I have one of these single-relay boards and I am trying to control it with my RasPi's GPIO. (I'm a complete noob).
I am using WiringPi and in this particular case I'm using pin 1 (aka BCM pin 18) as the control pin. From the relay board, I have the + pin wired to the RasPi's 5v, the - pin to RasPi's ground and the S pin to the control pin.
As soon as I connect the wires, the relay clicks and its led turns on. If I run a program that turns it on and off every 3 seconds, the relay's led turns on and off, but the relay stays connected (it doesn't click either). If I disconnect the control pin or gound then it clicks and turns off.
What am I doing wrong? Do I have to ground something else? I thought that by sending a LOW signal to the control pin, I was effectively sending it 0v, which should turn off the relay, but that doesn't seem to be the case.
I've gotten it to work by using the 3.3v pin on the RasPi instead of the 5v. Could anyone explain why the 5v + GPIO pin on LOW doesn't go to 0v, but to 1.5? Will having my 5v relay connected to the 3.3v damage it?