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Comment on PCB Design Review Request: ESP32 Smart Relay Board

I haven’t got enough time on my hands right now to review the whole desingn, but one thing that jumps to mind is that you’ll want to use an antiparallel diode on each relay coil to suppress the negative voltage spikes when switching it off.

Be sure to keep adequate distance between high and low voltage traces. The ground plane seems awfully close to the N trace.

Other than that, I’d happily welcome more PCB and/or personal project discussions!

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Starfighter@discuss.tchncs.de ⁨1⁩ ⁨year⁩ ago
It is my understanding that the ULN2003A (U4 and U5) has integrated flyback diodes. From the datasheet:

Each consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diodes for switching inductive loads.

Good call on that ground plane. I’ll scoot the relays a little bit to the right. That should resolve the issue.

Thanks for your feedback! :)

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- joulethief@compuverse.uk ⁨1⁩ ⁨year⁩ ago
  You’re welcome!
  
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