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Unread 12-24-2008, 07:56 PM   #1
Steve993
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Default LED Brake Light Conversion

I know there were a few threads on RL about this and a bit of scattered information. I eventually figured out what LED's I needed, but the big question always remained. What would it look like? Well I hope this post answers that question for others. First, the specs. I used 24 LEDs from superbrightleds.com. Then I used their series/parallel calculator here, http://led.linear1.org/led.wiz. The numbers I punched in are 14.8 for the Source Voltage, 2.2 for the Diode Forward Voltage, 29 for the Diode Forward Current (mA), and of course 24 for the number of LEDs. If you compare the diode forward voltage I put in compared to the specs of the LED itself you can see that I am above the recommended, but below the peak. My reasoning is that I really don't care if I shorten the life of an LED from a million hours of use to 100,000. That and my car is only putting out just over 14 volts when running. So I should be fine. [As a quick disclaimer: what works for me and my configuration may not work for others.]
The calculator told me to do four groups of six LEDs and use 56 ohms resistors. I got everything wired up and tucked back into the brake light for the pictures below.

I may have went overboard on comparisons. However I was never satisfied with the end results people posted previously, if at all.

FYI: The YouTube videos have the lights hooked up to a 12v bench power supply as opposed to the 14ish volts from a running car.
http://www.youtube.com/watch?v=qPcbb_C5Yog
http://www.youtube.com/watch?v=zssucLFLPMA

The basket handle isn't attached for these shots and the wires were too short for the LED light I had so I had to rest it outside of the housing.

Incandescent with 14v from running car.
Click the image to open in full size.

LED version with 14v from running car.
Click the image to open in full size.

Animated version
Click the image to open in full size.

And I know my drivers side brake light was burnt out!

Anyway I hope some of this info will be helpful to others out there wanting to do the conversion. I'll probably do this conversion for a couple of buddies of mine 993s, but I'm kind of entertaining the thought of selling this as a completed brake light. (I'd have to get the old incandescent version back though, convert that, sell that one, repeat, etc.) The light itself can go in either the basket handle or roof/glass mount third brake light.
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Unread 12-27-2008, 12:51 PM   #2
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Great work!
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Unread 03-12-2009, 02:12 AM   #3
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That's awesome, nice work Steve. I'm putting this on my list of things to do the next time I have a bulb burn out in the 3rd brake light.
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Unread 08-17-2009, 12:48 PM   #4
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Steve,
Interested in doing this as well. I presume the first link points to the actual bulbs you purchased?


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Unread 08-17-2009, 03:54 PM   #5
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Quote:
Originally Posted by AOW162435 View Post
Steve,
Interested in doing this as well. I presume the first link points to the actual bulbs you purchased?


Andreas
Yep those are the exact ones I bought.
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Unread 08-17-2009, 04:41 PM   #6
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Steve,
Thank you! One more thing - are the resistors 56 ohm, or 560 Ohm? I found this site and am a bit confused....

If these are wrong, could you point me to a known source?


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Unread 08-17-2009, 08:38 PM   #7
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Quote:
Originally Posted by AOW162435 View Post
Steve,
Thank you! One more thing - are the resistors 56 ohm, or 560 Ohm? I found this site and am a bit confused....

If these are wrong, could you point me to a known source?


Andreas
Yeah you want 56. My source was local, so there's a chance you've got a electronic supply place near you. Radio Shack has been getting away from this type of stuff, but they might have it or may be able to order it for you if you can't find 56 ohm online.
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