TDA0161 are monolithic integrated circuits that can detect the variations in high frequency Eddy current losses. They can be designed for detection of metallic body. They can act as oscillators with the help of external tuned circuit. The output signal level is altered when any metallic object is approaching towards the coil of the circuit. Basically, the output signal varies due to change in the supply current. The supply current does not depend upon the supply voltage. It becomes high when any metallic body is approaching else remains low. The normal high output is 10mA whereas normal low output is 1mA.

When the metallic body is at the remote place, the Rp (tuned circuit loss resistance) becomes higher than the external resistance R1 which connected between pin 2 and pin 4. Hence the oscillation is sustained and the value of supply current becomes 1mA.

When the metallic body is approaching near the coil L1, the value of Rp (tuned circuit loss resistance) becomes smaller than the external resistance R1. As a result the oscillation comes to halt and the value of supply current becomes 10mA.

Project Source Code

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