OpenSprinkler › Forums › Hardware Questions › OpenSprinkler Pi (OSPi) › Did I get the wrong relay? › Reply To: Did I get the wrong relay?
Have you just connected the two wires from the valve directly to two terminals of a particular relay ? If so then that wont work. There are two very separate circuits here and both of them need power. Firstly, the logic side of the relay (i.e. the side connected to the OSPi) needs a 5V supply but the Relay side of the board (the big green screw connectors) needs 24V to drive the valves.
The board you have looks fine. Just connect the positive side of a 24V supply to the input pin on one of the relays, then connect the NO (normally open) pin to the active wire on the valve, then connect the common wire on the valve to the ground wire from the 24V power supply. That way when the OSPi “closes” the relay switch, the relay will connect 24V across the valve.