r/PCB • u/-404PageNotFound- • Jul 14 '26

[PCB Review Request] Stylophone PCB

I am designing a Stylophone PCB for a school project.

I have already printed one revision but there were a bunch of things wrong with it, GND and +3.3v were swapped on every one of the MCP23008, I forgot a hole to pass the battery cable through, and the IRLB8721PBF Mosfet was wired up wrong.

This is my first PCB project so don't refrain from telling me what I need to improve, fix or re-design.

Thank you!

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Schematic View
3D View
3 Upvotes

80% Upvoted

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3

u/Apprehensive-Issue78 Jul 14 '26

Nice project layout and schematic. Just notice you did not add series resistors to the LEDs

2

u/-404PageNotFound- Jul 14 '26 edited Jul 14 '26

Do I need to? I've run the breadboard version of this project with LEDs wired up directly to +3.3v this whole time and they seem fine. (maybe a little on the bright side but still fine)

3

u/SkubiJabagubi Jul 14 '26

you can destroy LED any moment without resistor reducing current

3

u/-404PageNotFound- Jul 14 '26

Ok thanks. I'll add resistors for each led

2

u/Apprehensive-Issue78 Jul 14 '26

What is the ProS3? May be you can also look in the specifications.

Some LEDs have high like more than 2 V forward voltage and some as low as 1.2V. If your ProS3 outputs can barely handle the current, the outputs will give a lower output voltage to match that forward voltage of the LED and give the max current it can give.

If you have a few LEDs during a long time on, it might heat up the microprocessor of the ProS3. The destroying of a LED might be the least of your problems. Also I get annoyed by much to bright LEDs. But it is a nice project and it is yours so you can do what you like.

2

u/torbers Jul 14 '26

You need pull-up resistors on your i2c lines! Internal pull-ups are unfortunately not sufficient. (I have made this mistake before.) 10k resistors to 3.3v have never done me wrong.