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.

DTMF keypad

 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.