I'm using a Sainsmart 16 relay module, and relays turn ON when I send LOW voltage signals from my Arduino ports to the control pins on the board.
That said, I'm controlling a 12v water valve that uses TWO signals- one to open the valve, and a separate signal to close the valve... It needs two relays that are always doing the opposite thing. I want to conserve a digital pin on my Arduino and do two things at once using a transistor... where if I want water, the opposite signal is sent to the OFF relay. something like:
If I need my water valve to open, I send a LOW signal to the pin/relay to the water valve OPEN relay, but at the same time, that low signal CLOSES a 5v circuit, that turns my water valve CLOSED relay to HIGH (aka turning my water valve CLOSED relay... OFF. .
It's a really weird circuit and I don't thing an NPN is going to work... Can anyone tell me if a PNP is the right way to go/which one I should purchase?