DTMF Based Remote Control System

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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. 

Download this file (DTMF Based Remote Control System.pdf)DTMF Based Remote Control System[Project Report]93 Kb

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