Re: controlling voltage supply to control rotation of a moto
The only way DC motors are controlled nowadays is with PWM. PWM is done on a chip, voltage control is very expensive and complex in comparison. You can get $1.50 PICS that have 10 bit PWM built into them. Some Ucontrollers have 4 or more PWM channels built into them. You run that through a MOSFet H-Bridge and you can control a 20 HP DC motor, forward and reverse. For control you need some form of feedback which is typically an encoder, but it can also be a voltage feedback (which is just the encoder signal (frequency) converted to a voltage.
PS: I don;t get why people still talk about the 16f84 which is a legacy chip. Please look at the 16f627 and 16f628. They are way cheaper than an 16f84 and come with a 16 bit timer with capture and compare,a two 8 bit timers with 10 bit PWM. Plus they have a serial port, plus 2 analog comparators plus a selectable (1 of 16 I think) voltage reference for the comparators. Slightly more expensive chips come with multichannel A/D.