LED's and Resistors on DCC

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K

kz9

Member
Ok so I am going to try and finish up ditch lights on a Loco I bought off of a member. The bulbs are 1.5v and going on a Digitrax board using DCC.

I have searched but am getting conflicted results to what value of resistor I have to use.

Any pointers? This is my first LED job/conversion and I have plenty more to do after this.

Is there any good reference materials so I don't have to bother members everytime I have a question?

Thanks!
 
Anywhere from 680 ohm - 2200 ohms will work depending on the brightness you want. if they are white LEDs then they usually operate between 2.6 and 3 volts.
 
There is a formula for calculating the needed value.
Voltage (output on decoder)-Voltage of LED/current of LED=ohms

From memory, some past installs used values similar to the following:
13V-2.5V/.015A(15mA)=700ohm
 


Come to think about it they might be small bulbs? they say to test them with a 1.5volt battery before installing.

Details West make the kit. LED and grain-of-rice bulb should still need the same resistor at the rated voltage?
 
Don't know if this will help but there are nice little calculation tools like this one http://www.free-track.net/english/hardware/calcled/?PHPSESSID=296b05f75e70b9a21397af380570fb9a

Here's a few more

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

http://ledz.com/?p=zz.led.resistor.calculator

Just make sure you select the proper number of LEDs.

I have another question though. I have 2 Bachmann DCC locos and would like to convert or add LEDS as the current incandescent lights are not very bright. Does anyone know the specifics of doing this? I can probably answer my own question my testing the voltage supplied to the running lights and then using a resistor if even needed to keep from killing the LEDs but just wanted to get some input from someone with experience doing this first.

Bye the way these are about the cheapest darn LEDs you are going to find.
http://www.dealextreme.com/details.dx/sku.1105
 
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