DTMF based Home automation

By | August 25, 2013


This project demonstrates a novel method which enables users to control their home appliances and systems from remote using a phone-based interface. To access the control unit, the user should send an authentication code (DTMF) along with the required/desired function/action to his/her home control system via telephone or cell phone. Upon being properly authenticated, the cell phone-based interface at home (control unit) would relay the commands to a microcontroller that would perform the required function/action, and return a function completion code that would be sent to the source of the original command (user’s cell phone).

Parts of the Systems:

1.      Micro controller: We are using micro controller 8051 to implement the overall system. Proximity sensor established near door will be connected to any digital IO pin.

2.      AC Control: We will use a relay to control electric appliances. These relays are connected to the IO pins through triggering mechanism of transistors.

3.      DTMF Decoder: we will use MT8870 as a DTMF tone decoder to find the keys pressed.

 Hardware Block Diagram:


8051 Microcontroller:

We will use 8051 microcontroller to build this system.
The 8051 architecture provides many functions (CPU, RAM, ROM, I/O, interrupt logic, timer, etc.) in a single package

  • 8-bit ALU, Accumulator and 8-bit Registers; hence it is an 8-bit microcontroller
  • 8-bit data bus – It can access 8 bits of data in one operation
  • 16-bit address bus – It can access 216 memory locations – 64 KB (65536 locations) each of  RAM and ROM
  • On-chip RAM – 128 bytes (data memory)
  • On-chip ROM – 4 Kbyte (program memory)
  • Four byte bi-directional input/output port
  • UART (serial port)
  • Two 16-bit Counter/timers
  • Two-level interrupt priority
  • Power saving mode (on some derivatives)

  Programming Language: Embedded C


On authentication and receiving proper digit switch ON/OFF appliances.


1.      Switch off all appliances

2.      Monitor DTMF reception

3.      If code detected  Switch on/off appliance

4.      Go to step 2




Leave a Reply