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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.

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INTRODUCTION
Long distance computer communication has become a challenge of the present day technology. Recently these computer communication networks are also termed as information networks. Presently there are many information services for information exchange like Teletex, Electronics mail, Video teleconferencing, Facsimile transmission (FAX), which are quit efficient but expensive too.
But there could be a situation where the terminal from which we want to down load or upload few lines or files or say information, may be “OFF” from the mains. Thus all the technologies are failed. And this is, where our project “Telephone Controlled Switch” comes into picture.
To establish an interactive page link with such a terminal ( which may be placed anywhere in the world ), we have to put the mains “ON” and then communicates with it using Modems on a telephone network. To materialize such a system we would require some circuitry which would receive commands on telephone line and can switch mains load “ON” or “OFF” ( i.e. the “Telephone Controlled Switch”).
The two major parts of the system are, the hardware configuration and software design. In the subsequent section we will deal with each block as well as the required software in detail.
Our project is to eliminate the problem by using such a circuitry, which can switch the remote terminal ON/OFF without anybody being present at the remote location. This aim is achieved by using TCS (Telephone Controlled Switch).
The TCS (Telephone Controlled Switch) designed here is capable of controlling up to eight main powered loads with the aid of commands received via telephone. Any tone-dialing (DTMF) telephone set or hand-held tone dialer may be used to send commands to the switching unit and remotely control a wide range of mains appliances in and around home, factories, industries etc. This system is designed to have a personal access code and with system feedback facility.
SYSTEM BLOCK DIAGRAM AND OPERATION
OPERATION:
The circuit is connected to the telephone network just like any normal telephone set. On being called, the circuit waits for predetermined number of ring signals and then answers the call (electrically it lifts the receiver). Next it waits for preprogrammed system access code, which the caller must transmit with the DTMF keypad on his telephone.
The unit is capable of switching up to light loads ON and OFF. By virtue of relays, high voltage and currents may be switched, so that loads may include mains powered ones. Reception of correct system access code is acknowledged with a short tone, which the caller can here.
UNITS OF TCS :
Ring detector Unit:
The ring detector Unit consists of a diode bridge, voltage controllers, an opto-coupler, Voltage and some other components. The main function of this unit is to detect a ringing signal and rectifies it. This rectified signal interrupts controller.
Switching Unit: -
The switching unit consists of a double pole double throw relay the . This unit switches the in coming Telephone line to the DTMF decoder after call is detected.
DTMF decoder Unit : -
This unit consists of a DTMF decoder IC 8870. Which receives signals from the tone pair and generates a 4-bit code recording to the received input. These 4-bit code are given to the  controller unit.
Micro controller Unit: -
This unit is the heart of all the circuitry. The unit controls all the operation performed by the ICS. This unit is composed of 89CSI  controller.
Assurance tone generator Unit :-
For the feedback purpose to confirm about device status to person at remote location, musical IC UM 66 is used as assurance tone generator.
Driver Unit :-
This unit consists of driver transistor and current limiting resistor. These transistors switches ON & OFF & controls the corresponding relays ON & OFF. This unit receives control signals from the part 2 of  controller.
Relay Unit: -
This unit consists of 7 relays ( single pole double through ) (12 v/2 Sov/5A). These relays are driver ON or OFF by driver unit & thus it switches the mains line ON or OFF & thus the load. The relay having different rating can be used recording to the desired application.