Is it possible to connect the 555 PWM circuit to this H-bridge circuit with comparators? If it is how will I connect it?
If you are still using the first LM311 circuit as per your URL, connect your PWM signal directly to one input
OR the other. You'll get speed control in one direction or the other. Make sure your 555 circuit is powered from the same supply as the LM311s, or less.
If you wire your H-Bridge up like the second LM311 circuit, i.e. the one with the two LM311s wired together so there is only one direction input, you can wire your PWM signal to said direction input and achieve what's called
Locked Anti-Phase control. This is different than
Sign/Magnitude control, which is perhaps more conventional.
Sign/Magnitude control requires two inputs, one for direction (sign) and one for speed (magnitude); the latter is where your PWM is applied. Locked anti-phase control uses a single input where both speed and direction are encoded. PWM duty cycles under 50% represent one direction of rotation, signals over 50% the other. (A 25% duty cycle would be half-speed in one direction, 75% would be half-speed in the other direction, and 50% is off.)
Now I don't know how much hysteresis the LM311 H-Bridge has, so you may experience some funky behavior with a PWM signal of around 50%, ±10%.
See the following and download the manual for more info, if desired:
**broken link removed**