress though...

[limpid nest]

Good or bad? I thought they were bad but I've avoided ali

[ember laurel]

a month if you're lucky

[limpid nest]

Oof yeah

[supple yew]

Are there Kicad parts and footprints for Adafruit specific stuff like the feather connectors and board size?

[marble scaffold]

i'lll get a better screenshot in a bit

also ik these trace widths are all over the place

i way over built certain sections (ex: the trace for the battery is 70mil!) because i was worried about current draw

and the layout is a bit of a mess too

[ember laurel]

any reason you have the motor connectors there, and not just close to the motor drivers?

in general, you should try to keep the loop area as short as possible there - because this is your main current part

[marble scaffold]

don't really have a reason

might redo this pcb to lay it out better

[ember laurel]

try to put those drivers close to the terminals

and the power input also close

the other chips aren't so important for high power

[limpid nest]

Also maybe polygons for the motor pins/terminals?

[ember laurel]

how much current is this?

@marble scaffold this is only a 2 layer board?

[limpid nest]

Looks like it

I think this is easyEDA, not sure if it can do 4+ layer

[marble scaffold]

this is kicad

i can do 4 layer but i want to keep costs down

[marble scaffold]

yep

[tough matrix]

I'd certainly suggest making traces from motor drivers to terminals a lot thicker.

[limpid nest]

You've got room for that for sure

[tough matrix]

@marble scaffoldI liked the website placeholder you put there 🙂

[limpid nest]

I initially read it as ohana.gg and fondly remembered Leelo and Stitch

[verbal moss]

Cheers, looks useful for wide input voltage range, and few additional components needed to integrate.

Thanks @tough matrix, added to my list of potentials for other projects. Need ~2A for current one.

[verbal moss]

Nice find, thanks @ember laurel. Pricey, but it's small and efficient, and in stock!

Update... Looks like DROK and similar use https://www.monolithicpower.com/en/mp2315.html. But MPS recommend MP2393 for new designs. Good luck finding available stock that's cheaper than just using these boards.

if need <= 1.2A then consider https://www.adafruit.com/product/4739 (using https://www.monolithicpower.com/en/mpm3610a.html).

[heavy jasper]

For MP2393 - generally I've found MPS's website to have better stock of their products than they have through distributors - at least as long as you don't need more than their general-sale maximum (which they have as being for product development - but for most folks is probably bigger than their production runs)

e.g. MP2393 is availble at $1.65/unit for 1

w/ 5-dollar shipping in 3-4 business days

[tough matrix]

unfortunately jlcpcb doesn't carry MPS bucks for assembly

[heavy jasper]

Yes that being the key restriction - for hand-soldering (or consignment to an assembly house that's willing to re-reel it), easily available.

[median wind]

Does anyone know where can I find information about turning state diagrams into a flip flop design?

[heavy jasper]

I think this is more of a general "projects" question - but in general you need to be able to make a circuit that takes as inputs (current state, any external inputs) and produces output state, then feed "output state" into a flip-flop for storage. A good search term is "sequential logic" and more specifically, synchronous sequential logic.

or in general, textbooks/classes that are introductions to digital design pretty much all talk about this at some point.

[distant raven]

Can you implement a turing state machine with TTL logic?

I learned it with fpga

Or easily implement I should say

[heavy jasper]

Theoretically - absolutely yes

and folks have done CPUs on breadboards with TTL logic

[distant raven]

Right, storing in registers (which I guess is just a bank of flip flops and tristate buffers)

[heavy jasper]

in practice - I would personally much prefer to use an FPGA, even for learning - with breadboards/TTL logic and such it's way too easy to accidentally mess up your circuit by bumping it

[distant raven]

Which is why I said “easily”

[limpid nest]

I'm currently replacing a (non breadboard) circuit that changes state if you set your coffee cup down near it

It's wild

[distant raven]

I liked designing logical circuits with transistors but there was a point where I really could only move forward with a microcontroller or fpga

I even made flip flops and adders with NPN transistors in nand gate ripple adder configuration

Lots of fun if you’ve never done it

[limpid nest]

You're just trying to make me regret not doing an EE degree more than I already do!

It's working!

[distant raven]

Lol, I did that outside of my degree because they were not doing enough

SR Latch with NPN transistors

And the 555 off to the side to eventually pulse the SR latch

This is how I learned the practical function of different logical circuits

[tough matrix]

getting ready to order my 2-channel motor controller from JLCPCB.

If anyone cares to take a look, here is the schematics

[distant raven]

RP2040?

Yup, should have just opened the schematic lol

[spice turtle]

Do your encoders have external pull ups?

Might want to add pull up resistors on board just in case

(and just dont populate them if you are using an optical encoder)

in my experience, using a RC filter doesnt really work that well, but using pull up resistors of say 10k, work pretty well if you are edge detecting

[tough matrix]

thanks
normally the magnetic encoders I've seen do have built-in pullups, but indeed, I may add it as an option

bigger problem is that my board only provides 3.3v to encoders, and some need more than that.

but I don't want to add another level shifter...

[thick willow]

Can we trust datasheets or do some companies lie about it?

Sometimes I find some pretty inexpensive chinese components, but I'm always wondering if their quality could be lower or something. I usually try to stick to components of big reputable companies, but I'm wondering if I should begin using chinese stuff

[cinder anchor]

Are there any reliable ways of testing the components to make sure they meet spec and are reliable? You know, like the IKEA robot arm pushing the rocking chair down, repeatedly 100k times. 😄

[thick willow]

That's not the kind of route I would like to take. Testing failure modes would be extremely slow and expensive too

[cinder anchor]

So, I guess then it just comes down to what you consider to be an acceptable failure rate. When you say: "Chinese stuff" are you implying that what you're buying from the "big reputable companies" isn't made in China?

[thick willow]

No, just talking about chinese companies , as opposed to western/japanese companies that just use chinese workforce.

[cinder anchor]

Well, most of the components will be made in China, anyway... I think the only difference is the level of quality assurance and support. I order things off of AliExpress all the time, and so far I have received very few components that were not as advertised.

[cinder anchor]

What type of components are you buying, if you don't mind me asking?

[thick willow]

isolated dc/dc converters

[cinder anchor]

Hmm. I would say buy a smaller batch first, then check them out, and if they are comparable to what you'd get from a trusted seller, order more.

[heavy jasper]

For the most part… if there is an actual data sheet, and it’s provided by/matches the actual manufacturer and part number of what you’re buying (that is - it’s not someone trying to pass off a counterfeit), then generally the specs on the data sheet are fairly reliable. It then becomes about knowing which specs might be important but not listed (and as such uncontrolled).

I would really really not trust things like bare ICs (that is - I try to only trust first-party sales by the manufacturer, or sales through authorized distributors of parts that are known in-date.), but assembled modules at least have some modicum of effort put into them.

[cinder anchor]

Harry to the rescue.

[heavy jasper]

And you can kind of do a bit of an informal failure analysis- say I have thousands of $ of equipment that I want to power by this dc-dc - then I might shell out the extra money for the confidence and peace of mind.

Where the top of that food chain is risk of bodily harm or death to you or anyone else (say…. medical devices) - there even the manufacturer’s word isn’t necessarily good enough and it’s time to start combing through their third-party testing / certifications.

[thick willow]

That makes sense. I'm currently just prototyping, so I guess I'll just use inexpensive stuff that i find in ali/ebay. But as soon I decide to design the final version I'll stick to reputable sellers like digikey or mouser.

[heavy jasper]

The best gut sense I have is generally the classic “if it’s too good to be true” pricing.

[thick willow]

I still was wondering if some companies would outright lie in their datasheet. I figured that if some are willing to spend quite a bit of effort in counterfeiting ICs, lying in the datasheet figures wouldn't be a big deal at all

[heavy jasper]

There’s outright fraud - e.g. counterfeiting chips - but much much more common is lies by omission and/or just not assigning specs to things.

e.g. for a power supply, your DC voltage might be good but it has absolutely horrendous AC noise and ripple.

Usually in such cases - the figures of merit are just not specified, which means there’s nothing you can take back and say “this product doesn’t meet your specs, I want a refund.”

[thick willow]

yeah...

well its good to know that we can trust the values

I've seen lot of ppl not being very honest when doing science (p-hacking, arbitrarily discarding data that doesn't support the hypothesis, etc) that I figured that here they could also do that kind of stuff to get the values a little better than what they actually are

another question: are there any risks that isolated parts of a PCB might charge up and develop a voltage that might arc the isolated parts?

[heavy jasper]

Not impossible, but hard to give better guidance without more info - generally with the regulators on their own won’t do that, at worst you might get some AC voltage /noise coupling between the halves (most commonly due to inter-winding capacitance in the transformer windings not having an AC return path), or maybe some DC but it’s not backed by a ton of energy - when you start adding bigger ground loops is where there can sometimes be interesting times.

[cinder anchor]

thanks for summing up the entire pharma industry so neatly 😉

[thick willow]

Why would there be ground loops if grounds are isolated?

