I am currently working on a super lowcost motorcontroller, to control a 24V DC motor max 7 amps. The motor has a hall element that gives me a pulse per revelation of the motor. I have a gearing that gives me approx 45 pulses pr. revelation of the shaft.
I plan to PWM control the speed of the motor using a sawtooth generator and a comparator with a MOSFET. But I need to control that I actually run at the desired speed. And if not (due o load etc.) I need to turn up the power. The user will simply set a speed with a potentiometer and expect the unit to run at this speed regardless of load. (within the capabilities of the system of course)
However I cannot figure out how to do this. I suspect that converting my pulses to a DC and combining with the controlvoltage is the way to go. But I am stuck. Normally I would do this using some sort of uC since I am not that strong with pure analog electronics, but I cannot use uC and software due to the low-cost issue for this product.
Could anyone point me in the right direction? Or provide a link perhaps? Any and all help is gladly appreciated.
Thanking you all in advance.
Best regards Henrik