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Memorytwo 12-02-2008 12:30 AM

DIY LED tail lights
I kinda wanna retofit my taillights with LEDs, luckily, the Jeep Tail lights are pretty much square so theres not a big problem with having to shape the pcb.

but im curious of 1. how to crack open a tail light assembly with out breaking anything.
2. how to do "dual filament" but with out having to use 2 sets of lights.

ive seen some plans, but they're pretty much non-descriptive.

Christ 12-02-2008 01:55 AM

1: Heat up the lights slightly, something like 150*-200* for 30 mins in the oven, but don't quote me on that, try it on a junk tail light first. After you heat them up, you should be able to wedge a wide, thin object (read: steak knife) between the lens and the housing, and gently pry up on it... This is how I get headlight lenses apart, even the plastic lenses. It doesn't fog them up or anything.. and I've put them in for up to an hour @ 200* to heat up the crap that seals it.

Before prying too far, check around the lens/housing for little clips. Once you've done the mod, you can re-seal the tail lights by cleaning off all the tar, and re-applying silicone sealant to the divot where the edge of the lens goes in the housing. (You'll see what I mean)

As far as the dual filament idea, I have no idea at 2am... check back later.

SVOboy 12-02-2008 01:56 AM

Any reason now to buy drop ins? I would prolly buy some cheap replacements from a junkyard and just hack them up big time to make it look fun, :)

Christ 12-02-2008 02:27 AM

I'm now kinda wondering about the dual intensity thing...

Daox 12-02-2008 08:59 AM

I second Ben's suggestion on drop ins. I'd wander over to SUPER BRIGHT LEDS home and take a look at what they got. Its not exactly cheap, but they are comparable lights of similar outputs so you know it'll work good. They also have dual intensity bulbs there.

McTimson 12-02-2008 09:03 AM

The dual intensity could be controlled by different voltages. LED's have different brightnesses at different voltages, especially if you get the really bright ones. If you could make a circuit that would output like 2.7V when the lights are on, and 3.3V when the brakes are applied (I'm just making those voltages up, the actual voltages are dependent on the LED's used), it should work. You'd need something that would output those voltages regardless of the input voltage, because the input will probably be fluctuating between 12 and 14V.

dichotomous 12-02-2008 09:09 AM

my cherokee had tail lights where the cover bolted on, they were stock, do yours or are grand cherokees different. essentially that would make it very easy to open up and drill some LED holes

MazdaMatt 12-02-2008 10:38 AM

i'm guessing that there are two wires leading to the brakes if there are two intensities... you could just make alternating strings of LED's connect to each light. ie first row is brakes, second row is lights, third row is breakes, etc...

If you wanted ALL the led's on at one time for low and high brightness you could do something with a 555chip (google it, you'll find a billion sample circuits and kits to use a 555). You set it to a VERY HIGH frequency 50/50 square wave for lights and you set it to solid 'ON' for brakes.

Everything i do at work that requires a dual- (or multi-) intensity LED we will drive it with a solid voltage for high or a square wave of various duty % for various intensities.

Christ 12-02-2008 01:37 PM

I was initially thinking the every other row thing..

Since I didn't think about it before, your jeep might actually just pull away from the taillight housing.. some jeeps were equipped with a rubber seal instead of actually being glued shut.

some_other_dave 12-02-2008 01:51 PM

I recommend the every-other-row thing over flickering the lights with the 555 chip. There are a number of Caddies out there that have the flicker rate set low enough that I can see the lights "strobe" in my peripheral vision, and it is very distracting on the road. My GF complains that it gives her a headache, as well.

So, for the sake of those of us who are sensitive to that, please use the every-other-row (or similar) solution instead of blinking the lights. Or if you blink them, use a frequency faster that 100 Hz.


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