CORDLESS SECURITY SYSTEM
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Joined: Jul 2010
16-07-2010, 02:32 PM
CORDLESS SECURITY SYSTEM
MINI PROJECT REPORT
Submitted in partial fulfillment of the requirements for the award of the degree of B.TECH IN APPLIED ELECTRONICS & INSTRUMENTATION from THE UNIVERSITY OF KERALA
SABARINATH P M
RENJITH E R
NIEL V JOSEPH
S6 Applied Electronics And Instrumentation,
COLLEGE OF ENGINEERING TRIVANDRUM
front sheet3.doc (Size: 1.33 MB / Downloads: 225)
Nowadays more effort and work is done to make security system defect less, reliable and intelligent. Every loophole is identified and cleared. ËœCORDLESS SECURITY SYSTEM Ëœis such an effort which is a highly improved version of present security system.
With the breach of security, the owner is alarmed through an RF transmitter receiver system. Simultaneously some preventive and defensive action is triggered .
The project and implimentation implements the security system in a car .Any theft attempt cause an alarm to sound in the remote held with the owner who maybe at a distance from the car. Moreover the system makes the engine temporarily nonfunctioning. An alarm also triggered in the vehicle.
But the key striking feature is that it is highly economical. It is compact in size, consumes very little power and user friendly.
Low cost and high reliability
Consume very little power
Range of up to 75 meters.
Security breach has become a serious problem today. So it is essential to update ations the present system. Cordless security system is a right choice. It can be implemented in a home, museum or even a bank for it provides great reliability. Unlike most of the present system it has much more key features like alarming the owner who maynot be near the site and also ensures the prevention of the theft in any case.Can be installed in the locker rooms of banks as it is highly reliable.Its highly viable as it can be modified with ease according to place where it is implemented.If in case of security of car it switches off the battery temporirly,in case of home system it is modified to alert the neighbour and police.Thus its applications are wide and practical.
Features and Application
Block Diagram and Description
Circuit description and working
Assembly and Testing
TRIGGERING AND TRANSMISSION:
The initial part of the security system consists of three parts.
SCR SWITCH:Any theft attempt triggers the scr switch to fire.This triggers corresponding relays. First one is a simple scr switch from the door. When door opens it will open and when door is closed it is also closed. Scr switch which is normally in off state. When someone opens the door scr circuit is triggered.
RELAY NETWORK: Scr triggering causes three relays to on state.One of them is coupled to the encoder circuit for transmission.The other one cuts-off the battery of the car temporarily.Final relay in the initial section causes an alarm to sound .
For transmission an RF transmitter module is used .The module requires an encoder HT12E which is shown in the block diagram.The encoder is required to convert parallel data to serial before it is given to the transmitter .The address pins are also specified.Transmitter uses a frequency of 434Mhz and transmits digital data.An antenna is used to increase the range of transmission.Range of upto 75 meters is practically obtained.
RECEIVER AND RESPONSE SYSTEM:
RECEIVER AND DECODER:The receiver data pin receives the digital data transmitted and this serial data is decoded by HT12D to obtain the parallel data out.Here only one of the data pin of the decoder output is used.This is high in case of any theft attempt and it sounds an alarm . Within a range upto 50 meters the owner is alerted.
CIRCUIT DISCRIPTION AND WORKING
Here is an easy-to-build car anti-theft guard. The circuit, shown in Fig. 1, is simple and easy to understand.
When key-operated switch S2 of the car is turned on, 12V DC supply from the car battery is extended to the entire circuit through polarity-guard diode D5. Blinking LED1 flashes to indicate that the guard circuit is enabled. It works off 12V power supply along with current-limiting resistor R4 in series.
When the car door is closed, door switch S1 is in Ëœonâ„¢ position and 12V power supply is available across resistor R1, which prevents transistor T1 from conducting. In this position, antitheft guard circuit is in sleep mode.