[heavy jasper]

The same AC coupling business - not quite a ground loop in the true sense, but interesting /weird coupling paths.

[thick willow]

I was thinking more in some external source that could charge up the isolated parts like atmospheric charges?

[heavy jasper]

ESD is kind of the canonical one there

[thick willow]

So I was wondering if connecting both grounds through a high impedance path would make sense or would be just stupid

[thick willow]

I was refering more to the academia, you know "publish or perish"

[heavy jasper]

You can - and it’s good to have pads for on a PCB (also to have pads for some high-voltage capacitors across the planes in case you run into said noise coupling problems and need an AC return path)

In the end this kind of comes down to what’s acceptable for you given your intended use of an isolated converter - e.g. do you know you’re going to have a fixed ground offset between the sides, that sort of things.

[thick willow]

I see... I'm currently just trying to isolate a computer USB from voltages that could damage it if currents decide to take the wrong path

Plan is to power the isolated part from the USB VBUS as well instead of requiring a separate power source

I was checking Analog ADUN ICs, but their solutions end up requiring lots of ICs and passive components, their solutions are expensive and take quite a bit of valued PCB real estate. Then I found some very integrated isolated dc-dc modules that were also very inexpensive. So I figured that they might be a better alternative. I'm not really sure what advantages these Analog complex solutions would give, except higher flexibility.

[spice turtle]

Depends if you are making it universal or for yourself. But even if it gets 3.3V, your pull ups will do the job of translating the levels anyway.

[digital rock]

I am trying to design a board with all through hole components and I’d like to replace this board https://www.adafruit.com/product/4654. The key with this board is the true disconnect to provide battery saving mode. I can find the smd chip but that doesn’t help. Can anyone help with a path to explore to design the boost circuit with a true disconnect functionality ?

[digital rock]

Would something like this work? https://www.digikey.com/en/products/detail/analog-devices-inc-maxim-integrated/MAX608EPA/2115843

[heavy jasper]

The “true disconnect” tends to just be another power switch that prevents the output of the boost from connecting to its downstream load - you can just make a normal boost circuit, then add a load switch after it.

[digital rock]

Ty that gives me a thread to explore

[limpid nest]

I need to switch 8 signals at the same time, is there such a thing as a N-Channel FET (or other transistor) array where all the transistors share a gate/base?

ah there it is, I assumed it would be harder to find

[limpid nest]

I feel like I'm losing my mind. I have +3v3 in one power rail and GND in the GND rail on the opposite side of the breadboard. When I put a my meter across 3v3/gnd with the black probe at one end of the BB, I read +3v3. But when the black probe touches another part of the BB's GND rail, I get -1.2V. What on earth??

specifically when I touch the ground pin of my unpowered breakout board.

which is tied into the GND rail

3v3 and GND are from an external PSU. That's the only ground point in the "active" part of the circuit

It seems to have something to do with the breakout board that's connected to ground but I don't see how it could.

since the board isn't powered as of yet

I'm a goofus

are opposite ends of a power rail usually not connected on a breadboard?

[tough matrix]

indeed, long bb are usually split in the middle.
was burned by it too

[limpid nest]

hmmm

IDK how that could give me a negative voltage but who the heck knows

I swear I've learned this before. I'll probably learn it again

wow this chip I'm using has some major downsides. E.g. LEDs are just on when it's unpowered...

[frigid seal]

What's the next step up above LTspice? I'd love to be able to use TI's component models but I can't seem to make LTspice accept them.

[worldly schooner]

https://www.ti.com/design-resources/design-tools-simulation/models-simulators/overview.html
If you're only using TI parts, PSpice for TI might be a nice pickup? There are some limitations if you import third-party models, though?

TI apparently cannot support LTspice directly for some unmentioned legal reasons, apparently.

https://e2e.ti.com/support/tools/simulation-hardware-system-design-tools-group/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/796765/i-need-an-ltspice-models-for-some-of-the-ti-components-please

[proper anvil]

Does it make more sense to add a small chip capacitor to each servo, or to add a single large electrolytic somewhere? trying to prevent brownouts when the servos are moving

[fervent lance]

how can I do connectors like those https://ae01.alicdn.com/kf/H25bb4f71ba11462d86b40a612e4731eb4.jpg , flat made out from the pcb with on easyeda?

[verbal moss]

What servos are you using, how far apart? Answer may depend on your servos and other factors. Seen Capacitor section in https://learn.adafruit.com/16-channel-pwm-servo-driver?view=all , they recommend n * 100uF per servo, but that guidance probably assumes SG90 or something else not too large is being used. PCA9685 16 channel breakouts usually come with a single 1000uF cap, personally have had good experience with those (48 SG90 servos moving in sync. Not sure if that will hold true for my 192 servo build), hth.

[tame sigil]

What do you mean connectors like those?

[unreal flax]

Possibly he means card-edge connectors with gold fingers.

[tame sigil]

If you mean card edge connectors there are user made libraries for common card edge connector types that you should be able to find.

[ember laurel]

@thick willow my experience with most Ali/eBay AC/DC PSUs has been pretty bad. 95% of what is on offer is absolute junk, and any CE or FCC markings you’ll find are just markings.

Some are just plain and outright dangerous. If you ever want to take your device to market, and pass electrical safety and EMC tests, you have to use proper supplies from reputable companies.

[spice turtle]

If you have the room, use multiple low esr caps to provide for more of a current boost. Otherwise one large, low esr cap should do.

[ember laurel]

@proper anvil the datasheet for your motor driver says to connect a capacitor to ground for every power supply line.

additionally, it mentions BEMF, and using 10uF ceramic (low ESR) capacitor

not sure if you'll see some bemf

something like this:
https://lcsc.com/product-detail/Multilayer-Ceramic-Capacitors-span-style-background-color-ff0-MLCC-span-SMD-SMT_Samsung-Electro-Mechanics-CL31B106KBHNNNE_C89632.html

[fervent lance]

Yes

[tame sigil]

there are user made card edge connector libraries for common card edge connector types that you should be able to find.

[fervent lance]

I'm not trying to use any standard, I'm just trying to learn how to use the software; I'm using easyeda, I'm not finding any way to batch place pins, wires nor other components, googling "easy eda batch placing" or similar keywords ends on nothing

[tame sigil]

You can select multiple components or pins by left clicking while holding ctrl or shift key at the same time

Havent used easy eda quite a while cant remember exact key

[fervent lance]

nothing, both do not work, also when I place pins, then delete them, then place other pins, the number does not reset, I mean if I do delete pin 1,2,3 and the place other pins, they will be 4,5,6 and not 1,2,3 ; I'm sorry for asking silly questions, but I'm quite new, and I don't quite know what to even google

[limpid nest]

If you have a big pour around a pad, 2 Oz is a big heat sink

[noble forum]

So, I want to build my own esp32 board, literally just a barebones poc. One of the big things I want to do is add a lipo battery. What are some of the ICs for charge and discharge people recommend.

[limpid nest]

I'd recommend looking at what the feather line uses

[distant raven]

Mcp73831

Great single cell LiPo charger

If you want to use multicell packs, I’d have to look but TI makes a few good ones

[tough matrix]

is it in stock?

[spice turtle]

looks like only DFNs are in stock

[minor niche]

https://github.com/adamalfath/sentsor-core-esp32micro
https://github.com/adamalfath/sentsor-core-esp32dev
check these two for reference

[noble forum]

Haha. Thank you!

[minor niche]

the first one is just 30 by 30 mm I think

[noble forum]

Holy crap. That’s perfect. That’s exactly what I wanted.

The documentation in this is amazing.

[minor niche]

hahaha glad it helped

[distant raven]

LCSC I believe has the mcp73831

If you order like one or two of these you can get them from Digi-Key

I found this part with the Digi-Key mobile app. https://www.digikey.com/en/products/detail/BQ24170RGYR/5142989

It’s for 1-3S LiPo battery packs

It doesn’t show a lead time which usually means stock is hidden to keep people from buying out the whole stock

Sometimes it’s a bug but I’ve found you can still do one or two in an order

[limpid nest]

Are general circuits questions OK here? I feel like I'm losing my mind

[unreal flax]

Go for it, probably a good a channel as any.

[limpid nest]

Ok thx

So I think the outlet is just busted tbh but I might as well confirm here.

I've got continuity between all the contacts on the plug and on the outlet. But when I plug it in, no power

I assume there's an open circuit somewhere in the outlet

I am running a brief errand but I'll check voltage in a second

Only thing that's slightly hinky is the corrosion on the ground lug but that shouldn't prevent current flow

[bright thistle]

What's the cable attached to?
@limpid nest

Did you try it in another outlet to be sure the device is not pining for the fjords?

[limpid nest]

The outlet I used was confirmed good

I'm replacing the outlet pictured

[limpid nest]

Made the mistake of touching my PSU board. Need a heat sink!

I'm only powering LEDs from it but I guess they are using a good bit of power

[ember laurel]

@limpid nest wht requires so much power?

and what generates the heat?

