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Electronic Eye Security System

The electronic eye security systems available in the market are expensive, and programming is very difficult for a microcontroller based system. Here is a simple and inexpensive electronic eye security system that you can build easily.

Main objective of this project is to design a security system based on a photo-sensing arrangement. It uses dual comparator LM393 that is widely used in many commercial applications. Here, it is used to sense the input signal through a light-dependent resistor (LDR). Comparator output drives a buzzer and a relay.

Fig. 1: Author’s prototype

This concept is very useful as a burglar deterrent in places like banks, malls, jewellery stores, hotels and homes. Fig. 1 shows the author’s prototype.

Circuit and working of electronic eye security system

Circuit diagram for the electronic eye security system is shown in Fig. 2. It is built around 12V-0-12V, 750mA secondary transformer (X1), 1N4007 rectifier diodes (D1 through D3), LDR (LDR1), filter capacitors C1 and C2, 5V voltage regulator 7805 (IC1), dual comparator LM393 (IC2), 12V multi-tone high-gain buzzer (PZ1), transistor TIP122 (T1) for driving PZ1, transistor BC547 (T2) for driving 12V, 1C/O relay for controlling an electrical appliance or bulb (B1), and 10-kilo-ohm potmeter VR1.

Circuit diagram of the electronic eye security system
Fig. 2: Circuit diagram of the electronic eye security system

When light falls on LDR1, its resistance drastically decreases, which leads to triggering an alarm to alert the user.

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This system is suitable for securing cash boxes and lockers. The circuit is placed inside the cash box or locker in such a way that, when the burglar opens it and uses a torch light to find the valuables, light falls on LDR1, which acts as an electronic eye.

Signal output from LDR1 is fed to IC2. Output from IC2 activates the alarm when light falls on LDR1 during a burglary attempt. At the same time, bulb B1 glows as a visual alert to thwart the burglary attempt.

Case 1. If reference voltage at pin 3 of IC2 is less than sensor voltage at pin 2 of IC2, output goes low automatically. This indicates that no light is falling on LDR1. Low output of IC2 is fed to T1 and T2. As a result, both are in cut-off state and so no current flows through the buzzer, keeping it in silence mode. Similarly, no current flows in the relay, and so B1 does not glow.

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Case 2. If reference voltage at pin 3 of IC2 is greater than sensor voltage at pin 2 of IC2, output goes high automatically. This indicates that light is falling on LDR1. High output of IC2 is fed to T1 and T2. As a result, both transistors are in on (active) state. Current flows through the buzzer and relay. The buzzer produces a loud alarm to alert you or people around you and, at the same time, B1 glows as the circuit completes through relay RL1’s contacts.

parts list of electronic eye security system

Construction and testing

An actual-size, single-side PCB for the electronic security system is shown in Fig. 3 and its component layout in Fig. 4. After assembling the circuit on the PCB, enclose it in a suitable plastic box.

Actual-size PCB layout of the electronic security system
Fig. 3: Actual-size PCB layout of the electronic security system
Component layout of electronic security system PCB
Fig. 4: Component layout of the PCB

Download PCB and Component layout PDFs: click here

Pamarthi Kanakaraja is assistant professor in Usha Rama College of Engineering and Technology, Andhra Pradesh


    • Yes, the circuit is perfectly working. The advantage is that it is an inexpensive security device working something like a surveillance system. Whenever light falls on the sensor (LDR1) in the circuit, an alarm sounds to alert the owner. This circuit costs below Rs 1000.

  1. Bridge rectifier produces efficient output and ripple or noise free voltage but for that you need four diodes instead of two diodes. Here, the circuit will work even if it is not a ripple free or pure DC output. You can use bridge rectifier here also, in that case you don’t need a centre-tapped transformer.


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