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.
-ABC

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.

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, :)

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

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.

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.

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

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.

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.

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.

-soD

buy a couple SV650S (2003 or newer) tail lights, two rows of LED's on each, VERY bright, all set up, would probably fit each side of the jeep too, then you'd have quad lights

I read in an earlier post about putting lights in the oven.... If you're going to do that - do it with a heated oven with the oven off.... NEVER underestimate the additional radiant heat when that element kicks on....

I've personally taken apart sealed headlights (to reseal) with a heat gun. Just some quick passes to soften the glue/sealant :)

That said, the drop in variety is the easiest way to go.... Probably much cheaper too (an economist would probably tell you that you'd spend more time than buying what someone already figured out). Unless, of course, you want the individual diode look - something purely aesthetic.

If you don't want to have to do anything complicated you could simply wire the LEDs in parallel with one resistor per LED.
http://www.captainslug.com/temp/turnsignals.jpg
Make an array board out of plastic with holes drilled in the spacing/pattern you want.
Then you can solder the negative leads all together, or make separate circuits and lighting patterns for running and braking. I did the latter because it was easier.
http://www.captainslug.com/temp/xb-600_005.jpg
http://www.captainslug.com/temp/xb-600_006.jpg
http://www.captainslug.com/temp/xb-600_007.jpg
Or if you want dual intensity you could simply wire the running light circuit to deliver a slightly crippled supply to power to the array, then have the braking circuit supply full voltage.

You can buy LEDs (often with resistors) in bulk lots of 50, 10, or 1000 factory direct through eBay.
http://stores.ebay.com/Chi-Wing-LED-...QQftidZ2QQtZkm

6000mcd LEDs will be more than bright enough for brake lights.

I dunno what the tail light pattern is, but I dont think i can do the every other row thing.
http://www.truckaddons.com/images02/...98tailligh.jpg
the taillight is thin compared to most cars, and id want it to be fully lit.

i need to examine one up close, but im pretty sure its a sealed unit.

also i remember seeing a method of doing the dual intensity with 2 sets of resistors. I dont know how they did it, but 2 feeds into a resistor each, then they converge into 1 row of leds. (with multiple rows of leds) my question is how big are the resistors?

oh also, i hear you cant judge how bright the LED is simply by its MCD? I'd probably prefer wide angle leds with as bright as possible?

and if its a multi coloured tail light, should i get red for the red part, and amber for the amber part, or should i just get all white?


edit:http://keld.eu/led/index.htm found the dual intensity method.
i dont know how to read schematics so can someone explain how they did it? thanks.

Every other row will be plenty bright enough to light up the whole lens. Especially since you can put like 12-15 rows at least of 3mm LEDs in the width of the lens.

If you don't like every other row, you can also do every other LED, staggered in each row...

So it's like
.0 (1) 0 (1) 0 (1) 0 (1) 0 (1)
(1) 0 (1) 0 (1) 0 (1) 0 (1) 0
.0 (1) 0 (1) 0 (1) 0 (1) 0 (1)
(1) 0 (1) 0 (1) 0 (1) 0 (1) 0

And the (1)'s are running/parking lights, while the 0's are brake lights.

And in the lower red section, you can make it so the (1)'s are running/parking, and 0's are turns.

Catch what I mean?

You can get rid of the hot-spots that LEDs normally have (bright point of light) by filing the tops so they're flat instead of domed.

oh i forget, i dont know if jeeps have mechanical or electronic flasher relays, but would an electronic relay automatically fix the flash rate in cars?

Yes, you can get LED-specific flashers. Which you will need if you replace both conventional brake lights with LEDs. I have a cheap one I didn't end up using if you're interested.

Or alternatively you can solder in a 3 ohm 20 watt resistor between the B+ and common negative on both of the LED brake lights and that will solve the issue.
LEDs offer so little electrical resistance compared to incandescent bulbs that the coil in the flasher relay trips much faster. So adding the resistor fixes that issue.
1. You can, but the LED will only deliver it's rated output at the specified voltages. 3,000mcd LEDs are fairly bright, but 6,000mcd LEDs are EXTREMELY bright (6,000mcd = 6 lumens). LEDs are just very directional, and you'll need to use a bunch of them.

2. Depends on how heavily tinted the lens is. 6,000mcd White LEDs for all three should work fine. Most yellow/amber LEDs are too dim to really work anyways.

3. The L+ is the supplied 12v+ power for the running brake light. The B+ is the supplied 12v+ power for the activated brake light.
L+ powers the LEDs through a set of resistors that end up delivering about 80% of the rated power to the LEDs so that they're not at full intensity.
The B+ delivers the remaining amount of voltage (since the L+ is always on) to bring the LEDs to their full intensity.
http://upload.wikimedia.org/wikipedi...symbol.svg.png
LED symbol

The wiring for brake lights have a common negative. So the cathode of the sets of 4 LEDs are wired to that.
That schematic should work fine for any 2.2 volt 25mA LEDs. You can increase or decrease the array size by adding or removing sets of 4 LEDs from it.

This circuit is a bit simpler: http://www.sca40.com/led/

when you're all done, count your flashes per minute.. I'm pretty sure NHTSA says 60-120 flashes per minute.

