I have an older Atlas RS-3 (China) which runs beautifully but unless it is going fast it’s light is almost invisible. How does one replace these lights with say an LED?
I don’t think a new bulb or LED will do what you want. I think you need to be looking at a constant lighting circuit.
Your current setup uses whatever power is available to light the lamp. Give it more power and the lamp gets brighter.
A constant lighting circuit will give it a set amout of power to the lamp no matter what the throttle setting is.
This may help: http://www.mrollins.com/constant1.html or http://www.mrollins.com/constant.html
You can’t. The voltage will still be the same; I assume this is DC? With DC, turning the speed control increases the voltage to the track, the light gets brighter the more voltage is applied.
If you really want to replace the lights, you just pop off the shell, and put a new lamp or LED in. You may need a resistor to decrease the voltage going to the light so it doesn’t blow, and remember, LED’s only light up when the polarity is correct.
EDIT: Didn’t see your post, pcarrell. You’ve got it right!
Looks like we were both hitting it at the same time!
Part of the problem is the light board, if you don’t want to put in a constant-lighting circuit you can remove the light board and hardwire everything, then you can put in Walthers 12V bulbs which will glow very brightly even at low speeds. Both lights will be on all the time there is power to the track, so the headlights won’t only be on in the direction of travel…but real engines didn’t reverse their headlights like our model ones to anyway!!
Of course switching to DCC would solve the problem too.
I am still using DC and did not want to put a lot of effort into constant lighting with the eventual conversion to DCC.
I got some small Miniatronics http://www.miniatronics.com/ 12v lights. I also got brass tubing and glued the tubing inside of the shell with 3M Automotive Weather-strip adhesive, a better product than Walthers Goo.
Typically I make the tubing 1-2 inches long and it butts up against the front headlight lens. Obviously the light bar is removed. The Miniatronics bulb goes into the tubing just as the shell goes on. Leave a long pigtail on the bulb so it can go deep into the tubing.
On my units I only do the front. A big improvement over the dim light bar set up on older Atlas / Athearn units.
Jim
Thanks to all who answered my query. I had hoped to find a simple answer but I suspected a more complicated problem in electronic circuitry. I’ll have to think about it some more.
Thanks again to all those who helped.
Jim
I was playing around with some LED’s a while back and found them to be a lot brighter at lower DC voltage than a bulb. I found very little difference between the brightness at say 1/3 throttle and full throttle. Since they are a diode, they seem to have more of an off/on lighting effect than a ramp up to full brightness.(to some extent)[2c]
This is probably not the answer that you’re looking for, but I use MV Products lenses, with no bulb, wires, or circuit board.
This leaves more room for extra weight and makes the loco easier to disassemble for maintenance. In my opinion, the first time that the light flickers as the loco momentarily loses power, the illusion of “prototypical” is lost anyway. [swg]
Wayne
That’s a good point about the tube for the bulb, I’ve done that on some of my diesels and it does make a difference. I don’t think I’ve gone over an inch however, probably less in most cases. Still worked OK.
Unless there is dirty track involved, I never had a problem with ‘flickering’ on DC with a good 12v bulb hardwired in. The light usually came on about the time the engine had enough power to start moving (or a little before…in fact I made a few pictures where I was able to give the engine just enough power where the headlight lit up but the engine didn’t move).
I rarely run above 30-35 MPH even on passenger trains so engines rarely got full power, and I found the 12v bulbs gave a nice bright glow but weren’t overpowering.
Below is the schematic diagram of the simpliest constant brightness circuit for DC power.
The arrowhead symbols are silicon diodes. A diode allows current to flow “with the arrow” and blocks current flow “against the arrow”. Silicon diodes are not perfect conductors. For some quantum mechanical reasons that I no longer understand, a conducting diode shows a small voltage, 0.7 volts, across it. Unlike resistors, the 0.7 volt diode drop stays at 0.7 volts no matter how much current is flowing thru the diode. Ordinary wire, and resistors show increased voltage as the current goes up, but diodes are different. In this circuit, two diodes are in series, so the 0.7 volt diode drops add together yielding 1.4 volts, just right to light a 1.5 volt incandescent lamp or two.
Motor current flows thru the diodes and the diodes create a constant 1.4 volts. You get 1.4 volts no matter how much or how little motor current flows. So the lamps glow at constant intensity, not matter what the throttle setting. Why four diodes instead of just two? Answer: you need the second set of diodes to conduct when the engine is operated in reverse. DC motors are reversed by chang
Here’s a simple, nifty and small circuit I found for a constant-lighting circuit for locomotives.
http://www.pollensoftware.com/railroad/circuit.html
A source for both the LM334z and the required resistor is Jameco Electronics:
Click Here for the LM334Z.
I use the Miniatronics “Golden-Glow” 3MM LEDs.
Since you hook this circuit directly to the motor (or track pixkups), you don’t need to worry about the existing circuit board, beyond disconnecting the original light.