Total Power Draw for Zymkey 4i/5i

What is the total power draw for the 4i/5i? I was looking at adding one to a Pi 4; however, as far as I can tell they block both of the Pi’s 5v power pins and the 3.3v pin which will prevent using a fan for active cooling which the 4 really needs. Is it safe to split off one of the pins for a fan or are they all maxed out? Will we see a future revision of the board which exposes one or more of the power pins?


  • Nominally 5mA maximum, from the 5V supply. So there should be plenty of capacity to run your fan too.
  • How would you like to see the power pins to be ‘exposed’ ? Send us a sketch.


You could do a 1x2 connector and pull the unused 3.3v and 5v beside the microUSB port, same form factor pins as the GPIO pins that are covered. If there is space you could pull a 1x4 or 2x2, two 5v, 1 3.3v, and a ground for convenience of plugging in a two pin power/ground device.

As long as there is space to pull the traces it should be a fairly simple change, direct lines not going through any parts on the board.