Metal detector 8

  
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This example describes a metal detector which uses a PLL (phase locked loop) digital integrated circuit MCl4046, it can emit the alarm signal when detects metal objects, and it can determine detected material which is based on current meter`s instructions. The device is suitable for detection of nails in wood, the metal objects in sand, wires in w
Metal detector 8 - schematic

alls and so on. The working principle. The metal detector circuit is composed of dection circuit, PLL phase-locked loop circuit and sound alarm circuit, it is shown in Figure 8-74. Detectioncircuit is composed of the detection coil L, the transistor Vl, resistors Rl-R3, capacitors Cl-C5. PLL phase-locked loop circuit consists of integrated circuit ICl, resistors R4-R8, capacitor C7-Cll. Sound alarm circuitis composed ofthe transistor V2, comparing amplifier integrated circuit IC2, buzzer HA, resistors Rg-R14. Rl-Rl4 use 1/4W carbon film resistors or metal film resistors; Rl5 uses 1/2W metal film resistors. RP uses small potentiometer or variable resistor. Cl, C2, C7-C9, Cl2 and C13 select monolithic capacitors; C3-C6 and ClO use high-frequency ceramic capacitors; C11 uses fine-tuning capacitor (semi variable capacitor). Vl and V2 use S9018 or 2SCl815 NPN silicon transistor. ICl uses MCl4046B PLL PLL CD4046 integrated circuit; IC2 uses PPC393C type operational amplifier integrated circuit.



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