DTMF based Home Automation System using Microcontroller

Normally, many home appliances can be controlled by switches. But, nowadays we often see the automation of home appliances using many technologies. This article presents the DTMF based home automation system using microcontroller. Dual Tone Multi Frequency (DTMF) is a signaling system for identifying the keys on a DTMF keypad. It is used for telecommunication signaling over analog telephone lines in the voice frequency band between communication devices and telephone handsets.

DTMF is a short form of Dual Tone Multi Frequency. So, when you make a call to a customer care, they will ask you to press any number. When you press any number from your mobile, one particular action takes place because of dual tone multi frequency. When a button is pressed from the mobile keypad, the act immediately generates a tone of two frequencies. These tones are called column and row frequencies.

 Here, in the above depicted figure,the column frequencies are high frequencies, and the row frequencies are low frequencies. These row and column frequencies are selected for DTMF in such a way that they don’t have harmonic relation with the others. As a result, they will not generate same tones. The row frequencies are somewhat lower than the column frequencies.

DTMF Based Home Automation System using Microcontroller Circuit Diagram

Required Components

DTMF based home automation system controlling circuit mainly consists of these following components:

• ATmega8 Microcontroller
• HT9107BIC
• Relay
• AC Load
• Crystal Oscillator
• Resistors
• Capacitors

The decoder IC consists of an in buil top-amp, and to separate the low and high frequencies, the output of an operational amplifier is given to the pre filters. And then, it is passed through the code detector and frequency circuits –thus 4-bit binary code is latched. The tone which is generated from the mobile is sent to the operational amplifier through the capacitor and resistor of the DTMF at pin1.

• Here, pin1 is a non-inverting pin, which is connected to pin4 that is Vref.
• Pin3 is the output of the operational amplifier, which is feedback to pin2 using 100Kohm resistor.
• Pin7 and pin8 are connected to crystal oscillator.
• Pin15 is a data valid pin. When DTMF tone is detected, this pin becomes high.
• The Procedure of the signal from frequency detection to digitalization is done by steering circuit that consists of 10k resistor, capacitor, RT/GT and EST.
• Pin11 and Pin14 are output pins of DTMF that are connected to PB0 to PB3 pins of controller.
• PD0 and PD1 are output pins of controller that are connected to relay. Relay output is connected to different sources like fan, light, etc.

Circuit Working

When the DTMF controlled home appliances circuit is powered,then the controller continuously checks the inputs. When 1 is pressed from the DTMF or mobile keypad, the decoder IC decodes the tone and generates 1 (0001), which is given to the ATmega8 microcontroller, which in turn generates high output at the pin PD0 and this is connected to a relay.Here, the relay is used to switching the circuit and thus light is turned on. If the received output is 2, then the light will be switched off. In the same way, if the received input is 3, then the fan will be switched ON and if it is 4, the fan will be off.

Mobile Controlled Home Appliances

Home appliances control system can be accessed by a mobile phone to control coordinate and monitor home appliances. This system allows for a user to remotely control the home appliances using a mobile phone. This system is a flexible and powerful tool that performs this service from anywhere and at anytime. The working principle of a typical mobile controlled home appliance is like this:

The home automation system is connected to a cell phone via a headset. To activate the mobile phone unit on the home appliances, the caller has to make a call. After three or four rings the mobile phone user picks up the call.To access the system and to control the home appliances, the user has to enter the password.As the caller enters a specific password, the relays get activated.If the password is wrongly entered four times in a row, from the interface – an error sound is generated. And thus, security is kept intact because these passwords are known and owned by selected persons only. For instance, this system includes an alarm unit which is used to provide anon/off device. This is capable of notifying regarding the nature of the event, that is, up to five different numbers over a telephony network.

Advantages of DTMF based Home Automation System

The advantages of DTMF based home automation system are

• It can be controlled from anywhere.
• It decreases wastage of electricity when anyone forgets to switch off the fans and lights.
• Its cost is very low compare to other technologies like GSM.

DTMF Projects

The following list provides various DTMF based projects ideas for engineering students that are more helpful and very interesting projects for electrical and electronic engineering students.

1. Load Control System using Dual Tone Multi Frequency
2. DTMF Controlled Garage Door Opening Based on Cell phone
3. Home Security System Using DTMF
4. Industrial Automation based on DTMF
5. DTMF based Electron Voting Machine
6. Dual Tone Multi Frequency based Switching System for Power Efficiency
7. Dual Tone Multi Frequency based Pick and Place Robot
8. Controlling of Water Pump based on Dual Tone Multi Frequency
9. Irrigation System based on Dual Tone Multi Frequency
10. Stepper Motor Control using DTMF
11. Dual Tone Multi Frequency based Infrared Proximity Sensor
12. Controlling of Human Less Boat for Ocean Research Applications Using DTMF
13. Display of Telephone Numbers Using DTMF on Seven Segment Display
14. Programmable FM Remote with 89C51 Microcontroller using Dual Tone Multi Frequency
15. I2C Protocol Based Automatic Dialing to Any Telephone on Detecting Burglary
16. Home Appliances Control System using Dual Tone Multi Frequency
17. Dual Tone Multi Frequency based Mobile Switching Device
18. Cell phone Controlled Robot without Microcontroller
19. Dual Tone Multi Frequency based Robo Car
20. Dual Tone Multi Frequency based Agriculture Field Motor
21. Control System
22. DTMF based Agriculture Pump Control and Remote Industrial Loads

Thus, appliances in home are controlled via switches that control the electricity to devices. As the world is becoming more and more advanced, we find new technology coming in deeper into our personal lives, i.e., home automation. This article gives the information about a DTMF controlled home automation system with a microcontroller and also DTMF based project ideas. Furthermore, for any information regarding this article,give your feedback and comments in the comment section below.

 Photo Credits:

•  DTMF keypad & DTMF Project Ideas by electronicshub
• DTMF Based Home Automation System Circuit Diagram by electronicshub
• Mobile Controlled Home Appliances by saveetha