Large Scale Central

Outrageous Passenger Lighting!

Problem Solving
#21

Not to try to change your mind John, but to be clear:

Track pickup > diode > LED > CL2 > other track pickup

for each led, there are 3 components for each “light”, the CL2 instead of a resistor.

So no difference in complexity, and the benefit of the led being a constant brightness regardless of track voltage, while your resistor based design must be designed for worst case maximum track voltage, so dimmer at lower speeds.

The resistor-based system will turn on at a slightly lower track voltage, but I would bet that in both cases the LED will light before the loco moves.

Regards, Greg

#22

Thanks Greg. You are right; I didn’t make my self clear. Not more complex in how it would be wired, but rather more complex in obtaining the parts. They are cheap enough from Mouser; but I hate to pay shipping on a few dollars of parts. Resistors and diodes I can buy locally.

You still may have talked me in to it though!

#23

Daktah John said: Resistors and diodes I can buy locally.

Not if Radio Shack goes…

#24

The LED will begin to turn on when the voltage across the LED reaches the required voltage specified for that LED color A white LED will start emitting light around 3.0- 3.6 volts. Any other components in series with the LED i.e. CL2N3, diodes or resistors the voltage drop across these components in series with the LED will add to what the track has to be for the LED to start lighting. The CL2N3 will prevent the max current at 20 ma and help in dropping the additional track voltage above what the LED circuit requires to operate.

#25

John, I think I bought 50 of the TO-92 package (like a small transistor) and 50 of the SOT-89 (small surface mount).

Shipping was cheap as well as the parts and I have a nice long term supply (although my visiting buddies seem to mooch a few here and there ha ha).

Greg

#26

Greg, that’s what friends are for. :wink:

#27

In my own experience, the CL2’s greatest advantage is that you don’t have to deal with resistances at all. I use them (one actually) to power from one to six cars (three to 18 LEDs). One car or three of six, the same current is delivered to all cars. I wire the LEDs in parallel, and they work finde. I built a printed circuit board to speed installation and reliability. Now all my passenger trains have the circuit in their combine, and use m/u wiring which looks like air lines, to connect the cars.

Very nice.

#28

Another advantage is constant current (brightness) irrespective of supply voltage.

Greg

#29

coach with LED lighting

So far, for me, the best part of this thread was about using the silvery laminate as reflectors. I’ve built most of my passenger car from Bachmann Jackson and Sharpe cars. After a couple of the rebuilds, installing LEDs, the cars seemed too dark still. So I painted the ceilings of the cars with (wait for it) ceiling paint. It’s a light white and designed to reflect light.

Now the cars are much brighter. On my next iteration of the rebuild, I 'll have to look for some of that stuff. Where did you find it?

#30

You can get the shiny foil tape in the heating section of Home Depot etc:

By the way, there’s still a lot of mention of dropping voltage for the leds… it is controlling the current is what the CL2 is all about, and it’s how you calculate the resistors too. I want to keep reinforcing this so that people new to leds understand not to be using a voltmeter to figure how to run leds.

Regards, Greg

#31

Dick F

You may actually like the white paint better than the foil tape.

White paint reflects 99% of the light that strikes the surface

polished metal only 45-65 %

White also scatters the light over the entire car interior

polished metal tends to focus the light into a smaller beam

think parabolic mirror effect

so i guess it depends what you want a narrow focused beam of light down the center of the car

or an even scattering throughout.

Bill

#32

My thoughts on lighting the old passenger cars, is that they shouldn’t be that bright nor well lit. Modern passenger cars used florescent lighting, the heavyweight cars used either florescent or incandescent lighting, but the old wooden passenger cars used oil lamps. That’s what the vents on the roof are for, venting the combustion gases from the oil lamps that were mounted up near the ceiling. The lighting used here on this thread I would be/will be using in my streamline passenger cars when they go into the shop for a refit. But my old wooden passenger cars will be using amber LEDs, spaced one per vent, and that should give the proper effect for lighting those cars.

That just my 2 cents worth. At todays exchange rates, that equals about .45 cents.

#33

I know this thread started on using a reflective surface on the inside of the roof to make them brighter and more diffused.

If you use the LEDs on a strip, they already have the proper dispersion, none of the light is going towards the roof.

So there’s two ways to go, get LEDs with light every which way and help disperse and reflect it, or get LEDs with a focused and definite wide angle of dispersion and point them downwards.

Regards, Greg

#34

great thread! it got me thinking (looking around too!)

here are some links that may be of interest too!

ttp://model-railroad-hobbyist.com/node/11738

http://www.trainelectronics.com/LED_Articles_2007/LED_104/index.htm

#35

Hey Cale- your first link needs an “h” in front of “ttp.”

-Kevin.

#36

Pretty funny discussion… Bruce Petrarca argues against the current limiting IC because it raises the voltage before the led can turn on.

But so does a resistor. By Ohms law, if you have an LED with a 3 volt drop operating at 20 ma, then all the voltage above that is dropped by the resistor or the current limiting CL2… by Ohms law, no exceptions, pure physics.

Will it take more voltage to “turn on” the CL2? That could be possible, but in my experience with this device, it “turns on” immediately and then stops limiting at 20 ma.

What is so funny is the argument is sort of moot, since most locos need over 3 volts on the rails to start moving.

If you want constant lighting, then switch from DC to DCC or another constant power system.

Greg