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INTRODUCTION


Nowadays everybody possesses mobile phones. They have become a part of every day life. Mobile phones have replaced almost all gadgets. Mobile phones with different functions are available. Some of the extra functions are music player, cameras, GPS etc. In this project robotic control is implemented using a cell phone thus adding one more utility to it. Here a cell phone is used to control the actions performed by a rover. Rover is a machine or car capable of wandering. DTMF (dual tone multiple frequency) tones are decoded by a DTMF decoder and processed by the micro controller. The micro controller is preprogrammed to output a particular binary code for a particular input to the motor driver, which in turn drives the two motors in a particular direction. Up to 12 controls are possible using this. Five controls are used in this project. Four are used to move the rover in either forward, backward, turn rightward or leftward directions. The last one is used to stop the rover.

Robotics is an area where lot of research is going on. Robots capable of implementing different movements are present. They perform tasks more efficiently than humans do.

ADVANTAGES
The conventional robots use RF circuits, which face problems of low frequency range, interference, complex transmitter, and receiver circuits. All these drawbacks are overcome using the cell phone operated land rover. The frequency range is the range provided by the service provider of the mobile network. The version of DTMF used here is touch-tone version.

DTMF DECODER
A mobile phone that makes a call to mobile attached to the robot. In the course of 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 'dual-tone multiple-frequency' (DTMF) tone. DTMF application associates with digital telephony, and provides two selected output frequencies (one high band, one low band) for duration of 100ms.
DTMF decoder decodes the DTMF tone into equivalent binary digits. DTMF receiver is the integration of both the bandsplit filter and digital decoder. The filter section uses switched capacitor technique for high and low group filter; the decoder uses digital counting techniques to detect and decode all 16 DTMF tone-pairs into a 4-bit code. The signal generated by the decoder is a direct algebraic summation, in real time, of the amplitudes of sine (cosine) waves of different frequencies. External component count is minimized by on chip provision of a different input amplifier, clock oscillator and latched three-state bus interface.
DTMF receiver offers small size, low power consumption and high performance. This separates high and low group tones, followed by digital counting section which verifies the frequency and duration of received tones before passing the corresponding code to output bus. The digital counting technique is used to determine the frequencies of the incoming tones and to verify that they correspond to standard DTMF frequencies.
Features
• Low power consumption.
• Internal gain setting amplifier
• Adjustable guard time.
• Power down mode
• Inhibit mode
PIC Microcontroller
PIC is a family of RISC microcontroller made by Microchip Technology. PICs use a RISC instruction set, which varies in length from about 35 instructions for the low-end PICs to about 70 instructions for high-end PICs. The instruction set includes instructions to perform a variety of operations on the accumulator and a constant or the accumulator and a memory location, as well as for the conditionally executing code and jumping/calling other parts of the program and returning from them, and specific hardware features like interrupts and one low-power mode called sleep. Microchip provides a freeware IDE package called MPLAB that also includes a software simulator as well as an assembler.
Devices called “programmers” are traditionally used to get program code into the target PIC. Most PICs that Microchip sells nowadays have ICSP (In circuit Serial Programming) and/or LVP (Low Voltage programming) capabilities, allowing the PIC to be programmed while it is sitting in the target circuit. Many of the higher ends flash based PICs can also write to their own program memory. All PICs (except dsPICs and PIC24s) handle data in 8-bit chunks, so they should be called 8-bit microcontrollers.
Microcontroller core Features
• High-performance RISC CPU
• Only 35 single word instructions to learn
• All single cycle instructions except for program branches which are two cycle
• Operating speed: DC – 20 MHz clock input DC – 200 ns instruction cycle
• Up to 8Kx 14 words of FLASH program memory,
Up to 368 x 8 bytes of Data Memory (RAM)
Up to 256 x 8 bytes of EEPROM data memory
• Interrupt capabilities (up to 14 sources)
• Eight level deep hardware stack
• Direct, indirect and relative addressing modes
• Power-on Reset (POR)
• Power up Timer (WDT) with its on chip RC oscillator for reliable operation
• Programmable code-protection
• Power saving sleep mode
• Selectable oscillator options
• Low-power, high speed CMOS FLASH/EPROM technology
• Fully static design
• In-Circuit Serial Programming (ICSP) via two pins
• Single 5V In-circuit Serial Programming capability
• In-circuit Debugging via two pins
• Processor read/write access to program memory
• Wide operating voltage range: 2V to 5.5V
• High Sink/Source Current: 25mA
• Commercial and industrial temperature ranges
• Low power consumption:
- < 2mA typical @ 5V, 4MHz
- 20mA typical @ 3V, 32KHz


MOTOR DRIVER
L293D is an integrated motor driver that can be used for simultaneous, bidirectional control of motors. It is a standard 16 pin, dual-in-line integrated circuit package. It has built in flyback diodes to minimize inductive voltage spikes. L293D is an ideal for controlling the forward/backward/brake/left/right motions of small DC motors controlled by a microcontroller such as a PIC or basic stamp. It is a high voltage, high current four channel driver designed to accept standard TTL logical levels and drive inductive loads (such as relays, solenoids, DC and stepping motors ) and switching transformers.
In the four-wheel drive system motors on a side is controlled in parallel. So a single L293D can drive the rover. For this robot, beads affixed with glue acts as support wheels. When constructing any robot, one major mechanical constraint is the number of motors being used. We can use either a two-wheel drive or four-wheel drive. Though four wheel drive is more complex than two-wheel drive, it provides more torque and good control. Two wheel drive on the other hand, is very easy to construct.
Two motors are connected to output pins of driver. Four output pins and six input pins are their. Each motor take two output pins. Two of the input pins are enable pins EN1 and EN2. EN1 is for enable motor 1 and EN2 for enable motor 2. Enable pin should be high for the working of motor. The direction of rotation of motor depends upon the values in input pins IN1 through IN4. IN1 and IN2 determine the rotation of motor 1. IN3 and IN4 for motor 2. If IN1 and IN4 are high, IN2 and IN3 are low then two motors are run forward . Just opposite of this inputs runs motor backward. If IN2 and IN4 are high, IN1 and IN3 are low then left turn, that is, motor 1 forward and motor 2 backward. Opposite of this inputs produce right turn.
Features
• Wide supply voltage range : 4.5V to 36V
• Separate input logic supply
• Thermal shut down
• High noise immunity inputs
• Output current 600mA per channel
• Peak output current 1.2A per channel
• Internal clamp diodes
• Enable facility

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