You can call up on your colleague's mobile number and ask him/her to turn on or off the lights or other appliance of your office. You may be any where in the world at that time, as mobile network allows to to talk to anyone present anywhere in this world. But your colleague is too much for this simple job! Your may replace him/her with this smart gadget and let it operate the appliances. But how it will do that? well, it will listen to the audio output from a mobile phone and try to recognise the DTMF tones present in the output sound. DTMF is a way to encode numerical data into an audible sound which is then sent over an audio channel. Keypress on the other mobile will generate DTMF codes.
Keys like 1,2,3 and 4 are used to switch on/off up to four loads like light, fan, water pump in a building.
The user(who is away from home) using his/her mobile phone calls another mobile (which is present at the home and is attached to the this system) and then press keys on his/her mobile phone to controls the load in the home. The mobile attached to the system receives tones from the user's mobile and sends them to the DTMF decoder module over an audio cable. The DTMF decoder module converts this tone to a 4 bit binary number which is then sent to a ATmega8A AVR microcontroller which controls output relays using four of its port pins. These relays can be used to switch AC mains powered appliances like bulbs and fans.
Things required
| S. No | Item | Image | Cost |
|---|---|---|---|
| 1. | 28 PIN AVR Development Board |  |
Rs. 286 |
| 2. | DTMF Decoder Module with Audio Cable |  |
Rs. 130 |
| 3. | Relay Board |  |
Rs. 100 |
| 4. | Connecting wires |  |
Rs. 50 |
| 5. | 12V 1A Adapter |  |
Rs. 134 |
| 6. | Mobile phone with 3.5mm audio socket | - | - |
| Total Cost | Rs. 700 |
You can buy all of the required parts from eXtreme Electronics web store and get them delivered to your doorsteps!
Connections
Table: Connection between DTMF decoder and AVR development board
| DTMF Decoder Board | 28 PIN AVR Development Board |
|---|---|
| Std | PC4 |
| Q4 | PC3 |
| Q3 | PC2 |
| Q2 | PC1 |
| Q1 | PC0 |
| 5V | VCC |
| GND | GND |
Table: Connection between Relay Module and AVR development board
| DTMF Decoder Board | 28 PIN AVR Development Board |
|---|---|
| V | 12V |
| S | PB0 |
| G | GND |
NOTE: You can connect up to four relay boards to the circuit. Connect the S pin of the relay boards to PB1, PB2 and PB3 pins.
Program
Load your AVR development board with the HEX file of this project using eXtreme Burner AVR and also set high fuse = E1 and low fuse byte to D9
Tip
For best results
- Keep the volume level of the mobile phone (connected to the system) between 70-90%
- Mute your mobile, this will prevent it from picking up noise from the surrounding and sending them along with DTMF. When your mobile is muted, it will only send clean DTMF signals which will be easier to decode.
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Hanumant, Keivanjan, Alijraar, Ismail, Ragab Ali, DAWAR KATFUN PHILEMON, Florence, Shakir, Hanumant Dhande, Oleg, Jalil Ahmad, Girish Harmukh, Chockalingam, Adil, Thinleha6787, Rakesh, Aniket, Mahendra Pawase, Onome, Pushpa K, , Bibin Chacko, Davor, Abdulmajeed, Anurag,