When someone opens the car door, switch S1 becomes Ëœoffâ„¢ as shown in Fig.2. As a result, transistor T1 conducts to fire relay â€œdriver SCR1 (BT169) after a short delay introduced by capacitor C1. Electromagnetic relay RL1 energizes and its N/O contact connects the power supply to piezobuzzer PZ1, which starts sounding to indicate that someone is trying to steal your car. To reset the circuit, turn off switch S2 using car key. This will cutoff the power supply to the circuit and stop the buzzer sound.
Connect switch S1 to the car door and keep piezobuzzer PZ1 at an appropriate place in the car.
But this sound will not be sufficient , when the owner is inside a building like a shopping complex or somewhere away from the car. For this we incorporated a Transmitter-Receiver circuit. The data sent from the car can be received by a receiver in the hand.
There is a relay2(RLA2) which grounds the input terminal (10) of the encoder(HT12E) to ground. ie, the input of the encoder is logically 0. This data is sent through the transmitter. When the receiver receives and decodes it with the decoder(HT12D) due to logic 0 output through the pin10 the piezobuzzer(PZ2) will not make any sound. When someone opens the car, the switch s1 is opened and the third relay will energized due to the activation of the scr circuit. Now the connection with ground is disconnected. So the input terminal of encoder is logically high. This data is transmitted . At the receiver this will make high output & hence the piezobuzzer (PZ2) starts to make sound. This will continue even when the door of car is closed. This sound will stop only when we switch of the receiver or switch when switch s2 is made off.
Also there is an extra security that when someone opens the car, the relay will energize and the third relay (RLA3) will break the ignition circuit - automatically immobilizing the vehicle. When the circuit is switched on again the relay will not energize; and the vehicle's ignition circuit will remain broken. You must press S2 to energize the relay. It then de-energizes the first relay (RLA1); while the third relay (RLA3) energizes and completes the connection to the ignition circuit.
The design of car immobilizer has a number of advantages. It requires only one extra relay(RLA3). It operates automatically when switch s2 for the transmitter circuit is turned on - so there's no need to remember to activate it separately. To de-activate it you'll need to have the ignition key and you'll need to know the whereabouts of the push-switch. S2 only requires a single wire because its return is through the chassis. It carries no load other than the current required by the relay-coil. So almost any small "momentary-action, push-to-make" switch will do. For extra security S2 could be key-operated.
_ Operating voltage _ 2.4V~5V for the HT12A
_ 2.4V~12V for the HT12E _ Low power and high noise immunity CMOS technology
_ Low standby current: 0.1_A (typ.) at VDD=5V _ HT12A with a 38kHz carrier for infrared transmission medium
_ Minimum transmission word _ Four words for the HT12E
_ Built-in oscillator needs only 5% resistor _ Data code has positive polarity
_ Minimal external components _ HT12A/E: 18-pin DIP/20-pin SOP package
_ Burglar alarm system _ Smoke and fire alarm system
_ Garage door controllers _ Car door controllers
_ Car alarm system _ Security system
_ Cordless telephones _ Other remote control systems
The 212 encoders are a series of CMOS LSIs for remote control system applications. They are capable of encoding information which consists of N address bits and 12_N data bits. Each address/data input can be set to one of the two logic states. The programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal. The capability to select a TE trigger on the HT12E or a DATA trigger on the HT12A further enhances the application flexibility of the 212 series of encoders.
The 212 series of encoders begin a 4-word transmission cycle upon receipt of a transmission enable
(TE for the HT12E active low). This cycle will repeat itself as long as the transmission enable (TE or D8~D11) is held low. Once the transmission enable returns high the encoder output completes its final cycle and then stops as shown below.
If L/MB=1 the device is in the latch mode (for use with the latch type of data decoders). When the transmission
enable is removed during a transmission, the DOUT pin outputs a complete word and then
stops. On the other hand, if L/MB=0 the device is in the momentary mode (for use with the momentary
type of data decoders). When the transmission enable is removed during a transmission, the DOUT
outputs a complete word and then adds 7 words all with the _1_ data code.
An information word consists of 4 periods as illustrated below.
