i would like to know more about the metal detector circuit. Thank you in advance

report on metal detector of 557 from vegakit


Metal Detector Project

This circuit is most useful for security checking. Metal Detector available in the market are quite expensive.

This metal detector can be used to detect slightly big size metallic objects. It used a sensing coil. This coil should be kept near metallic objects for detection. Input of Circuit is a week colpitt’s R.F. range Oscillator. Sensing coil forms parts of tuned oscillator.

When coil is brought near a metallic object magnetic energy is observed and Oscillator fails to work. Then final transistor conducts and buzzer is activated. Use a 9 volts battery. After connecting battery, adjust the 4.7k preset till circuit just stop sounding.



PARTS LIST:-

RESISTORS

R1,R4 – 56K

R2 – 3K3

R3 – 22K

R5 – 2K7

R6 – 2K2

R7,R9 – 680E

R8 – 15K

P1 – 5K 3386 Trim



CAPACITORS

C1,C6 – .1PF (104) 100 KPF

C2 – 1KPF (102).001PF

C3 – 220PF

C4 – 270PF/100V

C5 – 12KPF/ 100V (.012/25V)

C7 – 100/25V



TRANSISTORS

Q1,2,3,4 – BC 547 PH



DIODE

D1,2,3,4 – IN 4148



MISCELLANEOUS

LED1 – 5MM Red LED

COIL1 – Metal Detector Coil

Buzzer – VK 27 CT (S)

Supply – 9v Snapper

PCB – VK 557 PCB