Metal detector 5

Published:2011/4/26 4:58:00 Author:Ecco | Keyword: Metal detector | From:SeekIC

The working principle.The metal detector circuit is composed of sound and light alarm oscillator circuit, it is shown in Figure 8-71. Oscillator circuit consists of inductor L, capacitor Cl, sensor switch integrated circuit ICl (includes oscillator, detector and comparator circuit, etc.) and the peripheral components. Sound and light alarm circuit consists of four NOR gate integrated circuit lC2 (Dl-D4) and light emitting diode VL, speaker BL and other components. When the inductor (detection coil) L detecting metal objects, the oscillator circuit oscillation, the loss is smaller, the pin 6 of ICl outputs low level, sound and light alarm circuit is not working, VL LED is not lit, the speaker BL does not ring. When the L detecting metal objects, the oscillator stops, pin 6 of IC1 changes into high level from low level, the DI and D2 inside NOR gate integrated circuit IC2 output low level, the light-emitting diode VL is lit; while enabling the audio oscillator composed of NOR gate D3, D4 and resistor R4, capacitor C4 works, it produces audio oscillator signal which is amplified by the V to drive the speaker BL alarm, and the sound will indicate the user they have detected metal objects.



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