# 3mm warm white LEDs for buildings and rolling stock



## pimanjc (Jan 2, 2008)

I just bought a set of 100 LED warm white Christmas lights from Sam's Club for $12.99. These are 3mm-2v LEDs. The color when taken out of the diffuser is about the same as incandescent bulbs. The diffusers might be use in the ceilings of passenger cars to distribute the light more evenly. I plan on using these with a resistor to make mars lights and light some buildings.


JimC.


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## vsmith (Jan 2, 2008)

I assume these are plug in, wonder if they could be used with 2 or 4 AA batteries?


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## pimanjc (Jan 2, 2008)

Rated at 2v, I assume they would work with one 1.5v alcaline, or two 1.2v rechargables. I plan on putting a 1000olm resister in series with them [in trains] and run at track or RC battery voltage. I might set up several in series and run them off a six volt battery for a structure.

JimC.


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## weaverc (Jan 2, 2008)

Warm white LEDs are called Yeloglo and can be obtained from Miniatronics in either 3 or 5 mm diameter. 
http://www.miniatronics.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=6_4

The rules of thumb for resistor use with Yeloglo LEDs are:
3 v no resistor
4-9v v use a 270 ohm restistor
10-16 v use a 470 ohm resistor

With a Blue white LED, use:
3 v no resistor 
5 volts or more use a 560 ohm resistor
A good 3v source is a CR 2032 coin battery. They last a long time and are small


An excellent source for LED information and wirinig diagrams can be found at:
http://www.bpesolutions.com/atechnical/LEDInfo.pdf


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## Torby (Jan 2, 2008)

If the diffusers are too big, go to Michael's or Hobby Lobby and pick out some clear beads. 

I glued LED's into beads and put sequins as reflectors.


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## pimanjc (Jan 2, 2008)

Carl,
I typically run 18v to 24v. That's why the 1000olm resistor.
JimC.


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## Dan Pierce (Jan 2, 2008)

Always use a resistor with LED's to limit the current as they will short out. 
On a AAA battery 1 amp is available and the led can burn plastic. 

Minimum resistor would be 10 ohms instead of direct battery feed!!!


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## Bill Swindell (Jan 2, 2008)

I have never seen a white LED that runs on less than ~3.5v.


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## Semper Vaporo (Jan 2, 2008)

Posted By Bill Swindell on 10/25/2008 11:22 AM
I have never seen a white LED that runs on less than ~3.5v. 


I run white LEDs on 3-V Lithium coin cells (CR2032, BR2335, CR1616, CR1220, and a few other p/n's). They will run for a week (CONTINUOUSLY) at near full brightness, and then for a month or more gradually getting dimmer. I have just poked the LED leads through the battery plastic packaging and left them that way for MONTHS (yes, quite a waste of a battery) and you can still tell the LED is lit, even in indoors daylight.


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## Bill Swindell (Jan 2, 2008)

My point was that white LEDs will not work properly on a 1,5 volt battery. At 3 volts, they are probably running quite a bit less that their rated 20 ma.


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## John J (Dec 29, 2007)

Hey Jim 
Thanks for the "Heads Up" on the lights. I think I will go get two or three boxes. 

My thought ( When I get to the village part of my layout) was to take a coil from a solenoid or relay coil and UN wind it. I was going sting the varnish Coated wire on power poles through the village. Then tap off for each house or building. I thought it would look kewl. Even run street lights too. 



PS Love spell check in this new editor.


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## Paul Norton (Jan 8, 2008)

Many years ago I installed a bright white LED in the headlamp lens of my FA-1. It was powered by two, alkaline AA cells in a Radio Shack battery holder hidden on the pilot. A mini-toggle switch under the pilot across from the bell activated this simple circuit which provided a constant intensity headlight even when the locomotive was stopped or reversed.


After a full summer of running, the cells finally pooped out. I dropped the pilot (4 screws) and replaced them with two, rechargeable NiMH AA cells. Unfortunately the result was disappointing because the NiMH cells only provided the minimum voltage required to activate the LED. It was time to upgrade the circuit. 
The original Radio Shack battery holder was replaced with a four cell holder. When filled with NiMH AA cells, the resulting battery pack produced about 5 volts. In order to bring the current (amperage) under the maximum limit of 20 milliamps for the LED, a 100 ohm resistor was added into the circuit. When the switch was thrown, the LED shone as brightly as before! 












LED Tester - Adding the female connector from an All Electronics two-pin plug set (catalog # CON-240) to a twin, AA battery holder makes a cheap and easy tester for 5 mm (headlight size) white LEDs. The battery holder with switch is available from Radio Shack and most electronic shops. The leads of the LED simply slip into the connector for testing.










LEDs are polarity sensitive. The longer lead is usually the anode (positive) and the negative lead (cathode) usually has a flat spot next to it on the base of the LED. I mark the flat spot with a black marker to avoid wiring mistakes.


Here are a couple of excellent links to add to your “Favorites” link folder, or better yet a Garden Railroading folder under favorites so they are easy to find.

First is the Ngineering LED Circuits tutorial. This is the easiest and best tutorial I have found to date. http://www.ngineering.com/LED_Circuits.htm

Second is the resistance calculator. http://www.ngineering.com/LED_Calculators.htm


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