I intend too rotate two motor at exactly the same speed. I intend to use proxitimy or optical sensors as speed sensors. Would like to know if their is any hardware availble to compare two signals from sensor, and would increment or decrement the pwm from 8051. else swoftware option. Also which of the above sensors would be more suitable, rotation speed will be slow app.300-500 RPM.Any information on the above would be greatfully recieved.