LED lights used inside engines and trolleys??

[LDBennett]

What LEDs are used inside Locomotives and street cars that have uniform illumination all the way down to the car barely moving (low track voltage on DC layout)? Are they available anywhere? Are there other components used along with the LED, like a voltage regulator? Anyone got the circuit if there are other components used?

LDBennett

[sd24b]

try miniatronics.  LED's operate at 1.5v.  you're going to need some resistors.  Phil

[railsider]

...resistors or maybe put the LEDs in series, if you want/need more than one in, say, a passenger car.

Here's how that would work: if each LED uses 1.5 volts, eight in series will eat up 12 volts. Just to be safe, wire nine in series and you have plenty of light for a coach or a trolley-car. Hang them inside the roof. You can get yellow LEDs that give a warmer light than the vivid blue-white of most white ones.

CAUTION: you have to be very sure that you polarize them correctly. The longer lead is by convention the positive (+) lead. Connect this to the shorter (-) lead of the next one, and so on, and the ends to wipers on the wheels. You will need to check to make sure that the + end of the string goes to the + rail and the - end to the - rail. Just one backwards will turn off the whole string.

If you are using DC control, then the lights go out in reverse and when you power down to stop the engine (the dimout is the same for conventional incandescent bulbs, although the older type will stay on in reverse).

DCC eliminates both these problems, since the track voltage remains on all the time and the DCC "turns it down" inside the engine itself.

ANOTHER PRECAUTION: I would check the actual track voltage during operation to be sure that it really is 12 VDC. If it's higher, you may need to add another LED.

If you only want one or two LEDs to illuminate a car or engine, then you will need to put a resistor in series, computed to deal with the current you are actually using.

There is also a way to wire two LEDs "back-to-back" so that when the input DC reverses polarity, one goes out and the other comes on. You'll need double the number of LEDs (buy 'em in big packages!) because you still have to deal with that voltage-drop equation. But they will light when the train backs up, if this is a consideration.

This will also work if you want to power LEDs from a low-voltage AC source. Most small power packs give you 16 VAC for accessories in addition to the DC track power. Remember, though, that with the higher 16 V you need to string 10 or 11 in series. And because they are LEDs on AC, they will flicker (at 60 cycles a second, looking like a neon sign). This might be a clever way to produce the effect of neon, in fact. I've never tried it, and the mechanics of building a box with black photo negative on the front  and scratched lines could be taxing. Has anybody tried it?

Railsider

[richg]

Open the unit and get your multimeter out and do some checks. That will solve most of your questions and you will learn a lot.

Links to a lot of LED info. May not be exactly like what you have but you will get an idea on what is involved.

As an example, the HO DCC tenders are different when it comes to wiring. The users here had to spell out the differences that exist. Nature of the beast so you do not waste your time complaining.

http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm

http://tinyurl.com/9ewwxjv

http://www.members.optusnet.com.au/nswmn/con_brill_dc.htm

I doubt the Powers That Be will draw out the circuits. It usually takes users to do this.

Rich