2

I'm considering making a Pi cluster (Let's say 8 Pi 3s), and instead of buying an 8-port USB charger and 8 USB cables of exactly the right length, could I use a powerful enough (8A?) 5V wall wart and then hookup wires to plug it directly into the 5V header on the GPIO on each of them. Would this be safe electrically and not damaging to the Pis, and if not would there be a method to make it so? Or is it best to do it the 'normal' way?

Thanks

Luke M
  • 747
  • 1
  • 7
  • 17

2 Answers2

3

I have a couple of remarks which won't fit in the comment:

First, while 1A per Pi should be sufficient (assuming no USB devices plugged in and WiFi/BT not used), you may get quite close to the limit at full load. You may want to disable HDMI and Bluetooth to increase the margin:

 # disable HDMI, to be run at every reboot
 /opt/vc/bin/tvservice -o

 # disable BT, to be run once
 echo "dtoverlay=pi3-disable-bt" >> /boot/config.txt
 systemctl disable hciuart

Second, don't use thin wires to distribute power. A wire carrying 8A should be at least AWG21, or 0.41mm² copper. You will lose about 0.7V per meter with wires of this diameter, so thicker wires are recommended for lengths exceeding 20cm or so.

Dmitry Grigoryev
  • 28,277
  • 6
  • 54
  • 147
2

Yes, you can power all your Pis from one power supply with sufficient capacity.

You lose the polarity and fuse protection of powering via the microUSB socket.

You can mitigate any risks by adding your own in-line fuse per Pi and taking care you plug 5V into a 5V pin and ground into a ground pin.

joan
  • 71,852
  • 5
  • 76
  • 108