CONVERTING FROM INCANDECENT TO LED?

[JFETTER2]

 WHAT IS THE BEST WAY TO GO ABOUT CHANGING OUT STADARD LIGHT BULBS IN LOCO'S AND REPLACE THEM WITH LED'S?

[tstage]

JF2,

Are you going to use these for headlights?  If you're talking HO, you'll want 3mm LEDs.

LEDs are diodes so current can only travel through them in one direction.  (Otherwise, it won't light up at all.)  They also need resistors soldered to them if they are connected to voltage higher than 1.5V.  (Otherwise, it'll go *poof*.)

I like to use LEDs for headlights but incandescent bulbs for exterior and interior lighting of buildings.  Incandescents work better than LEDs when it comes to Mars Lighting.

Tom

[Texas Zepher]

JFETTER2

WHAT IS THE BEST WAY TO GO ABOUT CHANGING OUT STADARD LIGHT BULBS IN LOCO'S AND REPLACE THEM WITH LED'S?

The best way is to do a lot of preparing and planning and depends on a lot of factors that you haven't even hinted at including the type of model.  I've got Stewart FTs down to an assembly line procedure I could probably do in the dark.

1.  Are the trains powered by DC, AC, DCC, or what?

2. Do you want the lights to be on constantly or controlled by a DCC decoder?

3. Measure the power to the current bulb.  Voltage.

4. Select diodes to be used.  I prefer the day-glow.  These are normal white (nasty blue-white things) LEDs with a yellow tinted lens embedded in the plastic case.

5. Get appropriate resistors to match the voltage and limit the current going to the LED. Often a 1000 ohm resistor will be a general purpose.  The perfect size is determine by the voltage and how brightly you want the LED to glow.  The smaller the resistor value the brighter the LED will glow until such time it blows out.  I like to add resistance until I can see the LED dim just slightly.  That way I know it is slightly current starved.

6. Figure out how to mount the diodes.

7.  Wire the resistor in series with the diode. 

[rrinker]

 For DCC, a 1K resistor is good with most white-type LEDs. To run on DC though, a 1K resistor will keep the LED mostly off until you are at full throttle. 680 or 750 ohm is better for DC, the LED will light up without going warp speed, and it will still be at a reasonably safe current level when you do crank it wide open.

                                                  --Randy