Ahh-- make it stop!

This circuit should give you a "N/C" (+12v) output that goes OFF when the "N/O" output (+12v) get's triggered from a (-) on the input. It works on my simulator, but I haven't soldered it up and tested with lights yet to confirm. AllElectronics.com has the parts or you can get NTE/ECG equivalents usually at a local electronics store. You may need to switch the +12v supply if you wish to be able to shut OFF all your lights.

Here's the transistors that can handle more then enough current for your needs. Notice the metal tab on the part. Do NOT mount that to metal on the car, Do NOT mount them to each other. Do Seperate them with something non-conductive that won't easily melt.

ok, well I understand the diagram 100% now, I just don't understand how it works.  Where can I read about transistors?  They seem very cool!  What else can they do?

Well, simply put, The "B" on the transistor is the Base which is kind of like one side of the coil of a relay. It's the trigger. With an NPN transistor, you need a Positive on the Base to trigger the "coil" With the PNP, you need a negative or ground on the Base to trigger. The E & C are Emitter & Collector. This is kind of like your "Common" and "N/O" on a relay. Current can only flow in one direction so if your passing +12V, you would generally use a PNP (Positive-Negative-Positive) and for NPN you would usually be passing a Negative or Ground. with little current/voltage on the Base, you can switch heavier current through the Emitter & Collector. Just like with Relays! Transistors can basically be used to drive lights, motors, whatever as long as you use the appropriate transistor for the current demands of the load. Search Yahoo for more info, especially with keywords like robotics, transistors, circuits. MOSFETs can also be used to do what you want, but I'm more comfortable working with transistors.

ok, awesome.  I am ordering them tonight.  Now transistors do not add more power, correct?  Like w/ a relay you use the trigger to turn it on, but the relay gets its own power.  Transistors don't have their own power, correct?  Its not a big deal at all I'm just trying to learn.

what kind of non conductive, non melting material for me to wrap them in?  How hot do these get?  Can I wrap them in duct tape or something?

Just to through in my two cents here, wouldn't have been easier to just wire your relays then put them into a cup and pour some casting or fiberglass resin over them? You probably wouldn't be able to hear them anymore.Certified Security Specialist

Always check info with a digital multimeter.

I promise to be good.

Tell Darwin I sent you.

I've been sick lately, sorry I won't be on much.

BumpNGlow wrote: what kind of non conductive, non melting material for me to wrap them in?  How hot do these get?  Can I wrap them in duct tape or something?

I suppose you could mount them to a thin piece of wood or Hi-Temp plastic. Normally/Ideally they are mounted to a metal heatsink with an insulator behind & in the screw hole because the metal tab is usually common with one of the pins, so grounding out the tab can possibly short out the transistor. How hot they get depends on how much current your drawing as well as the duty cycle (how long it's on at one time). Usually when I use them, it is for intermittent use like to switch something on for a few seconds. If my load is only say 1 Amp, then the transistor shouldn't get very hot if I'm using it like I mentioned. So sometimes I mount it to plastic (Hi-temp plastic would probably be good) or sometimes I just have the pins/legs soldered to a generic circuit board (I think they still sell these at Radio Shack) housed in a plastic case.