The human mind always needs information of interest to control system of his/her choice. In the age of electronic systems, it is important to be able to control and acquire information from everywhere. Although many methods to remotely control systems have been devised, the methods have the problems such as the need for special devices and software to control the system.This paper suggests a method of controlling devices using DTMF (Dual Tone Multi Frequency) tone generated when the user pushes mobile phone keypad buttons or when connected to remote mobile system. This system suggested consists of mobile phones normally registered in communication service and a system that can receive a call from another phone; also the mobile phone can be selected irrespective of the mobile phone model and mobile phone carrier. Here, we are developing a system with a PIC 16F877A Micro controller to control four relays that act as switch for four separate devices.
The remote control technologies have been used in the Fields like factory automation, space exploration, in places where human access is difficult. As this has been achieved in the domestic systems partially, many corporations and laboratories are researching the methods which enable human to control and monitor efficiently and easily in the house or outdoor. Controlling the domestic system regardless of time and space is an important challenge. As the mobile phone enables us to connect with the outside devices via mobile communication network regardless of time and space, the mobile phone is a suitable device to control domestic systems.
This project proposes a method to control a domestic system using a mobile phone, irrespective of the phone model and mobile phone carrier. Existing methods for control and monitoring, using mobile phones have usage problems because the cost and need for continuous control. One of the disadvantages is the lack of feedback during the process. Method proposed uses the DTMF (Dual Tone Multi Frequency) generated when a keypad button of the mobile phone is pressed by the user. The mobile phone user controls the system by sending the DTMF tone to the access point. Mobile communication network is larger than that of LANS, thus the user can take the advantage of mobile phones to control the system.
Phone on the transmitting side: The person who wants to switch on/o any device kept at the controller side calls from a phone and, once the call gets picked up, enters the password and tones for a corresponding device. Every key has to be pressed for a minimum amount of time to get it latched at the decoder IC. Mobile phone on the receiving side: The mobile phone on the receiver side picks up the phone automatically after 5 seconds, and then makes the tones available to the DTMF tone decoder IC through the headphone jack of the phone. DTMF Tone Decoder IC: The DTMF tone decoder IC converts the received tones to their respective binary values and then gives them as an input to the microcontroller.
The DTMF tone decoder ICs internal architecture consists of a band split lter section which separates the low and the high tone of the received tone pair, followed by a digital decode(counting) section which veri es both the frequency and duration of the receivedtones before passing resultant 4-bit code to the output bus. These 4-bits along with a bit which validates a received tone are given as an input to the port 1 of microcontroller. The Microcontroller: The +ve output bits of the decoder IC serve as an input to port 1 of the microcontroller. Then each tone is verified by the programmed microcontroller and once a correct sequence of code is received, output corresponding to the tones sent by the user is made available at the port 0, which is connected to relay through a relay driver. Relay Circuitry: The output from the port 0 of the microcontroller is given to the relay driver IC which drives the corresponding relay, to which the home appliances are connected.