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I have a Pi 3 project that has quite a few things attached.

  • 4 DHT-22s powered from the 5v rail (5m cable length, so I needed the 5v for the voltage loss). Wired in like this enter image description here

  • 2 Magnetic door reed contacts wired in like this

enter image description here

This all works. However I wanted to add 2 relays. One of those twin relay boards that take 5v & GND plus GPIO poins. When I do this, the DHT sensors or the reed contacts stop working randomly.

I am suspecting I am reaching a voltage issue / power issue with the Pi. The power supply is 2.5a.

How do I start resolving this issue with the power?

  • 1
    "DHT-22s powered from the 5v rail (5m cable length, so I needed the 5v for the voltage loss" - total rubbish I don't care why or how but connecting 5V to a GPIO risks damaging the Pi. – Milliways May 13 at 11:42
  • IMHO, you could get a good answer if you used a schematic instead of these diagrams. Here's how to use the schematic tool. – Seamus May 13 at 23:37
  • Both comments noted. I will action both today. – Senrab May 14 at 12:02
1

At the command line prompt type dmesg. The log will tell you if you are having power problems.

| improve this answer | |
  • I don't think the SoC necessarily experiences undervoltage (BTW you can dmesg | grep "Under-voltage" or grep "Under-voltage" /var/log/syslog) just because something on the GPIOs isn't getting enough juice, although it may. – goldilocks May 14 at 17:17

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