i have a bank of 4 12v relays that i was goin to connect to the outputs of my board. can i use these to switch my solenoid valves, each valve takes about 250mA.
Would work just fine, But how are you going to control the relays?
Are the solenoid valves AC or DC?
the solenoids are dc, was hoping to use power from the pin output to power up the solenoid
You won't be able to drive the relays directly from the Arduino - you'll need a transistor and a flyback diode. And once you add those there's not much point having the relays in this case, because with a transistor and diode you would be able to drive the solenoids directly.
so what i’d need is a 5v relay with switching capacity for 12v? what values of transistor and diode do you reckon i’d need?
so what i'd need is a 5v relay with switching capacity for 12v? what values of transistor and diode do you reckon i'd need?
No, you need a 12vdc external power supply able to supply all the solenoids, so 1 amp minimum, two amp recommended. Then you need 4 switching transistors and related resistors to allow the arduino output pins to turn on and off each solenoid. You also need 4 diodes wired across each solenoid coil terminals to suppress transients.