COMPOSITION OF INFORMATION
_ Operating voltage: 2.4V~12V _ Low power and high noise immunity CMOS technology
_ Low standby current _ Capable of decoding 12 bits of information
_ Binary address setting _ Received codes are checked 3 times
_ Address/Data number combination _ HT12D: 8 address bits and 4 data bits
_ Built-in oscillator needs only 5% resistor _ Valid transmission indicator
_ Easy interface with an RF or an infrared transmission medium
_ Minimal external components _ Pair with Holtek_s 212 series of encoders
_ 18-pin DIP, 20-pin SOP package
_ Burglar alarm system _ Smoke and fire alarm system
_ Garage door controllers _ Car door controllers
_ Car alarm system
_ Security system _ Cordless telephones
_ Other remote control system
The 212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holtek_s 212 series of encoders (refer to the encoder/decoder cross reference table). For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen. The decoders receive serial addresses and data from a programmed 212 series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. They compare the serial input data three times continuously with their local addresses. If no error or unmatched codes are found, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission. The 212 series of decoders are capable of decoding informations that consist of N bits of address and 12_N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address information.
FABRICATION OF PCB
The printed circuit board(PCB) provides the electrical interconnections various components and as well as provides mechanical support to the components.The components are soldered to the PCB.The quality of soldering directly affects the reliability of the circuit.The procedure for fabricating the PCB for any general project and implimentation is described below.
Â¢ PCB MAKING
The making of PCB essentially involves two steps.
2.Fabricating PCB from the drawing.
Â¢ PCB Drawing
Making of PCB drawing involves placement of components , locating holes ,optimum area each componenet should occupy, shape and size of pads for the componenets , track size and spacing and prevention of overcrowding of components at a particular area. With these details the sketch of the PCB is made.
Â¢ PCB FABRICATION
The fabrication of the PCB starts by transferring the PCB drawing onto a copper clad sheet. For a small number of PCBs a direct photographic transfer of the PCB drawing from a negative image of the drawing to a photo sensitised copper clad sheet is carried out. The copper from the unexposed area is later etched away.
For large quantity production, screen printing method is used to transfer the PCB drawing image to the copper clad sheet. For etching the copper clad sheet 20-30grms of ferric chloride in 75ml of water heated to about 60degree celsius may be used . The copper clad sheet is placed in the solution with its copper side upwards in a plastic tray. Stirring the solution helps in speedy etching. The dissolution of unwanted copper would take about 45min. If etching takes longer, the solution may be heated again and the process is repeated. The paint on the pattern can be removed by rubbing with a rag soaked in thinner, turpentine or acetone. The PCB can then be washed and dried. The pads are drilled with proper drill sizes of 0.9mm,1mm,3mm etc for the leads and mounting holes
ASSEMBLY AND TESTING
Assembly consists of soldering of components and wires on to the PCB and mechanical fitting of wired PCB and other assemblies. Testing is carried out even at design phase itself in breadboard level to verify the design, so that little or no circuit changes are required after designing the PCB.
Before soldering, all the discrete components are tested. The leads of the components are cleaned with a fine abrasive paper. The PCB also thoroughly cleaned by scratching the areas to be soldered. The leads of the components are bend properly, inserted into the holes and placed correctly. A small quantity of flux is applied to the component leads and pads to remove the oxide coating. The leads are soldered with good quality solder with sufficient heat from the soldering iron. Excess heat will result in improper soldering and may damage the component.
All the joints are checked after the soldering.
After soldering the components on to the PCB, the board is thoroughly cleaned for any residual flux and wire leads. All the components are checked for their value and for the proper orientation if applicable. Before ICs are inserted into the sockets, power applied to the board and voltages are measured at the IC power point. Power is switched off before the ICs are inserted.
1. Literature survey
2. Design of circuit
3. Testing of the circuit on breadboard
4. Modifying the circuit
5. Making pcb layout
6. Pcb fabrication
8. Results obtained
Our product is suitable for bank, home and other security threat areas. Being cost effective and simple its application will be wide. Power consumption is very low which is a key feature. Many modifications can be easily implemented making it user friendly.
The full report and circuit diagram is also available here:
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30-06-2012, 10:50 AM
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