In this project "Cell Phone Operated Land Rover", the robot is controlled by a 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 heard at the other end of the call. This tone is called DTMF (dual-tone-multiple-frequency).The robot perceives this DTMF tone with the help of the phone stacked in the robot. The received tone is processed by the (ATmega16) microcontroller with then help of DTMF decoderMT887o. 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 motors in forward direction or backward direction or turn. The mobile phone that makes a call to mobile phone stacked in the robot act as a remote.so this robotic project es not require the construction of receiver and transmitter units.
The important components of this mobile controlled robot are a DTMF decoder, microcontroller and motor driver.An MT8870 series DTMF decoder is used here. All types of the MT8870 series use digitalcounting techniques to detect and decode all the 16 DTMF tone pairs into a 4-bit code output.The built-in dial tone rejection circuit eleminates the need of pre-filtering. when the input signalgiven at pin 2(IN-) in single-ended input configuration is recognised to be effective, the correct4-bit decode signal of the DTMF tone is transferred to (pin11) through (pin14) outputs.The pin11 to pin14 of DTMF decoder are connected to the pins of microcontroller (pa0 to pa3).The ATmega16 is a low power, 8-bit CMOS microcontroller based on the AVR enhanced RISCarchitecture. it provides the following features: 16kb of in-system programmable flash programmemory with read-while-write capabilities, 512 bytes of eeprom, 1kb SRAM, 32(I\O) lines.outputs from port pins PD0 through PD3 and PD7 of the microcontroller are fed to the inputsIN1 through IN4 and enable pins (EN1 and EN2) of motor driver L293D IC, respectivily to drivetwo geared dc motors. Switch S1 is used for manual reset. The microcontroller output is not sufficientto drive the dc motors, so Current drivers are required for motor rotation.The L293D is a quad, high-current, half-h driver designed to provide bidirectional drive currents of upto600mA at voltages from 4.5V to 36V. It makes it easier to drive the dc motors. The L293D consists of four drivers. Pins IN1 through IN4 and OUT1 through OUT4 are the input and output pins respectively, of driver 1 through driver 4. Drivers 1 and 2, and driver 3 and 4 are enabled by enable pin 1(EN1) and pin 9 (EN2), respectively. When enable input EN1 (pin1) is high, drivers 1 and 2 are enabled and the outputscorresponding to their inputs are active. Similarly, enable input EN2 (pin9) enables drivers 3
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