Analog Four Quadrant DC Motor speed control

Discussion in 'The Projects Forum' started by Andile, May 12, 2014.

  1. Andile

    Thread Starter New Member

    May 11, 2014
    Good Morning guys
    I need some help urgently,I'm requested to design an Analog Four Quadrant dc motor speed control.I'm using a 555 timer to generate the pwm signal(20Khz) and I'm controlling my duty cycle using a variable resistor.I'm using mosfets for my H-Bridge circuit.I looking for a method on how to invert the 12V pwm signal output of 555 timer.I've tried using npn transistor but some how it does not invert,I think its becuase the 555 sinks and sources current,I've also tried using an op amp with a gain of 1 so that I just get the 180 degress phase shift,this also does not work,I'm getting a weird output.

    Can someone pleased help me,my connections might be wrong so if u can please send me a topology that I can use.My email address
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    You can google for "8 pin hbridge driver IC" there are a few types on the market.

    These will accept a single PWM signal, and generate phase and anti-phase outputs (the two outputs you need). The chip will also include deadband period to stop shoot-through in the hbridge.

    I think the last one I used was a "Vishay" brand IC.