WIRE BREAKING DETECTING DEVICE FOR ROTARY ENCODER

摘要

PURPOSE:To surely detect the breaking of wire of a cable of a rotary encoder by pulling down the output terminal of an output transistor (TR) and conducting a current to the cable even when the output TR is off. CONSTITUTION:When none of output cables of an A, a B, and a C phase has the breaking of wire and the output TR is on, currents are conducted through resistances 19-21 for current detection and TRs 22-24 turn on; and currents are conducted through pull-down resistances 28-30 to raise the input of a NAND circuit 32 to a high level while lowering the output level of the circuit 32 to a low level. Even when the output TR is off, the output level of the circuit 32 is low. Then, if a power cable or cable for power source wire breaking detection is broken, no current is conducted through a pull-down resistance 31 and the input of the circuit 32 becomes low, so a high-level wire breaking detection output 33 appears at the output of the circuit 32. Then, if respective output cables of the A, B, and C phases or a ground cable is broken, a high- level output 33 appears as the output of the circuit 32.