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Hand Crank Generator

Discussion in 'Electronic Basics' started by The Roberto, Apr 19, 2004.

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  1. The Roberto

    The Roberto Guest

    I'm trying to rig up a series of lights to a hand crank generator. The
    idea would be to have lights turn on when different voltages are reached
    by the generator. I've been able to do this using opamps, but we're
    trying to do this without any external power sources. Is this possible?
    Thanks for any help.

  2. CFoley1064

    CFoley1064 Guest

    Subject: Hand Crank Generator
    Hi, Roberto. You're asking for something that's doable, but you haven't given
    nearly enough information. Offhand, I'd say that, as long as you don't expect
    anything to light up below about 3V or so, you should be OK. A few questions:

    * AC or DC voltage?
    * How much current can you afford to spend on the lights? How much current can
    your hand crank generator produce?
    * Incandescent or LED desired/required? If high voltage, is neon an option?

    There are a lot of good analog meters which will give you an indication without
    all the wiring, and give you greater accuracy. One place to look is Surplus
    Sales of Nebraska, which has analog DC meters for around $20 USD. That might
    be a better way to go.

    Good luck
  3. John Fields

    John Fields Guest

  4. The Roberto

    The Roberto Guest

    It can crank in AC or DC (just a switch of a magnet). I measured it to just a few
    mA and at a plenty fast crank I get out about 12V. Incandescent lamps are
    preferred to LEDs and these lamps are the only thing that is going to be powered.
    This project is going to be an exhibit to show kids about energy use and give them
    the idea that it takes a more effort to generate more electricity, so it has to be
    done in some more spectaular way than just a panel meter (just following orders on
    this one, a meter would be fine by me)

    I suppose I would want the lights to start turning on at around 4V then 6 and 9.


  5. jtech

    jtech Guest

    play with adding resistors on the each bulb to control its current so they
    light with different voltage, might also add a zener arrangement to limit to
    lower bulbs. Or simply use different voltage bulbs and put a zener across
    the lower voltage bulbs to limit what the bulb gets so they dont burn out,
    along with a resistor in series with the bulb. Hope you get what im trying
    to get at. its late and my thinking is slow right now. have fun.
  6. CFoley1064

    CFoley1064 Guest

    Subject: Re: Hand Crank Generator
    Hi, Roberto. If you're only getting a couple of milliamps, you're not going to
    be able to get an incandescent bulb to light up. In fact, you're not going to
    get an LED to light, either. Even the "grain o' wheat" incandescent bulbs will
    probably bog down your generator. You should be able to run an LM3914 circuit
    off a 9V battery, and get results that way. The LM3914 will light up LEDs
    based on input voltage. If you set it up for a dot-type instead of a bar-type
    display, you should be able to get several hours of life out of a 9V Al Kaline
    battery. There are a number of kits available for this IC, which should fill
    the bill. Sorry -- I wish I had a better idea for you.

    Good luck
  7. The Roberto

    The Roberto Guest

    I should read what I write. I actually get several hundred milliamps. I'm
    estimating up to about .5A. It's enough to light up 3 incandescents (1.25V, .3A)
    in series adequately

    My first attempt at this was to use an array of zener diodes, but the lowest rated
    diode would suck up all the current. Someone suggested a current regulating diode,
    but the ones that I've found are only rated to about 5V (and a few mA). Is it
    worth a shot with these or something similar? Voltage regulating diodes?

  8. Seth Koster

    Seth Koster Guest

    What resistance did you use when measuring your amperage?
  9. Randy Day

    Randy Day Guest

    Just a thought, and *I haven't worked it through*,
    but why use the crank to power the lamps at all?

    Have a separate power source for the lamps. Just
    have the generator create a voltage, so that
    when the zener breaks, it turns on a transistor.

    I have no values for the resistors, so you'll
    have to experiment. MAKE R1 HIGH ENOUGH to limit
    the collector current at the max generator

    R2 biases the transistor off until the zener

    +v -( X )-+
    '-' |
    | R1
    \| ___ Zener
    |--|___|-+-->|--- to your generator
    <| |
    | .-.
    | | |
    GND | |R2

    created by Andy´s ASCII-Circuit v1.24.140803 Beta
  10. Get zeners of value 3.3V, 5.1V, 8.2V, and 11V.

    For each zener, get an NPN power transistor of some kind, and two 1k
    resistors. Tie the zener to the input voltage rail on the high side, and to
    one of the 1k resistors to the ground. Tie another 1k between the junction
    of the 1k and zener, and the base of the NPN. Tie the emitter of the NPN to
    ground, and connect up a lamp between the collector and input input voltage.

    As the voltage increases, when it gets to Vz + 0.7V, it'll turn on the NPN
    transistor, turning on the lamp.

    Do this in parallel for each of the zener values, and as the voltage
    increases, the lamps will turn on one at a time at voltages 4V, 5.8V, 8.9V,
    and 11.7V.

    One problem with this circuit is that the current through the lamps will
    increase as the voltage goes up. You might theoretically want to limit the
    current to some constant value through each lamp, so each lamp has constant
    brightness once its turned on. If thats an issue, I can work up a solution
    for you.

    Bob Monsen
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