I have a pair of Athearn blue box Geep’s that I want to replace the headlights with white LED’s and add red LED’s for the rear of the loco. This would be for use with DCC using currently installed Digitrax 123 AT decoders. I want to setup the LED’s so that the current “front” would show the white and the “rear” would display the red and change when the direction is changed. How difficult of a process would this be to accomplish?
Putting in LED’s would be easy, but getting it set up and programmed for DCC, thats probably a different story.
Its very simple, dont think about how complex it might be, think about how simple you can make it. Now, you could use a 4 function decoder, headlight, rear red, backup light, front red. Or you could make it simple and use the 2 function decoder you already have. The headlight function would be wired to the headlight, as well as the red LEDs at the rear. This way when the headlight is on your red LEDs at the back would be on as well. The rear light function would be wired to the rear light and the red LEDs at the front. If you dont understand what Im saying I could draw up a little diagram for you.
Good luck.
The light output leads on the Digitrax decoder put out full voltage. You will need to put a resistor in series with the LED(start with a 1000 ohm one if there is not info with the LED). There is a forward and reverse headlight output on the Digitrax decoder. By default they will light up in the direction the engine is moving. I am not sure about the red lanp. What are you trying to model?
Jim
You probably want to put a resistor in series with each of the 6 LEDs. In a normal headlight installation, a single resistor is used on the blue (common) wire. This works because only one of the two headlights is active at a time. In your case, you will have 3 LEDs active at a time. Since the LEDs will be dis-similar, you want to have a complete separate path through each of them so that each one gets the right voltage. You may end up using different resistors for the white and red LEDs, too.
I like the “golden-white” or “yellow-white” LEDs for headlights, rather than the bright white ones. The color is more pleasing and natural for headlights.
Having watched plenty of CR locos and modelled close to 100 units for clients and friends over the years, the headlights, front or rear do not change color. It’s the marker lights that are red and change with the direction of travel. I’ve used fiber optics to to light them from an led inside, (one for each direction). It’s a bit more work, but it looks really cool.
Yes you will need a resistor for each LED, and if you cant find the super small ones fiber optics work well. I too am assuming you want headlights and marker lights, the marker lights are very small, thus the need for tiny LEDs or fiber optic strands. The DCC guy at my LHS gets insanely small LEDs out of old computers and sells them for $1 each. I have used red ones for marker lights in engines and passenger cars and gold or white ones for ditch lights. But I am now doing more fiber optic work just because the tiny LEDs arent all that bright. For marker lights though they are perfect if you can find them.
…“I want to setup the LED’s so that the current “front” would show the white and the “rear” would display the red and change when the direction is changed. How difficult of a process would this be to accomplish?”
Tricky: white LEDs require 5 volts, red ones 2.1 volts, for starters.
Simpler to use (4) 1.4v. G.O.R.bulbs - 2 red, 2 clear - and 2 diodes per bulb to do what you want. Install bulbs and diodes in series with the motor, with diodes pointed in the proper direction. Much simpler. Side benefit: more realistic white.
No matter which way the engine is turned the clear bulbs will light when running forward, while the red will be on facing rear. A small resitor can be added to the red to ‘dim’ it, if desired.
You seem to have missed the question; Cannoli is hooking this up to a DCC decoder not DC, so how much voltage an LED uses is only relevant as far what size resistor to use with each LED.
The newer golden &sunny white LEDs are very natural looking, especially behind a lens. And no heat.
hmm, all the LEDs I use, red or white need 1.5v. hmmm…
this works with dcc and dc
Yes, it certainly would work with both, but why would you use it with DCC, (as it already has built-in constant reversing lighting) ?
He already has a decoder. The question is how to wire up LEDs for headlights and marker lights so that when the engine is traveling a given direction, the forward end has the headlight on and the trailing end shows red marker lights.
Please read the question before posting.
Interesting. ALL the WHITE LED’s I can find in the Mouuser catalog spec 3.5V - 5 volts as min’s. Typically voltage regulated LEDs take 5 V to illuminate
well he needs 3 lights and the decoder chip was not made for that
hence the circut I provided
jp I did read are you the post police
dont you think more lights needs more power ’
your not going to be able to use all the lights that are needed on the front and rear of the locomotive with the headlight from the chip
K
I’ve got 3 golden-white Leds (a good place to get them: http://www.richmondcontrols.com/), hooked up in a Kato SD40-2, (headlights and two ditch lights). with no probs whatsoever. I’ve had even 3-1.5v light bulbs with resistors hooked up to decoders, also without any probs. He shouldn’t have any problems hooking up a golden-white and two red LEDs; it’s just a matter of what current limiting resistors are needed and thats’s easy to figure out, there’s plenty of voltage.
Wow, how did this become so debate-able ??? Connect a white LED and a red LED to the front F-0 output - install the white in the front and the red in the rear. Do the same with the rear F-1 output with the white to the rear and the red to the front. Use the default setting for directional lighting. Travel forward - white to the front / red to the rear. Travel reverse - white to the rear / red to the front.
… oh yeah, “don’t forget the resistors” [}:)]
This was answered correctly in the second reply … why did it have to become so difficult ???
there must be a heatsinc under the heatshrink I think’
4.5v
K