Border Security System Using Encrypted LASER
Volumn 3

Border Security System Using Encrypted LASER

Mr.Nikhilsingh Chauhan    

Final Year Student

Department of E&T, PCE, Nagpur 


Ms.Pooja shivarkar

Final Year Student

Department of E&T, PCE, Nagpur 

Mr Vaibhav choudhary   

Final Year Student

Department of E&T, PCE, Nagpur 

Ms. Dhanashree khelkar

Final Year Student

Department of E&T, PCE, Nagpur

Mr. Sanghpal Ghagargunde

Final Year Student

Department of E&T, PCE, Nagpur

Mr.Aditya khokale

Final Year Student

Department of E&T, PCE, Nagpur

Professor Ms A.H Charkhawala

Department of E&T, PCE, Nagpur


This Paper is all about a new security device. After Simulation in the platform of Eagle it has been seen that it is very much efficient, reliable, easily maintainable, tiny in size. Where the other devices in the market are not efficient, various hazards are the in maintenance.  So interlocution can be made that it is very indispensable for a high security place where nobody are allow to enter for example Indo-Pak border.

Index Terms— Photo-transistor, LASER, NE555 Timers.  


This Border Security System is very useful in high command security place. In a high secured place where nobody is allowed to enter we can install it. These are easy to install and work therefore it can be set up at Borders with less difficulty and also at residential areas. In indoor systems can utilize the normal power outlets and jacks making them inconspicuous. At Borders these can be easily be hidden behind the bushes or plants without causing any damage. They consume less power when compared to the concertina fencing system as the whole, which is expensive. These laser systems can be installed in homes either by self or by hiring a technical person. By technological innovations cost of the installation process with working terms has been cut to a large extent. So, making laser systems one among affordable security system options can be verysafe. It has ability to work continuously; it does not detect only human beings but also  animals or any other movable object. Now we can use this system in a wide range of area. Here if someone tries to torch a fake laser at the photo-transistor by efficient programming we can distinguish between original Laser and fake Laser.


In this system we can mount number of laser in transmitter according to the level of security needed in the particular area, and same number of photo-transistor at the receiver pole. We will be transmitting data in bits from transmitter using ASK(amplitude shift keying) and same data should be received at the photo-transistors in the receiver area. Particular delays are added in between the transmission of bits so that if a person or movable object tries to pass through the laser , then the system can be able to detect. These system is made smart enough for ignoring alarm in case of rain , cause in outdoor system rain can cause false alarm.


3.1 Photo-transistor :-

Phototransistors are either tri-terminal (emitter, base and collector) or bi-terminal (emitter and collector) semiconductor devices which have a light-sensitive base region. Although all transistors exhibit light-sensitive nature, these are specially designed and optimized for photo applications. These are made of diffusion or ion-implantation and have much larger collector and base regions in comparison with the ordinary transistors. These devices can be either homojunction structured or heterojunction structured, as shown by Figure 1a and 1b, respectively. In the case of homojunction phototransistors, the entire device will be made of a single material-type; either silicon or germanium. However to increase their efficiency, the phototransistors can be made of non-identical materials (Group III-V materials like GaAs) on either side of the pn junction leading to heterojunction devices. Nevertheless, homojunction devices are more often used in comparison with the hetero junction devices as they are economical.

Generally, in the case of phototransistor circuits, the collector terminal will be connected to the supply voltage and the output is obtained at the emitter terminal while the base terminal, if present, will be left unconnected. Under this condition, if light is made to fall on the base region of the phototransistor, then it results in the generation of electron-hole pairs which give rise to base current, nothing but the photo-current, under the influence of applied electric field. This further results in the flow of emitter current through the device, resulting in the process of amplification. This is because, here, the magnitude of the photo-current developed will be proportional to the luminance and will be amplified by the gain of the transistor leading to a larger collector current.

The output of the phototransistor depends on varies factors like:-

  • Wavelength of the incident light
  • Area of the light-exposed collector-base junction
  • DC current gain of the transistor.

3.2 LASER:-

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser” originated as an acronym for “light amplification by stimulated emission of radiation” A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers.

3.2.1 Design:-

A laser consists of a gain medium, a mechanism to energize it, and something to provide optical feedback.[8] The gain medium is a material with properties that allow it to amplify light by way of stimulated emission. Light of a specific wavelength that passes through the gain medium is amplified (increases in power).

For the gain medium to amplify light, it needs to be supplied with energy in a process called pumping. The energy is typically supplied as an electric current or as light at a different wavelength. Pump light may be provided by a flash lamp or by another laser.

The most common type of laser uses feedback from an optical cavity—a pair of mirrors on either end of the gain medium. Light bounces back and forth between the mirrors, passing through the gain medium and being amplified each time. Typically one of the two mirrors, the output coupler, is partially transparent. Some of the light escapes through this mirror. Depending on the design of the cavity (whether the mirrors are flat or curved), the light coming out of the laser may spread out or form a narrow beam. In analogy to electronic oscillators, this device is sometimes called a laser oscillator.

3.2.2 Simulated emission:-

In the classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals. Thus, electrons are found in specific energy levels of an atom, two of which are shown below:

When an electron absorbs energy either from light (photons) or heat (phonons), it receives that incident quantum of energy. But transitions are only allowed in between discrete energy levels such as the two shown above. This leads to emission lines and absorption lines.

