adding LED back light to tender

[billgiannelli]

Hi all!
I want to add a back light to my tender.
I assume the it is best to use an LED?
I have a Digitrax sdhx166d decoder.
would I need a capacitor or Printed Circuit board?
thanks
Bill

[AGSB]

Simply look at the documentation for the decoder and it will tell you what coloured wire is for the back light. As the Digitrax conforms to NMRA Standards the back light will be the yellow and blue (common) wires.

[billgiannelli]

Hi AGSB,
thank you for your response and help!
Yes I know what wires to use.
I want to know if LED is the best way to go and if the LED needs a capacitor or Printed Circuit Board?
Also what power bulb?
thanks
Bill

[Doneldon]

Bill-

The documentation with your decoder should tell you what current is put out on the yellow wire. You shouldn't need a resistor but I can't say for certain without knowing the yellow current and the LED's need.

I think (but check it out in the documentation to be sure) that you can do Rule 17 lighting with your Digitraxx decoder.
                                                                                                                                                                               -- D

[billgiannelli]

Thank you for your responses!
So now I need to figure out how to mount the light on the tender.
There is a false plastic light that I plan to drill out to put the light through.
Would you advise I put in a plastic "lens" with the light bulb behind it?
thanks
Bill

[Brewman]

The output voltage on the common (Blue) wire is usually 12 volts. The other function wires ( White, Yellow, Green, Violet ) are actually switched grounds that complete the circuit to activate the lights. Most LEDs are 3.3 volts so you will need a resistor inline on the yellow wire or the LED will come on real bright once  
I used a resistor around 680 Ohm, a 1/4 watt should be enough but a 1/2 watt will work also. Remember, LEDs are polarity sensitive. The positive lead of the LED needs to go to the blue wire, negative side to the yellow wire.

[AGSB]

I repeat, read the documentation for the decoder. It tells you what you need to know, page 22 of the manual - LEDS, and 2 different voltage bulbs.

[Billm10454]

If you are going to use an LED you really don't need a lense

[billgiannelli]

Hi All!
Thank you for all your responses!
I see now that there is a more detailed manual online from the Digitrax web sight with all the answers!
thanks AGSB!
Bill:)

[AGSB]

No problem.

[Doneldon]

If you are going to use an LED you really don't need a lense

Bill-

Not always true. If you use a SMD LED you will probably want a lens because the SMD won't look good. They are
small so they fit in headlight castings but they are also square, which is very unusual for a locomotive light.

                                                                                                                     -- D