Cell Phone Operated Landrover or Robot - Electronics Engineering Project

INTRODUCTION: 

                                   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 coarse of a call, if any button is pressed, a tone corresponding to the button pressed is heard at the other end. This tone is called ‘dual-tone multiple-frequency’ (DTMF) tone. The robot perceives this DTMF tone with the help of the phone stacked in the robot.

                          The received tone is processed by the P89V51RD2 microcontroller with the help of DTMF decoder CM8870. The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the microcontroller. The microcontroller is preprogrammed to take a decision for any given input and outputs its decision to motor drivers in order to drive the motors for forward or backward motion or a turn.

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                           The mobile that makes a call to the mobile phone stacked in the robot acts as a remote. So this simple robotic project does not require the construction of receiver and transmitter units.

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BLOCK DIAGRAM:
                            

             The CM8870 is Dual Tone Multi Frequency Receiver (DTMF Decoder). The CM8870/70C decoder uses digital counting techniques for the detection and decoding of all 16 DTMF tone pairs into a 4-bit code. The filter section uses a switched capacitor technique for both high and low group filters and dial tone rejection. The CM8870/70C’s internal architecture consists of a band split filter section which separates the high and low tones of the received pair, followed by a digital decode (counting) section which verifies both the frequency and duration of the received tones before passing the resultant 4-bit code to the output bus.

         The microcontroller output is not sufficient to drive the DC motors, a high voltage and high current drivers are required. The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. It will become easier to drive DC motors with such drivers. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is high, the associated drivers are enabled and their outputs are active and in phase with their inputs. external high-speed output clamp diodes should be used for inductive transient suppression.

    

              CIRCUIT DIAGRAM:

PROGRAM:

                org 20h

                mov p3,#0ffh      

L1: mov a,p3

                anl a,#0fh

                cjne a,#04h,L2

                mov p0,#81h  

                ljmp L1

L2: cjne a,#01h,L3 

                mov p0,#42h

                ljmp L1

L3: cjne a,#02h,L4

                mov p0,#41h   

                ljmp L1

L4:          cjne a,#06h,L5

                mov p0,#82h   

                ljmp L1

L5: cjne a,#0ah,L1 

                mov p0,#00h     

                ljmp L1

                end