[distant raven]

So a while ago I posted about a photodiode amplifier circuit that I wasn’t getting a response on when polling the analog pin it was feeding. Turns out just one singular pin was not making contact. It wasn’t visible from magnified inspection. I only found out when I accidentally applied pressure to the op amp and suddenly I was getting the kind of input I expected 🙃

Applied more solder to the pins and voilà

So my design was great, I just couldn’t see that a pin was ever so slightly not making contact lol…

[limpid nest]

7V regulated to 3.3V powering 32 LEDs

[ember laurel]

linear reg?

[distant raven]

What’s the current requirement of the LEDs?

[limpid nest]

Not 100% sure. I'm testing out AW9523s on a breadboard. I have the LEDs fully "on".

[limpid nest]

Indeed, meant to say that

[ember laurel]

if you're using a linear reg to drop 7V to 3.3V, that is quite some drop in voltage, that will go all into heat

[limpid nest]

Yeah this is just for testing, and only using 7V because that's the barrel jack PSU I had.

I needed to use something greater than 5V for another project. This power unit does 5V and 3.3V

[ember laurel]

how much current are the leds supposed to pull?

[limpid nest]

Unclear. I need to dig thru the datasheet and see what current I can expect when the sink is fully turned on

I could stick my meter in series I guess

[ember laurel]

just measure the voltage drop over the series resistors, and use ohms law?

[limpid nest]

No series resistors. The chip is a constant current sink

[ember laurel]

hmm I see

measure drop over chip?

[limpid nest]

I was thinking of measuring drop and resistance

But I don't know if it's linear?

But if I'm breaking out the meter, I may as well just do an in circuit current test

[ember laurel]

yup

and the meter should always be maximum an arms length away

[limpid nest]

Yup

[ember laurel]

that's ohm's second law

[limpid nest]

Lol

Law 2.5 is check where the probes are in the meter. Ignored that one and I blew a fuse

[ember laurel]

darn

I was actually just going to write you about that 🙂

because you pull quite some I

[limpid nest]

Well I was gonna gonna measure one LED and extrapolate

[ember laurel]

still

what's your low I range?

150mA?

[limpid nest]

On the meter?

[ember laurel]

yeah

[limpid nest]

I'm not sure, I haven't gotten to work yet. It's a fluke 117

Resolution is 1 mA

[ember laurel]

hmm that thing has a 10 amp limit

[limpid nest]

I don't think I'm using anywhere near that

[ember laurel]

32 LEDs, 300mA each = 9.6A

not sure what kind of LED that is

[limpid nest]

These are just basic blinky LEDs, the kind with a 20 mA max

That's what the aw9523 is meant to sink

[ember laurel]

aha ok

[royal anchor]

I plan to design my first pcb. What is a friendly pcb designer software for beginners?

[limpid nest]

Hmm

People often recommend kiCad

It's free

And powerful

[worldly schooner]

KiCAD is usually today's go-to for PCB design. I sometimes recommend EasyEDA for its direct part library integration with JLCPCB/LCSC, but KiCAD is probably the first one to consider.

Eagle is the other popular option for its integration with Fusion 360, but it's starting to decline in popularity recently IIRC.

[limpid nest]

Autodesk is seeingly trying to merge EAGLE into fusion

[thick willow]

Do computer USB ports have any protection to avoid mains voltage to go through any of their pins?

[limpid nest]

I don't think so

Not as part of the spec

Some ports on some machines may have reverse voltage protection

Whether that protection can stand up to 120 VRms is another matter

[thick willow]

I got this https://www.maximintegrated.com/en/products/analog/data-converters/analog-front-end-ics/MAX30001EVSYS.html and couldn't find isolation in the PCB design and also no warning at all about using it only with isolated USB or an unplugged Notebook. So I'm wondering if there is some safety measure that I just missed, or Maxim assumes that the final user doesn't need any warning and will isolate the USB por anyway

Usually when there is risk of electrocution they write some big red warnings.... and considering that electrodes are put directly close to the heart I'm a bit puzzled

[ember laurel]

@thick willow Medical devices usually require you to have MOPP - Means Of Patient Protection. Depending on the class of device, you'll need 1-3 MOPP.

This, most of the time, is down to the power supply.

I don't think that the evaluation kit is classified as a medical device.

[thick willow]

Probably, still you would think they should either implement some power isolation or warn about the risks...

[ember laurel]

they have a small note about "Facilitates IEC 60601-2-47 Compliance Testing"

that standard just references the general standard (60601-1-1) when it comes to electrical hazards

the PSU is considered a part of the medical device

Using an already IEC60601 certified supply helps.

[cinder anchor]

What's the best, decently priced, PCB service? I looked at SparkFun's A la Carte, but it's a $950 fee. Which would be fantastic if I wanted to mass produce these guys. But, I don't...

Maybe someone could list the recommended vendors and then maybe we can pin that?

I know of PCBWay, JLC, I haven't messed with the Digi-Key service, and didn't Fritzing have some service too?

[limpid nest]

What's your goal? Hobby stuff as cheap as possible? Places like JLC are your best bet. Best quality:price ratio? Places like OSHPark are better

[cinder anchor]

It's for a power management system for my truck, so preferably something decently reliable, doesn't need to be super-fancy.

[limpid nest]

I've always found JLC's quality perfectly fine for my needs, but I'm not make a power management system that's going in a 50k+ truck (assuming). Probably worth the extra 15 bucks for OSHPark

Keep in mind that with these two examples, JLC gives you 5 boards, OSH gives you 3

[cinder anchor]

I only need 3.

[limpid nest]

That assumes 100% yield on your manufacturing

[cinder anchor]

Well, multiples of 3, rather.

[limpid nest]

You can get multiples of 3 from OSH

[cinder anchor]

How many would you suggest I get?

[worldly schooner]

SparkFun's A la Carte is specifically a PCB design service, the other guys usually just fabricate whatever you design.

[cinder anchor]

6-9?

[limpid nest]

You need 3 completed working boards?

at least 6

[worldly schooner]

Do you have a working design to send out, or are you just doing this for the first time?

[cinder anchor]

Oh. You know. First time. I know. I should give up and go home.

[worldly schooner]

Nononon

Don't do that, haha.

[cinder anchor]

lol

I was waiting for the, hey, you can try, good luck!

So, I have a fairly good idea of what I want on the board, though.

[worldly schooner]

It might be a good idea to prototype a design if you're uncertain about your design.

Perfboard and wires are a pain, but they do wonders in validating schematics.

[cinder anchor]

I have already prototyped this with a variety of controllers and different types of "switches" like old school relays and FETs.

[worldly schooner]

Oh, if you're confident in your schematic, converting to a PCB shouldn't be too bad then.

"Only need 3" means you probably should grab a couple extra, just in case. 5 would be a perfect quantity once you have a design, just in case one or two come out wrong.

[cinder anchor]

Here's my plan: DC-DC/MPPT control unit goes inside cab along with micro controller and other sensitive parts. Micro controller connects to the custom board in the bed of the truck (inside IP68 enclosure) via a single industrial CAT5 cable (already sourced, and yes, it was expensive) and I was thinking of doing something similar to the Ethernet ports that SparkFun designed for longer runs of Qwiic, and basically control it that way.

There's an example proto breakout from SparkFun that use FETs to switch 12 V power (but from a computer PSU) that I was hoping to adapt to just taking 12 V from the house battery (12 V 100 Ah LiFePo4).

I also found a SparkFun Qwiic GPIO module with 8 ports.

This was before I discovered the amazingness of Adafruit, so most of the stuff I have prototyped with is from SparkFun.

Should I use KiCad for this? What do you recommend?

[worldly schooner]

KiCad is probably best.

[cinder anchor]

I would need some pointers on my cobbled together design just to make sure I didn't mess up any resistors/capacitors/whatever diodes or grounds or whatever.

How do y'all feel about this project? Would it be doable by someone like me?

[worldly schooner]

Don't see why not. You seem to know what you want to do.

[cinder anchor]

I don't really have enough money to pay someone professional to design it, but I am totally open to sponsoring someone on GitHub in exchange for advice and help with finalizing the board.

[worldly schooner]

I'm sure someone here can help out in the department of "best practices" after you get a first pass of your design.

[cinder anchor]

Cool deal. I'll get started (again) on this.

My wife asked me how long the fridge is going to be sitting in the living room and used as a cat perch. I took that as a hint that I should probably finish this project sooner rather than later.

(we're putting a fridge in the truck on slide-out rails)

and then powering with a LiFePo4 battery, and I'm going to add some lights and whatever on there too

I have sourced most of the parts except for components for the board, so hopefully there's still some around 😄

And, I was thinking to outsource the board and all that so that others can build similar setups in their campers/overlanding vehicles.

OK. That was a lot of text. Sorry. I am done now.

KiCad question, Global Symbol Library Table, should I go with the default or is there some Adafruit-specific stuff I should use?

