Emergency stop circuit monitoring system

摘要

Monitoring system for an emergency stop circuit controlling a number of machines in a factory, to determine the location of an actuated stop button. The stop circuit consists of a supply line to a self-latching contactor and there is an emergency stop button in the circuit at each machine. A monitoring line runs parallel to the supply line and is connected to each section between adjacent stop buttons by high value resistors. When a voltage is applied to the supply line a current appears in the monitoring line whose magnitude depends upon the position of the actuated stop button and thus is connected to a voltage which is applied to a series of comparators driving light emitting diodes. Each comparator is provided with a different reference voltage from a resistive chain and since the L.E.D.'s are connected between the outputs of successive comparators along the chain, only the L.E.D. whose position represents the position of the actuated button is illuminated.