Simple variable square wave generator?

Discussion in 'The Projects Forum' started by Al Vince, Apr 10, 2016.

  1. Al Vince

    Thread Starter New Member

    Feb 24, 2015
    Hello, I was wondering if anyone had any suggestions with a simple circuit I am looking to build for a project. I would like to make the circuit as small and simple as possible. I will be using a quality regulated power supply for the input.

    - DC input 14volts
    - DC output a square wave adjustable up to 12 volts at 1.5A
    - Use a pot to adjust frequency output between 30hz to 100hz
    - Use a pot to adjust voltage output between 6 volts to 12 volts
    - Use a pot to adjust duty cycle output between 10% and 100%

    So for example.... say I can set the pots to output at 60hz - 9 volts - 30% duty cycle.

    Any help in pointing me in the right direction... maybe there is already a schematic or sample design I can use or modify? I am not an engineer, just a hobbyist.

    Thanks in advance!
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    use a 555 timer and tda2030 amp
  3. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    A single 555 chip can give you 10% to 99% duty cycle control with only one pot. Or, it can give you a 3.3:1 frequency range control with only one pot. But I don't think it can do both at the same time with one pot for each variable. Two 555's in series can.

  4. ian field

    AAC Fanatic!

    Oct 27, 2012

    The TDA20xx family of audio amplifiers are very similar to power op-amps - of which there are quite a few to chose from.

    Its not *THAT* difficult to wire them up as a square wave generator and save the 555.

    There's probably an example in the NS appnotes collection - they have several LMxxx parts that are almost identical to the TDA20xx ones.

    A simple 2 transistor astable can be made variable frequency by commoning the base resistors to a pot that feeds them Vcc - that uses more components than the 555 option, but the output stage can be as simple as a complementary pair of emitter followers.