Collection Schematic

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METAL DETECTOR USING BEAT FREQUENCY OSCILLATOR ELECTRONIC DIAGRAM

The NAND gates use CMOS 4011 chip, a low power component that is suitable for this battery-operated circuit. You can see that this chip is supplied by a 5V voltage coming from an LM7805L regulator. You might wonder what the purpose of this regulation is, since the power supply come from a  9V battery and the CMOS gates can handle the voltage of 3-15 Volt. The main purpose of the regulator is to keep a constant voltage source for the reference oscillator frequency stability, since the frequency is affected by the power supply voltage variation as the battery voltage drops in the long time of usage.

This circuit uses parts as follows :

•     U1: CD4011
•     U2: LM389
•     U3: 78L05
•     R1: 2.2k 5%
•     P2: 4.7k lin.
•     R3: 330k 5%
•     R4: 270k 5%
•     R5: 1k 5%
•     C1: 390pF (NPO)
•     C2,C3,C4: 10nF
•     C5: 10uF 16v electrolytic
•     C6,C8: 220 uF 16v electrolytic
•     C7: 100uf 16v electrolytic
•     C9: 100nF ceramic
•     P1: 4.7k log
•     L1: 22cm in diameter with 14 turns AWG 26
•     K1: SPDT toggle switch
•     J1= Headphone jack 1/4 or 1/8 inch
•     Other parts: 9v battery connector, speaker or headphones