07-03-2011, 10:09 AM
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TELEPHONE CONTROLLED SWITCH
INTRODUCTION
This project is based on VTU syllabus. The proposed system is based on ATMEL 89S52 µcontroller which is in our syllabus.
For doing this project we use some of the software like
1. Embedded C for programming the application software to the microcontroller.
2. Protel schematic software is used for designing the circuit diagram for this project.
3. Express PCB software is used for designing the PCB for this project.
ABSTRACT:
This project is mainly designed to access the switches of you are home from any remote place in the world. In early days the person is out of station and he forgotten to switch off the electrical appliance in his house. Then he cannot do anything his electrical bill goes out of reach. Using this project this problem will overcome. This is also helpful for industries. Where the person in charge of machines can switch ON the machines at correct time even his not presence.
% OF SOFTWARE AND HARDWARE:
1. Embedded ‘C’ 50%
2. Microcontroller and hardware 50%
TECHNOLOGY USED
DTMF: DTMF (dual tone multi frequency) is the signal to the phone company that you generate when you press an ordinary telephone's touch keys. In the United States and perhaps elsewhere, it's known as "Touchtone" phone (formerly a registered trademark of AT&T). DTMF has generally replaced loop disconnect ("pulse") dialing. With DTMF, each key you press on your phone generates two tones of specific frequencies. So that a voice can't imitate the tones, one tone is generated from a high-frequency group of tones and the other from a low frequency group.
OUR CHALLANGING WORK IN THIS PROJECT:
As embedded applications include more functionality, the challenge is making these functions accessible to the end user in a meaningful way.
1. Design the handheld hardware with relay,lcd,led.
2. Design the power supply selector circuit for peripheral and controller.
3. Write the programme for the main controller using embedded ‘c’ for 8051.
4. Design a I2C Driver for EEPROM operation.
5. Write diver for DTMF decoder.
COMPONENTS:
1. Power Supply Standard Type 7805, 5V DC
2. Micro controller-AT89S52-Atmel (Atmel.Com)
3. LCD (Liquid Crystal Display) 16x2 characters
4. Real Time Clock (RTC – DS1307)
5. Buzzer. Freq-1 to 18 kHz (5v-12Vdc)
6. Relay sugar cube from GOODSKY
7. DTMF Decoder 9200
WORKING PRINCIPLE:
When you dial the telephone number. After 3 rings the hardware lifts the line at your home and sends a signal to the micro controller that a call has come. The DTMF receiver at the microcontroller end will receive this DTMF tone and decode it and send to the micro controller as 4 bit data .The controller will receive this 4 bit data and check with it data base and compare the password .If it is correct Immediately the software in the micro controller will switch on the call receive relay and send a beep sound. Once the beep sound is heard in the ear piece of the phone what you will be dialing, then you has to enter password. The password is sent to the device through the telephone line as DTMF tone. .IF the pass word is incorrect then it will generate 2 tones showing that the password is incorrect. Once the password is correct, Then we have to enter the require devices to ON or OFF. For example: Imagine we have connected a Air conditioner to relay 1.The in the microcontroller program we have given the code 11 to ON the device relay 1 and 1 1 to OFF the relay 1 with device 1.So the person in the other end has presses the key pad 11 the DTMF decoder will receive this signal and decode and send the data t micro controller as 4 bit address. The controller will check this and see in the lookup table and make the relay 1 ON. When relay one is ON the device connected to his relay will ON. E.g. the Air conditioner will ON.
