led triggered by dome light and on/off/on

Although that circuit is simpler for omitting the relay, I think I will go with the relay instead. This is becuase I will likely add LEDs to this circuit, but in other locations and having the power source and dome light trigger junctioned for additional circuits would be more convenient than running more wire all over the place. Is there any real drawback to using a relay here?

Okay, that is what I thought. Thanks very much again for the help.

Hi I am new here but I was searching for this exact solution. I have wired my 2002 sunfire just like the diagram from jewster made without the switch, but the problem is when the dome light dims at the end my relay buzzes. my question is"is there a transistor or something I can put in the circuit to fix this?" maybe a transistor connected to dome light ground that can trigger the relay that transistor would have to be able to work under low voltage and up to 12 or 14 volts any help would be greatly appreciated.

Exactly. If they are LEDs, do not use the relay - it is not needed. Otherwise you could use a transistor with a current capability sufficient for the load (lights). In this case it would be a PNP. A FET may also be suitable - especially for dimming. The circuit depends on whether full brightness or dimming.

I found a solution to the relay buzzing https://www.the12volt.com/installbay/forum_posts.asp~TID~114184~get~last#585248 I just didn't want to run any thing extra on the circuit for the dome light. and I also plan on adding more to the circuit for my leds

But that might blow the dimming circuit (if it can't handle the cap current). Besides, why the heck use a relay if it is for LEDs?

does anyone know what does the dot's mean that kpierson draw

What dots?Kevin Pierson

The only dots I see are the symbolic contacts - ie, switch contacts. Also, if the wiring is done similar to my fig on the last page (ie, LEDs or relay powered by separate +12V - not what the dome-bulb sees (since it is being dimmed), then no dimming or chattering should occur. But if the only +12V accessable is the dome light bulb's power, then you need some sort of hysteresis to stop relay chatter - eg, an RC circuit, Schmidt trigger or other buffer circuit; maybe a timer.