DTMF Mobile controlled ROBOT is controlled with a mobile. In this project, the robot is controlled by a mobile phone that makes a call to the mobile phone attached to the robot. In the course of a call, if any button is pressed, a tone corresponding to the button pressed is heard at the other end of the call. This tone is called “Dual Tone Multiple-Frequency” (DTMF) tone.
The robot perceives this DTMF tone with the help of the phone stacked on the robot. The received tone is processed by the micro-controller with the help of DTMF decoder.
The micro-controller then transmits the signal to the motor driver to operate the motors & the robot moves accordingly. The working range is as large as the coverage area of the service provider.

Components used:

DTMFDTMF Technology:
DTMF stands for Dual Tone-Multi Frequency, the basic technology for Telephone system. DTMF is the generic term for Touch-Tone. DTMF signalling is used for telecommunication signalling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices.

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 frequency. For example, the key 1 produces a superimposition of tones of 697 and 1209 Hz.

DTMF Signalling

DTMF – Double Tone Multiple Frequency is a signalling method that use a mixture of two pure tone sounds.
Uses a set of 8 audio frequencies transmitted in pairs to represent 16 signals.
Applications – Widely used in Telecommunication systems, Robotics, Home Automation.


Table showing DTMF Low and High frequency tones and decoded output:


MT8870 DTMF Decoder IC:

The MT8870 is a DTMF receiver integrating the functions of both the band-split filter and the digital decoder. The filter section uses switched capacitor techniques for high and low group filters whereas the decoder uses digital counting techniques to detect and decode all the 16 DTMF tone-pairs into a 4-bit code.


The MT8870 DTMF receiver is small in size, has low power consumption and high performance. Its architecture consists of a band-split filter section, which separates the high and low group tones, followed by a digital counting section which verifies the frequency and duration of the received tones before passing the corresponding code to the output bus.

For more information about this project, click here.

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