Advice on LED's, grain of wheat or rice

Discussion in 'FAQs' started by forton, Jan 17, 2007.

  1. forton

    forton New Member

    I am using grain of wheat 1/4 watt bulbs with 200 ohm resisistors on my
    Athearn locos with a wired Digitrax decoder. It seems to work alright but
    the brightness is not what I would like. These are for my main
    front and rear lights.
    Should I switch to LED's?
    Should I switch to grain of rice?
    A different value resistor maybe?
    Perhaps someone has a good link to share for info and purchasing?

    All responses are appreciated,
  2. Russ Bellinis

    Russ Bellinis Active Member

    What is the voltage rating on your grain of wheat bulb. Some of the bulbs are rated at 14v, some at 1.5v, and some may be rated somewhere in between. When you put a resistor in series with the bulb, you reduce the voltage to the bulb. If you have a 1.5v or 3v bulb, you need the resistor to keep from blowing the bulb. If you have a 14v bulb, the resistor will reduce the voltage making the light much dimmer.
  3. forton

    forton New Member


    How can I determine the voltage of my grain of wheat bulb?
  4. kf4jqd

    kf4jqd Active Member

    I've switched over to golden glow LED's. I like them alot! One thing is, they're directional when lighting. When the the loco back up. The front light goes out. BUT I installed another one at the rrear of the locomotive. That one WILL light!

  5. Russ Bellinis

    Russ Bellinis Active Member

    It is on the packaging that came with the bulb. I've never seen any marks on the bulbs themselves. If you aren't sure, try checking how much voltage you have going to it. You could also unhook it from the locomotive and hook it directly to the speed control. Then start turning up the voltage while monitoring it with a meter. If it gets real bright at 1.5 volts or 3 volts, don't go higher. If it is dim at 1.5 or 3.0, then go higher a little at a time. Just check your voltage at each step up. Then you need to figure out how fast you are going to operate your trains. If your maximum speed is going to be realised at 9 volts and your bulb looks fine at 9 volts, you are good to go. If you need to use a resistor to drop voltage, some of the other guys may be able to tell you how much resistance you need to drop the voltage a specific amount. The way I would do it is to get an assortment of resistors and then hook them up one at a time, turn up the voltage to full power, and see what voltage I have coming out of the resistor. Then just use the one that gives the correct output voltage for what you want.

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