Simple control solution

January 2001 PLCs, DCSs & Controllers

A Red Lion motor drive controller, Model MDC, is used to control the speed of the film as it passes through the chemical solutions. A Model RPGC0061 (rotary pulse generator, 100 pulses/rev) is used as a feedback signal for the MDC. The RPGC is attached at a one-to-one ratio with a roller that measures 460 mm in circumference.

Customer requirements

* Control of the film speed in mm/min.

* Allow the operator to feed the film into the machine by 'jogging' the motor slowly.

* 'Ramp' slowly to the setpoint speed when a 'run' is initiated.

* Prevent the operators from starting the machine before the temperature of the chemical is brought up to setpoint (a Red Lion Model TCU with alarms is used for this function).

* If film speed error exceeds 300 mm/min alert operator with an audible alarm.

* Alarm will be reset via external pushbutton.

* Inform operator if RPGC signal is not received by the MDC.

The figure illustrates the simple implementation of all the functions required by the customer.

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