I'm working on a small brushed DC motor project. This project will be sporting the Mega168, running at about 1MHz, using the internal oscillator for the prototype.
The motor drives a small pump, triggered by a pressure switch monitoring the differential pressure of a moderately sized blower.
While I'm thinking that I don't really need to measure motor current, I'd like to monitor it and back off the PWM at a certain trip point.
I'll probably use one of the newfangled Allegro Hall sensors devices - which I have several in the parts bin.
My thought on this is to measure the motor current during the high time of the PWM drive signal. I'm thinking that I could connect the PWM output signal to a near by digital input and use that to tell the controller when the PWM output was high. This signal would then be monitored and used to synchronize the start of the ADC measuring the Hall analog current monitor.
While this will probably not work well for very short PWM high times, it should allow the bulk detection of motor over current during the PWM high time, I think.
Any thoughts??? Is there a better way?