556 (Dual 555) Configurable PWM Servo Motor Controller

This is a servo motor controller based on 556 (Dual 555) Timer Pulse Width Modulator. Variable resistor Rchadjp adjust the carrier frequency/rate of the PWM pulses. The frequency can be adjusted to lower than 40 Hz and the higher limit approaches 90 Hz. The corresponding periods of the limits are greater than 25 ms and approaches 11 ms. Rmindcadj adjusts the minimum output pulse width (minimum output duty cycle) which corresponds to the lower extreme of the servo motor position. Rposadj is the main user control , it is where the desired position of the servo motor is varied. Potentiometer Rctlvadj modifies the CONTROL voltage of the timer unit in monostable mode to compensate for inaccuracy of the timing resistors and capacitor. Note: There is no 556 in the Free Subscription version of Multisim which I am using. The units are 555, so there are separate power and ground pins for the two timer units.