Adjustable Square wave generator

Discussion in 'The Projects Forum' started by zohonie, Jan 20, 2011.

  1. zohonie

    Thread Starter New Member

    Dec 2, 2010
    I would like to find the easiest way to create an adjustable square wave. The wave needs to be centered at 2.5 V. The magnitude of the wave must be adjustable between 0 and 5 v by a potentiometer. The frequnecy also adjustable between 0-4Hz also by a pot. I'm very new to electronics so please be specific in your explaination. It would be best of there is a commerical board that can do this. Thank you.
    Last edited: Jan 20, 2011
  2. Wendy


    Mar 24, 2008
    A simple 555 circuit with an output pot and cap will do this. What kind of load are you driving? No time now, but I'll be glad to throw a quick schematic up in a couple of hours.
  3. Wendy


    Mar 24, 2008
    OK, there is no specific board that will do then that I know of, but there are many things I don't know.

    Start with this...

    555 Hysteretic Oscillator

    And add this to the output...


    An even better square wave can be made by using this schematic...


    Make R1 very small compared to R2 (say 1KΩ/100KΩ)
  4. tom66

    Senior Member

    May 9, 2009
    If you want a 50% duty cycle I'd recommend either adding a flip-flop to the output of the 555 or using an op-amp oscillator.
  5. Wendy


    Mar 24, 2008
    No need, the latter schematic will achieve better than 50.1% with the ratios described. Ever done the math?

    A hysteretic oscillator using a CMOS 555 will also be very square.
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    When you say "level from 0-5V", do you mean swings from -2.5 to +7.5v, or swings from 2.5V (0V) to 0-5V? In other words, is the 0-5V peak to peak, or change from the 2.5v bias?