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View Full Version : Need an LED for my car alarm


Autotechnica
02-21-2004, 03:53 PM
Anyone know what voltage's are used for LED's in car alarms? I'm getting mine installed on Monday and it's missing the LED. I have tonnes laying around from misc. computer parts. Will this work?

Thanks,

Bryan

SpoolinS6
02-21-2004, 04:08 PM
i think it should be like 3-6 volts easy
and if ur looking for the whole led assembly go to flee market they sell that shit cheap theyre !

Autotechnica
02-21-2004, 04:10 PM
Originally posted by M_powered
i think it should be like 3-6 volts easy
and if ur looking for the whole led assembly go to flee market they sell that shit cheap theyre !

Thanks Geroge, but the car alarm power supply puts out 12 volts though, that means I need a 12V LED doesn't it?

Bry

niko_gt
02-21-2004, 05:05 PM
most led's should be 2-3 volts, even the high output ones
best thing to do, is install everything, and run a volt meter across where the led' light should go, im gonna make the assumption that its a 3 volt led. *th-up* let us know

niko_gt
02-21-2004, 05:06 PM
and btw i dont think they have 12 volt led's???

Justin e36
02-21-2004, 09:31 PM
They use a 12V DC LED... and it depends on which LED's for your computer you're thinking of....

if it's LED's from your HD, Power case lights.. then it won't work... they'll get really hot and begin going dim in around 2-3 hours of being constantly on... (but they will last longer since they'll be pulsing). You need an actual 12V LED. Rice shops will have a bunch of them laying around and will prolly sell it off to a dollar for you. I bought a blue 12V DC LED for myalarm for a couple bucks... *shrugs*

in any case, it really does depend on the alarm system.. (i.e. compustar uses a different LED voltage for the window knocker)..

typicall though, 12V DC.

J

Mystikal
02-21-2004, 10:11 PM
djcontra is selling red ones for like $2.50 each or something like that, PM him.

T.Dot_E30
02-22-2004, 04:11 PM
I have 100's of resistors lying around. It reduces 12v to 3.3v i believe which is perfect for leds.

limmi know if you want one.

I also have blue leds.

SpoolinS6
02-22-2004, 04:13 PM
Originally posted by Autotechnica
Thanks Geroge, but the car alarm power supply puts out 12 volts though, that means I need a 12V LED doesn't it?

Bry

man i learned somethings about L.E.Ds in school if the alarm puts out 12vs u will need some resistors to bring it down to 5 or 6 volt due to running to much current threw the basic led will blow the **** out of it
i sudjest using resisters man *th-up*

jorge....

SpoolinS6
02-22-2004, 04:31 PM
oh and also you will neeed a one way resister for each of your connections for the volts not to go back to the alarm system or it may fry it !

T.Dot_E30
02-22-2004, 04:44 PM
Originally posted by M_powered
oh and also you will neeed a one way resister for each of your connections for the volts not to go back to the alarm system or it may fry it !

I've never heard of volts going back into anything and fryin it like that.......plus its putting out 12v.....hows reducing the volts gonna fry it.

SpoolinS6
02-22-2004, 04:45 PM
by making it a one way current
and reducing the volt is best for the leds not to pop !

T.Dot_E30
02-22-2004, 05:43 PM
Since when does current flow two-way?

Yes adding a resistor will increase resistance, lowering the voltage.

Autotechnica
02-22-2004, 05:53 PM
It's only one way current. The only way it will damage the PS system is if you bridge the +ve and -ve connections from the LED. Aside from that, it will only blow the LED and not damage the computer system.

Anyways, thanks for all your responses guys *th-up*

I plugged in the alarm system and measured the current. It must have stepped down the voltage from inside the computer because it was only supplying 2 volts to the LED's. I found a 2V LED from a computer board and I'm using that.

Once again, thank you guys very much for your replies.

Bryan

niko_gt
02-22-2004, 06:38 PM
hehe told you so told you so :) jk lol i assumed there was a 500 ohm resistor along the 12 volt path to the led.

theres' no such thing as a 12 volt LED, well there is but its the same thing as a 2 volt led just with a built in resistor