Hi friends, today we are going to build a very useful circuit which is Metal Detector. We all know about Metal Detector equipment which is widely used at security points. Same kind of Metal Detector we are going to build today. Our circuit is more powerful which can detect the presence of metal inside walls. If you want to drill a hole in walls, we can use this Metal Detector to check if there is any metal pipe like gas pipeline or water pipes, etc.
Features of Metal Detector:
- Detection Range: 8 cm (3″ approx.)
- Power supply: 9V Battery
- Power consumption: 30mA max.
- Output form: LED or/and Buzzer
- Coils: It consists of two windings around the ferrite core. Winding L1 has 120 turns and winding L2 has 43 turns. We are using copper wire having 0.3mm thickness.
- Diode (D1): 1N4148
- Zener diode (ZD1): 3V9
- Resistors: R1=330Ω, R2=R3=470Ω, R4=2.7KΩ, R5=10KΩ
- Capacitors: C1=1200pF or 3300pF, C2=47nF
- Transistors: T1=T2=T3=BC547B
- LED (LD1): 5mm red
- Trim potentiometers: RV1= 2.5KΩ, RV2=100Ω
- Push button SW1
Circuit Diagram of Metal Detector:
Test and Adjustments:
- Connect a 9V battery to the circuit.
- Keep the circuit where there is no metal in the vicinity.
- Turn preset RV1 fully clockwise.
- Turn RV2 fully anti-clockwise.
- Depress the push button and hold it during the final adjustments.
- Now turn RV1 anti-clockwise till red LED goes out.
- Now turn RV2 clockwise until the red LED weakly lit.
- Now when metal comes in the vicinity of circuit red LED will be more brightly lit.
You can observe that we have one buzzer in the circuit. This buzzer is optional. If you want the output of the circuit in the form of a buzzer, you can connect the buzzer as shown in the diagram.
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