Introduction: Digital Wireless Security System
In the Instructable, we are going build a Prototype of digital wireless security systems using RF Technology.
The project can be used for security purposes in home, offices, organizations etc.Since it's built with RF Technology and it's secured it most cheap and reliable system for small-scale purpose in industries.
Details about the projects:
It can have a range of 100-150 meters but its range can be increased with increase in length in the antenna. It is built with a keypad 4*4 interfaced with PIC 16F887 microcontroller and LCD.
Data that is sent through keypad is display onto the LCD 16*2.When the password is entered it checks the password that is stored in EEPROM memory of the microcontroller.
When the password is correct, it sends the signal wirelessly with the help of RF modules and it can controller anything with the help of controlling circuit.
Step 1: Components Selection and Power Supply.
The components were selected to make the project were:
1. PIC 16F887 microcontroller 8-bit .
2. LCD 16*2
4. RF modules 434 MHZ
5. HT12E and HT12D(Encodes and decodes)
7.Power Supply components:
7.1. LM7805(Linear voltage regulator)
7.1.2 capacitors(330uf ,0.1uf)
7.1.3 Simple Transformer
7.1.4 1N4007 Diodes
9. PIC kit 2 (programming purpose).
10. Crystal oscillator(22 MHz)
11. Female and Male connectors.
Step 2: Power Supply to Circuits
We developed a power supply in order to provide 5V to all electronic component like IC that we are using, microcontroller, keypad logic and LCD 16*2.
We developed a simple regulated power supply by considering a linear voltage regulator LM7805.
The transformer is used to step down the voltage and bridge rectifier converts an alternating sine wave into pulsating dc.The filter circuit is used to filter out the pulsating wave in order to obtain pure dc wave at the output.LM7805 maintains 5v output even if there is a change in the voltage fluctuation onto the input side to some extent.
The circuit is being designed and verified at Proteus simulation software 7.7.
Step 3: Transmitter Circuit Diagram
This is transmitter circuit diagram that is designed on Proteus software 7.7.
It contains a keypad interfaced with microcontroller PIC 16F887 and LCD 16*2 which displayed the password that is typed.It checks the password which is stored in EEPROM memory of microcontroller and if it is correct then it passes the signal wireless onto the receiver.
This software can be used to simulate whether our circuit and code are running efficiently or not.
Step 4: Details About Components
Keypads have been used extensively in automotive applications as well as food industries.
Programmed Keypads can be used in automated attendance system at schools, offices etc, where you enter your ID, which is displayed and at the same time stored, to mark your presence.
Automatic door locks are usually accessed with a keypad control system in which a particular code is dialed on the keypad to open the door.
Step 5: Liquid Crystal Display
LCD (Liquid Crystal Display) screen is an electronic display module and finds a wide range of applications.
A 16x2 LCD display is the very basic module and is very commonly used in various devices and circuits.
These modules are preferred over seven segments and other multi-segment LEDs.
The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even (unlike in seven segments), animations and so on.
Step 6: Watch It Working
There are encoder and decoder used to convert data into either parallel to series or series to parallel or vice versa.
They operate like a shift resistor only but the only difference of specific address.Shift Resistors convert the data parallel to series or vice versa
In order to communicate with these encoders and decoder as they are transmitting data wirelessly, we need to select the precise frequency by selecting the right resistance from the datasheet.Oscillator frequency should match each other.
RF modules are used to send the data wirelessly at 434 MHZ frequency.They are quite cheap and readily available in the market other than any other technology.
Antenna length decides how long communication can take place and of what frequency signal we can transmit.
Frequency * wavelength = speed of light
frequency = (speed of light)/ (wavelength)
Hmax=(speed of light)/ (wavelength)/4
This represents how the communication takes place between two devices when we are using encoder and decoders.
Wired communication circuit represents communication between devices without the use of RF technology.
Note: Proteus 7.7 can't be used to simulate wireless circuits.
Step 8: Transmitter Circuit
¨HT12E circuit along with rf transmitter
Encoder IC will convert the 4 bit parallel data given to pins D0 – D3 to serial data and will be available at DOUT. This output serial data is given to ASK RF Transmitter.
Address inputs A0 – A7 can be used to provide data security and can be connected to GND (Logic ZERO) or left open (Logic ONE).
Status of these Address pins should match with the status of address pins in the receiver for the transmission of the data. Data will be transmitted only when the Transmit Enable pin (TE) is LOW. 1.1MΩ resistor will provide the necessary external resistance for the operation of the internal oscillator of HT12E.
Step 9: Receiver Circuit
HT12D and RF Receiver
RF Receiver receives the data transmitted using ASK RF Transmitter. HT12D decoder will convert the received serial data to 4-bit parallel data D0 – D3.
¨The status of these address pins A0-A7 should match with the status of address pin in the HT12E at the transmitter for the transmission of data.
¨The LED connected to the above circuit glows when valid data transmission occurs from the transmitter to receiver. 51KΩ resistor will provide the necessary resistance required for the internal oscillator of the HT12D.
Step 10: Rf Transmitter and Receiver
This is circuit diagram of transmitter and receiver which completes the whole project.
Feel free to comment and ask doubts