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Dinamo Bike

  1. Dec 6, 2009 #1
    I have made a dinamo from my motor which I attached to my bike's tire
    and I placed the magnet on top of my motor. I give a good spin and then
    I measured the Voltage and it showed up to be 2.5 Volts at normal speed.
    The problem that I am having is that I can't get my small light bulb to work.
    I have attached a light bulb to my motor which generates electricity but I can't
    get it to work.

    Can anyone help me.

    Thanks,
     
  2. jcsd
  3. Dec 7, 2009 #2
    Is it a DC motor? You might use a white LED. Still better use two LEDs in inverse parallel configuration.
     
  4. Dec 7, 2009 #3

    sophiecentaur

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    Are you sure that the motor has a permanent magnet in it; it won't work at all if it hasn't? Also, brush (DC) motors do not make very good dynamos, although you should expect to get some current from it. As soon as good diodes became available, Automotive engineers used Alternators and all bicycle dynamos produce straight AC from the stator windings whilst spinning a permanent magnet around inside. Try measuring the voltage with a meter?
     
  5. Dec 7, 2009 #4
    I tried with LED it worked but the light bulb didn't
     
  6. Dec 7, 2009 #5

    sophiecentaur

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    Clearly your dynamo isn't producing much. You would probably need to use a 3V bulb but you've proved that the dynamo actually works! That's good.
     
  7. Dec 7, 2009 #6
    My dynamo generates up to 6.5 volts I checked it with my voltmeter.
    My light bulb is only 0.5 A. I checked my light bulb worked properly with a
    1.5 volt battary.

    Thanks
     
  8. Dec 8, 2009 #7

    sophiecentaur

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    The problem could still be with the bulb you are using. If it is a low voltage 0.5A bulb then it has a very low resistance and the dynamo just can't supply enough current to operate it. The internal resistance is so high that you are dropping too many volts inside the dynamo when connected to the bulb. Measure the Volts across the bulb when it's in circuit -they could be only a volt or two - which wouldn't heat up the filament so that it glows.
    I suggest that, as your dynamo open-circuit voltage is 6V, you need an equivalent bulb but rated at very low power (i.e. it will have a high resistance) so as not to take too much current. Bulbs are specified both for Voltage and Power / Current.
    As I said previously, the motor won't ever be a good dynamo but allows you to 'prove a point' about reversability.
     
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