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Need to change the output wave. Help?

Discussion in 'General Electronics Discussion' started by GoldBl4d3, Dec 6, 2013.

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  1. GoldBl4d3

    GoldBl4d3

    3
    0
    Dec 6, 2013
    I have this circuit design which outputs about 27 volts at 4hz square wave. What I need is to still output 27 volts but a 10hz square wave.

    How do I take this circuit, given its already built, and modify it to output what I needed?

    The LM358's are Operational Amplifiers

    [​IMG]
     
    Last edited: Dec 6, 2013
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,906
    2,098
    Nov 17, 2011
    As far as I can see the frequency is defined by R1 and C1. Change R1 from 2.4Meg to 1Meg and you should have almost 10Hz. You may need to tweak R1 to arrive at 10 Hz with the precision you need. You could use an 680k fixed resistor in series with a 475k potentiometer (used as variable resistor by connecting one end to the wiper).
     
  3. GoldBl4d3

    GoldBl4d3

    3
    0
    Dec 6, 2013
    Thanks a bunch for your help on this. I am going to make the changes and post an update. I see what you mean by using a 680k resistor in line to a 475k pot in order to be able to adjust the frequency.

    Do I need to use the 680k resistor and a 475k pot, or can I get something close to those numbers?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    9,906
    2,098
    Nov 17, 2011
    These values are just a suggestion. You could also use a 1Meg potentiometer. Using the fixed resistor with a smaller potentiometer gives you better resolution for fine adjustment. Other than that you can use any combination of resistor and potentiometer as long as the sum of the resistances is in teh 1Meg range.
     
  5. GoldBl4d3

    GoldBl4d3

    3
    0
    Dec 6, 2013
    That's what I thought, thanks for your help on this.
     
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