Continuity_and_coil_checker

Published:2009/7/19 22:57:00 Author:Jessie | From:SeekIC

Using this circuit, a short (up to about 1000) across the test probes provides enough power to produce audible oscillation. In this circuit, the LM3909 is connected as an audio oscillator. By probing two values in quick succession, small differences (such as between a short and 5Ω) can be detected by differences in the tone. A novel use of this circuit is found in setting the timing of certain types of motorcycles. A different tone can be hoard if there is a short (or no short) in the low-resistance primary of the ignition coil (a difference between a 1 -Ω resistor and a 1 -Ω inductor can be detected). Quick checks of transformers and motors can also be made with this simple circuit. National Semiconductor Linear Applications Handbook, 1991, p 399



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