Supply power to Pi and to XHAT separately

Picade
1

Hi,
I’ve modded my Picade to have the XHAT away from the Pi, in order to fit an oversized heat sink. That’s leading to constant undervoltage warnings, apparently due to the flat cable resistance connecting them together.

As I’m already powering the display with a separate PSU, my next attempt would be to power the Pi and the XHAT separately too.
I wonder if that would work, but more importantly, I believe I have to disconnect the power going from the XHAT to the Pi. Would someone identify which pins to disconnect?

Thanks

2

The pinout is here, the +5V is via pins 2 and 4.


It looks like the Xhat only uses pin 2 though

Doing this is might mess up the power button function on the Xhat. I don’t own one some I’m not 100% sure what happens when you push it. The Pi should still shut down but it will remain powered.
You could try plugging the power supply into the Pi instead of the Hat. The power button likely won’t work as advertised but it may save you from buying another supply and having to cut your ribbon cable…

3

It’s both pins 2 and 4 that you need to cut. If this Pi is permanently in this setup you could physically cut that pin off the GPIO with side snips (drastic), desolder it with some wick or a sucker and then pull it out with pliers (drastic but reversible), cut the wire in the ribbon cable (fiddly and hard to identify) or maybe remove the pin from the HAT end of the ribbon cable if that’s a possibility. As alphanumeric says though that’ll disable the power switch.

Edit: checked with the designers and apparently both 2 and 4 are used for 5v supply from the HAT to the Pi as there can be a fair bit of current flowing.

4

Might want to update the pinout, it only shows one pin being used. ;)

5

Good call, I’ll nudge Phil, thanks :)

6

Thanks you @alphanumeric, thank you @Matt.

  • First thing I’ll try is plugging the power on the Pi, if that works, would be great.
  • I am also going to try unplugging pins 2 and 4, as I don’t have to cut the cable or unsolder anything. The cable i am using allows me to unplug each pin.

You can see my setup here, before assembling the XHAT to a support. I though about getting a more capable power supply, like a 10A or something, but i suppose it wouldn’t work - If the problem is the resistance imposed by the rainbow cable, I would need more voltage, which isn’t ok as it could damage my boards, correct?

Picade
Picade715×1029 292 KB

7

Definitely don’t increase the voltage, no. Maybe you could just replace the two 5v wires on pins 2 and 4 with some thicker cable? There’s enough ground connections that those should be fine.