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Discussion Starter #1
I bought a roll of 300 12 volt leds recommended by GunnerJohn. Just curious how many people are using to light up a passenger car or caboose. Also curious about using a zener or resistor to reduce the voltage. Thanks; Don
 

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The Gunrunner thread on strips. The discussion starts later on page 5/6.

Joh,n first used a 150 roll, which was plenty, mine were 300. You can go the length of the cab, 3 or four sections, not too many members have done this. It is all relatively new. Dallee Electronics does supply them too. They show them on You Tube. The caboose is tricky instead of using the roof, I lighted from the deck.

The port hole caboose is on page twenty. I used two sections.
 

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I just bought a few of the 150's from Mouser for absurd prices. ;) Right after that, the 300 LED 5 meter rolls started showing up everywhere.

For passenger cars, I run them the length of the car for even lighting. For command-only operation, I recommend a single diode, a 220uf or 270uf 35V capacitor, and the CL-2 constant current regulator. If you also run conventional, I normally use a bridge rectifier and put a heatsink on the CL-2 for the higher voltages.

The CL-2 only puts out 20ma, but I find that more than sufficient for lighting even 18" passenger cars.

Here's a typical circuit.

Constant Current using CL-2 regulator.jpg

You can also use a variable regulator as a constant current source, this allows you to adjust the intensity to your liking. For higher currents, you can change the TO-92 part to the LM317T TO-220 part.

Here's the circuit for the adjustable regulator.

Constant Current using 3-terminal regulator.jpg
 

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Don, you can run LED's on as much as 20ma each, but you don't have to. If you run the whole LED strip at maximum power, it'll look like the sun is rising inside your passenger cars! With a total of 20ma feeding the strip in an 18" car, I get plenty of light, probably a bit more than I really want. For my next passenger car set, I'm thinking of using the variable model and cranking the current down to 10-15ma for the whole car to reduce the light a bit. A realistic level of lighting shouldn't be super bright.

Also, remember that it's 20ma at 12 volts.
 

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Discussion Starter #6 (Edited)
OK; I'm thinking for uniform light I will run them the length of the car. Any reason not to use a resistor? To drop 5 or 6 volts at 20ma it would be dirt cheap. For TMCC the brightness would not change.
Soldering to them looks a little delicate . Brings back memories of repairing 20 mill core memories back in the old days. Don
 

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Discussion Starter #7 (Edited)
Just tested a strip of 6; Very bright at 9vdc. I had a thought; Why not put 2 strips in series? Rating would be 24vdc and with tmcc they would be running at about 18 v. Don
 

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When you put a diode in series to get DC, you get effectively 9 volts, not 18. If you add a filter cap, you get closer to 18 volts or more given the low current consumption.

If you go much lower in voltage, the lights won't light at all.

You can use a resistor if that suits you, I prefer to control the current more precisely.
 

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Discussion Starter #11
Yes; TMCC but I will also use the them to replace my HO DCC car lights when they burn out.
I just checked; at 3.5 vdc I get low light out, at 5 vdc fairly bright, and at 8vdc and above almost to bright to look at.
John; Have you tried with just a diode? I would think the peak current would be hard on the leds eventually.
BTW, saw the thread on getting the cars apart; Thanks, probably saved me breaking something. Don
 

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I STRONGLY recommend you don't power LED's with no current limiting! They will die very quickly on over-current or excessive reverse voltage. Don't ask me how I know this. ;)

I'm sure the thread on opening the cars was amusing, I was sure frustrated when I first took a stab at those! I've opened many different ones, those are the hardest ones to crack.

My experience with the LED strips is that you don't get any light at all out of them below 7 volts, and by 10 volts they're quite bright. Remember, there are three white LED's in series for each group, so you have to get past the roughly 2.5V starting voltage for each of them for anything to happen.

These are the LED strips I'm using.

Ignore the fact that the Chinese don't know how to spell Voltage. :D


20130510_201953.jpg
 

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Discussion Starter #15
I got to thinking about what you said (John) and realized that 3 leds in series can not light up at 3.5 volts!!
I just figures out how I got the leds to light at 3.5 v, I used an HO power supply with pulse! Don
 

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All best are off if you're not using pure DC. As long as you have a pulse sufficient to light the LED, you'll get some light, dependent on the width and amplitude of the pulse.

And yes, my LED's are also Non Waterproot :D
 

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Discussion Starter #17
Did some messing around: full output on a KW with one diode and a 390 ohm resistor looked about right for 6 leds.
I have some bridge rectifiers on order. I will use those when they come in. I need the bridges because I will use a similar setup for DCC. Don
 

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My advice is for the caboose use a normal bulb 12 or more volts so will be dime
and no regulator so will flicker making an old oil lamp effect.
BTW caboose never was completely illuminated.
my 2 cents
Andre.
True.
The old cabooses only had a few oil lanterns for light.
 
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