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Simple Voltage Regulator Circuit Sought

Discussion in 'General Electronics' started by Rick, Jun 16, 2004.

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  1. Rick

    Rick Guest

    I am a Newbie to news groups so I apologise in advance for any
    transgressions in Nettiquette!
    I have recently completed rebuilding a 45 years old small motorcycle,
    as a project, and would like to improve the lighting/charging system.
    The electrical system is 6volt with a flywheel/magneto containing an
    ignition coil and a lighting/charging coil. The brake light,
    indicators, horn and neutral indicator lamps are powered directly from
    the battery, the headlight, taillight and instrument light are powered
    from the lighting coil. When the lights are switched 'on' the
    lighting circuit is paralleled to the charging circuit (a rectifying
    diode feeding the battery). The lighting coil has one end earthed to
    the frame. This means that the lights only work when the engine is
    running. With the lights switched 'off' a tap from the lighting coil
    is switched to the diode to provide a reduced 'trickle' charge.
    I would like to feed everything from the battery and use the lighting
    coil exclusively for battery charging. This would mean using a
    voltage regulator to avoid overcharging the battery. I envisage a
    circuit thus: coil, via rectifying diode and current limiting resistor
    then another diode, to battery positive. A Zener diode between the
    resistor and the second diode is connected to earth (frame) to control
    maximum voltage.
    My problems are:
    1. is this adequate, and (if so)...
    2. please, what values for the various components?
    A refinement would be some sort of indicator (e.g. LED) that glows
    when more current is flowing out of the battery than is being
    replaced, operating like the ignition warning light on a car. Is it
    possible to connect such an indicator, to which part(s) of the circuit
    and what components (besides the LED) would be required?
    I, and many other small bike enthusiasts, would be very grateful for
    any help on this matter. Please write to me at <>
    and thank you for your time and consideration.
  2. Robert Baer

    Robert Baer Guest

    Use one of those regulators from a car - even if it is of the older
    "vibrating relay" type.
  3. Guest

    That would be my recommendation as well, although it might be easier
    to find a 6-volt regulator in a tractor application.

    All the motorcycle regs I've dealt with simply ground the coil leads
    causing them to not produce any power. This is done before the diodes
    so you don't short the battery. You don't want to simply disconnect
    the coils because they will generate high voltage which can cause
    breakdowns and arcing.

    You might also be able to modify an older motorcycle mechanical type
    regulator. Basically, those look just like a relay that clicks exactly
    when the voltage is correct. Usually, you see people trying to swap
    these out for newer electronic versions for better reliability and
    voltage control. If at all possible, I'd try to find an electronic
    module. On a bike that old, I image the biggest problem is getting
    things reliable (well, after dealing with all the dried up gaskets).

    Just curious, what make/model of motorcycle?

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