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Topic: General PCB Check (Read 700 times) previous topic - next topic

450nick

Hi, before posting any schematics, I just wanted to test the water. I have been working on a design for a set of PCBs to build into a 3d printed housing I've designed, which hopefully with 3 teensy arduinos installed will work as a functioning dashboard for a project car that I'm building (though it is still in bits).

I would like to have the PCBs prototyped in China, so I can then power them up on the bench and start looking at making a working model. I've tested most of the bits on a breadboard individually, but this is the first time I'll put it all together.

Since the prototyping is a reasonable investment, I really don't want to screw it up. I've spent a lot of time checking and rechecking and redesigning where necessary and am pretty much at the point where I'm ready to send off for a quote. Since I'm relatively new to all this though, I'd really like someone with some experience to check over the schematic and maybe PCBs and make sure I haven't made any silly errors but I don't know anyone who could help me personally.

So my question is, would anyone on this forum be willing to help? It's a bit more than a question on the forum so I would be prepared to compensate for time spent within reason. I'm a mechanical engineer by trade so I'd expect the same if someone was asking me a similar question!

Thanks!

gilshultz

My experience with China was great. I used JCLPCB, everything is on line:
https://jlcpcb.com/?gclid=EAIaIQobChMIvY2ruvba5QIVRNbACh18ywuuEAAYASAAEgJp3PD_BwE I had very good results. I did my schematic capture with KiCad operating on Linux Mint 18.3, I think it is available for windows and Mac. This software is available free but it is worth donating something it is that good.  I have done all my routing manually with this, it works very well.  You will find there pricing very competitive. When you upload your Gerber files they will do a check with system and then again manually.  For me from uploading until I was assembling boards was in the range of 7 days. If this is your first experience with a PCB see if you can find a buddy to help you with the CAD.  It is like a new language.  It will run a DRC (Design Rules Check) for you.  They do not have a limit on board size or layers. The board matched my drawing exactly, including the mistooks. When they checked they found some and notified me about them.


Remember when you get your board back FAIL is an acronym meaning Forward Action In Life.
Good Luck & Have Fun!
Gil
This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

DrAzzy

I use DirtyPCBs for most of my PCB fab work. Dirt cheap, and they do good quality work. They do not DRC check it for you. If you submit something that doesn't meet the DRC, you generally just get back bad boards.

I have also used PCBWay - they are full-featured unlike DirtyPCBs, but they cost more.
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

CrossRoads

@450Nick,
What program did you design the boards in?
I use Eagle and could help with the Design Rule Checks to make sure that someone like iteadstudio could make successful boards for you.
You don't really send off for a quote, all the sites have online tools where you enter the board size and they tell you how much bare PCBs will be. Such as $19.90 for ten boards up to 100mm x100mm. Then shipping is whatever you select.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

450nick

#4
Nov 09, 2019, 06:38 am Last Edit: Nov 09, 2019, 06:45 am by 450nick
Hi thanks for the replies guys... Bob I've just dropped you a PM. I'm using Autodesk Eagle, and then the board overall assembly integration in Autodesk Inventor.

As my soldering skills are more on the automotive wiring level rather than small PCBs, I think I would like to have the board delivered fully assembled. For this reason I am trying to be very careful to specify the BOM clearly (the board includes 4 servos that aren't too common) and have had to make a couple of components myself in Eagle. There's a lot of stuff across 4 separate PCBs (two of them double sided) with board to board connectors between.

I've run the ERC and DRCs in Eagle and everything seems to check out, but little things like ensuring I have specified reasonable capacities for my components given an automotive environment, making sure the trace widths are sufficient for the loads etc. I have checked everything, but working in engineering I am well aware that things get missed even when you're not a novice - especially when you've been looking at it for a lot of time, so a sense check look over would be greatly appreciated, and I don't think that the PCB manufactures would necessarily do this? I know they'll check the BOM for availability, and will test the board for continuity and validate it against the schematic, but I don't think they'll sense check the schematic.

The last thing I want is to order them, plug them in and generate some kind of small explosion :)

At the moment I'm talking with RayPCB (https://www.raypcb.com/) and they seem decent, but their English is not perfect (though it is pretty good) so I am a little worried about misinterpretations... Any good suggestions for some more quotes?

DrAzzy

#5
Nov 09, 2019, 02:28 pm Last Edit: Nov 09, 2019, 02:29 pm by DrAzzy
If you post your layouts and schematics (as images) we can critique them.

