Process time control system

Abstract

A process time control system of a digital type has a sensor associated with a motor used for driving a product through a process length and logic circuits for providing a timing pulse corresponding to a time increment for the product to traverse a small process length increment. During this timing pulse clock pulses having a high pulse repetition rate, calibrated to correspond to a predetermined time increment per process length increment, are supplied to a BCD counter and compared by a digital comparator to a BCD number representing a preselected desired process time. The comparator and associated logic gates provide a signals for causing the count of an up-down counter to be incremented either down or up, respectively, according to whatever the BCD count is greater or less, respectively, than the preselected BCD number. A clock pulse source provides slow rate incrementing pulses for this purpose. A recycling binary counter repeatedly counts to its maximum count in response to high repetition rate clock pulses from a further clock pulse source. Another digital comparator compares the count in the up-down counter with the count of the recycling counter and generates a magnitude comparison signal whenever the count in the recycling counter is greater. This provides a pulse form drive signal of variable pulse width. The speed of the drive motor is in general dependent upon this pulse width. Hence, drive motor speed is varied to precisely control said process time.