DC voltage converted to square wave?

Discussion in 'General Electronics Chat' started by Eurokid, May 7, 2011.

  1. Eurokid

    Thread Starter New Member

    May 7, 2011
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    I have a pressure switch that puts out 0 to 5 VDC. I need to convert this signal to a square wave but I'm not sure how to go about doing it. Do I have to convert it to AC then to a square wave? or can i go from DC to square wave? I recently developed a interest in electronics so my knowledge of the subject is limited. Any help would be great.
     
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
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    What is the frequency range that you need? You may be able to program a cheap microcontroller to do what you need. Search for Arduino, they might have an existing design/program that does what you need. There are also IC's that convert voltage to frequency, I think National Semiconductor makes one.

    http://www.national.com/ds/LM/LM231.pdf
     
    Last edited: May 7, 2011
  3. wmodavis

    Well-Known Member

    Oct 23, 2010
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    Does the 0-5V vary in an analog fashion from zero to five volts or is it either 0 volts or 5 volts as suggested by your use of the term 'switch'? If it is in fact a pressure switch it should easily provide a square wavepretty much directly. A little more information on the functionality you want/need would be helpful in order to give you some helpful direction.
     
  4. Eurokid

    Thread Starter New Member

    May 7, 2011
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    Last edited: May 7, 2011
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
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    You are not making square waves. You are generating a PWM (pulse width modulation) signal. The duty cycle of a square wave is fixed at 50%.
    This chip will generate a fixed frequency 0-100% variable duty cycle signal from a 0-5 volt input:

    http://www.maxim-ic.com/app-notes/index.mvp/id/4502

    You will need to massage the 0-5v input to limit the PWM output to your desired range of 50-90%. As shown, it runs at 500Hz. That can be changed by choosing different R's and C's.

    You can get free samples of this chip from Maxim.
     
  6. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    You could probably just use a 555 timer in astable mode, couldn't you? It would be a lot simpler. I can post a simple PWM circuit, if you're interested.
    Der Strom
     
  7. Jessica Webb

    New Member

    Nov 5, 2014
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    I am interested.
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    That offer was 3 1/2 years old. Why don't you start a new thread and tell us what you need.
     
  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Hi Jessica,

    As pointed out, this thread is quite old. However, seeing as this is still on-topic I will go ahead and post it.

    Here is the PWM circuit I generally use. It is based around a 555 timer and a 393 comparator:

    [​IMG]

    The specifics are on this page:

    http://www.rmcybernetics.com/projects/DIY_Devices/homemade_pulse_controller.htm

    It is possible to create a PWM circuit with just one 555 timer, but it is much less accurate, and the frequency and duty cycle are not adjustable independently. I have found this circuit to be far superior.

    Hope this helps!
    Regards,
    Matt
     
  10. Jessica Webb

    New Member

    Nov 5, 2014
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    It does help, it does... except I figured out the problem in my original design---<snip> misconnected wire. TT

    Thank-you so much for restoring my faith in the 555 timer. All roads lead to... well, this design.

    Edit: deleted expletive.
     
    Last edited by a moderator: Nov 5, 2014
  11. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
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    Please watch your language, we're a family-friendly site here.
     
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