Line following robot
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Introduction
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The line follower is a self operating robot that detects and follows a line that is drawn on the floor. The path consists of a black line on a white surface.
The control system used must sense a line and maneuver the robot to stay on course, while constantly correcting the wrong moves using feedback mechanism, thus forming a simple yet effective closed loop system.
The robot uses the Atmega8 microcontroller (28 pins), 3 IR LEDs (Tx), 3 photo Diodes (Rx), DC motor Driver IC (L293D) & two 12v DC motors.
The first Rx receives an analog signal that depends on the intensity of light reflected by the black line of emitted beam by the TX. These signals are sent to the op amp which amplifies the analog signals (0 to 5v) that are fed to Microcontroller Atmega8 ADC port (port A).
The Microcontroller ATmega8 provides PWM to drive the DC motor with the support of Motor driver IC L293D.
Block Diagram
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Basic design and working
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The robot is built with ATmega8L, L293D, IR sensors, LM358, platform chassis. The robot is designed using two motors controlling wheels. It has infrared sensors on the bottom for detect black tracking tape .It captures the line position with the help of these optical sensors called opto-couplers mounted at front end of the robot. (Each opto-coupler consists of an IR LED and an IR Sensor).
When the sensors detect black surface, output of amplifier, LM358 is greater than 2v and for white surface the output is less than 2V. It reports to the microcontroller for accurate control and steering of motors. Microcontroller ATmega8L and Motor driver L293D were used to drive the motors
Input System (Sensor Circuit)
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Capture line position with optical sensors mounted at front end of the robot. For this a combination of IR LED’s and Photo diode is called line sensor. The line sensing process requires high resolution and high robustness. The distance between the two IR sensors is 15mm.
IR reflective sensors have one emitter (IR LED) and one receiver (photo diode) .If we have white surface it reflects the light and it will sensed by the receiver, similarly if we have black surface it absorbs the light and receiver can not sense light.
Processing System (Microcontroller ATmega8)
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Processing system acts as the Brain of robot, which generates desired output for corresponding inputs. For that we use microcontrollers. In present days, there are several companies that manufacture microcontrollers, for example ATMEL, Microchip, Intel, Motorola etc. We will be using ATmega8L microcontroller in our robot. It is an ATMEL product. It is also called AVR. Line follower robot requires simple microcontroller as it uses simple algorithms. We can use any microcontroller for that. But we use ATmega8, because it has following extra features:
. It is an ISP (In System Programmable) device. It means programming (Burning) of ATmega8 IC can be done without removing it from the system.
. It has on chip PWM (Pulse Width Modulation) circuit at three pins (Pin 14, 15 &16).
. It has an inbuilt 6 Channel ADC.
. It consumes low power than other microcontrollers.
Output System (Motor Driving Circuit & DC Motor)
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Motor Driver: From microcontroller we can not connect a motor directly because microcontroller can not give sufficient current to drive the DC motors. Motor driver is a current enhancing device; it can also be act as Switching Device. Thus we insert motor driver in between motor and microcontroller. Motor driver take the input signals from microcontroller and generate corresponding output for motor.
IC L293D: This is a motor driver IC that can drive two motor simultaneously.
For moving a robot we have two dc motor attached to wheels gearsThe robot uses the Atmega8 microcontroller (28 pins), 3 IR LEDs (Tx), 3 photo Diodes (Rx), DC motor Driver IC (L293D) & two 12v DC motors.
The first Rx receives an analog signal that depends on the intensity of light reflected by the black line of emitted beam by the TX. These signals are sent to the op amp which amplifies the analog signals (0 to 5v) that are fed to Microcontroller Atmega8 ADC port (port A).
The Microcontroller ATmega8 provides PWM to drive the DC motor with the support of Motor driver IC L293D.
Block Diagram
................................
Basic design and working
....................................................
The robot is built with ATmega8L, L293D, IR sensors, LM358, platform chassis. The robot is designed using two motors controlling wheels. It has infrared sensors on the bottom for detect black tracking tape .It captures the line position with the help of these optical sensors called opto-couplers mounted at front end of the robot. (Each opto-coupler consists of an IR LED and an IR Sensor).
When the sensors detect black surface, output of amplifier, LM358 is greater than 2v and for white surface the output is less than 2V. It reports to the microcontroller for accurate control and steering of motors. Microcontroller ATmega8L and Motor driver L293D were used to drive the motors
Input System (Sensor Circuit)
...............................................................
Capture line position with optical sensors mounted at front end of the robot. For this a combination of IR LED’s and Photo diode is called line sensor. The line sensing process requires high resolution and high robustness. The distance between the two IR sensors is 15mm.
IR reflective sensors have one emitter (IR LED) and one receiver (photo diode) .If we have white surface it reflects the light and it will sensed by the receiver, similarly if we have black surface it absorbs the light and receiver can not sense light.
Processing System (Microcontroller ATmega8)
................................................................................................
Processing system acts as the Brain of robot, which generates desired output for corresponding inputs. For that we use microcontrollers. In present days, there are several companies that manufacture microcontrollers, for example ATMEL, Microchip, Intel, Motorola etc. We will be using ATmega8L microcontroller in our robot. It is an ATMEL product. It is also called AVR. Line follower robot requires simple microcontroller as it uses simple algorithms. We can use any microcontroller for that. But we use ATmega8, because it has following extra features:
. It is an ISP (In System Programmable) device. It means programming (Burning) of ATmega8 IC can be done without removing it from the system.
. It has on chip PWM (Pulse Width Modulation) circuit at three pins (Pin 14, 15 &16).
. It has an inbuilt 6 Channel ADC.
. It consumes low power than other microcontrollers.
Output System (Motor Driving Circuit & DC Motor)
........................................................................................................
Motor Driver: From microcontroller we can not connect a motor directly because microcontroller can not give sufficient current to drive the DC motors. Motor driver is a current enhancing device; it can also be act as Switching Device. Thus we insert motor driver in between motor and microcontroller. Motor driver take the input signals from microcontroller and generate corresponding output for motor.
IC L293D: This is a motor driver IC that can drive two motor simultaneously.
DC motors: Dc motor is most easy to control. One dc motor requires only two signals for its operation. If we want to change its direction just reverse the polarity of power supply across it. We can vary speed by varying the voltage across motor. By using two motors we can move our robot in any direction. This steering mechanism of robot is called as differential drive.
Gears: The dc motors don’t have enough torque to drive a robot directly by connecting wheels in it. Gears used to increase the torque of dc motor on the expense of its speed.
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