Electronics for Loco's

Discussion in 'HO Scale Model Trains' started by Spongemike, Jun 19, 2006.

  1. Spongemike

    Spongemike New Member

    Hi There

    I'm just wondering, would adding a capacitor to a loco make much difference? The aim is to give it a bit of lag, and to make it less sensitive to voltage changes. Would I need any other components in the mix, or can the capacitor be added on its own? Are there circuit designs available online?

    Also, I'd like to replace the pathetic lights in my Athearn Loco's with LEDs, are there simple circuit designs available to acheive this? I'm not running (nor do I intend to in the forseeable future) DCC, I would just like something that looks better than a flickering lightbulb!

    And, while I think of it, anyone know where I can find standard electronic symbols online? It's been too many years since I fiddled with anything like this, and the only one I can remember is the one for a resistor!

    Cheers from NZ

  2. 60103

    60103 Pooh Bah

    There have been circuit boards for Athearn locos. They are intended to replace the "wireless" wiring -- the metal strips. I have one for an SD40 etc. that has headlights and ditch lights -- bulbs, not LEDs. Mine is waiting for me to figure out how to mount the ditch lights. I suspect they may have discontinued them when DCC boards came out.
    Don't know about the capacitors -- European and English locos have had them for half a century as radio interference suppressors -- small caps.
  3. lester perry

    lester perry Active Member

    The lights can be solved by using 1.5 volt bulbs & bridge rectifier(available at Radio Shack). you put the bridge rectifier in line between power & motor. I usually replace the metal straps with a wire which is soldered from one truck contact to the other then from second truck contact to bridge rectifier. The from bridge rectifier to the motor. Then connect the 1.5 volt bulb with one wire on each side of the rectifier. The bulb is then placed in the hole for the headlight. I have had 6 bulbs in one loco this way. If you use a 12 volt bulb you run the possibility of melting the plastic shell around it.
  4. cidchase

    cidchase Active Member

    Hi Mike,:wave:
    or just search for "electronic symbols"

    Some lists give you more than you ever wanted to know:D :D
    Some lists have symbols that seem somehow out of proportion,
    not incorrect per se, but awkwardly drawn. Look at a few on-line
    schematics to get a better idea of "standard" usage.

    The capacitor is not a bad idea, maybe. It would need to be good-
    sized, maybe in a boxcar or tender. It would interfere with a PWM
    controller like MRC, and would need to be non-polarized or have a
    rectifier (which would lose a little voltage,) but it could sure smooth out
    a dirty track or pickup problems, if it were big enough. Don or Andy or RC
    might have some suggestions.:thumb: Easy enough to test out, I guess.:) :)
  5. Russ Bellinis

    Russ Bellinis Active Member

    I saw an outfit at a GAT Show a couple of years ago that used a capacitor to smooth out power losses. They would demonstrate their product by running a locomotive on an oval of track with a 9 inch section of wood rail in the oval. The locomotive would run off the capacitor over that 9 inch section without a glitch.
  6. pgandw

    pgandw Active Member


    Introducing lag and slower response to voltage changes is usually done at the control end rather than at the motor end of the circuit. This is typically called momentum, and is used to simulate the role of a prototype train's momentum - they can't stop or start suddenly. Many momentum circuits (both DC and DCC) allow the operator to adjust the amount of momentum.

    As for using a large capacitor in the locomotive for momentum and coasting over dirty track, it can be done. But if the capacitor is large enough to make a real difference, you have given up direct control of the locomotive - the charge/recharge rate of the capacitor makes all your control signals lag, and by a non-adjustable amount.

    A large capacitor also filters the DC power to the motor, which adversely affects very slow speed running. Pulse width modulation, sawtooth generators, and pulse power (half-wave rectification) are all methods used to get around mechanical cogging of DC motors and otherwise improve very slow speed characteristics.

    My preferred method for doing what you want is to install a flywheel on the motor shaft (most better diesel drives already have one or two flywheels). The flywheel reduces sudden changes in speed mechanically, improves running ability over dirty track, and improves slow speed running by helping overcome motor cogging. A flywheel doesn't take up much more space than a large capacitor, doesn't interfere with the control system, and adds more weight than a capacitor.

    my thoughts, your choices

Share This Page