I bought two of the pumps with the PWM speed control. However, I do not entirely understand how to connect them.
I have a 24V DC power supply for the pump, and a 5V DC power supply for a Raspberri pi. I want to have the Pi output the PWM signal. But the red/black wires already connect to the 24V power supply (via a relay). Presumably the negative end of the two power supplies should be connected somehow? How do I do this?
Probably a stupid question - go easy on me please