Metal Detector Cirduit with IC TDA0161


Posted on Aug 16, 2016

The Metal detector project is designed for metallic body detection by sensing variations in high frequency Eddy current losses. Using an externally-tuned circuit, they act as oscillators. The output signal level is altered by an approaching metallic object. The output signal is determined by supply current changes.


Metal Detector Cirduit with IC TDA0161
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Independent of supply voltage, this current is high or low, according to the presence or absence of a closely located metallic object Between pins 3 and 7, the integrated circuit acts like a negative resistor with a value equal to that of the external resistor R3 and trimmer potentiometer PR1 (connected between pins 2 and 4). The oscillation stops when the tuned circuit loss resistance (Rp) becomes smaller than R3. As a result, ICC(close) = 10mA (pins 1 and 6). The oscillation is sustained when Rp is higher than R3, and ICC(remote) = 1mA (pins 1 and 6). Eddy currents induced by coil L1 in a metallic body determine the value of Rp.




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