Metal detector 3

Published:2011/7/29 2:45:00 Author:Ecco | Keyword: Metal detector | From:SeekIC

This metal detectors described in the example can be used as finding location of underground metal pipes, removal and the detection of metal garbage in beach swimming pool and residual nail in wood.The working principle.The metal detector is composed of detection oscillator, reference oscillator and audio amplifier and other components, it is shown in Figure 8-69. Detection oscillator consists of transistors Vl, V2 and detection coil Ll, capacitor Cl and so on. Reference oscillator consists of transistors Vl, V3 and inductor, capacitor C3 and other components. Audio amplifier audio is composed of power amplifier IC, the volume potentiometer RP and capacitors C6-C8 and so on. Before the end of Ll detecting metal objects, the operating frequency of detection oscillator and reference oscillatorare the same (are aboout 32OkHz), the emitter of V3 has no audio signal output, speaker BL has no sound. When the metal in the ground is detected by Ll, the detection oscillator frequency will become higher, V3 emitter outputs an audio signal, which is amplified by the lC to drive the audio speaker BL, and it issues calls to remind the user metal objects have been detected .



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