When an electron is excited from a lower to a higher energy level, it will not stay that way forever. An electron in an excited state may decay to a lower energy state which is not occupied, according to a particular time constant characterizing that transition. When such an electron decays without external influence, emitting a photon, that is called “spontaneous emission”. The phase associated with the photon that is emitted is random. A material with many atoms in such an excited state may thus result in radiation which is very spectrally limited (centered around one wavelength of light), but the individual photons would have no common phase relationship and would emanate in random directions. This is the mechanism of fluorescence and thermal emission.

An external electromagnetic field at a frequency associated with a transition can affect the quantum mechanical state of the atom. As the electron in the atom makes a transition between two stationary states (neither of which shows a dipole field), it enters a transition state which does have a dipole field, and which acts like a small electric dipole, and this dipole oscillates at a characteristic frequency. In response to the external electric field at this frequency, the probability of the atom entering this transition state is greatly increased. Thus, the rate of transitions between two stationary states is enhanced beyond that due to spontaneous emission. Such a transition to the higher state is called absorption, and it destroys an incident photon (the photon’s energy goes into powering the increased energy of the higher state). A transition from the higher to a lower energy state, however, produces an additional photon; this is the process of stimulated emission.

3.3.3 Gain medium:-

The gain medium is put into an excited state by an external source of energy. In most lasers this medium consists of a population of atoms which have been excited into such a state by means of an outside light source, or an electrical field which supplies energy for atoms to absorb and be transformed into their excited states.

The gain medium of a laser is normally a material of controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission described above. This material can be of any state: gas, liquid, solid, or plasma. The gain medium absorbs pump energy, which raises some electrons into higher-energy (“excited”) quantum states. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated.

3.3 NE 555 Timer:-

IC 555 timer is a well-known component in the electronic circles but what is not known to most of the people is the internal circuitry of the IC and the function of various pins present there in the IC. Let me tell you a fact about why 555 timer is called so, the timer got its name from the three 5 kilo-ohm resistor in series employed in the internal circuit of the IC.IC 555 timer is a one of the most widely used IC in electronics and is used in various electronic circuits for its robust and stable properties. It works as square-wave form generator with duty cycle varying from 50% to 100%, Oscillator and can also provide time delay in circuits. The 555 timer got its name from the three 5k ohm resistor connected in a voltage-divider pattern which is shown in the figure below. A simplified diagram of the internal circuit is given below for better understanding as the full internal circuit consists of over more than 16 resistors, 20 transistors, 2 diodes, a flip-flop and many other circuit components.The 555 timer comes as 8 pin DIP (Dual In-line Package) device. There is also a 556 dual version of 555 timer which consists of two complete 555 timers in 14 DIP and a 558 quadruple timer which is consisting of four 555 timer in one IC and is available as a 16 pin DIP in the market   

Fig3.3 555 Pin configuration.
Fig3.3 schematics of 555

4. Constitution of Border Security system:-

This system constitute of transmitter pole, receiver pole, Base station.

4.1 Transmitter Pole:-

A pole would be mounted on transmitter side, which constitute of number of laser according to intensity of security needed in that particular area.

In transmitter side a circuit is mounted having a micro-controller in which proper coding is done so that the different data is transmitted through different laser using ASK modulaton. This data is transmitted in encrypted format . so that the transmitting data should not be identified by intruders.

4.2 Receiver Pole:-

A pole would be mounted on receiver side, which constitute of same number of phototransistors as laser in transmitter side. In receiver side a circuit is mounted having a micro-controller which is used to determine the pattern of data falling on the phototransistor through laser. Here the data is decrypted to original format. If there is any change in data falling on the transistor then we get to know about it.

Fig.Transmitter circuit.

4.3 Base Station:-

If there is any change in data received at the receiver through laser then the receiver circuit sends a signal to the base station that something has caused obstruction in between the laser and phototransistor and sends signal to turn on the alarm.

5. Types of error detection through this system:-

  1. If someone tries to point false laser at the phototransistor.
  2. If some movable object tries to pass through the laser.
  3. Ignores rain because of proper delay coded in the code.

6. Results:-

 After trying various detectors at receiver we got following results:-

6.1 LDR at receiver

Fig. waveform of LDR at the receiver

6.2 Photodiode at receiver:-

Fig. waveform of Photo-diode at receiver

6.3 Photo-transistor at receiver:-

Fig. waveform of Photo-transistor at receiver

By studying this results we can see phototransistor is best which should get mount at receiver Pole.

7. Conclusion:-

As evident in above this paper suggest an idea to replace the traditional fencing system for security with a more technologically effective system. This paper provides following solutions:-

  1. Automatic monitoring for security breach.
  2. Low cost fencing system.
  3. Less number of manpower


  • Adel S. Sedra & Kenneth C. Smith.,”Microelectronics Circuit 6th edition”
  • Kogelnik, H., and Li, T., "Laser beams and resonators," Appl. Opt., vol. 5, Oct. 1966.
  • Gould, R. Gordon (1959). "The LASER, Light Amplification by Stimulated Emission of Radiation".
  • David O. Caplan, “Laser communication transmitter and receiver design”, J. Opt. Fiber. Commun. (2007), Rep.4, 225–362.


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