Bicycle Dynamos

Discussion in 'The Projects Forum' started by AFAS87, Mar 26, 2010.

  1. AFAS87

    Thread Starter Member

    Oct 9, 2008
    23
    0
    HI...

    my project is that to build a tachometer using Bike Dynamo and a PIC microcontroller.

    the problem is that the output of the dynamo is not dc voltage and i dont know its characteristic.

    any one has idea about this.

    thanks
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    I would guess the dynamo output is AC sine wave. If this is a school project you should be able to get an oscilloscope and test it. If the output is AC, and you will do frequency counting. A simple blocking diode will do the task. The term for what you will do is rectifying. Google rectifier and you will find info.
     
  3. AFAS87

    Thread Starter Member

    Oct 9, 2008
    23
    0
    thanks..
    i know that i need full-bridge rectifier.

    my question was about the characteristic of the denmo ac output voltage.
    i.e the maximum and the minimum,,, is it linear with speed or not?
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    I have hunch that the frequency will be linear but not the voltage. Anyway my advise to you is to base your application on frequency, using onboard counters. Not the output amplitude of the generator
     
  5. flat5

    Active Member

    Nov 13, 2008
    403
    17
    The dynamo consumes pedal power and is maybe more complicated to use than necessary for a tach.
    I'm thinking of a little magnet on the wheel and a reed switch (or coil) on the frame (or fork) to send pulses to be counted.
     
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