Security & Saftey

Electronic Eye Controlled Security System

We’ll see a simple Home Security application named Electronic Eye Controlled Security System in this project, which uses LDR as the main sensor and a few other components.


  • Introduction
  • Security System with Electronic Eye Control Principle of a Circuit
  • Electronic Eye Controlled Security System Circuit Diagram
  • Components of a Circuit
  • Circuit Simulation Video for an Electronic Eye Controlled Security System
  • Circuit Design for an Electronic Eye Controlled Security System
  • Power Supply Circuit Design
  • Logic Circuit Design
  • What is the Electronic Eye Controlled Security System Circuit and How Does It Work?
  • Applications for Electronic Eye Controlled Security Systems


An electronic eye, often referred to as a ‘magic eye,’ serves as a surveillance tool that keeps a vigilant watch over your home, particularly in the context of emerging automation technologies. Imagine a scenario where a doorbell automatically signals when someone approaches your residence. This not only enhances convenience but also bolsters the security of your home by detecting any unauthorized attempts at entry.

Electronic Eye Controlled Security System

The electronic eye circuit is presented in this project. Before diving into the intricacies of this circuit, familiarise yourself with the Light Activated Switch Circuit with LDR.

Electronic Eye Controlled Security System Circuit Principle

The core concept of this circuit is to activate the doorbell when someone nears the entrance. An LDR (Light Dependent Resistor) serves as the sensor to detect human presence. The status of a person is determined by the LDR’s light level. When an object is detected at the door, causing the LDR to darken, the buzzer is triggered, and the LED illuminates.

Circuit Diagram of Electronic Eye Controlled Security System

NOTE: Resistor R4 is 220Ω.

Circuit Components

  • 7805 Regulator
  • Resistors – 220Ω x 2, 1KΩ x 2, 100KΩ
  • 1N4007 PN Diode
  • Capacitors – 1µF, 10µF
  • Transistors – BC 547 x 2
  • Light Dependent Resistor (LDR)
  • Buzzer
  • LED
  • Bread board
  • Connecting wires
  • 9V battery

Electronic Eye Controlled Security System Circuit Simulation Video

Electronic Eye Controlled Security System Circuit Design

This circuit can be divided into two main components: the power supply and the logic circuit. The power supply section takes a 9V battery source and converts it to 5V. Meanwhile, the logic circuit comes into play when the LDR detects a shadow, activating both the buzzer and an LED.

Design of Power Supply Circuit

The power supply circuit consists of a battery, a diode, a regulator, and capacitors. Initially, a 9V battery provides power to the circuit. Specifically, a 1N4007 series P-N junction diode is employed in a forward bias configuration in this setup.

In this circuit, the primary purpose of the diode is to act as a protective measure against reverse polarity, preventing any damage if the battery is accidentally connected with the wrong orientation. This is achieved by configuring the P-N junction diode in a forward bias mode, which allows current to flow in only one direction, thus safeguarding the circuit. Across the diode, there is a voltage drop of 0.7V.

To regulate the circuit’s output voltage, a regulator is employed, specifically the 7805 IC. The “78” in the name signifies the series, while “05” represents the output voltage, which is set to 5 volts in this case. In addition to the regulator, two capacitors are used both before and after it. These capacitors serve to eliminate any voltage fluctuations or ripples, ensuring a stable voltage output from the regulator. This consistent voltage is then supplied to the logic circuit.

Design of Logic Circuit

The logic circuit comprises components such as a Light Dependent Resistor (LDR), transistors, a buzzer, an LED, and several passive elements. In a voltage divider setup, a 100K resistor is placed in series with the LDR. When the LDR is placed in darkness, its resistance is measured in mega ohms, but when exposed to light, this resistance gradually decreases. Consequently, the resistances in the series circuit vary.

When the LDR is unexposed to light, it exhibits high resistance, resulting in a logic high output. Conversely, when the LDR is exposed to light, its resistance decreases, leading to a logic low voltage at the output.

The output of the voltage divider is directed to a transistor, which inverts the input from the LDR. The second transistor drives the buzzer, with the diode serving as a safety precaution.

In this project, a 5V magnetic buzzer with two output pins is used. One pin is connected to the power supply, while the Collector of the second transistor is connected to the other pin. The LED is solely used as a visual indicator. When the output of the first transistor goes high, the buzzer starts ringing, and the LED also illuminates.

How to Operate the Electronic Eye Controlled Security System Circuit?

  • On a bread board, connect the circuit as shown in the circuit diagram.
  • Now, using a battery, connect the 9V supply voltage.
  • In the light, place the Light Dependent Resistor. The buzzer does not emit any sound, as you can see.
  • When the LDR is placed in the dark, the buzzer begins to sound. In addition, the buzzer’s LED will be switched on.
  • As the intensity of the light landing on the LDR grows, so does the sound made by the buzzer.

Electronic Eye Controlled Security System Applications

  • This is a component that can be utilised in doorbell circuits.
  • Garage door opener circuits can benefit from this.
  • Security applications can benefit from the usage of an electronic eye.

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