Electrical

Power

Supplying power always seems to be the most difficult part of electronic projects. Fortunately, this was straightforward.

This project uses three voltages:

• 120 vac (wall voltage)

• 24 vac (doorbell voltage)

• 5 vdc (Raspberry Pi voltage)

Here's a picture of the power solution.

120 vac

You have to start somewhere. Wall power goes into the metal junction box and is connected to the two outlets and the transformer. The switch will cut off power to outlets and transformer. The chicken decal is for grins.

24 vac

The transformer supplies 24vac from 110 vac. I bought this at a hardware store, it's nothing special and available in the irrigation section or the doorbell aisle. Buy something like this.

Irrigation valves are opened by applying 24 vac. This voltage is switched by the relays.

5 vdc

The Raspberry Pi runs on 5 vdc. Different models require different amps, but the RPi Zero is happy to run on less than 1 amp, which is within reach of most phone chargers. I thought about building a custom power supply, but I have a box of these chargers, so why bother?