# hookup LED lights



## tom h (Jan 2, 2008)

I usually use low voltage outdoor lights in my buildings, on my next one I was going to use some LED lights, can I just hook them up using my low voltage wire?

Can anyone tell me a good place to get them?

Tom H


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## lownote (Jan 3, 2008)

LEDs are polarity sensitive, so they will only light when connected one way.

Also you need to use a resistor to limit the current going to the LED. The value of the resistor depends on a couple things, including the specs of the led.


I use strings of LED "warmwhite" christmas lights. I cut them up as needed-0-one LED, 3, LEDs, six LEDs, etc. . You can usually assume that a white LED wants to see 3 volts and 20 milliamps.

Here's a calculator that will let you know what value resistor to use:

http://led.linear1.org/led.wiz

Enter the number of LEDs you want to use, the voltage they are rated for (probably 3 volts) and the "forward current" measured in milliamps or "ma" (usually 20 ma), and the voltage at your power supply (12 volts).

If you used 4 LEDs, for example, you'd need to solder a 1 ohm resistor to one leg of one LED. It sounds harder than it is


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## Greg Elmassian (Jan 3, 2008)

Not stated, but sort of implied... 

Literal question, yes you can hook the LEDs to the wire. 

Not asked: will it work? 

Normally outdoor lighting is run on AC... the LEDs want DC... 

Don't forget the wattage of the resistor! 

Best thing to do is put as many of them in series as the voltage will stand, then your dropping resistor is smaller and makes less heat... lower wattage (easier to find) 

Regards, Greg


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## White Deer RR (May 15, 2009)

You might root around at http://www.modeltrainsoftware.com/ledfaq.html 

You'll notice on item they sell is LED's with bridge rectifiers and resistors already installed. Since I'm just using 9 volt batteries to light a few small structures, I can't speak to those types, mine only need resistors. 

I purchased ten warm white LED's and some blinking red ones from them, and they were conveniently pre-wired with resistors. The blinking ones I bought were more suitable for say, a model police car than a crossing signal. 

Their service was prompt and the order was properly filled. I did find that the "bonus" of battery snaps with small switches already wired was not suitable for staying outdoors in the weather, although I would imagine they would be great on a train car that is stored inside. For future lighting I plan on using them again, and only purchasing what I must (like more robust light switches installed in small project boxes) at the shack-type retailer. Retailer Shack charges far, far too much for LED's.


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## Dan Pierce (Jan 2, 2008)

Christmas lights may be using the lower voltage 2 volt leds. These cost much less than the 3 volt versions. 



For 20 milliamp leds, figure 50 ohms per volt dropped for the resistor. So, 5 2 volt bulbs =10 volts subract from 12 gives 2 volts times 50 ohms is 100 ohms. 
Xmas bulbs are more towards 10 milliamps and then it would be 100 ohms per volt dropped.


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## East Broad Top (Dec 29, 2007)

The GE LED Christmas lights I use are the 3-volt variety. Now's a great time to buy them with everyone having clearance sales, if you haven't missed them already. They light at 1.5 volts, but they're rather dim at that point. 

I've been playing around with solar power, using the inexpensive solar LED walkway lights as a starting point. Essentially, I snip the stock (blue-ish) LED out of the circuit and run a long wire from it instead. This goes to the LEDs in the buildings. The warm white LEDs I use aren't as bright as the stock LEDs, but the color is much more pleasing. I have the advantage of modeling the pre-electricity era, so the lights I'm replicating are oil/kerosene lamps which aren't very bright to begin with. The effect, though, is pretty cool. Once it starts getting dark, the LEDs automatically turn on, and they stay on pretty much all night. I've had "experiments" in place for a few weeks now to get a feel for how things will work long-term. The solar panels definitely need some direct sun to charge the battery sufficiently to keep things on all night. I've found I can power 2 LEDs in parallel without affecting the longevity. The entire thing draws about 13mA from the battery, so the 400mAh NiCad battery included in the light seems to be fine. Note that the internal circuitry of the control bumps the 1.2 volts coming from the battery to around 2.1 or so going to the LED, so they're brighter than they would be connected directly to the battery. My plan is to build "solar farms" for each town along the railroad, and run wires from each panel to one or two LEDs, probably using one or two panels per building depending on the number of lights. (i.e., stations have interior lights and signals) It is admittedly pretty cool to look out in the back yard when I get home from work at night and see the buildings lit up. 

My biggest concern right now is to see how these things hold up to the weather. We're "supposed" to get a proper coating of the white stuff today (though it's pretty darned clear out right now), so I'm curious to see how that affects them. The "farms" will eventually be elevated near the top of the fence so they won't often be completely buried by the snow, but if they can withstand being buried by a few inches of the stuff, then I know I'm in good shape. If this experiment ultimately fails, I'll probably end up running some low-voltage power to them from one of the myriad 3-volt plug-in power supplies I've collected over the years. 

Later, 

K


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## DennisB (Jan 2, 2008)

There is a good article on LEDs on the www.ckgrs.com web site. Look under Past Articles. Regards, Dennis.


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## Madman (Jan 5, 2008)

Check out Ebay for your LED needs. Most of them are coming from China. They are very inexpensive, and are usually sold with resistors already wired to them. They will operate at twelve volts DC. The same suppliers also sell LED drivers, which are nothing more than a power pack for LEDs. The nice thing about them is that they can be installed outdoors. They operate on house current, 110 Volts, and put out 12 volts of DC current.


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## tom h (Jan 2, 2008)

Thanks for the info!!!!

Tom h


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## Semper Vaporo (Jan 2, 2008)

Posted By tom h on 31 Dec 2010 04:20 PM 
Thanks for the info!!!!

Tom h


A little late to the party here, but if you are planing to do this a lot, get Stan Silverman's "Handy Converter" program (http://www.stanstrains.com/). (He is an advertiser here on MLS, I think.) The program has a function to calculate all of this, including multiple strings of multiple LEDs, with resistors for each string and then draw a schematic and/or wiring diagram.


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## ORD23 (Jan 2, 2010)

Check out this guy on ebay: dmmwem I have purchased 20 yellow LED's, 3 red blinking LED's, and an 8 pack of DPDT switches for under $12 bucks (free shipping on switches and yes, he piggy backed the LED's on the shipment and and gave me free shipping on all the items I listed). The best thing about this guy was that everything was shipped quick (yep, he is here in the states), and he was very professional. He even has a schematic on each item posted so you can use to hook up your electronics, how neat is that? Check out his site and see all the goodies he sells, it's well worth it. I have his site listed as one of my favorites for future items. Hope this helps. 

Ed


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## hawkeye2 (Jan 6, 2008)

"Check out this guy on ebay: dmmwem"

Ed can you provide us with a link to one of his auctions, even a closed one would do. I searched for him but couldn't locate anything.


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## Naptowneng (Jun 14, 2010)

This the one?

http://shop.ebay.com/dmmwem/m.html?...amp;_rdc=1


Jerry


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