How many GPIO pins on Pi Zero for relays

Hi everybody! I'm setting up the hydrosys4 system for a large area with 24 watering lines. I want a relay to operate a solenoid valve on each line. I have already put together a system with 16 relays that is in test phase (not connected to valves yet). I would like to connect 8 more relays. The Pi Zero has 28 GPIO pins. Can I use any or all of these pins e.g. Pins 0,1,2,3,7,8,9,10 or are some not able to be used with hydrosys4? I would rather not use an MCP23017 if I don't need to. Please advise.

Switches just manually turn on relays in case one line needs extra water or for checking valves etc.

10 answers3 replies

13 Comments

hydrosys4

Feb 15, 2021

By the way, I'm in the process of testing some extension boards for very big setup, hopefully they will be available in my Tindie shop soon.

hydrosys4

Jun 24, 2021

Replying to

@sid Unfortunately the shipping service have a very high cost in my country, this the reason why I limit the country to which I can ship. As you said most of the money goes to the postal service. If this was a real business, for sure it would be not sustainable with the current prices of the boards.