You said ‘all lights come on but all but the last set go off straight away’ — I don’t quite understand this: what did you mean by ‘the last set’. Does the LEDs come in multiple sets, or did you mean the last one on the chain? I think you probably want to check the current requirement of these LED lights — OpenSprinkler DC can only handle 1 to 2 amps per station. If the LED current exceeds the amount, it won’t be able to supply the current required.