[verbal moss]

Already ruled out using Adafruit's Perma Proto boards? Have several one off, and v1 projects around the house using those. Only recently decided to invest time/money creating PCB design for compact project that'll have ~20 units. Mainly doing for the fun and experience of being able to rationalize learning how to design a PCB (EasyEDA + jlcpcb + smt assembly).

[worldly schooner]

Quoting a previous response, I have already prototyped this with a variety of controllers and different types of "switches" like old school relays and FETs.

[cinder anchor]

I have already prototyped it in various configurations in my lab. Now it's time to actually install it in the truck, and I want something that's going to be easy to repair/replace/service.

But, sure, I could cobble something together with perma-proto boards, a few feather splitters, and some bubblegum. 😉

Don't forget toothpicks. Solid McGuyver component.

Wow, KiCad defaulted to A4! It's so nice of it to remind me of my previous home and the simple life of Those That Can SI.

I am hoping I can hand-solder things onto this board. Only thing that worries me a little bit would be the QT connector. Everything else is bulky enough for me to use standard PTH components, and I have enough room in the enclosure (it's like 12"x9") to get away with it, and it probably won't hurt either since some of it is higher voltage/power to have it more spread out.

For 12 V and < 5 A, do I need to use different thickness of vias?

And, if so, how far away from other components do I need to place those?

I don't know anything about electrical interference and whatever, but I am assuming there's going to be some.

[cinder anchor]

Where can I find the KiCad symbols for these guys?

Or do I have to switch to EAGLE?

From what I can tell that looks like EAGLE, right?

[unreal flax]

Yes, that looks like Eagle.

[flat vigil]

kicad has a CONN 1x4 symbol that I've used for stemma connectors

[cinder anchor]

I haven't used KiCad before, and I am not even sure how many layers this will need if I design in EAGLE. I can't really afford a subscription, and I don't use the software that often.

I have used EAGLE, and it's pretty cool.

[flat vigil]

kicad 6 looks awesome

[cinder anchor]

it does

[flat vigil]

good time to switch

[cinder anchor]

oh, snap, I am on 6

@flat vigil can I use the KiCad symbols interchangably with what I'd use in EAGLE? How do I design the PCB with this and the stemma connectors?

Like, footprints and all that.

[flat vigil]

you can snag symbols out of eagle files but I'd encourage you to use the default kicad library

[cinder anchor]

yeah, I am using default right now

[flat vigil]

there are JST SH (iirc) footprints already

so conn 1x4 + jst sh will get you stemma qt

[cinder anchor]

OK, I will look around and make sure I get the correct one.

[flat vigil]

just make sure the pin order is right

[cinder anchor]

What is the correct pin order?

[flat vigil]

isn't it in your screenshot?

[cinder anchor]

lol

yes, it is

[flat vigil]

I don't remember off the top of my head

[cinder anchor]

hahaha, I am a dingus

[flat vigil]

time for me to get outside. good luck!

[cinder anchor]

Thank you!!!!

What does MT mean here?

Is it shielded or something?

[limpid nest]

I think that's the shield pins

Or what I call shield pins

Take a look at a stemma port, it has two larger "pads" on the sides towards back

I think they are also for mechanical stability

Super easy to rip up traces on a stemma port if those aren't soldered

[unreal flax]

Probably "mounting" pins.

[bright thistle]

Nice :3

https://aisler.community/t/introducing-aisler-push-for-kicad-the-best-way-to-get-your-kicad-design-manufactured-worldwide/249

[cinder anchor]

OK. I am gonna kick this KiCad symbol editor in the face shortly.

KiCad: I have selected these four rectangles, but, how do I actually change the width of them?

I try to change one of them, and it immediately tries to snap to grid, which makes it either super thin or chonky

Not a huge deal, but it looks kinda ugly without spacing...

Maybe if I remove the numbers and replace them with the text?

meh

[cinder anchor]

I am looking for the KiCad equivalent of this FET, how do I find it? https://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf

oh, found a symbol that works

https://octopart.com/rfp30n06le-onsemi-84794873#CadModels

[cinder anchor]

KiCad stuff. This is what I've got so far. I need to somehow add 12 V input voltage from battery and battery negative. Not sure how to wire any of that. PLS SEND HALP.

Basing this off of:
http://cdn.sparkfun.com/datasheets/Dev/Arduino/Shields/PowerDriver-Shield-v13.pdf
https://cdn.sparkfun.com/assets/2/e/4/6/c/SparkFun_Qwiic_GPIO_Schematic.pdf

this would be connected with STEMMA/QT to an Adafruit Feather rp2040.

[limpid nest]

A 1k resistor is going to make that LED very dim, FYI

Well

3.3mA may be OK but it may end up dimmer than you want

[cinder anchor]

other than that, how do I map an external 12 V source onto this?

Sources are here: https://github.com/NascentMaker/pwrbox

[limpid nest]

How do you mean "map"?

I'm on mobile so browsing is limited

[cinder anchor]

I basically just want to add terminals for 12 V power

from the house battery in the vehicle

[limpid nest]

Ahh

I'm not super familiar with the existing connection hardware in vehicles

[cinder anchor]

I can do any connector.

So whatever is best.

[limpid nest]

Also whats on the other end of JP1/JP2 et al?

[cinder anchor]

Ah, those are screw terminals that 12 V accessories are connected to. Like lights and a fridge.

[limpid nest]

Ahh ok

Fridge?

[cinder anchor]

Yeah, for my truck.

[limpid nest]

That runs on 12V?

[cinder anchor]

Yup. It draws less than an amp.

[limpid nest]

Wow

[cinder anchor]

Well. It was not cheap. 😄

($700 or so, and that's actually cheap compared to other brands)

[limpid nest]

So I'm assuming all of them are proper loads and you're not going to create a short thru the fet when you turn it on

[cinder anchor]

can you explain that a bit further? What does create a short mean?

[limpid nest]

Like just making sure you have some kind of impedance in the connection between the terminals of JP1 for example. It sounds like you do. Just thinking of mistakes I might have made on my first design.

[cinder anchor]

Oh. Wait, so if there's nothing connected to those terminals, will it short?

[limpid nest]

Nooooo

It was a passing concern

[cinder anchor]

ok

[limpid nest]

One note on the layout, advice I've been given is to have a "flow" to your diagram

I like to do board inputs on the left, "thinking" chips/main logic in the middle, and outputs on the right.

Not the only way to do it but it's "logical" to brains from cultures that use left to right writing

[cinder anchor]

Word. I will try to do something like that once I've gotten this to actually work.

[limpid nest]

Yeah I sort of assemble as I go and then do cleanups throughout

[cinder anchor]

I wonder if I can find a TCA9534 chip somewhere?

[limpid nest]

The fun part is next! Routing!

[cinder anchor]

Oh my god. I don't think anything routes.

[limpid nest]

Do you know about octopart?

[cinder anchor]

I've heard about it by way of searching for things and seeing it in search results. Never actually messed with it.

[limpid nest]

Useful in the chip shortage

It collates search results for parts and other things

[cinder anchor]

OK, lemme see if I can find this part.

oh, it's definitely available

[limpid nest]

Good!

[limpid nest]

Lol

[cinder anchor]

they're $1.59 each... I guess I am getting a bunch, just to be safe

[limpid nest]

You're gonna end up with a hoard of parts

It's relatively inevitable

[cinder anchor]

I already have a hoard of parts.

[limpid nest]

Lololol

[cinder anchor]

😄

[steel valve]

Making a custom PCB and the most important part of it is the power p much.

I have made these two schematic parts based on stuff from adafruit and sparkfun

And my question is, do I need to put anything to link them together

The USB C Charger Charges the Lipo, and the lipo goes into a 3.3v buck converter so that the voltage is always 3.3v since from my understanding in pcb design you should always have a consistent voltage

BTW the T shaped symbols on the left are GND forgot to add the indicator

[unreal flax]

Just naming the net "lipo" as you've done should link the two.

[steel valve]

No no no I don't mean that

I mean is it fine having VBAT Charging Pin 2 (Lipos +) and that same pin going into a step down converter

Buck
^
LiPo
^
Charge

[unreal flax]

Yes, that should be fine, though you'd want to have your charging current set large enough to both charge the battery and run the downstream circuit.

[steel valve]

I have it set to 12K (about 80mah)

Anyways cool, so I am doing it right. Does this same concept apply for a fuel gauge?

Pretty much due to the chip shortage I can't seem to find any cheap fuel gauges for lipos that are in stock on mouser/digikey (if you happen to know any please tell me) so I am gonna make an empty area on my PCB to put a fuel gauge when they finally come in stock hopefully one day 😂

[limpid nest]

Try octopart

Just in case

[steel valve]

I was originally intending to use a chip that is available on adafruit or sparkfun since those usually got a lot of useful info for a student like me but when I look on digikey or mouser they usually aren't in stock

Like on adafruit they use the LC709203F Fuel Gauge, and on Sparkfun they use the MAX17043

[cinder anchor]

OK, so this part: RFP30N06LE, a MOSFET is no longer manufactured. I am trying to find a comparable part, but I am not entirely sure I've got the right parts.

