Cell phone operated Robotic Arm

Abstract: - This is also pick and place type robotic application. But this has a unique feature that it is controlled from cell phone. Its all the movements are controlled from any cell phone. That means you can control this robot from anywhere in the world where GSM / CDMA network service is available. Isn't it very interesting ??!!!!????.....

The robot has built in GSM / CDMA cell phone that receives signals from other cell phone. One has to call the number of the cell phone (that is inside robot) from his cell phone to activate it. Then by pressing different keys from 0 - 9 form the phone he can control the movements of the robot. Its 4-axis robotic arm. Its all four motions are controlled by 2 DC gear motors and 2 servo motors.

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Let us start with mechanical structure of robot.

Mechanical Structure: -

it can be best understood with the help of snaps of the robot. here are some of the snaps.

As shown in above figures complete structure is made up of wooden.

The most important part is the grip. As shown in above figure (in top pose) it has structure like scissor. At the end of grip there are two gear teeth wheels. One wheel is attached with servo motor 1 (this is shown in back pose). So when servo motor 1 rotates to 180 deg it will rotate the wheel. Due to it is coupled with another wheel both will rotate and opens the grip. Now when motor rotates to 0 deg, both wheel moves reverse and grip closes. 

Complete grip rests on servo motor 2 (as shown in front and back poses). As the motor rotates 0 to 180 deg and back it will rotate grip clockwise and anticlockwise from center position in 3 to 4 steps.

Next comes the arm. The grip and both servo motors rests on one end of the arm and another end is coupled to DC Motor (as shown in front and back poses). As the motor rotates CW or CCW, the complete grip moves up and down.  

DC motor 1 rests on rotating platform rotated by DC Motor 2. As DC Motor 2 rotates CW or CCW, entire arm rotates CW / CCW.

This complete structure rests on wooden platform that also houses control circuit.

Now let us discuss the hardware and software used to control this mechanism. But before that first understand the block diagram of system

System Block diagram: -

The major building blocks are cell phone, DTMF decoder, micro-controller, DC motor and Servo motor driver circuits.

Cell phone: - This is very first and the most important part of the system because due to this only the entire system is activated and works. It will receive the signals from another cell phone and gives them as input to DTMF decoder. 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 gives 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 perform following tasks

• Open / close grip by giving actuating signals to servo motor 1 (SM1)

• Rotate grip in either direction by giving actuating signals to servo motor 2 (SM2)

• Moves up / down grip by giving actuating signals to DC motor 1 (DCM 1)

• Rotate complete arm in either direction by giving actuating signals to DC motor 2 (DCM 2)

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

Servo motor driver: - It receives actuating signals from micro controller in terms of negative pulses, inverts it and provides required current to rotate 2 servo motors in both directions

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