Will my PCBs work? - Page 1
Forum section: electronics / projects

author: Len
author_rank: Frequent Contributor
timestamp: January 21, 2022, 08:34:56 pm
content: These are the first PCBs that I have ever designed. Will they work?

author: cdev
author_rank: Super Contributor
timestamp: January 21, 2022, 08:40:01 pm
content: If you could upload the layout as a Kicad file or JPGs of the traces. The way you uploaded it isnt the best way to display your work.

author: Len
author_rank: Frequent Contributor
timestamp: January 21, 2022, 08:48:02 pm
content: I didn't think it mattered since there's no option to vote "yes".Here are the designs as uploaded to OSH Park:Main boardControlsFront panelI will upload all the design files when I have it finished and working.

author: cdev
author_rank: Super Contributor
timestamp: January 21, 2022, 10:28:03 pm
content: Quote from: Len on January 21, 2022, 08:48:02 pm

author: mariush
author_rank: Super Contributor
timestamp: January 21, 2022, 11:19:42 pm
content: Layout wise, it's OK but it seems to me like you could have done quite a bit better.For example on the 2Shapes board there's lot of space not used properly.For example :U1 could be moved up a bit and a bit to the right ... to have straight traces from the pins to the header. Lots of room unused to the right of that IC.U3 could probably be rotated clockwise 90 degree so that the +12v trace doesn't go under the chip and then below the chip, breaking all that ground fillIF you don't rotate the U3, those C12 , R11, R13, C3 could just as well be rotated 90 degrees and aligned for a prettier lookYou could rotate that D9 180 degrees and have the ground side land above U1Maybe bring C6 closest possible to U1 and have trace going to D11 and R17 go above D12 and have +5v go under those two.Also D11 and D12 or D9 and D10 could potentially be replaced with a 2-diode package, for exampleBAT54Sbut then your design would no longer be 100% through-hole... and i guess maybe your diodes need to do more than 200mA?Also do you need capacitors for Y1 or that's something with those capacitors built in?Feels like you had everything snap to 0.1" (2.54mm) but you could do better positioning by setting that to 0.05" (1.25mm)

author: Len
author_rank: Frequent Contributor
timestamp: January 22, 2022, 03:27:05 am
content: Thanks for the feedback. I'll work on better layouts on future boards but for this one I'll be happy if it just works.(Yes, Y1 is a ceramic resonator with built-in caps.)

author: inse
author_rank: Super Contributor
timestamp: January 22, 2022, 03:33:31 am
content: The golden rule of PCB design: first run will always need botch wire

author: Len
author_rank: Frequent Contributor
timestamp: January 22, 2022, 03:53:25 am
content: Quote from: inse on January 22, 2022, 03:33:31 amWe'll see!

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: January 22, 2022, 06:44:43 pm
content: 1/ Tracks as short as possible.2/ Keep high and low impedance tracks apart if you dont want cross talk.3/ I always use star grounding for anything taking a bit of current to stop ground signals.4/ Keep high impedance signals away from transformers or you can get magnetic induction in the traces.

author: MarkR42
author_rank: Regular Contributor
timestamp: January 24, 2022, 02:07:34 pm
content: They will definitely work, because the big component size and pin-through-hole means that even if they don't, they can be easily bodged without too much skill.There's loads of space for bodge wires, and I assume it's a 2-layer design, so should be totaly fixable even if there is a small mistake.

author: Len
author_rank: Frequent Contributor
timestamp: January 29, 2022, 08:33:52 pm
content: Quote from: inse on January 22, 2022, 03:33:31 amYup, one bodge wire was needed to make it work.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 29, 2022, 08:54:58 pm
content: Quote from: Len on January 21, 2022, 08:34:56 pmObviously not. Something is missing. Clue: You need to add the components.

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: April 07, 2022, 02:46:33 am
content: There are many reasons why a pcb might not work or not work correctly.1/ Single ended nets that should be multiple ended nets.2/ Tracks too thin.3/ Interference between tracks or tracks and transformers/inductors or wires carrying HF and high current or even mains.4/ Lack of shielding of wires.5/ Poor grounding.I remember a USB audio mixer project I did.The pcb came back and on the output was 1VAC hum.I narrowed it down to hum in the ground line.Had a look at the schematic and I had mixed in power supply ground with audio ground.The charging impulses into the smoothing capacitors were modulating the ground line and so the audio signal.So separated audio ground and made power supply in one side and out the other and connected ground once at power edge connector.Next revision came back totally different with very low noise level.I designed a USB scope. Worked fine except for some 10KHz ripple on wanted signal.I had run a signal track under a 7660 voltage inverter and its clock frequency was being induced into the track.Similar problem with 8MHz on signal.I had run signal next to 8MHz clock crystal and clock was getting induced into signal track.Audio amplifier, simply didnt work.I had forogt to add a tag to input ground track and it wasnt connected to power amp section ground and was floating.