This sounds like quite a project, so I definitely recommend trying to get people to sense check your design.
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

MorganS

Fully-assembled is an exceptionally expensive way to buy prototype PCBs. Something that takes an hour or two for an amateur to assemble will take a professional longer because they really have to check it and test it before it goes out the door.

Even in China, those professionals don't work for $5 per hour.

If this is your first PCB then you will certainly make a simple mistake. Do you want to spend hours on the phone with the assembler or do you want the $4 PCB in your hand so you can look at it and see you forgot one power wire?

I got into PCB design because I had a project with one particular component that was only available in surface-mount. (The ADXL345 accelerometer.) With a "laser" infrared thermometer and a frypan on the stove I was able to build that project on a PCB with very low cost in dollars or hours. The only delay was waiting 2 weeks for the version 2 PCB with the power trace I forgot in version 1.
"The problem is in the code you didn't post."

450nick

#7
Nov 10, 2019, 04:11 pm Last Edit: Nov 10, 2019, 04:12 pm by 450nick
If you post your layouts and schematics (as images) we can critique them.

This sounds like quite a project, so I definitely recommend trying to get people to sense check your design.
I tried to attach photos but maybe as there's too many it kept crashing the browser so I just put them on my OneDrive. There's also a zip file with the Eagle files and images in there too if anyone is interested...

OneDrive Link

Fully-assembled is an exceptionally expensive way to buy prototype PCBs. Something that takes an hour or two for an amateur to assemble will take a professional longer because they really have to check it and test it before it goes out the door.

Even in China, those professionals don't work for $5 per hour.

If this is your first PCB then you will certainly make a simple mistake. Do you want to spend hours on the phone with the assembler or do you want the $4 PCB in your hand so you can look at it and see you forgot one power wire?

I got into PCB design because I had a project with one particular component that was only available in surface-mount. (The ADXL345 accelerometer.) With a "laser" infrared thermometer and a frypan on the stove I was able to build that project on a PCB with very low cost in dollars or hours. The only delay was waiting 2 weeks for the version 2 PCB with the power trace I forgot in version 1.
You are probably right, but I'd be much more comfortable someone putting this together who has some experience. The trick is to not screw up the schematic as you say, hence hopefully checking it many times before pulling the pin...!

DrAzzy

That's a good point - I would really want to get a batch of bare boards and assemble them the first go around, because you *will* do something wrong. It is rare for the first rev ("Rev. -" in the industry, though some start from Rev. A) of a board to work 100%.
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

450nick

#9
Nov 13, 2019, 03:59 pm Last Edit: Nov 13, 2019, 04:14 pm by 450nick
Ok I tried a few more times and figured out that the forum doesn't accept .png images so here are the .jpeg versions. I would very much appreciate a bit of a peer review of the schematic if anyone has a few spare moments. The Eagle files are available on this link: OneDrive Eagle Files


450nick

#10
Nov 13, 2019, 04:09 pm Last Edit: Nov 13, 2019, 04:12 pm by 450nick
And rear PCB jpeg


450nick


MorganS

There isn't much we can say about the schematic without diving deep into the datasheets of each component. The only advice we could give quickly is artistic and it looks reasonably neat, given the number of nets you have.

The real question for a schematic is "Does it do what you want it to do?" Does it include all the correct control lines? Does it use Arduino PWM pins for analog outputs (I have forgotten that one a few times.) Do you have Tx and Rx on Serial the right way around? We can't answer those questions for you.

When you get to the actual PCB, then you will get more advice from the forum. Things along the lines of "Is that power trace wide enough for the current it's carrying? Does that high current trace go under any sensitive analog components? Where is the return current from that component flowing in the ground plane and does that go under any sensitive components?"
"The problem is in the code you didn't post."

450nick

Hi Morgan,

Thanks for your response! The PCBs and all Eagle files are on the link attached. 4 layer boards with ground planes and I think trace widths that work for the service I'm expecting.

For the schematic review, I'm really just hoping for someone with a trained eye to look over the boards and say, "this looks sensible". I have checked all nets, routes and connections and I am happy that everything is plugged in where it should be - the circuit isn't hugely complicated, there are just a lot of connections to route. I'm mostly worried things like resistor and capacitor values, particularly the ones interfacing with the I/O signals from the main car harness connector as I know auto environments are harsh electrically. I'm hoping someone can look at it and verify there are no silly errors to give me a little confidence to go ahead and order the boards Rev A.

As said above, I'm very happy to pay someone for their time to make a proper check if it will take more than a few minutes so that I can get a decent peer review on both schematic and board before proceeding.

MarkT

Nobody? :(
Quick glance - seems to be a complete lack of decoupling caps?
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

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