In this proposed project, one mobile phone which controls the robot will makes call to another mobile phone attached to the robot. If any button is pressed during call, at the other end of the call we can hear a tone corresponding to the button pressed. This tone is defined as ‘dual tone-multiple-frequency’ (DTMF) tone. By using the phone connected in the robot, this robot will recognize the DTMF tone.
By using DTMF decoder MT8870, the ATmega16 micro controller will process the received tone. The DTMF decoder MT8870 will decodes the DTMF tone into its equivalent binary digit and this binary digit is transferred to the micro controller. The micro controller is used to take the decision on any given input and outputs and its decision to motor drivers in order to drive the motor for a turn or forward motion or backward motion.
The mobile that makes a call to another mobile stacked in the robot is called as a remote. The construction of receiver and transmitter units is not required in this proposed robotic project. When we are transferring telephone signaling over the line in voice-frequency band to the call switching center, we used DTMF signaling. For telephone tone dialing we are using ‘Touch Tone’ version of DTMF. Each key will be assigned with a specific frequency (consisting of two separate tones) by the DTMF so that it can be easily recognized by the electronics circuit. In real time, the signal generated by the DTMF encoder is the direct algebraic summation 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. In table I we had shown the tones and assignment in a DTMF system.
DTMF decoder, micro controller and motor driver are important components of this rover. Here we are using MT8870 series DTMF decoder. MT8870 series Decoders will detect and decode all the 16DTMF tone pairs into 4-bit code output with the help of digital counting techniques. The built in dial tone rejection circuit eliminates the need for pre-filtering. The correct 4-bit decode signal of the DTMF tone will be transferred to Q1 (PIN11) through Q4 (PIN14) outputs, after the input signal given at pin 2(IN-) in single-ended input configuration is recognized to be effective. When the input signal given at pin 2(IN-) in single-ended input configuration is found to be effective, the correct 4-bit decode signal of the DTMF tone is sent to Q1 (PIN11) through Q4 (PIN14) outputs.
An 8-bit, low-power, CMOS micro controller which is based on AVR enhanced RISC architecture is called as ATmega16 micro controller.
- Its in-system programmable flash program memory size is 16kb with read-while-write capabilities.
- EEPROM is 512 bytes.
- SRAM size is 1kb.
- 32 general purpose working registers, which are directly connected to arithmetic logic unit (ALU). It allows accessing two independent register by one single instruction, executing in one clock cycle.
- It has 32 general purpose I/O lines and the resulting architecture works very efficiently.
For driving two geared dc motor, output from port pins PD0 through PD3 and PD7 of the micro controller will enable pins (EN1 and EN2) of motor driver L293D and are fed to inputs IN1 through IN4. In this architecture, Switch S1 is used for manual reset. Current driver are required to drive the DC motors because only micro controller output is not sufficient.
Later we can improve the land rover to serve future requirements. To roam around, land rover requires four controls. To serve other purposes of land rover, we will configure the remaining eight controls by making some changes in the source program of the micro controller.