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Discussion Starter #1
I just installed a new alarm in my T-Bird since my last one took a dump. Anyways, the new LED sucks (dim orange) and it runs off of 12v straight.. So I want to replace it with a blue LED. First, I need to ask, if I bought the LEDs in the auction below:

ebay

Can I run a few in series to make them survive the 12v source from the alarm unit? Can I install an inline resistor or something to make ONE of them stand the 12V continuously?

Second, what other sites can I use to find small (5mm) blue LEDs? In 12-14V would be best.

Thanks.

PJ
 

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Johnny Five is Alive, TCCoAAC Member
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Do you want it to blink?

if so your gonna need some more work to it ;o) or buy a blinking L.E.D.

However..

now.. for fun math ;o)


LED Forward Voltage 3.3V
LED Forward Current 30mA

VCC 12Volts

R = [ VCC - VF ] / IF

R = [ 12 - 3.3 ] / 0.030

R = [ 8.7 ] / 0.030

R = 290 Ohms

Now, 290 Isn't a very commin, go with a 300ohm Resister. do the formual backards will give you your current..

300 = 8.7 / ?
300 * ? = 8.7
.029, or 29mA (your below the max, your safe..

ok.. second question.. www.digikey.com ;o)

have fun.. Feel free to email me or PM for any other questions..
 

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Discussion Starter #4
WkStill, you're the man! Too bad there wasn't a lot of time left on the auction. The alarm's cpu would have taken care of the blinking. I'm gonna have to take more time searching on that website. 99% of the stuff I don't even recognize-- not that I am an electrical wiz.

OK. I may PM you with more Qs later.

PJ
 

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Just hit up Radio Hack......LED and resistor will be like 3 bucks.........Navy Trained Electrician for Nuclear Power Plants (sound important don't I........hahahaha)

--Craig
 

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Sheepish
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Check this out...

http://linear1.org/ckts/led.php

Also, I'm not sure about the alarm in your car, but my Viper dosn't require a special blinking LED. Because when it's in Valet mode the LED is on steady. But yeah, wiring up a blue LED to a 12v source is child's play. Plug in the correct numbers into that calculator, and it'll tell you what resisitor you need. If you get like $4 Blue LED from Radio Shack, the thing is bright enough to be a freakin flashlight. I've got one in the front of my computer and it'll light up a rather bright 5' circle on the wall across the room.
 

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Johnny Five is Alive, TCCoAAC Member
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jezz. just take the fun out of it AJ ;o)
 

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Refrigerator Raider Hater
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you can put LED's in series or parallel, but remember you need current limiting resistors for each branch.

If you want a bright LED your going to need ALOT more current than 30ma, more like 100-200ma. the ones in our trunklid lights are ~ 260ma. expect to pay $2 to $5 for ONE.

a 10 degree viewing angle sucks. for what your talking, I'd suggest an "UFO LED"

making an LED blink is as easy as an "RC" chip, two resistors and a capacitor. those componets, along with power, make a square wave generator.


<----- currently has 51 of 67 credits for ELT degree.
 

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Discussion Starter #9
Well, I don't need a blinking LED. And I agree that 10 degrees isn't that great... But what the heck is a UFO LED? With my minimal time searching, I found that VARAD makes some nice LEDs that would work for my application. I haven't been in Radio Shack for a few months. I didn't know they carried those types of LEDs. The only blue ones I've seen are the ones that are simply white LEDs with blue painted lenses-- and they glow green and look cheap. I am looking for those diodes which actually emit in blue wavelengths. If anyone can provide a link to what they consider to be the right candidate, please post it.

PJ
 

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Refrigerator Raider Hater
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PJ-4.2L said:
But what the heck is a UFO LED? If anyone can provide a link to what they consider to be the right candidate, please post it.

PJ
Basically a UFO-LED is a 1mm ultra-bright LED with a diffuser. they usually have 4 prongs, and an example is the ones in our tail lights.

www.questlink.com has a listing of 164 "ultra-bright blue led"'s. have fun!
 
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