I'm using a rasperi pi 4 and want to run a water pump with it. Connecting the water pump directly to the rasperi pi (ground and 5 V) is working. But I want to be able to control the pump via GPIO and I also read somewhere that it isn't really healthy for the rasperi pi to connect a motor to it. (I'm pretty new.)

So basically I ordered some 5V relays(they are from Az Delivery if that helps). I think I have attached it correctly to the pi because if I turn on the GPIO 20 (connected to that one) on, I hear a click and the LED turns on. But the Waterpump isn't running. I ordered multiple relays and tried 3 already so I don't think they are broken. Is there a power issue? The waterpump was running when I connected it directly to the rasperi pi... And I also tried connecting the relay to the 3V on the pi, didn't work either

Here you can see the relay. I think the red led means that the relay is on.

1 Answer 1


This isn't how a relay works. The relay board is just a switch that can be turned on and off by a low power signal from a raspberry pi GPIO pin. You will need to provide a separate power source to power the pump.

Try using a 9V battery or similar to power the pump. Connect the +ve pump wire to the 'normally open' (NO) pin on the relay board, and the -ve wire from the pump to the -ve terminal on the battery. Connect the +ve battery terminal to the middle pin on the relay board. Then you should be able to use the GPIO pin to switch the pump circuit on and off.

  • 2
    The voltage of the battery or power supply should match the specification of the pump. If the pump works with 5V, then 9V might be too much.
    – Bodo
    May 10, 2022 at 13:33

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