[limpid nest]

It's a crapshoot these days

[unreal flax]

The fuel gauge should do the right thing so long as the current sensor is placed so that it reads both the charge and the discharge current, i.e. if it's electrically next to the battery.

[cinder anchor]

How would I formulate that search?

"30A, 60V, ESD Rated, 0.047 Ohm, Logic
Level N-Channel Power MOSFETs"

[limpid nest]

Make sure you need a power mosfet

How did you arrive at the first choice?

E.g. for your fridge, you don't need 1.8 kW of power

[cinder anchor]

yeah, true

[steel valve]

Huh octopart is p nice, found this variant of the adafruit chip they use, but I have zero idea how this is put onto a pcb

https://www.mouser.com/ProductDetail/onsemi/LC709203FXE-05MH?qs=y6ZabgHbY%252BxSp%2FsRUFstUw%3D%3D

[limpid nest]

Oh yeah

[limpid nest]

That's gonna be tough to do with hobbyist tools

[steel valve]

yeah

ima check the max ones

cause who knows maybe theres a place i didnt check already

f no place with a chip alone of the MAX17043

[cinder anchor]

so, I am trying to flip this FET switch with 3.3V, what am I looking for as far as the gate charge, drive voltage, vgs, and all that?

[limpid nest]

VGS you want as 3.3V or less

Not sure about gate charge

[cinder anchor]

k, makes sense, thanks

[limpid nest]

Np

[cinder anchor]

like, this one? https://www.digikey.com/en/products/detail/vishay-siliconix/SQP60N06-15-GE3/9861091

[steel valve]

Oh yeah, if I were to add an ON/OFF switch to my pcb, where would I make it cut stuff out at?

Inbetween the lipo and the buck?

[cinder anchor]

I'm mostly making sure that it'll handle switching on/off at temps ranging into like 100'F or so.

[steel valve]

Or after the buck converts the current to 3.3v

[cinder anchor]

before the buck

[steel valve]

Ok thought so just making sure

[unreal flax]

You could also take advantage of the EN pin on the buck to disable the regulator without needing to have a full disconnect switch.

[cinder anchor]

What about this one? Would I be able to switch this one with 3.3V or 5V? https://www.digikey.com/en/products/detail/vishay-siliconix/IRFZ34PBF-BE3/13540556

[steel valve]

WDYM without needing a full disconnect switch

[unreal flax]

Like you wouldn't need to run the main power current through a switch. If you're just flipping the EN pin, it gives you some freedom to use like a tiny DIP switch or something.

[steel valve]

Oh so I could use a button instead of a switch if I have the button go to EN?

[limpid nest]

I don't think this is a good choice. The threshold should ideally be < 3.3V if you want to use MCU logic to drive it. The threshold is the bare minimum you need to get any current to flow whereas the drive voltage is at minimum rdson

[steel valve]

That's cool, what footprint do most arduinos that have dip switches use?

[limpid nest]

See this https://electronics.stackexchange.com/questions/367274/what-is-drive-voltage-for-a-mosfet

[steel valve]

Cause I am tryna use parts people typically use in arduinos or similar since its easier to find those types of parts in stock usually

[unreal flax]

I think a button versus switch would be kind of independent.

[cinder anchor]

So, would this one work?
https://www.digikey.com/en/products/detail/vishay-siliconix/IRLZ34PBF-BE3/13540582

[limpid nest]

Also I'd go with SMD but I'm a glutton for soldering punishment

[cinder anchor]

I can't solder SMD, brah.

[limpid nest]

It's not toooo bad

Looks pretty good, you can dump 10 amps down that bad boy at 3.3V V_gs

Might be worth getting heat sinks while you're at it

[cinder anchor]

sweet, that's what I am going for

I have heat sinks already

[limpid nest]

Oh you want to use that much current?

[cinder anchor]

no, not really, but I want to make sure I have plenty of overhead

[limpid nest]

Ah gotcha

[cinder anchor]

mainly because as far as I understand it, MOSFETs are entirely dependent on ambient temperature when it comes to throughput... Is that correct? So I want to make sure that even in a hot environment (like the stupid south of the US where it's like 100'F) my stuff will still work.

[limpid nest]

They are heavily influenced by temp yeah

There are often derate curves in datasheets

[cinder anchor]

thanks

[limpid nest]

Np!

[cinder anchor]

OK, order placed.

[steel valve]

So are you saying to do something like this for EN or am I not thinking right on how the button is wired

Whoops meant for LIPO to go to the first part of the button

[unreal flax]

You no longer have the pullup to the lipo voltage, so that probably won't work. Either have a pullup to lipo and a switch to ground, or a pulldown to ground and a switch to lipo.

[steel valve]

wait is this what you mean im confused

[unreal flax]

Time to whip out the old ASCII drawing... LIPO--/ ---+---EN | GND--/\/\--+

With the switch open, the resistor pulls EN down to ground. With the switch closed, EN sees the lipo voltage.

[steel valve]

Ok I think this is what you mean then

[unreal flax]

Nope, that has a direct connection between LIPO and EN, so the resistor and switch won't do anything.

[fiery parcel]

So recently I made a prototype of a project im working on... it consists of a CLUE board, an amp+speaker, a little battery charger, and an RFID scanner, all open source from Adafruit. Is this something i'd be able to plunk into a single circuit board design?

(with reasonable effort)

[steel valve]

Are any of these two what you mean

[unreal flax]

Can you explain why my diagram is confusing you?

[steel valve]

What are the slashes

[unreal flax]

The ---/ --- is the switch, and the --/\/\-- is a squiggly-line resistor symbol.

[steel valve]

Oh

[unreal flax]

Sorry for the crappy drawing, heh heh.

[steel valve]

Is this more like it

or this

[unreal flax]

Yep, those are both equivalent, and exactly what I meant.

[steel valve]

Ok cool

Now, there is one more main thing I can think of RN that I wanna add to my PCB which is a CH340G since I assume it is necessary for programming the Artemis by USB

Are CH340G chips blank?

Do they need stuff loaded onto them before they can do the USB to Serial stuff

[unreal flax]

They should just be power-up and go.

[steel valve]

Ok cool so I could just implement one and it would work ok

[steel valve]

Am I thinking this right with how I am wiring it or did I mess up on the VCC VC part

[unreal flax]

I'm not familiar with the chip offhand, I'm afraid.

[steel valve]

Ah ok

This is an example diagram I found of how to wire a CH340E

Which I based my version of the CH340E schematic on

[unreal flax]

You might want to consult the part datasheet to cross-reference things. Usually they'll have a reference schematic recommended by the manufacturer.

[steel valve]

What's the purpose of a JTAG connector?

Is it just an alternative to programming via USB?

Is it for loading a core onto a chip assuming it is blank?

[unreal flax]

It's primarily a low-level debugging interface (halt processor, read registers, step through code, examine variables, etc.), but as part of that it can also do things like loading firmware onto a device even if there is no bootloader code there already.

[limpid nest]

How do folks handle powering say an itsy bitsy or a feather that they have mounted in a PCB? I need to power both the board and a breakout and another device, all potentially at different voltages.

[spice turtle]

Easy. Multiple voltage regulators and a large enough input voltage to accommodate them. Say I have a motor that uses 24V, but the FET drivers need 12-15, but my encoder needs 5V and my mcu uses 3.3V. I would use different regulators for that. In this case, you step off the closest voltage to reduce power draw, so you wouldnt tap off the 24V line to power 3.3V, the power the regulator would have to dissipate would be pretty large even at low current.

opps, I accidentally started Autocad instead of eagle. I was going to show an example

Note: If you are wondering why I didnt use SMPS's for any of the lines its because I had issues with my MCU + a microchip brand SMPS. I solved it by using a linear regulator.

2nd Note, the regulators also show the incorrect part #, on the BOM they are correct.

just little things

[tough matrix]

depends on what power source you are using.
If you start with a power source of >=6V (e.g. 2s or 3s LiPo), you normally bring it down to 5V using a buck; then you can feed this 5v to ItsyBitsy/Feather (where it will be regulated to 3.3v by built-in regulator). You can also use your own regulators, as suggested by Nerdz, for other voltages

or you can get a ready-made multi-voltage power distribution board - they are commonly used in drones, e.g. https://usa.banggood.com/Matek-FCHUB-6S-Hub-Power-Distribution-Board-5V-and-10V-BEC-Built-in-184A-Current-Sensor-for-RC-Drone-FPV-Racing-p-1147591.html?rmmds=detail-left-hotproducts&cur_warehouse=CN&trace_id=4a421643999479307

[cinder anchor]

I was just about to ask a similar question, ha! If I have a 12 V input source from a battery (100Ah 12V LiFePO4), and I want to feed that into 6 MOSFET N-CH 60V 30A TO220AB, and then out to various 12 V accessories like lights and a fridge, do I need any kind of regulators and the like, if so, what do you recommend?

