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Make a Robot that responds tocommands from your

mobile phoneDecember 10, 2012 by spidertm

DTMF Controlled Robot

Introduction

This project is similar to the functioning of an

ordinary remote control system which consists

of, a transmitter and a receiver. Therefore two

mobile phones are required for effective Follow
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transmission and reception by DTMF .The robot

is controlled by the mobile phone held by the

user, which communicates with the mobile

phone attached to the robot. In the course of a

phone call, if any button is pressed, a tone

corresponding to the button pressed is heard at

the receiver end, which is called Dual Tone

Multiple frequency (DTMF) tone. The robot

receives these tones via the receiver mobile

phone which is on board. The received tone is

processed by the microcontroller with the help

of DTMF decoder IC CM8870DE . This IC

communicates with the motor driver IC l293d

through the microcontroller interface which

drives the motor in forward, reverse, right and

left directions according to the users key press.

The microcontroller featuring in this project will

be the AVR microcontroller,ATmega8.

Why build a DTMF ROBOT?

Conventionally, robots controlled by wireless

communication employ radio frequency(RF),

which have the drawbacks of limited workingrange, limited frequency range and the limited

control. Use of a mobile phone for robotic

control can overcome these limitations. It

provides the advantage of robust control,

working range as large as the coverage area of

the service provider, no interference with other

controllers and up to twelve controllers.

Although the appearance and the capabilities of

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robots vary vastly, all robots share the feature of

a mechanical, movable structure under some

form of control. The control of the robot

involves three distinct phases: perception,

processing and action. Generally, the preceptors

are sensors mounted on the robot , processing is

done by the on-board microcontroller or

processor, and the action is performed using

motors or with some other actuators.

Project Overview

Here the robot is controlled by the mobile

phone that makes the call to the mobile phone

attached to the robot.During the course of the

call, if any button is pressed, control

corresponding to the button pressed is heard atthe other end of the call. This unique tone is

received by the mobile on the robot, and is

decoded with the help of the CM8870 IC.

The received tone is then processed by the

Atmega8 microcontroller into its equivalent

binary digit, according to which it is pre-

programmed to take a decision for any given

input and outputs its decision to the motor

driver, in order to drive the motors forward,

backward or for rotatory motion.

The mobile that makes a call to the mobile

phone kept in the robot acts as a remote. So this

simple robotic project does not require the

construction of receiver and transmitter units.

This project can be sub divieded into 3 parts

1.The input (DTMF decoder IC-CM8870)

2. Controller (ATMega8 microcontroller)

3.Output (The motor driver IC and motors)

Now lets us look into each aspect in detail.


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1.Input: (DTMF

decoder circuit)

When you press the

buttons on the

keypad, a connection

is made that generates two tones at the same

time. A Row tone and a Column tone. These

two tones help in identifying the that key you

pressed to any equipment you are controlling. If

the keypad is on your phone, the telephone

companys Central Office equipment knows

what numbers you are dialing by these tones,

and will switch your call accordingly. If you are

using a DTMF keypad to remotely control

equipment, the tones can identify what unit youwant to control, as well as which unique function

you want it to perform.

When you press the digit 1 on the keypad, you

generate the tones 1209 Hz and 697 Hz.

Pressing the digit 2 will generate the tones 1336

Hz and 697 Hz.

Sure, the tone 697 is the same for both digits,

but it take two tones to make a digit and the

decoding equipment knows the difference

between the 1209 Hz that would complete the

digit 1, and a 1336 Hz that completes a digit 2.

Thus each key in the keypad gives different 4 bit

binary number in the output(pin no

14,13,12,11).This binary no is processed by the

microcontroller to give specific output to the
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motor.

Motor Driver:-L293D

L293D is a dual H-bridge motor driver

integrated circuit (IC). The current from the

microcontroller is only of the order of 1A which

is not sufficient to drive the motors. Therefore

motor drivers are used which act as currentamplifiers since they take a low-current control

signal and provide a higher-current signal which

is used to drive the motors.

L293D contains twoinbuilt H-bridge driver

circuits. In its common

mode of operation, two DC motors can be driven

simultaneously, both in forward and reverse

direction. The motor operations of two motors

can be controlled by input logic at pins 2 & 7 and

10 & 15. Input logic 00 or 11 will stop the

corresponding motor. Logic 01 and 10 will rotate


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it in clockwise and anticlockwise directions,

respectively.

Enable pins 1 and 9 (corresponding to the two

motors) must be high for motors to start

operating. When an enable input is high, the

associated driver gets enabled. As a result, the

outputs become active and work in phase with

their inputs. Similarly, when the enable input is

low, that driver is disabled, and their outputs are

off and in the high-impedance state.

Control with MCUs

The AtMega8 microcontroller used in this

project has 8Kb of flash memory with 20 general

purpose input/output pins. These input/outputpins can be used to receive input from the DTMF

Decoder as well as to send output signals to

control the motors. However the MCUs PORT

outputs are not powerful enough to drive DC

motors directly, we need some kind of drivers to

facilitate this. A very easy and safe is to use

popular L293D ICs. It is a 16 PIN chip. The pin

configuration is as follows.This chip is designed

to control 2 DC motors. There are 2 Input and 2

Output pins for each of the motors. The

connections are as follows:
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The behavior of motor for various input

conditions are as follows

If we want to rotate the motor clockwise, we

make the left upper switch and right lower

switch closed (which corresponds to A low and B

high above) and if it has to rotate in

anticlockwise direction, we close the right upper

switch and the left lower switch which

corresponds to A high and B low. Also for the

forward motion of the vehicle we make both

motors rotate in clockwise sense (say) and for

backward motion, both motors should rotate

anticlockwise. For right turn, right motor should

stop and left motor should rotate in clockwise

direction and for sharp right turn right motorrotates in clockwise direction and left motor in

the anticlockwise direction. A similar technique

is followed for left turn and sharp left turn which

you can easily guess.So you saw you just need to

set appropriate levels at two PINs of the

microcontroller to control the motor. Since this

chip controls two DC motors there are two more

output pins (output3 and output4) and two

more input pins(input3 and input4). The

INPUT3 and INPUT4 controls second motor in

the same way as listed above for input A and B.

There are also two ENABLE pins they must be

high (+5v) for operation, if they are pulled low

(GND) motors will stop.

Code:

/*
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DTMF Controlled Robot

PORTD pin 0,1,2,3 goes to motor driver l293d

PORTB pin 0,1,2,3 is connected to output of

CM8870 DTMF decoder IC

*/

#include

#include

int main(void)

{

DDRD=0xff;

DDRB=000;

while(1)

{

switch(PINB&0b00001111)

{

case 0b0010://Key 2

{

PORTD=0x0A ; //1010 both motor front

continue;

}

case 0b0100://Key 4


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{

PORTD=002; //0010 right motor front

continue;

}

case 0b0101://Key 5

{

PORTD=0x0F;//1111 SUDDEN STOP

continue;

}

case 0b0110://Key 6

{

PORTD=008; //1000 left motor front

continue;

}

case 0b1000://Key 8

{

PORTD=005;

continue;

}

default:

continue;


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MAKE YOUR OWN

ACCELEROMETER

CONTROLLED

MOTOR VEHICLE

THE LEGACY BEHIND A

HELLO ~ KVR

}

}//end of switch

return 0;

}

//

//

//

//

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