What is a Metal Detector Circuit?
Metal detectors are simple electronic circuits that operate by emitting an electromagnetic field from an inductive search coil. Whenever a metallic object comes within the vicinity of the detectors search coil, it gets energized and transduces a target response to the metal detectors circuitry in order to alert the user. Metal detectors are commonly used for various safety reasons in places such as airports, hotels, banks, and police stations, etc, usually to detect if someone is carrying a firearm. So, in today’s tutorial we are going to go over a step by step process on How To Make A Powerful Metal Detector Circuit Using NE555 Timer IC.
NE555 Timer
The heart of this powerful metal detector circuit is a NE555 precision timer IC. NE555 is a precision timing circuit capable of producing accurate time delays or oscillation. A NE555 has three basic modes of operations. In the time delay or mono-stable mode of operation, the timed interval is controlled by a single external resistor and capacitor network. In Bi-stable mode, the output can be configured to latch on a certain voltage level for an indefinite period of time and can be sent back to the zero states by resetting the IC. For an a-stable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor.
Here the NE555 timer acts as a monostable multivibrator. A monostable multivibrator (MMV) often called a one-shot multivibrator, is a pulse generator circuit in which the duration of the pulse is determined by the R-C network, connected externally to the555 timers. In such a vibrator, one state of output is stable while the other is quasi-stable (unstable). For auto-triggering of output from a quasi-stable state to a stable state, energy is stored by an externally connected capacitor to a reference level. The time taken in storage determines the pulse width.
Hardware Component
You will need the following parts to build this project:
| S.No | Component | Value | Qty |
|---|---|---|---|
| 1) | Timer IC | NE555 | 1 |
| 2) | Inductor Coil (magnet copper wire) | 100mH/24 AWG | 1 |
| 3) | Capacitor | 10uF, 2.2uF | 3 |
| 4) | Buzzer | 5V | 1 |
| 5) | Resistor | 47K | 1 |
| 6) | Soldering Iron | 45W – 65W | 1 |
| 7) | Soldering Wire with Flux | – | 1 |
| 8) | DC Battery | 9V | 1 |
| 9) | Battery Clip | – | 1 |
| 10) | Veroboard | – | 1 |
| 11) | Jumper Wires | – | As per need |
555 Timer Pinout
Useful Steps
1) Solder a 8 – pin IC jacket on the veroboard.
2) Solder the +ve pin of the 2.2uF capacitor with pin 2 of the IC and the -ve pin with pin 1 of the IC. After that, solder another 2.2uF capacitor on the board, +ve pin with 10mH search coil and -ve pin 6 of the IC.
4) Solder the Buzzer on the veroboard.
5) After that, solder the +ve pin of a 10uF capacitor wit pin 6 of the IC and the -ve pin with the +ve of the buzzer.
6) Place the 555 timer IC in the IC socket.
7) Solder the 100mH inductor coil between the 2.2uF capacitor and pin 3 of the IC.
8) After that, connect the battery clip between pin 1 and pin 8 of the IC.
9) Power up and test the circuit using a 9V DC battery.
Working Explanations
The working of this circuit is actually pretty simple. Here the NE555 timer is working in mono-stable multivibrator mode. On powering up the circuits, the timer IC primes up and starts to generate a stable low output. when the search coil inductor hovers over a metallic object, the metal surfaces causes the search coil to become energized and signals an input to pin 2 of the timer IC.
The output from pin 3 of the timer IC passes through a smoothing capacitor in order to remove any residual noise. After that, the output signal moves on to the 5V buzzer and signals the user about the presence of a metallic object. you can easily mount up this circuit on a plastic handle in order to make it more portable.
Applications
- Industrial metal detectors serve in places such as food, beverage, textile, garment, chemicals, pharmaceutical, lumber, plastics, and packaging industries.
- They are also used for different hobbies such as beachcombing, coin shooting, prospecting for valuable metals such as gold and silver.
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