tail light array

Ok I'm planning to build led arrays for my brake lights and I allready have a design in mind. My question Is this, I need to make the array capable of two different brightnesses for the brake and for the night running lights. The easiest way I can see to do this is to run the runninglights off of a resistor a d then give the full 14.4 volts for when I hit the brake. Is It safe to run an LED at lower than its rated current? I will have the array set up for 14.4

Thanks alot
matt

 

[MountaineerGreen]

Semi trailers with LED's use two sets of LED's. The running light set is not quite as bright, the brake set are a brighter LED. Just put the two sets next to each other in rows, it should work.

 

[seth247]

have already ordered the LEDs

 

[BWilliams]

It is perfectly safe to run LEDs befow their spec voltage, and brightness will scale as such. So, if you are planning to hardwire the boards to the stock wiring, you can either make a separate row of LEDs for the running lamp (like how new Caddies have their tails) or just wire the whole board to both the running and brake lights to have the whole array light up. When you hit the brakes, it'll come to full brightness as you'd expect with a regular lamp.

In either case, the only resistor you need is the one to pull the voltage down from the 14.4 source to the 3.3 diode voltage. If the parking lamp voltage is lower then 14.4v already (which I assume it is, hence why it's dimmer), you don't need an extra resistor to dim the lights.

EDIT: if the voltage supplied by the parking lamp circuit is still 14.4v but simply with a current-limiting resistor to dim the lights, then you would need a second resistor between the stock wiring and the array.

 

[seth247]

Anyone know?

 

[Exploderpilot]

See post #4?

 

[seth247]

Thanks bwilliams thats what I wanted to know! I think the reason the 2nd fillament is dimmer on the bulb is because the fillament itself has more resistance. But I will find out soon enough.

Thanks alot

 

[MustangP51]

Running LEDs at a lower voltage wont hurt them at all. You can change just how dim you want the running lights to be by changing the the resistor ohms values. What is the max continuous voltage that the LEDs you bought can handle?

 

[seth247]

1.9 vf .020amps I believe.

 

[Sandy]

I run a device from Ron Francis Wire Works specifically setup for wiring LED Stop/Tail/Directional setups.

Other than that you can segment your tail lights.

One set for running lights, one set for brake lights, made up of brighter LEDs and some for directional.

How are your tail lights setup now ?

 

[seth247]

go to http://led.linear1.org/led.wiz and put in the following numbers
supply voltage: 14.4
led forward voltage: 1.9
led forward current: 20 miliamps
number of LEDs:50

My array will be solution 2 5X10

 

[seth247]

I Got all the LEDs in and I still have to buy the resistors and some spare tail tights incase a jack somethin up.

But I'm still debating on the pattern, I was planning on having the whole array dim for the running lights and come to full brightness for the brake. But then I thought the other day that it would be cool to do an X pattern on each light for running and then the rest come on for braking (just to make sure Everybody knows I'm driving an X-ploder!)

But will this be too much for the Tulsa hi-po's do you think?
might just be a big shiny red target.

 

[BWilliams]

The X may get you into trouble.. if anything, the best way to wire it so that you only have some lights come on with the running lamps is to do something like the Cadillac tails that only light up along the outside edge with one row of LEDs. That would require a little more wiring work then just using the LEDwiz calculator. though.