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I want to get an LED strip and stick it right along the top of the back window, right at the headliner. I want to hard wire it to a switch, but also have it powered from the dome light. This way I'll be able to switch it on and off, and have it come on when I open a door. How would I wire it so as not to fry it if it is on when I open a door?

12V source ------------Switch-----------------LED Strip-----ground
Dome light circuit------Diode---------|


That is assuming that the led strip accepts 12VDC input.

ZeroChad wrote:
That is assuming that the led strip accepts 12VDC input.

Yeah, that's correct. This might be too much to ask, but could someone draw a little picture?

Or just use a 3-way switch.

supermike wrote:

ZeroChad wrote:
That is assuming that the led strip accepts 12VDC input.

Yeah, that's correct. This might be too much to ask, but could someone draw a little picture?

I tried to do a lame ascii drawing. You will tap into a switched, 12V source, and run it to the switch, then connect it to your leds. Tap into the dome light circuit on the roof, solder in a diode, then tap in to the wire you installed after the switch.

Or as brian suggested, use a SPDT on-off switch, wire the normally middle prong to your led. The normally-closed prong to the dome light circuit, and the normally-open prong to a switched, 12V source.

I think I'll try the switch first. Are all 3 prong switches SPDT or are some SPST?

supermike wrote:I think I'll try the switch first. Are all 3 prong switches SPDT or are some SPST?

For the most part thay are all SPST. That is what you're looking for.

what kinda diode

Simple diode to avoid short circuit. Diode allows the current just to flow in one direction. W/o it the light will be on all the time...

A 1N4001 should be fine if your led stip draw stays under 1A (which it should). You can find them at Radioshack.

I found a switch I had laying in my room, used a continuity tester to test it the way you said to wire it, and it looks like it'll work! Thanks for the help!