LED Tail light help needed PLEASE!!!!!!

[jeepfreek]

Here's a problem somebody might be able to help me with. I want to install LED lights on a custom rear bumper for my Samurai and hers the catch...

I want to run them at 6 volts when the tail lights are on and then bump the voltage to 12 volts when the brake is aplied. Sounds simple don't it!!!

The reson for this is kind of easy to understand. If i run a standard 2 inch round LED light with 12 LED's they are bright! But nobody can tell if the braks are on because they are the same intensity. So by running the tails at 6 volts, When i apply the brakes the lamps almost double in intesity and Boom... Nobody kills me because they didn't see my brakes come on!!!!

I tried a drop resistor from JCWitney and that didn't work so can't anybody help me. My Zukicon really needs a rear bumber / pull point so i can stop riping off bumper ends at Tellico.

[slowrockr]

What kind of lights did you get? There shouldn't be any reason to have to wire in a resistor like that.
I used led's from a trailer supply place on my YJ. Yes they were bright with just park lights, but when you apply the brake pedal.....they were REALLY bright.

[jeepfreek]

These are the 2 wire lights for marker use but by using them it will allow me to run 2 red's an amber and a small round driving light per side in a 3"x11" space which will leave me plenty of room between each side so they wont seem to be one big long light.

[slowrockr]

Ahhh ok, I understand now. What about using a resistor from the coil on an older car? If my memory is correct alot of the older Dodge and Ford coils were 6V and used a resistor to knock the voltage down.

[jeepfreek]

That would be a ballist resitor. I bought some 1 watt resistors from RadioShack and they didn't work. The drop resistors from JCWitney didn't work either. Somebody said that it was because the lights have such a low amp draw. What i'm thinking is some kind of voltage converter or what ever you could call it. It would allow me to drop the voltage of the tail light wire to 6 volts and then place a simple diode in there and run the brake wire in front of it and Eureka! instant circut and simple right? Thing is it's been 20 years since high school electronics class and the smarts aint here anymore.

[John Deere]

Have you tried more than one ressistor? I had to do that on my motorcylce to get the blinker to blink right. Maybe that will help.

[roktoy]

I think this relay setup will provide you with 6V running and 12V brake.

Side note:
LEDs actually emit by running some fixed current through them. They are
typically connected to a power supply with a series resistor to set the current.
If they use say a 1k ohm resistor to set a current of say 10mA, then swapping
to something like 2k ohm would cut the current roughly in half. Halving the
power supply current accomplishes about the same thing.
Jay

[jeepfreek]

Okay. I don't understand what the relay is doing? How does this relate to an automobile? Where does it get the 6 volts or how?

[Thorsteenster]

Most likely from your battery, unless you have something else providing voltage.

[Grizzly4x4]

Darn it Jay, I was gonna suggest a relay.

You need a relay because you need to have two separate circuits going into one bulb. The tail lights need to have two separate inputs (tail and brake) and a way to switch between them to power the single input LED.

If you just put a drop resistor inline to get 6v, how can the lights ever see 12V?

[Rok_Dok]

Relay is the way to go....

take wire directly from fused 12 v supply.... now get a dc/dc converter for 12 to 6v, run running lights on 6v with a blocking( protect from reverse voltage) diode. When the brake pedal is pushed it should activate the relay which will supply another 6v through the same line giving you 12v total in series. this should work in theory

[Cole82]

Why not add another light to the bumper? My sammy has 2 red and one amber 2" lights.

[roktoy]

Originally Posted by Grizzly4x4

Darn it Jay, I was gonna suggest a relay.

Beat ya!

Originally Posted by jeepfreek

Okay. I don't understand what the relay is doing? How does this relate to an automobile? Where does it get the 6 volts or how?

Maybe this will help. When the relay is in the top relay state, both lights get the 12V for your brake mode.

In the bottom relay state, the two LEDs are connected in series across the 12V, or 6V across each of the LEDs for running lights.

Jay

[jeepfreek]

I'm thinkink like ROK DOK and trying to find a 6v/12v converter with no sucsess.

Cole82, that is exactly what i want at the rear of my Zuk but you must be running 1 red for tail and the other for stop. My problem is that I want both to be lit at same time on tail at 6v and both to be lit on stop at 12v. were talking a vehicle with only 56" in total width and dark grey at that, having sombody see me is very important. These things are not known to have a real bad impact suvival rating.

Roctoy, I see what your diong but will changeing the amount of load be effective. I will try to do a mock up of this setup on the work bench and see if it works.

[Cole82]

Originally Posted by jeepfreek

Cole82, that is exactly what i want at the rear of my Zuk but you must be running 1 red for tail and the other for stop. My problem is that I want both to be lit at same time on tail at 6v and both to be lit on stop at 12v. were talking a vehicle with only 56" in total width and dark grey at that, having sombody see me is very important. These things are not known to have a real bad impact suvival rating.

Yes one red for tail and one red for stop. When the tails are on, there are ony two lights on. When you hit the brakes 5 lights are on. I think people can see when all five lights are on you are coming to a stop.

Good luck on the voltage drop relay. Hope you getit to work.