CLOSED_LOOP_TRACER

Published:2009/7/8 2:13:00 Author:May | From:SeekIC

The tracer, consisting of both a transmitter and receiver, is designed to follow a closed-loop wire or cable system. It follows an induced voltage path created by feeding a low-current, audio-frequency signal through the cable. When the pick-up coils come within close proximity of the current-carrying cable, a small voltage is generated in each coil, and that induced voltage is then processed by the receiver's circuitry. The circuit is built around a 567 phase-locked loop (PLL) configured as a variable-frequency, audio-generator circuit, which is designed to produce a square-wave output at pin 5. Potentiometer R4 allows the oscillator to be easily tuned to the receiver's frequency. Transistor Q1 isolates the oscillator from the load and matches the impedance of the primary of T1. Resistor R3 limits current flow through Q1. The low-impedance secondary of T1 supplies the cable drive signal.



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