Understanding Long-Range Cordless Burglar Alarm System

Nowadays crime and robbery rates are on the rise. We often see cases of robberies in news or newspapers. In houses, jewelry shops, offices, showrooms there are many valuable items and assets that are also prone to robbery at any time. If anyone out of safety concerns places them in a safe place like lockers, they cannot provide someone to look after them throughout the day. In such cases, the only option remains is the burglar alarm systems; these alarm systems are electronic alarms designed to alert a user from unspecific danger. These alarm systems make use of sensors to ensure security while opening or closing the doors and detecting the motion of the robbers.

In such cases, the only option remains is the burglar alarm systems; these alarm systems are electronic alarms designed to alert a user from unspecific danger. These alarm systems make use of sensors to ensure security while opening or closing the doors and detecting the motion of the robbers.

Burglar alarms are classified into two main types: home burglar alarm or industrial burglar alarm and perimeter intrusion detection.Therefore, this article is intendened to give a brief idea of implementing two types of burglar alarm systems with 8051 microcontroller and 7555 timer.

Automatic Dialing to any Telephone Using I2C Protocol on Detecting Burglary:

The security burglar alarm project is designed  toinform the concerned authorities about an unauthorized access to secure areas like museums, residential houses,  show rooms and banks. As the crime rate is increasing day by day and burglars are becoming smarter by every passing day, the security system for commercial setups likebanks, shops and houses need to be fool proof.

This proposed system makes sure that at any moment if any unauthorized person tries to open the bank locker or any other safety lockers in houses,  a telephone number will be dialed through the telephone line connected to it as shown in the circuit given below.

Circuit Operation:

• The entire burglar alarm system gets power from a  regulated power supply which consists of a transformer, rectifier and voltage regulator.
• An EEROM is interfaced to the microcontroller for storing the contact numbers to which the call is to be made.
• Microcontroller is programmed by using embedded C language  and Keil compiler. If someone tries to entire into the room forcefully, then the microcontroller gets an interrupt through the hidden switch mechanism interfaced to it while programming.
• By using DTMF tone generator with microcontroller and EEROM, the microcontroller automatically dials the number which is stored in the EEROM.
• Relays are used to perform the operation like telephone calls from the telephone line. The 8051 microcontroller fetches the information from the EEROM using I2C protocol and displays the information on  LCD Display.

This type of burglar alarm system is of cord-type, and it is limited for small distances due to usage of cables. This alarm system is discussed here to give a brief introduction of security burglar alarm system. But cordless type of burglar system is highly efficient and reliable than the cord-type.Therefore, a cordless burglar alarm system, which is capable of operating at long distance range is given below.

Long-Range Burglar Alarm System using Laser Torch

Laser torch-based security burglar alarm system normally works in darkness only. This long range photoelectric burglar alarm system works during the day time also to protect and alert you about the burglars in your commercial buildings, banks, big compounds, etc. This burglar-alarm circuit comprises both laser transmitter and receiver sections, which are to be placed on the opposite pillars of the entry gate.

These circuits are implemented with simple and low cost basic electronic components as compared with the above discussed circuit such as timers, transistors, and other miscellaneous components. Whenever anyone tries to interrupt the transmitted laser beam falling on the receiver, the buzzer alarms as an indication to catch the burglars.

The range of this cordless security system using laser torch is around 30 meters, which means both the transmitter and the receiver are placed up to 30 meters apart. The laser torch transmits light up to a distance of 500 meters. The range of the transmitted light can be increased by placing the phototransistor sensor properly. To avoid false triggering by sunlight, the photo transistor sensor is placed in the circuit such that it doesn’t directly face sunlight.

Transmitter Section:

• The transmitter circuit is powered by 3V DC supply. The 7555 timer acts as astable multivibrator , which produces a frequency of 5.25 KHz.
• One end of the laser torch is connected to the emitter of NPN transistor T1, and the other end of the laser torch is connected to the  ground. The timer is connected with a set of components to switch the laser light at certain frequency.
• When the circuit is switched ‘on’ the transistor drives the laser torch so that it produces the light waves corresponding to the frequency.

Receiver Section:

• The entire receiver circuit gets power from 12V DC supply. This receiver section makes use of photo darlington transistor 2N5777 (T2), which is interconnected by a resistor and capacitor for sensing the laser beam transmitted from the laser torch.
• The generated output beam signals from the darlington transistor are given to the two stage amplifier followed by switching circuit.
• When ever the laser beam falls for long period of time on photo Darlington transistor T2, relay RL1 gets un-energized and the buzzer does not sound and LED doesn’t glow.

• If any burglar tries to interrupt the laser beam falling on photo- darlington transistor T2, then npn transistor (T6) stops conducting and drives the NPN transistor T7 into conduction.
• As a result, of this conduction, LED1 glows and the relay RL1 starts energizing and produces the piezo electric buzzer sound, which is determined by the values of the capacitor C10 and resistor R15.
• Meanwhile, the large indication load (230V AC alarm for louder echoes or any other device for temporary indication) also gets activated as it is connected to 230V AC mains supply via normally opened (N/O) contact of the relay RL1.

This is all about the burglar alarm system with cord- type and cordless security systems for short-range and long-range distances to detect the burglars taking place in homes, offices and banks etc. For any technical help or guidance regarding the implementation of these circuits or components selection and its rating, you can contact us by commenting in the comment section given below.

Photo Credits:

• Burglar Alarm System by geekycube