led tail lights

[sccarguy]

Hello everyone. I have some experience with basic 12v electrical systems. I need some help with a circut. I want to make some LED tail lights for my car. I would like to build the circut with 14 LEDs. any help would be appreciated. Starting from scratch. Thank you!

 

[BrownOut]

Somebody is gonna say it, so it might as well be me. Altering your taillights may be illegal. Please check your state laws before preceeding.

 

[sccarguy]

As long as they provide the same functions as OEM equipment there are no laws prohibiting changing or altering tail lights.

 

[Diver300]

LEDs need the current to be controlled, not the voltage. For instance, if you have an LED rated at 50 mA and 2 V, if you supply it with 30 mA (60 % of rating) it will be somewhat dimmer, and if you supply it with 70 mA (140 % of rating) it will be somewhat brighter and will probably burn out in a minute or two.

If you supply it with 1.2 V (60 % of rating) it will not light at all. If you supply it with 2.8 V (140 % of rating) it will explode.

So you need to supply a certain current, and if that is not perfectly accurate, it doesn't matter too much.

The simplest method is to use resistors in series. There are various calculators on the web to tell you what resistors to use, but do make sure that you design doesn't vary too much between 12 and 14 V, as that is the sort of change you get when the alternator starts working. For instance, if you have 5 LEDs in series, each rated at 2 V, then the voltage across the resistor will vary between 12 - 5 x 2 = 2 V and 14 - 2 x 5 = 4 V, so the current, and therefore brightness will double when you start the engine. The solution is to have fewer LEDs in series.

You can also use a current control circuit. That has the advantage that the current will be more constant when the supply voltage varies, and you can use more LEDs in series, which means fewer parallel strings so less current consumption.

There are also various LED driver circuits that use inductors to boost the voltage. That would let you run all 14 LEDs in series, and it would be efficient, and the current would be accurately controlled. It is the most complicated and expensive solution.

BTW, I found that my car turns off the alternator for a few seconds if the accelerator is floored rapidly. I guess this is to improve acceleration by removing load. It causes the voltage to drop by over a volt, and that is while driving. I certainly wouldn't want the lights to be varying lots as a result of that.

 

[bountyhunter]

As long as they provide the same functions as OEM equipment there are no laws prohibiting changing or altering tail lights.

Absolutely wrong for sure in California. Lights may not be mdified in any way except with exact OEM parts or parts certified to be exactly the same. To get certified they have to be submitted for testing to CARB and get tagged with a CARB approval number.

 

[bountyhunter]

Hello everyone. I have some experience with basic 12v electrical systems. I need some help with a circut. I want to make some LED tail lights for my car. I would like to build the circut with 14 LEDs. any help would be appreciated. Starting from scratch. Thank you!

I can say with about 99.999% certainty that whatever you come up with will not be bright enough... guess how I know?

The only plug in LED replacements bright enough are 3W Luxeons from superbrightleds.com. The "multi LED" equivalents are too dim.

http://www.superbrightleds.com/cgi-...ispPage&Page2Disp=/specs/115x-xLX3.htm#photos

 

[audioguru]

E-bay sells LED rear lights for cars. All the little cars modified with them here are either ticketed by the cops or rear-ended because they are too dim.

 

[bountyhunter]

E-bay sells LED rear lights for cars. All the little cars modified with them here are either ticketed by the cops or rear-ended because they are too dim.

Heed the words, believe them later. Stay away from ebay LEDs. Out here I keep seeing the tricked out Acuras (lowered, wide wheels and loud pipes) running the custom rear lights. I almost drove into the back seat of one on San Thomas Expressway when he suddenly stopped in daylight. Absolutely never saw a brake light on his car until we turned so the sun was at right angles.

 

[sccarguy]

Good thing im not in California My only problem with buying the lights already made is the only set I can find for my car is $700, they are not ebay, they are OEM. I would much rather play around with a few different LEDs and setups than spend that kind of money. Its not something that I need to do right away. I also like the idea of making them myself as I am a perfectionist and like things to look a certain way, the OEM assemblys do not look very appealing. Any useful info is appreciated.

 

[Joe G]

check on the numerus youtube videos, there are quite a few how-to's on them, a good way to get your feet wet and see how some people have done them. some are pretty cool,
while others are "are you kidding- that cant be legal/safe". and use the search function at the top of this forum, there are alot rite here.

 

[sccarguy]

Thank you, I will check out youtube.

 

[bountyhunter]

Good thing im not in California My only problem with buying the lights already made is the only set I can find for my car is $700, they are not ebay, they are OEM. I would much rather play around with a few different LEDs and setups than spend that kind of money. ///Any useful info is appreciated.

The 3W luxeons LED bulbs I posted the link to are "drop in" replacements for any standard 1156 (single) or 1157 (dual filament) bulb, which occupy about 99.99% of all the tail lights and turn signals in existence. They go into the existing socket and have integrated heatsink.

 

[sccarguy]

anybody can buy those, kind of loses the "custom" appeal and not a nice clean look. In my experience with other "drop in" replacements related to LEDs they never perform as expected. I would rather spend months testing different LEDs and have a custom tail light that looks very classy than use a "drop in" replacement.

 

[bountyhunter]

anybody can buy those, kind of loses the "custom" appeal and not a nice clean look.

OK, it's a LED replacement lamp doesn't change the look of the car.

In my experience with other "drop in" replacements related to LEDs they never perform as expected.

These are about 50% brighter than the incandescent bulbs they replace and about 500% brighter than the typical LEDs people buy and stick in their cars.

 

[Joe G]

Originally Posted by sccarguy »
In my experience with other "drop in" replacements related to LEDs they never perform as expected.


3w leds are REALLY bright, they will blind you,

 

[sccarguy]

Ok

I guess my simple question was just too easy for some people..... Anyone who has any info related to the topic I posted about(building a circuit) please feel free to chime in. Hopefully it's not to much to ask that you don't force you opinion of a product you believe in on others and just help with my original request rather than turn the thread into a debate.

 

[Joe G]

this is my first third-brake lite to try, it had a 1117 voltage reg, set for 60ma each led. i've since upped it to 10 leds with 2 reg.@ 70ma. I used OSRAM LS E65F-BBDA-1-1 power top leds on them.


**broken link removed**
**broken link removed**

 

[bountyhunter]

Originally Posted by sccarguy »
In my experience with other "drop in" replacements related to LEDs they never perform as expected.


3w leds are REALLY bright, they will blind you,

That is no joke. Do NOT ever look directly at them without the tail light lense in place.

 

[bountyhunter]

Hello everyone. I have some experience with basic 12v electrical systems. I need some help with a circut. I want to make some LED tail lights for my car. I would like to build the circut with 14 LEDs. any help would be appreciated. Starting from scratch. Thank you!

OK. Here is help with the "circuit":

String the LEDs in series pairs and put a resistor in series with each pair from the 12V line. Current through the LED pair will be about 6V/RESISTOR. Consult LED specs to see what the correct value of current is for your LED.

Set aside about $100 in the design budget for paying the moving violation.