ROVER 2010 PREFACE The main objective of this project is to design an obstacle detection and collision avoidance robot with help of IR sensors embedded around the body of robotic vehicle. This design can be used in fully automated vehicles like cars, moving materials in industries and similar other commercial applications. Starting with an overview of the system the document would cover implementation details like components used, circuits and algorithms, problems faced during designing of the obstacle detection and collision avoidance robot. It has also been described that how the microcontroller program has been embedded in the microcontroller with the help of a burner device. Some suggestions on improving the design and its commercial application have also been discussed in the later part of the document. The Reference and Resources page has a list of relevant books, websites, electronic shops and commonly used parts & their prices. 1
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ROVER 2010
PREFACEThe main objective of this project is to design an obstacle detection and collision avoidance robot with help of IR sensors embedded around the body of robotic vehicle. This design can be used in fully automated vehicles like cars, moving materials in industries and similar other commercial applications. Starting with an overview of the system the document would cover implementation details like components used, circuits and algorithms, problems faced during designing of the obstacle detection and collision avoidance robot. It has also been described that how the microcontroller program has been embedded in the microcontroller with the help of a burner device. Some suggestions on improving the design and its commercial application have also been discussed in the later part of the document. The Reference and Resources page has a list of relevant books, websites, electronic shops and commonly used parts & their prices.
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ABSTRACTThe robot uses three IR sensors to sense any obstacle in its path. The data coming from those sensors are fed into voltage comparators where the sensor data is compared with a fixed reference voltage. After the comparison of sensor data and the Vref, the voltage comparator gives output as OV for presence of any obstacle and 5 V for absence of obstacle. This output of comparator circuit is fed into the microcontroller in which decision making program is stored .The microcontroller process uses the output of comparator circuit according to the program stored in it and gives output at another port. The output of microcontroller is fed into the motor driver circuit which amplifies the low output current coming from microcontroller so that its output becomes capable to drive the DC motors fitted in the robotic vehicle base.
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Block diagram of Rover
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Circuit diagram of Rover
The output of voltage comparator circuit is fed as input in the microcontroller at port 0.The output of microcontroller is taken at port 1 and port 2 and fed into motor driver L293D. Following pins are taken as input in the microcontroller:
• Pin 0 .0 - Left sensor
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• Pin 0 .1 - Front sensor
• Pin 0.2 - Right sensor
Following pins are taken as output from the microcontroller
For motor 1• Pin1.0 . • Pin 1.1
For motor 2• Pin2.0 • Pin 2.1 Eight 10k pull up resistors are connected to the microcontroller at port P0. Rest of the ports have inbuilt pullup resistors, so there is no need to connect pull-up resistors to port1 , port2 and port3.
COMPONENTS USED
• IR Transmitter and Reciever
• Microcontroller (AT89S52)
• Motor Driver(L293D)
• Timer (LM555)
• DC Motor
• Voltage Regulator(LM7805)
• Variable Resistance
IR Transmitter
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The IR Transmitter block is used to generate IR signal. It uses timer IC555 in astable multivibrator mode to generate square wave which have continuous pulses of 50% duty cycle of frequency 38 KHz.
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Circuit diagram IR transmitter
IR receiver Tsop (1738)
Description
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IR sensor (TSOP 1738) which gives normally 5v at its output but. after receiving infrared light , output of sensor is 0v.
The TSOP17.. — series are miniaturized receivers for infrared remote control systems. The demodulated output signal can directly be decoded by a microprocessor.
Features
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• Improved shielding against electrical field disturbance
• Output active low • Low power consumption • High immunity against light • Continuous data transmission possible (up to 2400 bps) • Suitable burst length 10 cycles/burst
Circuit diagram IR receiver
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IR sensor Module
MICROCONTROLLER (AT89S52) The AT89S52 is a low-power, high-performance CMOS 8-bit microcomputer with 8 Kbytes of Flash programmable and
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erasable read only memory (PEROM). The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip the Atmel AT89S52 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.