I know that's the rule for PA, and it applies equally to the turn signals and the hazard lights.

what does 820 ohm *9 and
330 ohm *9 mean?

i see that the 820 is the "Bigger" resistor, but i think it means thats the running lights
and the 330 is the smaller one to provide full flow?

oh and *9 is apparently 9 total for his project.

Those are resistor values for 1/4 watt resistors in 820 ohm, 330 ohm, and 270 ohm ratings.
More resistance = less power delivered

I'm not sure what the spec on the LEDs he used are. But should you want to double check his resistor choices you can use an LED calculator.
http://www.hebeiltd.com.cn/?p=zz.led...tor.calculator

Don't resistors convert electricity into heat?

Isn't that kinda defeating the purpose of the electricity savings from using LED's anyway?

Not being smart here, I'm genuinely asking.

Obviously there is still an economic advantage in never having to change the bulbs again, but damn, it's only a very small amount you're saving, and that's if you changed them ALL on scheduled intervals.

oh wow i just saw the ducati one. ive seen that one before, but i didnt realize that it had dual intensity. its only 2 resistors or something for that entire array!

EDIT:i am personally doing it to get brighter lamps. I have seen my brake lights during the day, and theyre a bit dim compared to some of the newer cars.
i realize that resistors arent effective, but it would also be nice if you can save some electricity so the alternator doesnt have to work so hard.

Yes resistors convert power into heat so that the resulting output is reduced.
How much power is consumed by resistors is dependent upon the layout of the circuit.

However LEDs are still MUCH more efficient at turning power used into usable light. That light output is also very controlled.
I'm currently working on replacing a 310 lumen incandescent bulb that consumes 18 watts with a 430 lumen high power LED that consumes only 8.5 watts (resistor included).

The more significant difference between the two is service life.

Using half the power to make more light is quite significant.. I wouldn't play it off, personally.
Thank you for clarifying.. I planned on making LED lights for home use. (Screw them in just like the fluorescent replacements.)

what light is this for? and wow i didnt know they made LEDs up that high, i do know they make 5W luxeon leds, but i didnt realize they made 8.5W ones.

The brightest LED Luxeon makes can output 540 lumens at 6.6W (provided you don't have to use a resistor). The resistor used to power the LED from a 12volt supply ends up consuming almost 2 watts.

Could you not use two LED circuits to break the 12v down to 6 and 6?

I can't remember which type of circuit you'd use... I think you'd use two series circuits in parallel.

+[-|-|-|-|-|-]-
+[-|-|-|-|-|-]-


+ = input
- = output
[-|... = LED's in series


Something like that.. but it's probably wrong.

No. The Luxeon High-power LED operates at 9.45 volts and consumes up to 700mA.
Endor Rebel - Cool White, Tri-Emitter, 435 Lumens @ 700mA [7007-PWC-08-3]

You can wire regular LEDs in series sets in order to reduce the power wasted by resistors. The further you do that the more the array loses the ability to handle voltage drift. Something that's kind of important when you're powering them from a battery.

what?

So basically, you'd have to ensure a stable 12v signal to the input in order to run enough LED's to not use resistors at all...

i know you need to use at least 1 resistor because its not all Volts, it has to do with either the watts or amps, i dont remember. the led's cant really handle the something of the feed so you need a resistor to "clean it up."

Correct.
If you had a perfectly stable 13.2 volt source you could string six 2.2 volt LED in series with no resistor at all.
The fewer LEDs you have in series and the more resistors you add the wider the input voltage the array can handle without overvolting the LEDs. But you end up consuming more watts with resistors.
4 LEDs in series with one resistor for them will generally offer the best balance between the two.

I smell a dirty word... compromise. blech.

4 leds and 1 resistor, i know is because its specifically for a car i believe.
parallel sets of 4 leds is roughly at 12v per set. but i think the resistor is still required because the line voltage fluctuates between 12ish to 14ish.
dont quote me on this though.

I wouldn't waste time with the turn signals; keep them incandescent (just remove one wire from the bulb and use it for your led parking lights. - keep the old bulb in place and just power the high filament)
Unless you spend a huge amount of time with your turn signals on. Less cost, less hassle, less risk of not working and losing hazards as well, and no flasher change to worry about.

Bah, that's too easy. :P

There are frenched style tail light kits for the jeep TJ/CJ wranglers that use what appear to be the same lights used on big rig tractor trailers. They are dual intensity and can be seen forever. Not so DIY but its a clean install.

but i have a ZJ, a 1994 Grand Cherokee. the "mods" for tail lights are slim. Just Nasty looking Altezzas.

Hi,

I'm a little concerned with the optics of doing this: LED's have such a narrow beam, that getting them actually reflecting and (highly) visible from all angles. Some of the LED replacement bulbs have a center "hot spot" that shines straight back, and they have some around the rim to bounce off of the reflector, so you can see it from the sides, etc. Has anybody tried these?

7443 LED bulb Specifications

3156 and 3157 LED bulb Specifications

As opposed to these:
7443 LED bulb Specifications

if youre gonna make your own panel of LEDs to put into the taillight, like i eventually will, they sell "flat top" leds that have a wider viewing angle.