Frequency Divider

Discussion in 'The Projects Forum' started by jpanhalt, Jan 15, 2011.

  1. jpanhalt

    Thread Starter AAC Fanatic!

    Jan 18, 2008
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    As part of another project, I used a typical triangle wave and comparator to get a voltage-controlled PWM signal. In order to get the characteristics of the input:pWM that I wanted, I quadrupled the frequency of the triangle wave.

    I think I have a way to divide by thee or two, etc. without changing the pulse width, but it is complicated. (Negative edge triggered monostable + some logic.) Does anyone know a simple way to divide by two while retaining the original pulse width. It is for servo control and must be analog.

    John
     
  2. hgmjr

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    Jan 28, 2005
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    How about if you implement a divide by two and then use the output of it together with the original signal and feed them into an AND gate. That will suppress every other pulse while preserving the original signal.

    hgmjr
     
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  3. jpanhalt

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    Good idea. I will try it tomorrow. My idea was a long, negative-edge-triggered monostable followed by an XOR + AND gate. I could get divide by any number (almost), but it seemed overly complicated.

    Thanks. Any other ideas?

    John
     
  4. jpanhalt

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    @hgmjr

    Thanks for the kick in the right direction. I never learned to use Boolean and Karnaugh, so I just go to truth tables. This morning with a fresh mind, I got the divide by 4 that I needed using a CD4047 and an AND gate. I now have a duty cycle (roughly 0 to 100%) to servo pulse width controller. Right now, the servo output is 0.9 to 2.9 mS for the full range of duty cycle, but those pulse widths are easily adjusted.

    John
     
  5. hgmjr

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    So you have achieved the desired goal?

    hgmjr
     
  6. jpanhalt

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    Yabba dabba doo. :D

    John
     
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