DTMF Based Load Control System (Home Automation): Electronics Project

This project works on the principle of DTMF (Dual-tone multi-frequency). This circuit can be used to control or on/off the load i.e. electric equipment like a fan, bulb, water pump, etc.

We know that in industries, loads are distributed over large distances, and it is not convenient to operate all those equipment time to time and it is also time to consume.

Also in agricultural fields, water pumps and other electric systems are spread over the large area and it is hard to operate these systems to farmers. We can use this circuit in the home too, therefore this can also be called as DTMF based home automation project. Keeping all these problems in mind, a DTMF based load control system is designed as follows.

In DTMF based load control system, a cell phone (mobile) is connected to the circuit from its audio output (audio jack) to receive the tone generated by the operator mobile. Whatever audio signal (in the form of frequency) is received from mobile then decoded (to its digital code) by the use of DTMF decoder which is one of the main parts of the project. Then this digital code goes to 8051 microcontrollers which on/offs respected relay to control that electric equipment. a relay driver IC is interfaced with the microcontroller to actuate the relays.

Components required:

Sr. no Equipment Quantity
1 IC 8051 MC 1
2 MT 8870 DTMF IC 1
3 Crystal (3.579545mhz) 1
4 VOLTAGE REGULATOR 1
5 2 LINE LCD DISPLAY 1
6 CRYSTAL OSCILLATOR(11.0592mhz) 1
7 DIODE 1
8 PUSH BUTTON 1
9 LEDS 4
10 RESISTER(220O,4.7kO,10kO) BOX
11 CAPACITORS(10uf,1000uf) 5
12 RELAYS 2
13 Bc547 2

DTMF based load control system block diagram
DTMF based load control system block diagram

DTMF based load control system circuit diagram
DTMF based load control system circuit diagram

Software requirements: Keil compiler

Languages: Embedded C or Assembly

DTMF IC (MT 8870) Pin configuration

MT 8870 pin diagram
MT 8870 pin diagram

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How to make DTMF Decoder: Electronics Project

Circuit diagram of DTMF decoder

Photo1904

Components

1) Breadboard.

2

2) IC 7805 and IC MT8870 (DTMF IC):

3

2) 9V battery:

4

3) four small LED:

5

Capacitors: 1) 0.1uF 2) 22pF 3) 22oF 4) 10uF

6

connecting wires and cutter:

7

Resistors: 100K, 100K, 330K.

8

Crystal Oscillator (KDS 3.5795)  i.e. 3.57MHz

9

Cellphone connector (If possible use NOKIA):

10

1) Step 1:  Insert the DTMF IC (MT8870) in the breadboard.

11

2) Step 2: Ground pin no 5, 6 and 9.

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3) Step 3: Now connect the four LED’s to pin no 11, 12, 13, 14 with respect to ground.

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4) Step 4: Connect two 22pF capacitors to pin no 7 and 8 with respect to ground (Don’t worry it has no polarity)

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5) Step 5: Connect a crystal oscillator to pin no 7 and 8.

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6) Step 6: Short pin no 1 and 4.

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7) Step 7: Insert IC 7805 anywhere on the breadboard.

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8) Step 8: 330K resistor between pin no 16 and 17.

18 19

9) Step 9: Connect 0.1uF capacitor to pin 17 with respect to 5V.

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10) Step 10: Connect pin 10 and 18 to 5V

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11) Step 11: 100K resistor between pin 2 and 3.

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12) Step 12: Connect one pin of 100K resistor to pin 2 and leave other for next step.

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13) Step 13: Connect negative end of 10uF (50V) capacitor to another end of 100K resistor and leave +ve terminal for next step.

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14) Step 14: Connect a mobile headphone jack (+ve) to the positive terminal of capacitor and other terminal grounded.

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15) Step 15: Make proper grounding by connecting wire.

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16) Step 16: Connect the 9V battery to 7805 IC. Middle terminal to ground.

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17) Step 17: 5V output given by 7805IC is connected to uppermost row.

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18) Connect your mobile to the audio jack.

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19) Press any key on Keypad you will see corresponding BINARY number of that digit. Please make sure that your keypad tones are ON ( To make keypad tones ON go to Settings>Tones>Keypad tones>ON)

30Thank you.

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Watch YouTube video for this project.

https://www.youtube.com/watch?v=OF3SfGyvgbg

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If you like this article, please share it with your friends and like or facebook page for future updates. Subscribe to our newsletter to get notifications about our updates via email. If you have any queries, feel free to ask in the comments section below. Have a nice day!