AT89S52
Pin Configurations:
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Pin Description Vcc Supply voltage GND Ground
Port 0
• Port 0 is an 8-bit bidirectional IO port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as inputs.
• Port 0 can also be configured to be the multiplexed low-order address data bits during accesses to external program and data memory.
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• Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pull-ups are required during program verification.
Port 1
Port 1 can be used as input or output, In contrast to port 0, this port does not need any pull-up resistors since it already has pull-up resistors internally. Upon reset, port 1 is configured as an input port. To make port 1 an input port, it must be programmed as such by writing 1to all its bits
Port 2
• Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. • The Port 2 output buffers can sink/source for TTL inputs. When 1s are
written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs.
• Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that uses 16-bit address.
• Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.
Port 3
• Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. • The Port 3 output buffers can sink/source for TTL inputs.
When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs.
• Port 3 also receives some control signals for Flash programming and programming verification.
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RST
Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device.
ALE/PROG Address Latch Enable is an output pulse for latching the low byte of the address during access to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes.
XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2 Output from the inverting oscillator amplifier
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier that can be configured for use as an on-chip oscillator, as shown in Figure below. Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven, as shown in Figure below.
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MOTOR DRIVER(L293D) The Device is a monolithic integrated high voltage, high current driver designed to accept standard TTL logic levels and drive inductive loads (such as relays solenoids, DC and stepping motors) and switching power transistors.
The L293D can drive current of up to 600mA with voltage range of 4.5 to 36 volts. It is suitable to drive small DC-Geared motors, bipolar stepper motor etc.
Specifications . Supply Voltage Range 4.5V to 36V . 600-mA Output current capability per driver. Separate input- logic supply
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Thermal Shutdown
High-Noise-immunity inputs
PIN CONFIGURATION
Pinout of L293D
Circuit implementationL293D L293D motor driver needs two voltage levels• 12V at pin no.8 • 5V at pin no. 1 ,9 and 16. The main function of driver is to amplify the 15mA current,
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coming from the microcontroller which is incapable to drive 50mA rating motor it can give output current upto 600mA.
L293d as Driver Circuit
The driver circuit basically consists two H-bridges for diving small DC motors. In a H-bridge circuit there are four transistors of which only two are in ON state which are located diagonally. The two pairs of transistors gives the bidirectional rotation of motor.
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OTHERS
TIMER(LM555)
General Description
The LM555 is a highly stable device for generating accurate time delays or oscillation. Additional terminals are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running frequency and duty cycle are accurately controlled with two external resistors and one capacitor.
LM555
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ASTABLE OPERATION
If the circuit is connected as shown in Figure (pins 2 and 6 connected) it will trigger itself and run as a multivibrator. The external capacitor charges through RA + RB and discharges through other resistor. Thus the duty cycle may be precisely set by the ratio of these two resistors.
In this mode of operation, the capacitor charges and dis charges between 1/3 V and 2/3 V.
DC MOTOR (12v -50mA)
DC Motors are very commonly used in robotics. DC motors can rotate in both directions depending upon the polarity of current through the motor. These motors have high speed which can be reduced with the help of gears and traded off for torque.
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Dc Motor(45rpm)
Here a bidirectional DC motor is used so that the motors can move in both forward and backward directions ,dodging any obstacle that comes in its path.
VOLTAGE REGULATOR
(LM7805) The LM78M05, a three-terminal positive voltage regulator employs built-in current limiting, thermal shutdown, and protection mechanism which makes them virtually immune to damage from output overloads. With adequate heat sinking, they can deliver in excess of O.5A output current.
Features
• Output current in excess of 0.5A • No external components• Internal thermal overload protection• Output voltages of 5V
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CIRCUIT IMPLEMENTATION voltage Regulator is needed as because we have different voltage level requirement in different components e.g motor requires 12v supply but circuits like microcontroller board and voltage comparator require only 5 V supply.
