feedback on my first PCB

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Nate
Posts: 3
Joined: 03 Aug 2022, 01:01

feedback on my first PCB

#1 Post by Nate » 03 Aug 2022, 01:29

I've used protoboards many times for simple solutions but my latest project is too complex for that. Attached are my Diptrace files for my first real PCB! It has two 16 channel IO expanders and 40 optocouplers. I think it's ready to be made, but I thought I'd ask here for feedback first.

I plan to solder all the components on myself, since I have all the ICs in hand. I suppose it'd be nice if I didn't have to solder 40 SMD resistors!

Any feedback before I get it made would be great! :)
5147-ak9G.png
5146-rGRH.png
5145-dwZD.png
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Tomg
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Posts: 1876
Joined: 20 Jun 2015, 14:39

Re: feedback on my first PCB

#2 Post by Tomg » 04 Aug 2022, 09:38

Initial Observations
1) Schematic: since there is nothing on sheet 2 it can be deleted.
2) Schematic: typically, ICs will have the reference designator prefix "U" (e.g. U1, U2, U3, etc.). You can always add text labels next to ICs to clarify functions (e.g. DOOR1, DOOR2, DOOR1.1, DOOR1.2, etc.).
3) PCB: change the mounting holes to individual pads of the appropriate dimensions to get rid of most of the DRC errors.
4) PCB: insufficient gap between mounting hole and trace connected to DOOR1(pin 16)...
gap1.png
5) PCB: rotate the upside-down reference designators (use softkey F10 to activate the Move component texts mode) so all can be read from the same angle.
6) PCB: if desired, you could play around with creating a ground plane (copper pour) on the back side of the board to replace all of the ground traces.
Hope this helps.
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Tom

Nate
Posts: 3
Joined: 03 Aug 2022, 01:01

Re: feedback on my first PCB

#3 Post by Nate » 04 Aug 2022, 14:12

Thanks for checking it out!

I figured it was odd to use names for my ICs, but the board is just for me.

I changed mounting holes to a keep out. Not sure why having them plated wasn't working.

I rotated the silkscreen labels and improved (I hope) a bunch of things. Pads are 0.9/1.6mm. Traces are 1mm, probably unnecessarily thick but I had room. I used a copper pour for GND on the back and 3.3V on the front. That made routing a lot easier! Since I have through hole components I didn't need any vias. I kept traces on the back to a minimum. Pour clearance is 0.5mm, I guess that's large but it seems OK. Thermal relief spokes are 0.4mm and where there are less than 4 spokes I increased it to keep 1.6mm total.

I'll just have the board made, I'll do placement myself. Hot air station is on the way! I used some through hole components because I have the ICs on hand. The ICs will have sockets.

In the future I'll likely use all SMT. This project showed me how much easier it is versus a protoboard. Never again do I want to dork around for hours soldering bridges and wires! I'm already excited for my next project, now that I have a lot more flexibility in parts I can choose and layout/fabrication is so much easier.

A little more about the board: for scale the board is 9.78cm x 8.51cm (3.85" x 3.35"). It has two 16 channel I2C IO expanders and 10 quad optocouplers. I'll use the 32 pins from the expanders (open drain! have to keep reminding myself those output pins are ground) plus 8 output pins from an ESP32 to have 40 optocoupler channels. Those close 24V logic level contacts for 10 sliding doors, the 4 commands for each being open, close, stop, and lock.

I think it's ready to submit for fabrication! I'll give it a little time, in case you guys have any more feedback. Cheers!

Nate
Posts: 3
Joined: 03 Aug 2022, 01:01

Re: feedback on my first PCB

#4 Post by Nate » 04 Aug 2022, 14:21

EDIT: I made a post before this one, but it's pending moderation. Not sure why this one posted without that.

Updated pics:
top-3d.png
bottom-3d.png
top-layout.png
bottom-layout.png
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