How do I use separate power supplies for a connected Pi and Uno?

Using Arduino General Electronics
1

I am using a Raspberry Pi4 as a “PC”. It is programming an Arduino Uno via a USB cable. It also powers the Uno. The Uno has two small sensor boards attached which are happily sending out pressure, temperature, and humidity data.

This places a fairly high load on the Pi and it started getting too hot and misbehaving after an hour or so. So I mounted a small fan above the Pi board and this solved the problem.

However, the next step now is to attach an Adafruit 2.8” TFT capacitive touch screen shield to the Uno so that I can program it to display the three readings. When that works, I can remove the Uno from the Pi and run it as a standalone indoor environment display.

I suspect the extra load of the sheild may push the Pi over the power limit. How can I power the Uno separately whilst it is still attached and being programmed by the Pi?

Many thanks for any ideas.
Andre

2

Where is the Pi getting its power from ?

3

From a Pi power supply feeding a small USB connector on the side of the Pi.

4

Attach a ground wire from the RPi and the Uno. Use the Uno's power plug to supply power to the Uno separately from the Pi and with the 2 grounds connected they are at the same potential and can read each others thingies.

5

Great! Thank you very much.

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