OnOff Shim @ Pi 4 - Unter-voltage issues?

This is my second attempt to use a Pimeroni OnOff Shim at my Raspberry Pi 4B to build a so called Phoniebox. I receive repeatable “Under-voltage detected!” messages if using the OnOff Shim inside my setup:

  • On my Rapsberry Pi 4B I connected analog speakers (Trust Compact 2.0, 6 Watts peak). The Power is drained via USB connection from the Pi.
  • Neuftech card reader connected via USB)
  • 27" Monitor (Dell U2715H) connected via HDMI
  • Powerbank (EasyAcc PB26000MS) as power supply

Setup A) Powerbank connected via USB-C directly to the Pi: No under-voltage issues at all.
Setup B) Powerbank connected to Pimeroni OnOff Shim via Micro-USB. Shim connected via jumper wire to the Raspberry Pi. Under-Voltage during startup and during playing audio samples.
Setup C) Like Setup A but speakers and card reader are disconnected: No issues at all.

I changed the jumper-wires, USB cables and tested the setup with two different Pimeroni OnOff Shims. I’m pretty sure that I’m not to stupid to solder the pins properly.

@Support: Is there a issue with voltage or amperage inside the Shim circuits, if used Pis with higer consumer load?

It could be the jumper wires from the shim to the Pi. The thinner the wire the more resistance they have and the bigger the voltage drop across them.
The official Pi 4 power supply has 18 gauge wires in it.
The jumper wires are I think 24 gauge? Which is a lot thinner
If you can double up your jumpers. Pin 2 and pin 4 on the GPIO are both +5V and there are numerous grounds.

I already use jumper wires from Elegoo (28 awg) and connected Pis pins 2,4 (5 Volts) and 6,9 (Ground) to the OnOff Shim.

I’d like to put the Pi inside a case with a cooling fan (eg. Miuzei case). Therefore connecting the Shim directly or through an extension board (AZDelivery GPIO extension board) won’t work for me. A ribbon cable would possibly lead to the same issues like the jumper wire.

I believe, I need an adapter with strong wiring from the Shim pins 2, 4, 6, 9 to an USB-C plug which could be connected directly on the Pi 4B.

Do you have some advice or better ideas?

28 gauge is thin by the way, the higher the number the smaller the diameter of the wire.
Also, does the on off shim have a header on it? Just wondering what the jumpers are plugged into?
The On Off shim has a 2.5A limit, I’m not sure thats an issue just pointing it out. Thats all you’ll get anyway if your using the Official Pi 3 Micro UBS Power supply. The Pi 4 USB C power supply is good up to 3A,

My power bank (EasyAcc PB26000MS) is able to supply DC 5 Volts, max. 4.8 Ampere output.

I’m wondering where the “2.5A” limit comes from, because the USB protocol specification on Wikipedia mentions up to 5A/5V on Battery Charging (BC) 1.2 otherwise it provides max. 1.5A at 5V?!

FYI: On my 1st Shim I soldered the included header, on my 2nd Shim I soldered a 2x 6 pins header strips.

Just a question from a rookie: If I

  • use a AZDelivery GPIO Extension Board
  • place 2 times an OnOff Shim on top of the GPIO connectors
  • connect on each Shim an USB cable from my power bank (4.8 Ampere only).

… would I be able to provide in 4.8A (2x 2.5A) in total to my Raspberry Pi 4?

The ON Off shim itself may have a 2.5A limit based on the components used? You’d have to ask Pimoroni if thats what the limit is based on. It may also be because the recommended power supply to be used with it, the Official Pi Foundation Power supply is limited to 2.5 A. All I can tell you is the product page says
“Supports up to 2.5A power supply”
You can contact Pimoroni Tech Support via e-mail via this link.
And drop a link to this thread in the e-mail. I don’t work for them and don’t own an on off shim, so I’m not sure what to tell you about the 2.5A limit, only that as far as i know, that board was designed to be used with a Pi 3B+ or earlier. Running a Pi 4 and your other bits on top of that might be too much for it, current wise.

This thread Onoff shim for pi4? may be of interest.