Metal detector is a most common device that is used for checking human being, parcel or bags in shopping malls, offices, cinema halls, theaters, etc. To assure that peoples are not carrying any metals or illegal things like guns, knife, bombs etc.
There are different types of metal detectors like hand held metal detectors, relic hunting detectors, walk through metal detectors and ground research metal detectors. Metal detectors can be built easily and the circuit for a basic metal detector not more complex.
In this project, we have designed a simple or common DIY Metal Detector using very simple components that can be used in our homes, offices and gardens.
- TDA0161 Proximity Detector IC (1)
- 47nF Capacitors (Ceramic Capacitor code 473) (2)
- 1KΩ Resistor (1/4 Watt) (1)
- 330 Ω Resistor (1/4 Watt) (1)
- 100 Ω Resistor (1/4 Watt) (1)
- 5 KΩ Potentiometer (1)
- 2N2222A (NPN Transistor) (1)
- 5V Buzzer (1)
- 220 Ω Resistor (1/4 Watt) (1)
- 5mm LED (1)
- Coil (copper wire of 26 – 30 AWG is taken and it is wound in to a coil of diameter 5 – 6 cm and 140 – 150 turns)
The LC Circuit, which consists of L1 inductor (coil) and C1 capacitor, is the main part of metal detector circuit . By using LC Circuit, which is also called as Tank or Tuned Circuit, the (TDA0161) IC work like a oscillator and oscillates at a specific frequency. When the LC circuit senses any resonating frequency from metal that is close to it, electric field will be built up which will lead to produce current in the coil and changes in the signal flow throughout the coil. Variable resistor is used to change the nearly sensor value equal to the LC circuit, it is accurate method to identify the value when the coil is not close to any metal. When the metal is detected, the LC circuit will have changed output signal. The changed signal is reached at proximity detector (TDA-0161), which will detect the change in the output signal and give response accordingly. The output of the sensor should be than 1mA when, there is no metal near the coil and it will be a 10mA (usually greater than 8mA) when metal is detected by coil. When the output pin is high, the R3 resistor will supply positive voltage to transistor Q1. Q1 will be turned ON and LED will Blink (not shown in the circuit) and buzzer will be activated.
- This Metal Detector can be used to detect metals like iron, gold, silver etc.
- whereas it’s a simple project, we can also used for detect nails, metal scraps etc. which are not easily noticing by naked eye.