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Astable speed control.

  1. Feb 23, 2009 #1

    madmike159

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    I am making a project to control the speed of a DC motor using an astable. I need to be able to change the speed of an astable (555, or one made from gate) using about 8 different voltages.

    The only way I can think to do this is with a MOSFET was a voltage controlled resistor, but no one can ever get these to work.

    Can any one think of another way of varing the astable's speed or a way to implement the MOSFET?

    Thanks :biggrin:
    Mike
     
    Last edited: Feb 23, 2009
  2. jcsd
  3. Feb 23, 2009 #2
    Call me stupid but whats an "astable"?
     
  4. Feb 23, 2009 #3

    madmike159

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    Its also known as an oscillator, it creates continuous pulses at a set speed. It is often used in timing circuits.
     
  5. Feb 23, 2009 #4

    MATLABdude

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    That means that you're getting a periodic waveform (e.g. a square wave for a clock) instead of a single pulse (monostable) or toggling the state (bistable)

    As for the original post, if you're using a microcontroller for this, you're better off using the PWM generation feature. You can also use a digital potentiometer, but these are usually digitally controlled. Unless you want to start cascading comparators to control a parallel-input digital pot.
     
  6. Feb 23, 2009 #5

    madmike159

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    No I think I'll stick with my VCR. I will look into the other ideas though, thanks for the help.

    If any one has any more ideas it would be much appreciated.
     
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