LM7805
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VARIABLE RESISTANCE
Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle. The track may be made from carbon, ceramic and metal mixture or a coil of wire (for low resistances). The track is usually rotary but straight track versions, usually called sliders, are also available. Variable resistors are often called potentiometers in books and catalogs. They are specified by their maximum resistance, linear or logarithmic track, and their physical size. The standard spindle diameter is 6mm.
Mechanical designIt is made up of light weight material , steel which provides easy movement of the robotic vehicle. It has folowing provisions in it: • Slot for DC motors.
• Rear support wheel. • Slot to clamp sensors. • 12V battery holder.
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ALGORITHM
While (1)
{
Read sensor input
if left_obstacle
{
Stop
Move back
Move right
}
elseif right_obstacle
{
Stop
Move back
Move left
}
elseif front_obstacle
{
Stop
Move back
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Move left
}
elseif left && front obstacle
{
Stop
Move back
Move right
}
elseif right && front obstacle
{
Stop
Move back
Move left
}
elseif left && right obstacle
{
Stop
Move back
Move left
}
elseif left && front && right obstacle
{
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Stop
Move back
Move left
}
else
Move forward
}
}
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SCREEN SHOTS OF KEIL PROGRAMING
Program written for the microcontroller chip is compiled using the well known compiler keil uvision 4 which provides extensive library for various microcontrollers and then converts the program into hex file which is used to burn the flash of the microcontroller. It also provides various utilities for debugging and simulation.
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SCREEN SHOTS OF LOADING PROGRAM
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PROBLEMS FACED
FAULTY MlCROCONTROLLER BOARD
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The first microcontroller we used had its write enable failed. Perhaps it was damaged during transportation. Then we used other microcontroller but after burning the microcontroller using the first code it seemed that no program was written at all in the flash memory. Later on we found that the microcontroller had some inherent problem and we had to replace it.
Keil programming
The microcontroller board was not giving output as it seemed that no program was stored in microcontroller although we had burnt the program. After detailed analysis of the program we found that we had not defined certain pins and then we made necessary modifications in our program. Moreover we had to burn the flash memory several times because the initial program did not take into account several scenarios which became evident only after test run. Finally after several iterations through the program we finally created a robust code.
MOTOR DRIVER CIRCUIT
Initially we decided to use ULN2003 as motor driver circuit as it is a darling on pair connection which also amplifies current but we were unable to drive the motor with the help of this IC. Then we decided to use L293D which as it has itself built-in two H bridge circuits. This time we were successful to drive both the motors.
EXCESSIVE HEATING OF LM7805
we observed that when power supply was given continuously for more than 6 to 7 mins. LM7805 got heated upto undesirable level enough to burn human skin. To overcome this excessive heat we incorporated almnini heat sink with both the LM7805 ICs.
FUTURE SCOPE
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Some of the improvements that can be made are the following:
• The rover can be made to follow a specific pattern with slight change in the program. Such improvement could be used in industries where robots have to only traverse a specific path.
• The rover can be instructed dynamically over the wireless to follow a particular path depending upon the information sent to the base station. Such systems can be used as intelligent transport systems without the need of a driver.
• The rover can also be used as vaccum cleaner with slight change in hardware and programming.
• The rover can also be used as lawn mover after making necessary changes.
• It can also be used as firefighting robot after incorporation of thermal sensors and fire fighting mechanism and change in code.
• It can also be used as mine detector after addition of mine detecting module and necessary change in programming.
• Increment in number of sensors to enhance the obstacle detection capability
• It can also be used as a spy robot.
DATA SHEETS
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REFERENCE AND RESOURCES
• The 8051 Microcontroller and Embedded Systems Using Assembly and C Second Edition byMuhammad Ali Mazidi
• Basic electronics by Millman Halkyies
• understanding electronic components by fillopovic d miomir
• Wikipedia/microcontroller
• www.engineeringprojects.org
• http://indianengineer.blog.co.in
• www.8051projects.com
• Basic Tutorial for Keil software Written by www.microdigitalEd.com
