In this project, the robot is controlled by the 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 heared at the other end of the call. This tone is called ‘dual tone-multiple-frequency' (DTMF) tone .The robot perceives the DTMF tone with the help of the phone stacked in the robot.
The received tone is processed by the ATmega16 microcontroller with the help of DTMF decoder MT8870.The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the microcontroller. The microcontroller is programmed to take a decision for any given input and outputs its decision to motor drivers in order to drive the motor for forward or backward motion or a turn.
The mobile that makes a call to the mobile stacked in the robot as a remote. So this simple robotic project does not require the construction of receiver and transmitter units. DTMF signaling is used for telephone signaling over the line in voice-frequency band to the call switching center. The version of DTMF used for telephone tone dialing is known as ‘Touch Tone'. DTMF assigns a specific frequency (consisting of two separate tones) to each key so that it can easily be identified by the electronics circuit. The signal generated by the DTMF encoder is a direct algebraic summation, in real time, of the amplitude of two sine (cosine) waves of different frequency, i.e., pressing ‘5' will send a tone made by adding 1336Hz and 770Hz to the other end of end of the line .The tones and assignment in a DTMF system are shown in table I.
The important components of this rover are a DTMF decoder, microcontroller and motor driver. An MT8870 series DTMF decoder is used here. All types of the MT8870 series use digital counting techniques to detect and decode all the 16DTMF tone pairs into 4-bit code output. The built in dial tone rejection circuit eliminates the need for pre-filtering. When the input signal given at pin 2(IN-) in single-ended input configuration is recognised to be effective, the correct 4-bit decode signal of the DTMF tone is transferred to Q1 (PIN11) through Q4 (PIN14) outputs.
The ATmega16 is a low power ,8-bit ,CMOS microcontroller based on AVR enhanced RISC architecture .It provides the following features:16kb of in-system programmable flash program memory with read-while-write capabilities ,512 bytes of EEPROM ,1kb SRAM,32 general purpose I/O lines and 32 general purpose working registers. All the 32 registers are directly connected to arithmetic logic unit ,allowing two independent register to be accessed in one single instruction executed in one clock cycle .The resulting architecture is more code-efficient.
Output from port pins PD0 through PD3 and PD7 of the microcontroller are fed to inputs IN1 through UN4 and enable pins (EN1 and EN2) of motor driver L293D, respectively, to drive two geared dc motor. Switch S1 is used for manual reset. The microcontroller output is not sufficient to drive the DC motors, so current driver are required for motor rotation.
The land rover can be further improved to serve specific purpose .It require four controls to roam around .The remaining eight controls can be configured to serve other purposes, with some modification in the source program of the microcontroller.