[limpid nest]

I phrased poorly. I was thinking how do you deal with reverse voltage or power supplies fighting each other if you want to power the adafruit mcu via a pin? Like someone could plug their laptop in to the MCU and that could be an issue

[spice turtle]

Im guessing those batteries are regulated already, unless they are actually outputting 14.4VDC (4 in series, assumed 3.6V each), which should be OK to use for other stuff since its rated to take a charge voltage that high anyway.

[cinder anchor]

https://www.sokbattery.com/products/100ah-12v-lifepo4-deep-cycle-battery

they have a BMS

[spice turtle]

Look up an Ideal "OR" gate circuit. You can make one with two shottky diodes or you can use FETs. They make sure only one supply is selected at a time.

[limpid nest]

Hmm, would have to see if that can be done on the mounting board

[spice turtle]

There are ideal OR gates out there, and come in SC-70 packages

[empty hollow]

Are adafruits internal eagle libraries open source? It would be amazing to have access to those so that making pcb's and intergrating adafruit boards into our own footprints becomes easier.

[limpid nest]

You can export the parts from a specific board. It often exports a lot more

[empty hollow]

Oh wow. Didnt know that was possible. Thank you.

[tough matrix]

Adafruit feather already has this kind of setup: it can be powered from BAT or USB, and each input is protected from backpowering (USB, by a diode; BAT, by a MOSFET). So for Feather, just connect your 5V power to BAT pin and that's it - no worries

[limpid nest]

What if someone plugs in a lipo? I'm just trying to think of all failure modes

[tough matrix]

so you are thinking of dealing with 3 potential ways of powering, LiPo, USB, and external power source? then yes, you need addiitonal protection

for reference, here is a piece of Feather schematics:

see the MBR120 Schottky diode and a FET?

it uses FET rather than diode on VBAT to minimize voltage drop; a diode, even a Schottky, has about 500mV voltage drop (I think - need to double-check)

[limpid nest]

No I'm just thinking of down the line when I'm not here and someone doesn't read my documentation

Tbf it's their fault if they don't read but if I can doofus proof it...

[tough matrix]

If you use ItsyBitsy, there is no LiPo connection, so there is less temptation for someone to connect an LiPo

[limpid nest]

That was my next question, does the itsy have a BAT pin?

[tough matrix]

There is a BAT pin, which you can use for connecting external power supply

[limpid nest]

Ahhh

Cool

Thx!

[tough matrix]

That's ItsyBitsy:

(not sure why they decided to use Schottky and not a FET here. Maybe just because FET is larger?)

[limpid nest]

I would guess so

But diode drops your voltage where a fet wouldn't, I think

[tough matrix]

yes, diode is more of a voltage drop

[limpid nest]

Voltage drop across RDSON but with the right fet that's going to be very small

[tough matrix]

actually, for diode they are using, it is not too bad: Vf=300mV at 100mA

https://www.onsemi.com/pdf/datasheet/nsr0320mw2t1-d.pdf

nice

[limpid nest]

That's not bad

[cinder anchor]

In the EAGLE schematic editor (9.x), what are the blue Bus lines for?

[unreal flax]

They allow you to group together multiple nets, so an 8-bit parallel bus would be just one blue line. Individual wires can branch on and off of a bus.

[cinder anchor]

Also, what kind of terminals do I need to use for 12V and <15A? Can I use the regular screw terminals from the Adafruit site?

[cinder anchor]

Interesting, do you have any examples of this?

I mean, all I've got is an I2C bus over STEMMA/QT.

[unreal flax]

https://www.youtube.com/watch?v=3c4PcVPb2hQ

It's not really worth the hassle for an I2C bus, since that's just two signals.

[cinder anchor]

figured as much, thank you for the link

oh, that is freakin' sweet

but, I obviously don't need it

[ember laurel]

In that feather schematics, does VBUS really go right to the gate on the mosfet, without any ESD protection diode for VBUS?

And also without any Pulldown on mosfet gate.

[cinder anchor]

So. How do you import images for silk screen stuff in EAGLE?

[cinder anchor]

here's what I have so far, hopefully someone has some spare time and can take a look at these...

[tough matrix]

there is a pulldown on the gate, but no esd protection: https://cdn-learn.adafruit.com/assets/assets/000/057/242/original/arduino_compatibles_schem.png?1531010817

do you think ESD protection could be useful? after all, vbus is nominally only 5v

[tough matrix]

I'll take a look tonight. But not everyone has Eagle, so it would be better if you also uploaded schematics and view of the board as PDF

[ember laurel]

@tough matrix well, touch the DC positive pin with your fingers after walking across a carpet, and you might fry the mosfet?

[distant raven]

Interesting thought. I wonder if anyone accidentally did that..

Just completely nuke being able to use a battery on their feather because they didn’t discharge static electricity before touching their board lol

[ember laurel]

I just tend to put esd diodes on anything that can be touched by human hands

[distant raven]

On the other hand, the mosfet Adafruit uses is actually pretty well rated for ESD

[ember laurel]

You can get up to 5kV or so - which can mess up a lot of stuff

Microcontroller inputs for sure

[distant raven]

Yeah

[tough matrix]

can you recommend some esd diodes to use? there are so many to choose from

[distant raven]

Any TVS diode would work in the expected operating voltage range

I found this part with the Digi-Key mobile app. https://www.digikey.com/en/products/detail/DRTR5V0U1SO-7/4457889

[cinder anchor]

Here's the PDFs, as requested!

Do I need some kind of isolation for the 12 V high power parts? I couldn't figure out how to do that. I actually ended up downloading EAGLE for Linux. While the new KiCad is really, really nice, it doesn't have an auto-router. Something I definitely need because I have no clue what I am doing. As you can tell.

[unreal flax]

Just to warn you, autorouters pretty much suck until you get into seriously professional tools, so I'd encourage you to climb the manual-layout learning curve.

[limpid nest]

Yeah autorouter doesn't know what parts not to route close to for example

I've gotten away with auto routing for low power boards but 12V 5A isn't something I'd do with it.

[cinder anchor]

OK. I feel like I am definitely in over my head here.

[limpid nest]

Eh you can get there. Just listen to advice and be careful

[proper anvil]

Okay.. after much deliberation I think I've settled on this design for my PCB wristwatch.. easily my most complex board, and also the smallest, and my first time doing battery management/discrete mcu/LED matrix, so im looking for an idiot-check before I place an order: (There's definitely some form over function going on but im hoping I can get away with it 😆 )

it is an attiny85 and DS2417 RTC to run off a 3.7v lipo, which charges off 5V, and controls 28 LEDs (2-6 are on at once) through two shift registers.
The attiny should be able to detect when +5V is connected, and turn off all the LEDs to keep draw low while the battery charges.
24 of the LEDs are in a matrix, and then the remaining four are individually controlled- I did this because at any given time, 2 LEDs in the matrix will always be on, but 0-4 of the individual ones will be on. I didn't put them all in the same matrix, because I didn't want the LEDs to get dimmer depending on the amount of LEDs on. I can PWM the individual ones to approximately match the matrix ones.
The LEDs will be constant on rather than be triggered by a button press, which is a personal preference of mine, at the expense of battery life.. After some (to be determined) amount of time (when the battery is almost dead) it will enter 'power save', and turn off the LEDs so the RTC can maintain the time setting for a few more hours/days until I get it on the charger. Time setting will be done at the time of programming which is crude but this is a version 1.
ideally programming would be done before installing the attiny, but I added pads to potentially be able to do it (although im not sure if it'll actually work in-circuit)

[verbal moss]

Stepper motor PCB... https://www.youtube.com/watch?v=OzqSzFZa2DY
Transparent PCB... https://www.youtube.com/watch?v=3a5fNPUIqAE

[verbal moss]

@tough matrix thank you for recommending https://www.4pcb.com/trace-width-calculator.html in #general-tech message

The trace width calculator and other info helped me define wider tracks in EasyEDA Design Rules. Helping speed up manual/auto routing. The rules are used by PCB checks as well. My clearances and via sizing is wrong tho.

[cinder anchor]

I'll take a look at this!

[cinder anchor]

@tough matrix I am playing around with that calculator and from what I can tell, external layers is the way to go because 15 A with a temperature rise of 10 C at 30 C ambient would require 16.4 mm internal traces. 😄 Those are some chonkers.

External Layers In Air gives me 6.29 mm.

Question, though, the light red traces on this board are about 4-4.5 mm wide, but they look like they're covered by something, is that silk screen on top of them?

[tough matrix]

15A??
that's some serious current for a PCB.

I'd suggest getting thicker copper layers, at least 2oz copper

[limpid nest]

Also keep in mind that 2oz copper is quite the heat sink

So soldering may become difficult

[cinder anchor]

It's for switching 12 V. At the most it'll probably not use more than 2-3 A per trace...

Realistically speaking. I was trying size up. But, I take it that's not how you do it?

