I want to switch on an LED and I have to use a momentary switch on a separate circuit(too much trouble explaining why). I want it to go like this... push on momentary switch, LED goes on, release momentary switch, LED stays on until power in its circuit is switched off. I tried using a spdt relay but couldn't do it properly. I read on a thread that its possible but can't seem to do it right. Could someone there help me as Im a beginner. Thanks

Greg,

We need more information regarding the circuit.

What is the voltage and amperage of the circuit?

Why do you want a "Delay", in the circuit?

The left sketch assumes both relay coil and LED are same voltage. I do not believe this is exactly what you want, as you state the momentary switch is on a separate circuit, which means that the relay and LED are of different voltages, which does make more sense, but cannot be done with only a SPDT relay.

So to illustrate, I gave one sketch with both relay and LED at same supply voltage using the SPDT, and another showing a DPDT relay, which is what is needed to have the relay and LED on different supply voltages.

Cannot be done with just a SPDT relay and having two supply voltages. Must use a relay that has two sets of contacts.

Look these diagrams over, and we can continue from there.