make a square wave squarer

Discussion in 'General Electronics Chat' started by JingleJoe, Jul 30, 2011.

  1. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    Technically it's a pulse wave not a perfectly square wave as the pulse width will be modulated, however, it's just not square enough (see attachment below). What I've got is the top picture, what I would like is something more like the bottom one.

    View attachment squarer.bmp

    What circuits would you use to make a square wave squarer?
    To aid your decision here are some simple specs; The voltage I'm operating at is 8 volts however I can go as low as 5, square wave peak to peak is (almost) equal to supply voltage. Frequency is in the audio range (20Hz to 20KHz)

    I'd like a low parts count and simple circuit but lets see whatever inventions you can conceive.
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
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  3. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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  4. iONic

    AAC Fanatic!

    Nov 16, 2007
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    A simple example with 555 timer IC

    [​IMG]
     
  5. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    Thats in a NOT gate configuration isnt it? I've got loads of 555 timers so that makes it easier too :)
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
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    It's pulse width is controlled by the input so yes. The first (color) illustration in the link I gave you shows this.

    There are many logic IC's that integrate a Schmitt trigger into their input so you may have an opportunity to save on parts count.

    You can build your own as in this demo:
    http://www.falstad.com/circuit/#$+1...+-1+out o+19+64+0+226+5.0+6.4+2+22+out+vs+in
     
  7. blueroomelectronics

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    Jul 22, 2007
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    What's the application?
     
  8. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    I want to say "a secret" but that's unhelpful :p
    Audio is the application, making sound waves.
     
  9. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
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    I would use a 555 timer to make a PWM and then send that through a schmitt trigger. Only problem is that the common schmitt trigger is an inverter so just "re" invert the signal (because it will be the invert of the original signal) and you "should" have a near perfect square wave :)
     
  10. iONic

    AAC Fanatic!

    Nov 16, 2007
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    If the OP is sending Audio in I don't think you need a PWM. You can un-invert with the same configuration on another 555 or use a 556.
     
  11. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    I do need a PWM if what I want to hear is pulse width modulation :p I've got a handful of 556's so I can use one of them, or recombobulate a bit of the other circuitry to make the audio PWM wave upsidedown, or rather the right way up for the schmitt trigger to turn back to the right way around... I often worry that I don't make sense.

    It's at times like this I wish I had a dual trace oscilloscope, I have four single trace oscilloscopes but 3 are valve based and not very good or broken. It would just make looking at these waves so much easier as one could compare the inversion/more square with the original directly.

    Anyways, thanks chaps, me and the schmitt trigger are going to get along very well :)

    One last thought: are there schmitt trigger IC's one could recomend?
     
  12. KJ6EAD

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    Last edited: Jul 31, 2011
  13. SgtWookie

    Expert

    Jul 17, 2007
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    The 40106 is a 4000 series CMOS logic IC that has six Schmitt-trigger inverters.

    The 4093 is one of the most useful of the whole series; a quad Schmitt-trigger 2-input NAND gate. By connecting NAND gates various ways, you can create the functionality of any other gate. This also can be done using NOR gates, but the 4093 and the 40106 are the only two 4000-series that I'm aware of that have Schmitt-trigger inputs.
    See this Wikipedia entry:
    http://en.wikipedia.org/wiki/NAND_logic
     
  14. JingleJoe

    Thread Starter Member

    Jul 23, 2011
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    Almost! I dont quite know how to put it, but I'm put off making that one for some reason, the sound is certainly interesting but I have my own ideas ;)


    Additionally, thankyou Sgt *salute*
     
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