CELL PHONE OPERATED ROBOT
This project introduces the use of mobile phone for robotic control. This technology is more controller friendly as it doesn’t interfere with other controllers and can use up to twelve controls. It also has the advantages of robust control and provides working range as large as the coverage area of the service provider.
The robot is controlled by making a call on the mobile phone attached with the robot. In the course of the call if any button is pressed a ‘dual-tone multiple-frequency’ (DTMF) tone is heard at the other end of the call. The cell phone mounted on the robot perceives this tone and then the robot processes it by the ATmega16 micro-controller with the help of DTMF decoder MT8870.
Mechanical Assembly:
As shown in above figure four wheels are attached with chassis made up of any metal (like iron). Shaft of two DC motors (around 150 RPM or more) are directly coupled with real wheels. So as both motors rotate CW, the land rover moves forward. And as both motors rotate CCW, it will move backward. to turn it left right DC motor rotates and to turn it right left DC motor rotates. Also it will take forward-left & forward-right turn as well as backward-left & backward-right turn if required. For that, either of the motors (left or right) is rotated CW or CCW. For example if left motor rotates CW, land rover will take forward-right turn and if it rotates CCW then backward-right turn. Similarly for right DC motor.
System Block Diagram :
Major building blocks are cell phone, DTMF decoder, micro-controller, DC motor driver circuits:
Cell Phone: - First the system is activated by calling the SIM card number inside the phone. Afterwards it will receive DTMF code signals dialed from another cell phone and give it to DTMF decoder.
DTMF decoder: - The function of this block is self understood. It will take DTMF input given by cell phone decode it and gives 4-bit digital output to micro controller. It also generates an interrupt every time when it gives digital output.
Micro-controller: - You can call this block as the heart of entire system because it actually performs all the controlling actions. Depending upon the code given by DTMF decoder it will move the rover forward, backward, left or right by rotating both DC motors.
DC Motor driver: - It receives actuating signals from micro controller in terms of high / low logic, amplifies (current) it and rotates 2 DC motors in both directions.
DTMF decoder: - 
As shown in figure it is made up form readily available MT8870 chip that is widely used for DTMF based application. It receives DTMF tones and generates 4-bit digital output corresponding to received DTMF signal of digits 0 - 9 and other signals (like *, # etc) also. It receives input form cell phone to its pin no 2. It amplifies it through internal op-amp amplifier. If it receives valid DTMF tone, it will produce pulse output on StD (pin no 15). This is indicated by green LED connected as shown. The 4-bit digital output is latched on pins 11 - 14 and that is given to micro controller. The StD output is also given to interrupt pin of micro controller through transistor that will generate negative pulse every time when DTMF signal is received. This negative pulse will generate an interrupt. All the movements of robotic arm are controlled by cell phone digit switches 1 to 8. The 4 bit digital output corresponding to these switches form MT8870 are as given here
Keypad switch on cell phone
|
4 bit digital output
| |||
D
|
C
|
B
|
A
| |
1
|
0
|
0
|
0
|
1
|
2
|
0
|
0
|
1
|
0
|
3
|
0
|
0
|
1
|
1
|
4
|
0
|
1
|
0
|
0
|
5
|
0
|
1
|
0
|
1
|
6
|
0
|
1
|
1
|
0
|
7
|
0
|
1
|
1
|
1
|
8
|
1
|
0
|
0
|
0
|
- Micro-controller:
Control of the motion of the robot depends upon the code it receives from DTMF decoder as given in table:
4 bit digital input
|
Hex code
|
Movement – controlling action
| |||
D
|
C
|
B
|
A
| ||
0
|
0
|
1
|
0
|
F2h
|
starts moving forward
|
0
|
1
|
0
|
0
|
F4h
|
Take a left turn
|
0
|
1
|
0
|
1
|
F5h
|
Stop moving
|
0
|
1
|
1
|
0
|
F6h
|
Take a right turn
|
1
|
0
|
0
|
0
|
F8h
|
Start moving backward
|
- DC Motor driver: -
As shown in figure L293D is quadruple H-Bridge driver chip that is widely used for DC motor and stepper motor driver applications. It receives inputs from micro controller as shown on its input pins 2,7,10 & 15 and rotates two DC motors in either direction
So to move the land rover forward or backward - left or right one has to send following data on port:
Motion
|
W (P2.0)
|
X (P2.1)
|
Y (P2.2)
|
Z (P2.3)
|
data
|
Move forward – rotate both motors CW
|
1
|
0
|
1
|
0
|
05h
|
Move backward – rotate both motors CCW
|
0
|
1
|
0
|
1
|
0Ah
|
Turn left – rotate right motor CW
|
0
|
0
|
1
|
0
|
04h
|
Turn right – rotate left motor CW
|
1
|
0
|
0
|
0
|
01h
|
- Source Code :
#include
void main(void)
{
unsigned int k, h;
DDRA=0x00;
DDRD=0XFF;
while (1)
{
k =~PINA;
h=k & 0x0F;
switch (h)
{
case 0x02: //if I/P is 0x02
{
PORTD=0x89;//O/P 0x89 ie Forward
break;
}
case 0x08: //if I/P is 0x08
{
PORTD=0x86; //O/P 0x86 ie Backward
break;
}
case 0x04:
{
PORTD=0x85; // Left turn
break;
}
case 0x06:
{
PORTD=0x8A; // Right turn
break;
}
case 0x05:
{
PORTD=0x00; // Stop
break;
}
}
}
}
Upload the program and enjoy moving the robot using any cell phone.
Hope you liked and stay connected for more interesting projects like this.
Thank You
