Mobile Laser Security System


At present many high costly commodities are stolen from several houses, Industrial institutes, commercial areas, and from Banks in Bangladesh. The criminals are into the cash room of the banks and then stole a lot of money . It is caused for want of proper security system.

Because of the want of proper security system and insufficient man power. The criminals are achieved their destiny to inter into the securable area of the houses, offices, Banks, and industries.

So, if we can improve our security system by the help of technical knowledge, then all of stolen are closed immediately. For this result damages and losses can be totally reduced from Bangladesh.

This project is aimed at designing and implementation of  an electrical supply controller circuit. .

Origin and Definition of the system

The origin of the word security comes from secure. There are some valuable goods in our society which is limited. Basically we fall in the despair in the absence of authority or occupier of those security less resources. Which system is invented to prevent the wealth losses and stolen security system is called security system.

Types of security system:

  1. Manpower security system.
  2. Laser security system by using cellular technology.
  3. Alarm security system.
  4. CCTV security system, etc

Definition and applications.


Definition: A transformer is a static or stationary piece of apparatus by mean of which electric power in one circuit is transferred into electric power of the same frequency in another circuit . It produces neutrally induced emf according to Faraday,s Law of electromagnetic induction.

Types of transformer:

  1. Current transformer.
  2. Potential transformer.

So, e = M(dI/dt).



Definition: Diode means two electrode device. Di(two) and electrode are joined then make diode. Diode has two connecting terminal or lead. Actually diode is a one-way device when apply forward bias it acts Low resistance and allow to pass current but apply reverse bias then it shows high resistance that insulator and not allow to flow current. Diode is mostly used as rectifiers. That is for converting Alternating current to diode current.


Application of diode:

The main application of semiconductor diodes in modern electronic circuitry are as follows:

A). As Power or Rectifier diode. They convert AC current into DC current for DC power supplies of electronic circuits.

B)    As signal diodes in communication circuits for modulation and demodulation of small signals.

C)     As Zenar diodes in voltage stabilizing circuit.

D)   As a narrator diodes for use in voltage controller tuning circuits as may be found in radio and television receivers.

E)    In logic circuits used in computers. Also we  use(In-4007) diode in the  construction of Mobile laser security system.


Definition: A capacitor is a device that stores energy in an electrostatic field. A capacitor can draw energy relatively slowly from battery and it than can release the energy rapidly. Generally a capacitor consists two conducting plates which are totally isolated from their environment and exist in the vacuum.

Types of capacitor:

  1. Cylindrical capacitor.
  2. Parallel Plate capacitor.


Capacitance: The ability to store charge in a capacitor is called capacitance of that capacitor. When we charge a capacitor, we find the charge q that appears on the capacitor plates is always directly proportional to the potential difference between the plates

So q      v.

=> q = c   v.

Circuit diagram of capacitor


We used a full wave Bridge Rectifier in our Project. It is the most frequently used circuit for electronic DC power supplies. It requires four diodes (IN-4007).

circuit diagram of Full wave rectifier

Working Procedure of a Rectifier:

During the positive input half cycle, terminal M of the secondary is positive and N is negative so diodes D1 & D3 becomes forward biased(ON) whereas D2 & D4 reverse biased(OFF). Hence, current flows along MEABCFN producing a drop across RL. During the negative input half-cycle, secondary terminal N becomes positive and M negative. Now D2&D3 are forward-biased. Circuit current flows along NFABCEM  as shown in figure-2.5. Hence. We find

Bridge rectifiers

wave shape

that current keeps flowing through load Resistance RL in the same direction AB during both half cycles of the AC input supply. Consequently point A of the Rectifier always acts as an anode an point C as cathode. The output voltage across RL is as shown in figure- Its frequency is twice that of the supply frequency.



The main function of a filter circuit is to minimize the ripple content in the rectifier. We know the output of rectifiers contain harmonics. Filters can be used to smooth out the DC output voltage of the rectifier and these are known as DC filters. The DC filters are usually of L,C, and LC type, as shown in fig:2.8 . Due toe rectification action, the output current of the rectifier contains harmonics also and an AC filter is used to filter out some of the harmonics from the supply system. The AC filter is normally of LC type.

FilterNormally the filter design requires determining The magnitudes and frequencies of the harmonics.


Light emitting diode is a forward biased P-N junction which is  emitting the visible light when energized. Two colure of the emitted light depends of the type of material used as giver below:


A)    Ga, As—————————-infrared radiation(invisible).

B)    Gap——————————-Red or green light.

C)    Ga,As,P—————————Red or yellow( amber light).

LEDs emit no light when reverse biased. In fact, operating LEDs in reverse direction will quickly destroy them. LEDs are used as input power required, output power wave length of emitted , efficiency , turn on and turn off time, light intensity and brightness etc. We are used LED as a input power indicator.


