How to Make Metal Detector – Final Year Project

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

  1. Detection Range: 8 cm (3″ approx.)
  2. Power supply: 9V Battery
  3. Power consumption: 30mA max.
  4. Output form: LED or/and Buzzer

Components required

  1. 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.

    Metal detector coil
    Metal detector coil
  2. Diode (D1): 1N4148
  3. Zener diode (ZD1): 3V9
  4. Resistors: R1=330O, R2=R3=470O, R4=2.7KO, R5=10KO
  5. Capacitors: C1=1200pF or 3300pF, C2=47nF
  6. Transistors: T1=T2=T3=BC547B
  7. LED (LD1): 5mm red
  8. Trim potentiometers: RV1= 2.5KO, RV2=100O
  9. Push button SW1

Circuit Diagram of Metal Detector:

Metal detector circuit diagram
Metal detector circuit diagram

Test and Adjustments:

  1. Connect a 9V battery to the circuit.
  2. Keep the circuit where there is no metal in the vicinity.
  3. Turn preset RV1 fully clockwise.
  4. Turn RV2 fully anti-clockwise.
  5. Depress the push button and hold it during the final adjustments.
  6. Now turn RV1 anti-clockwise till red LED goes out.
  7. Now turn RV2 clockwise until the red LED weakly lit.
  8. 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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Police Siren Alarm: Electronics Mini Project

Hi friends, in this series of mini projects today we are going to make one simple mini project of police siren alarm using IC 555 (timer IC). This mini project generates a sound like police siren using astable multivibrator circuit of NE555 timer IC. You can make this project as your first or second year engineering mini project. This is one of the simple but useful mini projects and all components used in the circuit are easily available.

Components required

  • Two NE555 timer ICs
  • Resistors and Capacitors as shown in circuit diagram of police siren alarm
  • Speaker (64 ohms, 560mW)
  • 12 V DC power supply

Circuit Diagram

Police Siren Alarm using 555
Police Siren Alarm using 555

Working of Police Siren Alarm Circuit

As discussed earlier this circuit uses two NE555 timer ICs which are connected as an astable multivibrator. This circuit can be operated on the 12V dc power supply (you can also use 9V battery). To generate a siren sound we have used a speaker having specification as 64 ohms and 560 mW.

In this circuit, IC1 is used as slow astable multivibrator which works at 20Hz and having duty cycle as 50%. IC2 is fast astable multivibrator and having high frequency than IC1 nearly equal to 600Hz. These frequencies of IC1 and IC2 depend on values of resistors and capacitors used in the circuit.

Because of two different frequencies of IC555 and output of first is connected to the second it produces sound like a police siren.

See also: Rain detector with alarm – mini project.

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Rain Detector with Alarm Circuit: Electronics Project

Hi friends, today we are going to make a simple mini project which is rain detector with alarm. This mini project generates sound using speaker whenever rain starts. The circuit diagram of this mini project is very simple and you can make this project as your first or second year engineering project for electronics and electrical students.

Components required

  • Resistor: 10K, 330K
  • Transistor: BC548, BC558 (other equivalent transistors can also be used)
  • Speaker
  • 3V DC supply (you can also use two 1.5V normally used cells in series)
  • Probe (it is nothing but a set of two open ended wires)

Circuit diagram

Rain Detector with Alarm circuit
Rain Detector with Alarm circuit

Working Principle of Rain Detector

The working of this rain detector mini project is very simple. In this mini project, we are using a probe placed in a small plastic container. Whenever raining starts water get collected in that plastic container. As water is the conductor of electricity the contact between two open ended wires (probes) takes place and current start flowing towards the base of NPN transistor BC548. Here collector of BC548 NPN transistor is connected to the base of BC558 PNP transistor. Therefore when NPN starts conducting PNP also starts conducting.

Due to conduction of PNP transistor current starts flowing through the speaker and it generates an alarm. As in this mini-project, we have used a resistor and capacitor in series it causes the first transistor to turn on and off continuously till there is rain water present in the plastic container. This on and off period depends on the values of the capacitor, resistor and inductive coil of the speaker. Because of capacitor charging and discharging period it continuous to turn on and off continuously. This on and off condition of the transistor causes to generate a siren-like alarm from the speaker.

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Water Level Indicator Circuit: Electromics Mini Project

Today we are going to make a project which will detect the preset water level and when water is reached to this level it will generate a sound.

Objective:

The objective of Water Level Alarm Circuit is to generate a sound with the help of buzzer when a water level in a tank reached to its preset level (Predefined mark).

Components Required:

Following are the required components for making water level alarm circuit:

  1. IC NE555 (Timer IC)
  2. Resistors: R1 = 1K; R2 = 100K;
  3. Capacitor: C1 = 2.2uF (15V)
  4. Buzzer
  5. 3V DC battery

Circuit Diagram:

Water Level Indicator Alarm Circuit
Water Level Indicator Alarm Circuit

Description of Water Level Indicator

Here is the simple water level alarm circuit using 555 timer IC which will produce an audible sound when the water level reaches to its preset level. This circuit uses 3V DC power supply. Therefore this circuit is quite handy to use.

This circuit of water level alarm is based on the astable multivibrator which is wired around IC1 (NE555). The operating frequency of this astable multivibrator depends upon the values of capacitor C1, resistors R1 and R2 and the resistance across probes at A and B. when there is no water up to the level of probes, because of open circuit astable multivibrator will not produce any oscillations hence the circuit will not produce sound. When the water reaches the level of probes, the circuit will be completed and some current flows through the water. Thus astable multivibrator produces oscillations proportional to the values of C, R1, R2 and the resistance across the probes. Now the buzzer will beep to indicate that the water is reached to its preset level.

Notes

  •  Probes can be made of two insulated copper or aluminum wires.
  •  Preset level means the level that you want to detect the water in the tank.
  •  Place the probes to a preset level, so that it will close the path and generates sound using the buzzer.

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How to Interface Buzzer with Microcontroller Electronics Project

Function

This project shows how to interface a buzzer to the microcontroller. When a push button has pressed a buzzer will on and off 30 times and then stops.

Components

  • AT89C2051 microcontroller
  • Push button switch
  • Buzzer
  • Capacitors: 33pF,33pF,10uF
  • Resistor 8.2KO

Circuit diagram

A circuit diagram for interfacing buzzer to the microcontroller is shown in the figure below. Bit 7 of port 1 is directly connected to a small buzzer. This type of connection is possible only when the current required for the buzzer is less than 20mA. The port output is in current source mode so that the buzzer will turn on when the output is at logic LOW. Bit 0 of port 3 is connected to the push button switch which is held at a logic high by the pull-up resistor.

simple buzzer interface circuit diagram
simple buzzer interface circuit diagram

simple buzzer interface
simple buzzer interface

Program description

The buzzer is initially OFF. When the push button is pressed, the buzzer is turned ON and OFF 30 times, with a one second delay between each output.

Download

Click here to download .C and .HEX file

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