I have a desk lamp that doesn't have a switch because it was custom made. I discovered that it is bright enough to light the whole room. I figured I'd solve the switch problem by designing a circuit that would allow me to turn it on and off from two locations: my bedside table and my desk (my room is very small).
I'd position the circuit somewhere along the power cable. My power board has a spare built-in USB port so I figured it'd make sense to power a relay from that. The lamp is a 7.5 W, 240 VAC globe. The circuit I came up with is as follows:
Because I'm a still a novice electrical engineer, I have a few technical questions:
- Does it matter which AC wire I put the relay on? Could I just pick any wire and put the circuit in the middle of that?
- What am I looking for in a relay that could pull this job off? Suggestions welcome.
- From my very basic knowledge of electronics, I know you can't just put a solenoid in a circuit without something to take the load - hence the existence of R1. What would be a good value for R1? My guess is that if it's too low, the relay would get hot, and if it's too high, the relay wouldn't work.
If you see issues with this circuit or have better design ideas, be sure to leave a comment.