1. INTRODUCTIONS OF METAL DETECTORS
2.DIFFERENT TYPES OF METAL DETECTORS
3. CIRCUIT COMPONENTS OF METAL DETECTORS
4. COMPONENTS DESCRIPTIONS
5. BLOCK DIAGRAM OF METAL DETECTOR
6. CIRCUIT DIAGRAM OF METAL DETECTOR
7. WORKING OF METAL DETECTOR
8. APPLICATIONS OF METAL DETECTOR
In the year 1960, the first metal detector was established and was used in industrial applications and mineral prospecting. Metal detector is an electronic instrument which is used to detect metals nearby.Metal detectors are useful for finding metals hidden within objects like bombs, knives, guns within the luggage bags of the person carrying them in public places like theatres, shopping malls, parks, airports, hotels, railway stations or metal objects buried underground.If the sensor comes near a piece of metal this is indicated by a changing tone in earphones, or a needle moving on an indicator.
Different types of metal detectors:
In this project I m going to use 555 Timer IC because this has the simplest circuit design than other metal detectors.
Circuit components for metal detector
- +9 Battery (supply voltage)
- 555 IC
- 47KΩ resistor
- 2.2µF capacitor (2 pieces)
- Speaker (8Ω)
- 170Turns of 10cm diameter coil (any gauge would work)
Battery (Voltage supply)
When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode.The terminal marked negative is the source of electrons that when connected to an external circuit will flow and deliver energy to an external device. When a battery is connected to an external circuit, electrolytes are able to move as ions within, allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit. It is the movement of those ions within the battery which allows current to flow out of the battery to perform work.
555 timer IC
The 555 timer chip is extremely robust and stable 8-pin device that can be operated either as a very accurate Monostable, Bistable or Astable Multivibrator to produce a variety of applications such as one-shot or delay timers, pulse generation, LED and lamp flashers, alarms and tone generation, logic clocks, frequency division, power supplies and converters etc.
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements.
A capacitor is a two-terminal, electrical component. Along with resistors and inductors, they are one of the most fundamental passive components we use.
Speakers are transducers that convert electromagnetic waves into sound waves. The speakers receive audio input from a device such as a computer or an audio receiver. This input may be either in analog or digital form. Analog speakers simply amplify the analog electromagnetic waves into sound waves.
Electromagnetic coil , formed when a conductor is wound around a core or form to create an inductor or electromagnet. Ignition coil, an electromagnetic induction coil used in internal combustion engines to create a pulse of high voltage for a spark plug.
Block diagram of metal detector
Circuit diagram of metal detector
Working of metal detector
The above figure shows the circuit diagram of metal detector. The 555 timer IC here acts as a square wave generator and it generate pulses with frequencies audible to humans. The capacitor between pin2 and pin1 should not be changed as it is used to produce audible frequencies. In the circuit there is an RLC circuit formed by 47K resistor, 2.2µF capacitor, and 150turn inductor. This RLC circuit is the main and metal detection part.
Fig:this picture shows that as the metal detector comes near coins the” Beep Beep” sound is heard.
Remember the coil wound here is a air cored one, so when a metal piece is brought near the coil, the metal piece acts as a core for the air cored inductor. By this metal acting as a core, the inductance of the coil changes or increases quite. With this sudden increase in inductance of coil the overall reactance or impedance of the RLC circuit changes by a considerable amount when compared without the metal piece.
So whenever a metal is brought near the coil, the impedance of RLC changes making the signal to change resulting in variation to sound generated in speaker.
Applications of metal detector
- Security screening – They are used in airports to screen passengers, checking bags in public places and in public events.
- Food processing – They are used in food processing industries to detect fragments of metal so as to avoid food contamination.
- Civil engineering – They are used in finding reinforcement bars inside the walls.
So, now your Project is Ready to work ,Keep enjoying this project.
So, Friends I hope you understand this project very well . In upcoming Tutorial I will be back with some new interesting Projects and we will discuss about some useful development topics. Here if you want to recommend that what I should write in upcoming Tutorial then please leave your comments. and if u need any help or query please don’t Hesitate to discuss with me. Thank You 🙂