I'm building a motor controller for a robot that will have a very limited number of IO pins available. I need to drive two motors from only 3 pins, and Locked Antiphase PWM, where the motor is alternately driven forward and backwards by the H-Bridge, with duty cycle determining the net current, looks very attractive. The fact that it 'just works' when the robot is on a slope (rather than accelerating down it when given a small forward momentum) is an added bonus.
Does this circuit, utilizing the SN754410 H-Bridge and a couple of transistors used as inverters, look reasonable? Am I doing anything obviously wrong here?
Also, a couple of auxiliary questions:
- In 'regenerative braking' mode, the motor may drive current back out the H-Bridge. If I'm powering the whole circuit off a (non-rechargeable) battery, is this liable to damage the battery? If so, can I protect against it with diodes?
- How can I determine what frequency of PWM I'll need to avoid significant idle current draw with Locked-Antiphase and a given motor, other than experimentally?