Motor monitoring circuit for needle printer - has two comparators connected by threshold diode, with current sensing resistance controlling first comparator

摘要

The monitoring system for the motor for the paper advancing mechanism for a needle printing machine uses a circuit with two comparators. The motor also controls the operation of the printing head. The supply line is connected to a transistor bridge circuit with a power line with a current sensing resistance connected to the positive input of the first comparator. The second comparator which switches off the motor is connected by a diode to the first comparator, acting as a threshold device. The positive input of the second comparator is connected to the junction between two resistances forming a switching system. The return coupled output is connected to an indicator lamp.