[tough matrix]

I do use the calculator, but I never worked with more than 5A current, so the idea of 15A on PCB scared me.

but 3A is very reasonable

[cinder anchor]

I intend to use this in my truck to control power to 12 V things, primarily a fridge and lights. Fridge is rated for 7.5A/3.7A Current DC.

Fridge uses 0.715kw/24h (no load in Max mode running at 0'F).

[limpid nest]

Where in the truck?

[cinder anchor]

Bed, on a slide mount.

[limpid nest]

Make sure you get a very water proof enclosure

[cinder anchor]

You think IP68 will do it? 😉

[limpid nest]

Indeed

How are you doing the connections thru the enclosure?

[cinder anchor]

Yeah, I didn't mess around when I selected enclosure. It's a Polycase.

Glands.

[limpid nest]

Polycase is nice

Glands to screw terminals?

[cinder anchor]

So cables go into enclosure via glands, and yes, then I will have screw terminals inside the enclosure.

I might use a bus bar, too.

[limpid nest]

If it's intended to be fairly permanent that's a good way to do it

[cinder anchor]

Yeah, the enclosure will be permanently mounted to the side of the bed on some BuiltRight Industries panels.

Whole bed is also covered with a Retrax Pro XR.

[limpid nest]

I meant the connections too. Like if you don't intend to disconnect often

[cinder anchor]

Nope, do not intend to disconnect unless something needs to be repaired.

[limpid nest]

Noice

[cinder anchor]

This'll go in a 2020 Ford Ranger SuperCab (long bed). We've got a tent (hard shell) mounted over the bed. It's going to be a sweet camping set up. And, road trip mobile.

I have yet to see several of the more scenic national parks in the US.

But, that's not about PCBs. Sorry.

[limpid nest]

No complaints here

Yellowstone is great

[cinder anchor]

I really want to see Yellowstone.

[limpid nest]

Big Sur too

[cinder anchor]

There's so many of them. We have a road trip planned on a map, it's going to happen in the next year or two.

[limpid nest]

You need serious income and or time off to see a major proportion of them

But seeing any is a privilege

[cinder anchor]

Yeah. I intend to take a couple of months off.

[limpid nest]

Nice

[cinder anchor]

So, for this project, how do I isolate the rest of the board from the 12 V stuff?

Or, is that not necessary? I was thinking if there's spikes on the 12 V from the DC-DC charger or MPPT solar charger, I am pretty sure that the DC-DC charger will absorb spikes from the alternator...

And, ESD?

[limpid nest]

I don't think 12V is enough voltage to arc or break thru the insulation of the PCB

[unreal flax]

Soldermask. Silkscreen is the white ink.

[cinder anchor]

Thank you for clarifying! That makes way more sense.

[cinder anchor]

so with the soldermask on top, would those traces be considered external/in air?

Or are they internal?

[unreal flax]

Yes, generally still external. The soldermask doesn't provide much thermal insulation like being inside a PCB sandwich does.

[cinder anchor]

Cool. So, it looks like those traces would support 5-6 A then with that width.

[cinder anchor]

Are there any good alternatives to https://componentsearchengine.com/ as far as KiCad imports of symbols/footprints go? For Linux, mind you. For whatever reason these guys wrote the KiCad plugin to only work with Windows. While the EAGLE plugin works for Linux as well.

It's like... We are going to support this super expensive paid product, but, KiCad, which is open source, and completely anchored in Linux, yeah, we're only going to write a plugin in Windows for it.

It's also written in VBS. Hmm. Now I am kind of tempted to reverse-engineer it and create a Linux plugin...

Ick. No. I am not doing that.

[cinder anchor]

alright, switched back to KiCad. Here's my progress so far.

[fervent lance]

nice kicad chops ;)

[tough matrix]

@ember laurel in continuation of ESD protection discussion, it got me thinking. I have a design of motor controller where I use P-MOSFET for reverse polarity protection:

[ember laurel]

Ok?

[tough matrix]

would you advise me to add ESD protection diodes as well?

power input is expected to be in 5-18V range, typically from a battery

or in this case, since gate is already protected by a Zener, it is not necessary?

[ember laurel]

add it

is that mosfet tolerant for 8kV on D/S ?

[tough matrix]

There is no ESD info in datasheet

https://datasheet.lcsc.com/lcsc/2001041631_Alpha---Omega-Semicon-AO4407C_C469397.pdf

[ember laurel]

ok, that tells you?

[tough matrix]

that probaly it is not 🙂

[ember laurel]

🙂

[tough matrix]

(feeling like a student at an exam)

went looking for a TVS with breakdown voltage in 20+v range...

[ember laurel]

sounds reasonable

do you expect your input voltage to go above that range?

IE, do you handle back-emf in some way?

[tough matrix]

not really

[ember laurel]

I think you should be fine with any ESD diode that's breaking down just anywhere between your VBUS and mosfet absolute max Vds

[tough matrix]

thanks! will look for one

mosfet max vds is 30v, so the range is rather narrow

[ember laurel]

https://lcsc.com/product-detail/TVS_Shenzhen-Jinkaisheng-Elec-SMF24CA_C362065.html

I think this one will fit your bill

regarding input power to motor driver, I had quite some issues with sparks on the DC input plug, due to a lot of bulk capacitance

(which is of course nice to have for motors, unless you want to make a lot of noise)

I ended up making this to combat it:

my inrush current spike got really high without adding a limiter like this

[tough matrix]

Thanks! lookign at the datasheet now

[tough matrix]

Looks good to me, except I am somewhat nervous about traces going between SMD pads of TCA9534 - I'd prefer to avoid it if possible. You have run DRC to verify that all clearances are OK, right?

[cinder anchor]

I did, but I'm not sure it's good. Redoing the entire thing in KiCad and manually laying down traces.

Gotta beef up the traces for the 12V high power stuff anyway.

[supple pollen]

I'm also playing with an inrush current limiter. It ramps up the current over the course of about a second (the steep part on the left), then current limits (the less steep part). This curve is just what I had been hoping for.

[distant raven]

Oh that’s neat

[median wind]

I tried labeling my pins in fritzing, but when I mark the negative ones by using ' (for example QA') it appears as "'" instead

ironically "2̅Q̅B̅" displays better, but that's just a crutch I happened to find just now, is there a better way to do this?

@ me if you have a better idea to represent this please 😅

[elder peak]

@tough matrix I've been using these guys for that application: https://www.digikey.com/en/products/detail/TJ40S04M3L%2CLXHQ/264-TJ40S04M3LLXHQCT-ND/12352740?itemSeq=355938547

It's of course, out of stock and who knows when it'll show up.

[ember laurel]

@supple pollen here is what I had before the inrush limiter

You notice it a lot more in slow motion 🙂

[tough matrix]

but it is also sensitive to ESD, so it also would require TVS diode, right?

[tough matrix]

wow... how much bulk capacitance do you have there??

[ember laurel]

about 800uF

not sure how much my supply has, but I bet a lot

[elder peak]

Naw, it has built-in TVS diodes.

[tough matrix]

I am confused... the datasheet says "This transistor is sensitive to electrostatic discharge and should be handled with care."

[cinder anchor]

Can I use vias? Are they OK? Or avoid them?

[tough matrix]

vias are fine.
(unless if you are doing very high frequency signals, like HDMI )

[cinder anchor]

Nah, just trying to figure out how to route this GND, and was wondering if it was OK to via it underneath some digital GPIO traces...

[limpid nest]

Yeah board design of any complexity without vias is nigh on impossible

Some signals can't have them of course

Like shurik said

[verbal moss]

Do people use 0 Ohm resistors or something else to help tracks crossover (instead of vias) when required to make 1 sided PCB? e.g. required to make Aluminum backed PCB that needs to help shed heat generated by components.

[supple pollen]

Wire jumpers can work too.

[limpid nest]

Oof just imagining the hassle of placing those resistors in your schematic!

[cinder anchor]

Can I get some feedback on this board?

I also have complete KiCad files upon request.

[limpid nest]

You might consider a 12 position terminal block

Nothing wrong with what you have but 12 position would be more mechanically stable

[cinder anchor]

Other than that?

Will it blend?

[limpid nest]

Typically supply symbols are vertical

[cinder anchor]

OK

[limpid nest]

Gnds are down

[cinder anchor]

Huh?

[limpid nest]

Your IC doesn't have any decoupling

[cinder anchor]

The +3V3 should be vertical, same orientation as the resistors?

[limpid nest]

Yes

[cinder anchor]

What about GND?

Also, what's "decoupling"

lol

[limpid nest]

One sec I'm looking at this on mobile

[cinder anchor]

thanks

sorry

[limpid nest]

Decoupling capacitors smooth the power into the IC

You can probably get away with a .1 uF but it depends on your power supply

Also I would personally go with 4.7k pull-ups rather than 2.2k

[cinder anchor]

Why 4.7k? How does that affect things?

[limpid nest]

It's just a rule of thumb. It's been a while since I looked at the math

[cinder anchor]

Power supply is a 12 V battery (with BMS) that outputs 12.8 V.

