I’m using Arduino to position a 250 pound 70’x42’ Amateur Radio antenna on top of a 120’ tower. The code powers the rotator and reads back pulses (9576 pulses/360 degrees) to determine where it is pointed. As implemented there is tremendous stress on the system when it starts and stops. What I need to do is smoothly accelerate and de-accelerate the rotation. The motor draws 15-20 Amps at 55 VDC. I am driving some high powered FETs. I want to use the PWM feature ‘analogWrite’ to ramp the speed up and down. Unfortunately, the maximum PWM frequency that I can drive the FETs at is about 200Hz.
What I need to know is how to set the PWM frequency to less than 250Hz on my Diecimila. It seems I would only need to change the value of some internal counter. Your help is greatly appreciated.