# Building custom led brake light boards



## z_Qwkls1

Ok guys here is my dilemma. I have a 1973 IH truck, the tail lights suck basically and I know just using a plug and play 1157 led bulb will too.



I would like to construct two circuit boards using red 5mm led's for the brake/tail lights and white for the reverse lights.



My question: obviously I have to use a regulator which I've already learned from searching the site, but what is the best way to build these so that the lights are on with the running lights and when the brakes are applied they become 2-3 times brighter?



Dual fillament LEDs or what? I am new to this game and would appreciate any help, advice or anything to get me rolling on this project.



Thanks guys,

Garrett


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## Changchung

Hi, welcome to the CPF, I have doing this kind of circuits for a long time, is more easy what you think, first option, run each 3 Leds with a 330ohm 1/4 resistor, them put a large resistor for all the red Leds something like 1K 5 watts resistor to reduce the light, this is for the parking light, you have to use a pair of diodes to separe the two points, I can make you a diagram if you like, the most easy way is, use 5mm 120 degrees Leds to the parking light and 5mm 20 degrees Leds for the stop, you can use around of 20 Leds for each funtion and side, I mean, 40 Leds in eash side, that will be a very good amount of light... For the white Leds you can use the 20 degrees Leds and run it with a 220 ohm resistor for three Leds in serie... Put the all you can...


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## SemiMan

You may make your life easier if you use SuperFlux type (people call them SpiderLeds) from a high quality LED mfr. They can handle higher currents and you can also buy different lighting patterns such as oval patterns. I would caution that it is difficult to achieve a bulb like distribution and you very well could be liable if an accident occurs even though overall your light may be better (but is it better on all angles? ... or is it too bright?).

The ones of these designed for automotive are more tightly binned for voltage and even binned at two different currents so the resistor implementation from Changchung will work out well. Keep in mind the voltage can be anything from 9V (dead at the side of the road) to 16V (high regulator). Generally you design the maximum current around the high voltage and check that you have enough light at the nominal battery voltage 12.8. RED leds decrease in brightness alot when they are hot, so check your implementation out inside the fixture on a warm day after it has been on a while.

Because of that reduction in light output, it is not unusual for the LEDs to be run at less than their rated current. I.e. that 330R resistor listed above depending on the LEDs could result in 24mA into the LED at 15V (high, but not unusual at all for older vehicles). Than can be quite high for a 5mm LED and it will reduce in light output quite a bit when hot. 24mA into a Superflux though would not be as bad as they have better thermal qualities and take higher current (in general). 

Some other implementations use a low duty cycle PWM for the tail function and full on for the brake function. It makes for a lot less issues with resistor selection, binning, etc.

This is the type of LED I mean http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CP42B-RKS-CL0P0AA4-ND This part is designed for channel letter ... it has an almost batwing like distribution. That may actually work out better as a bulb replacement.

This one may work well too http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=492-1172-ND

Semiman


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## rwolff

z_Qwkls1 said:


> Ok guys here is my dilemma. I have a 1973 IH truck, the tail lights suck basically and I know just using a plug and play 1157 led bulb will too.
> 
> 
> 
> I would like to construct two circuit boards using red 5mm led's for the brake/tail lights and white for the reverse lights.
> 
> 
> 
> My question: obviously I have to use a regulator which I've already learned from searching the site, but what is the best way to build these so that the lights are on with the running lights and when the brakes are applied they become 2-3 times brighter?
> 
> 
> 
> Dual fillament LEDs or what? I am new to this game and would appreciate any help, advice or anything to get me rolling on this project.
> 
> 
> 
> Thanks guys,
> 
> Garrett


 
There's an easy, legal way to go with LED conversions, but it means giving up the original form-factor (save the parts for later restoration in case you want to reverse the mod). There are commercially available LED stop/turn/tail modules available in at least 3 form factors (4" round, 6"x2" oval, and rectangular) sold through heavy-truck supply places. Also, there are "universal" LED modules (look like those on Jeep CJs, and many "straight trucks") with red LED stop/turn/tail and white LED reverse lights (and in many cases, white LED license plate lamp on the left one) sold through various automotive and truck supply places.


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