[limpid nest]

2.2 is probably fine

[cinder anchor]

k

[limpid nest]

Where is 3.3V coming from?

[cinder anchor]

QWIIC connector.

[limpid nest]

What's the Power supply providing that?

[cinder anchor]

Which goes to a Feather RP2040.

[limpid nest]

Ahhh

[cinder anchor]

Which will be powered by a buck converter, it will be housed inside the cab.

[limpid nest]

Hmm I'm trying to decide if you should have more than one value of cap for decoupling

Let me pull-up my PC and look at the feather RP2040 3.3v regulator

It's probably a switching regulator so we'll want to take into account the frequency when speccing caps

[cinder anchor]

ok

Would there be any point in putting some kind of power converter on the board itself?

Oh snap. I forgot one very important thing.

[limpid nest]

It depends on the power draw of the IC, and transistors. Probably pretty low such that the regulator on the feather can handle it. How far are you running cable between the feather and the board?

[cinder anchor]

Approximately 9-10 feet. I am going to use these:
https://www.adafruit.com/product/4756

and do I need one of these? https://www.adafruit.com/product/4903

They have mount holes so I am not going to go through the hassle of putting those components on the board itself.

[limpid nest]

you're likely to have voltage drop over that length

[cinder anchor]

That's what the active terminator is for

since there will definitely be a voltage drop

anything over like 100 mm is basically not going to work well without the extender

I also have a few of these:
https://www.sparkfun.com/products/16988

Which might be better?

I've tested them with around 15 feet of CAT5e and they worked fine.

(against a similar set up as the board I posted, but it's a breakout from Sparkfun)

Maybe even put that RJ45 directly on the board instead?

well... hmm, lotta tiny components

one surface mount component is enough for this guy

probably easiest to just mount them next to the board in the enclosure

[limpid nest]

Hmmm hard to say. I think the active terminator might be best since it doesn't introduce another cable type to the mix

/protocol

[cinder anchor]

It's just using 4 wires, but over an ethernet cable. Which is way sturdier than a little QT cable

I think the active terminator and the sparkfun component do the exact same thing, basically

and I do have about 20 ft of industrial CAT6e, which was pretty darn expensive, and that's what I was going to use

[limpid nest]

It's up to you, either will probably work. You can probably find IP rated ethernet pass thrus for your enclosure

[cinder anchor]

inside a conduit, but also, the cable is shielded, resists oils and all kinds of other crap

I think acids too

lol

it was probably overkill

but, YOLO

[limpid nest]

The ethernet option doesn't have active termination though, may have voltage drop issues there

[cinder anchor]

hmm

The breakout uses NXP’s PCA9615 IC, which converts the two default I2C signals into four differential signals, two for SCL and two for SDA. The differential signals are sent over an Ethernet cable, which attaches to the breakout through the on-board RJ-45 connectors. The differential signaling allows the I2C signals to reach distances of up to 100ft. while still maintaining their signal integrity!

That's from the Sparkfun breakout.

[limpid nest]

Signal integrity, doesn't say anything about the 3.3V line not drooping

[cinder anchor]

Yeah. You're right.

What about using the 12 V coming into J7 and hooking it up to a buck or similar on the board?

Probably something I can stick a giant heat sink on.

[limpid nest]

That would work. You could also use the 5V from the feather

Buck that, less heat

and it's OK if it droops a bit

how far are you running again?

[cinder anchor]

10 feet (approximately) from inside the cab to the back of the bed by the tailgate.

[limpid nest]

gauge depends on the solution we go with huh

Hmm

[cinder anchor]

Yeah... hmm.

The Arduino is going to be inside the cab because it needs to sit near the DC-DC charger so it can tap into the RS-485 modbus crap.

[limpid nest]

hmm

[cinder anchor]

The DC-DC charger is not IP-rated, so it needs to be somewhere dry and safe.

[limpid nest]

tough problem to solve

[cinder anchor]

I thought about buying Redarc's DC-DC charger which is IP-68 and can withstand like 185'C, but, it's almost $500, and the DC-DC charger I bought from Renogy was like $180.

So, mounting it in the cab is a compromise. Already checked to make sure it'll fit in the little compartment under the rear passenger-side seat.

So, the IC's voltage supply is 1.65V ~ 5.5V. Wouldn't the 3V3 from the RP2040 still work even with the voltage drop over 10 feet of ethernet cable?

[limpid nest]

Yeah the IC would work, but it's "high" voltage may not be enough to trigger your fets

Or at least turn them on enough to not have a high RDS_ON, and you'd be burning battery power

[cinder anchor]

hmm

https://www.digikey.com/en/products/detail/vishay-siliconix/IRLZ34PBF-BE3/13540582

these are the fets I have

so maybe we do need a buck converter on the board to step down from 12 V to 5 V?

[limpid nest]

to 3.3 surely?

You'll need a 3.3V reference at the very least for your I2C bus

Checkout page 29 https://www.ti.com/lit/ds/symlink/tca9534.pdf?ts=1644188631370

I'd go with a 0.1 uF and and 1 uF cap

I recommend SMD but you have space for thru hole. Just note that the + terminals need to be as close to the VCC pin as possible

[cinder anchor]

Oh, we need it to be 3V3?

[limpid nest]

Yeah kinda

You could do mixed signal but it would be more complex

You'd need 2 regulators for one. You need 3.3V for your I2C bus because 5V would damage your feather's GPIO. There are ways to do voltage translation but it's more parts

[cinder anchor]

OK, so we stick to 3.3V

[limpid nest]

I would recommend piping your 5V from your feather over and bucking that down to 3.3V

Less heat generated == less power burnt. Esp if you bring in 12V from your battery, you'd just be wasting battery potential on your buck

[cinder anchor]

from what I can tell, this feather doesn't have a 5V pin?

[limpid nest]

Hmmm

one sec

[cinder anchor]

https://www.adafruit.com/product/4884

[limpid nest]

how are you powering the feather? USB?

[cinder anchor]

Probably off of a buck converter.

[limpid nest]

but like with a USB cable from the buck or feeding power into a pin?

[cinder anchor]

power into a pin, preferably

[limpid nest]

Then just pick off that trace for 5V

[cinder anchor]

I have the feather mounted on this guy:
https://www.adafruit.com/product/2926

[limpid nest]

Ah that's a little tougher

Hmm, you could do two wires in one terminal. Kinda janky but it would work

[cinder anchor]

I mean, it's a proto board too, so I can solder on more screw terminals, no?

[limpid nest]

I don't see where there's room for that

[cinder anchor]

yeah, maybe not

I could solder on a jumper cable into the middle and put a 2-terminal in the middle. Pretty sure there's enough clearance under the feather for one of those terminals

basically underneath the rp2040 itself

and there's definitely clearance

[limpid nest]

Hmm you could use protoboard and a terminal block to make a splitter

[cinder anchor]

that's what I was thinking

there's protoboard underneath

the ones in the middle are free-floating

[limpid nest]

Yeah that could work, you could even use solder to get from the USB pin to the terminal block

and GND pins

[cinder anchor]

word

[limpid nest]

I was told that 10 uF chip resistors are really a 10, 1, and .1 in parallel but I can't find info on that anywhere. Does anyone know if that's true?

[unreal flax]

I've never heard that. People often will gang up decoupling capacitors like that in parallel, but it's done as 3 separate components.

[limpid nest]

Indeed

[azure stirrup]

So, I have bought this arduino shield. I was wondering if I can solder sockets onto the prototyping area and attach an I2C device. It needs to connect to PWR, GRND and SDA and SCL

[unique patio]

certainly. can just solder a small strip of header jack, an then add jumpers to the appropriate pins. It looks like most of the pins on the right have jumper holes for this purpose

[azure stirrup]

what about 5V and GND can i use the ones in the middle?

[unique patio]

i think so. I do not see a good diagram of the tie points you can use.

[azure stirrup]

what is a tie point?

[unique patio]

just a pad you can solder a jumper to

"ties" two things together

[azure stirrup]

ah

[unique patio]

The picture of the bottom of the board is not helpful

[azure stirrup]

Here is a cleaner picture

[unique patio]

all the holes with a border (ring) around them can be used for jumpers

[azure stirrup]

perfect thanks

[elder peak]

I'm really hazy on the actual ESR/ESL/et al implications but a 10 uF ceramic chip resistor is better able to do the things that a 10 uF electrolytic resistor can't in terms of frequencies absorbed.

[elder peak]

Also, a 10 uF ceramic MLCC is basically a stack of smol capacitor layers, but not so much like differently valued ceramics in parallel and more like a stack of 0.1mm ceramics.

[cinder anchor]

I have updated my PCB because the traces I had were super undersized...

here's the KiCad files

I am guessing I've probably missed something important, so any help appreciated!

And yes, I designed (actually bought it on VectorStock for $1) a logo before I even had a working circuit board. Doing the things we're decent at is much faster, and I needed a break from KiCad. 😄

I routed +12V and GND for the MOSFETs on the back.

And crickets... 😦

[limpid nest]

I'd do a ground pour