Wiring an LED, Help.

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May 31, 2003

Fern

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Wiring an LED, Help.

I got an alarm LED (I think its from DEI) and I want to wire it to coem on when the car is shut off since I dont have an alarm installed yet. What can I wire it to so it does this? There is a positive and a negative wire for the LED. Is there somewhere in the car this can get wired to so that it will turn on when the car is turned off?? Thanks for the help

May 31, 2003

TeSt DrIvE

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IM not 100% sure, but I think you can wire this up to your ignition switch, however you only have a powere and ground wire, i think you need a separate wire for instance to run to the ignition?

JUst an idea not sure though

May 31, 2003

Mystic3030

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You need to use a relay....if you search I think there was a thread with instructions for it a couple months ago.

Jun 1, 2003

Oishi

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no need for an expensive relay...use a cheap npn transistor and some resistors(3)...if you don't know what they are then i don't think its a wise decision to start wiring anything...

from igntion (or any +12V source that is always on) connect a resistor to the base of the transistor...emitter of the transistor should be connected to the floating ground of the accessory plug....connect the collector to the +12v source via a resistor...but at the same collector/resistor node connect another resistor then the anode (positive) of the LED and then the cathode (negative) to chassis ground...
calculation of the resistors are easy enough to calculate on your own..

Jun 1, 2003

luvvegas777

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sounds complicated, maybe a real alarm purchase would save a lot of money on painkillers

Jun 2, 2003

tbone323

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I thik you've prolly confused 99% of the ppl in this forum with that response, not everyone knows what us 1% do, lol. I like the response tho to scare the kid into NOT f-in with his electrical system when he doesn't know the difference between +12 and GND

Quote:

Originally posted by Oishi
no need for an expensive relay...use a cheap npn transistor and some resistors(3)...if you don't know what they are then i don't think its a wise decision to start wiring anything...

from igntion (or any +12V source that is always on) connect a resistor to the base of the transistor...emitter of the transistor should be connected to the floating ground of the accessory plug....connect the collector to the +12v source via a resistor...but at the same collector/resistor node connect another resistor then the anode (positive) of the LED and then the cathode (negative) to chassis ground...
calculation of the resistors are easy enough to calculate on your own..

Jun 3, 2003

Oishi

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thats pretty much what i had in mind...if you don't know hot from gnd then just wait till you actually get your alarm installed so they'll do everything for you...
if i added a diagram it will make it a whole lot simpler but yes i'm that lazy...