LDR means light dependent Resistor. It is made by a single layer of photosensitive martial. It is also called a photo resistor of photo conductor, photo conductive cell.

Principle: It is based on the principle that the resistance of certain semiconductor materials decreases when they are exposed to radiations. In other words. Such materials nave high dark resistance and low irradiated resistance.

Construction: The four materials normally employed in photo conductive cells are cadmium sulphide(cds), cadmium selienide(edse), lead sulphide and thalamium sulphide(tis). The simplified two dimensional model of the commonly used cds cell is shown in fig: 2.10       and its circuit symbol in fig: 3.10


As shown , The two electrodes are extended in  an inter digital pattern in order to increase the contact area with the sensitive material. In this way, It is possible to obtain a large ratio of dark to light resistance.

Working procedure:

The illumination characteristic of the cell is that when not illuminated the cell has a resistance of more than 100 kilo ohm. It is known as its dark resistance. When illuminated the resistance falls to only a few 100 ohm. We use the LDT is as on-off switch.

Relay circuit:

Definition: Relay is a means of which an electric circuit can be controlled (opened or closed) by the change in the same circuit or other circuit. An electro-mechanical relay, has one or more coils, movable elements. Contact system, etc. The operation of such relay depends on whether the operating torque/force is greater than the restraining torque/force.


Type of Relays:

  1. Attracted Armature type Relay.
  2. Balance Beam Relay.
  3. Induction Disk Relay.
  4. Induction cup Relay.
  5. Moving coil Relay and Moving iron Relay.
  6. Gas operated Relay.
  7. Rectifier Relay.
  8. Static Relay.

It is a electronic device which is energized by AC of DC voltage. It has 2 way contact .

A)      Normally Open(NO).

B)      Normally close(NC).

We used in security system is 12V,6A. Relay circuit which has operate 12V DC source.

Laser Box:

It is a device which makes laser beams or light. We use this box for the adjust laser light.

Laser box

Mobile set:

It is a electronic device that operate DC power. Mobile switch(call) is operate by 2 wire short from our main circuit (laser unit).

Mobile set

Application :

If any cause circuit the laser in the main time two wire of mobile is short circuited and calling. This system is very interesting because. It can record the sound of video or catch the photo in that place man. It can send massage with Address.

Working procedure at a glance

Principle of the total system:

The process of laser security system from laser box. At first we should keep the system with continuous power supply. Because, the laser security system will be disable without continuous power supply. For this precondition, also we have a substitute way. We can use battery or DC source for the precondition.

If we through the laser ray continuously on the Light depended resistor (LDR). LDR have two types of characteristics.

  1. When we through the laser ray continuously LDR acts as conductor.
  2. If anybody or any caused is happened i.e. in absence of laser ray LDR acts as a switch or resistor.

For the reason of inter into the securable place laser ray will intercept and laser ray will be discontinuous.  So the discontinuation of ray operates the LDT as a switch.

Physical outlook of the laser security system

But LDR is connected with Relay ax shown in fig: 3.2. Then the mechanism of Relay adjusted Mobile set send a call to another Mobile set which is carried by authority. At last effective steps can be taken due to wealth losses or limited resource damages.

Block Diagram:

Block diagram

Synchronization of the activities

We are explained about the source type in the previous chapter. We use 220v Ac source to completion our project as shown in the figure: 3.3.

  1. AC Power supply: We apply AC 220V for Transformer input.

2.  For step down 220V AC to 12V AC purpose, a transformer-(220V-12V)

     is used.

3.  And then we are placed a bridge rectifier in the printed circuit board to convert 12v-AC to 12v-DC.

4. Also we are placed a capacitor on the rectifier output as shown in fig:  to reduce ripple factor and harmonics. For producing pure DC.

 5. Then we connect a LDR between rectifier output and Relay circuit input.

Circuit diagram:

Circuit diagram6. We connect a mobile set by connection of send button to the NO and NC port.

7. At last we adjust a laser box as if it is straighter of the LDR input.

To operate the laser security system this synchronization of activities have to maintained.


Now we may added that Our project Laser security system by using cellular technology is an interesting topic which has extended our interest about security system.

Mobile laser security system is very important system for security and safety. Always plug the input from the AC 220v power source. Avoided any short circuit, Polarity must be detected than connected all the connection.

To complete our project on the laser security system by using cellular technology,  we are using only general ringing function of two mobile set.

We hope that, our thinking domain will extend successfully in future.


1. We propose that, in future the laser security system using cellular technology can be increased significantly for security purpose.

2.  More advanced function of video, audio can be added to the system in future by using ultramodern electronic devices.

3. To complete our project on the laser security system using cellular technology, we are using only simple ringing function of two mobile set.

 4.  But our proposal will extend successfully in future.

Security System