DIY dtmf module and interfacing with arduino uno

In this post, we are going to make dtmf module and interface it using arduino.

My prototype

Theory of  DTMF:

Full form of dtmmf is dual tone multi frequency. The DTMF telephone keypad is laid out in a 4×4 matrix of push buttons in which each row represents the low frequency component and each column represents the high frequency component of the DTMF signal. Pressing a key sends a combination of the row and column frequencies. For example, the key 1 produces a superimposition of tones of 697 and 1209 hertz (Hz). Initial pushbutton designs employed levers, so that each button activated two contacts. The tones are decoded by the switching center to determine the keys pressed by the user.

How to use DTMF module

The picture says it all. If you have any doubt regarding this, let me know. Feel free to comment here.

You can connect PWDN pins to ground from microcontroller or through hard wiring. Choice is yours, I suggest the method of hard wiring. In this, I had opted for hard wiring.

First check it manually. Connect +5V piin to 5 volt and GND pin to ground. Now connect 3.5mm audio jack (male) to Input. If it is not working try another mobile phone.

DTMF MODULE in action.