LINE FOLLOWER ROBOTIC CIRCUIT

Principle:      

This circuit consists of ATmega8 microcontroller, two IR sensors, motors and motor driver IC. The line follower robot needs mechanical arrangement of the chassis. Assume a two wheel robotic vehicle with a castor wheel. The two IR sensors are mounted on the robot facing towards Earth.

When robot is placed on the fixed path, it follows the path by detecting the line. The robot direction of motion depends on the two sensors outputs. When the two sensors are on the line of path, robot moves forward. If the left sensor moves away from the line, robot moves towards right. Similarly, if right sensor moves away from the path, robot moves towards its left. Whenever robot moves away from its path it is detected by the IR sensorIR sensor consists of IR transmitter and IR receiver on a board. When the vehicle is moving on a black line, IR rays are continuously absorbed by the black surface and there is no reflected ray making output high. Whenever, the robot moves out to the white surface, it starts reflecting the IR rays and making the output low. Thus depending on the output of IR sensor microcontroller indicates the motors to change their direction.

Components:-

ATmega8 microcontroller
Motor driver IC (L293D)
Motors
Resistors-R1 to R4.
IR transmitters – IR TX1,IR TX2
IR Receivers -IR RX1,IR RX2


Design of IR Sensors:

IR sensor circuit consists of mainly IR transmitter and IR receiver. IR transmitter is similar to an LED. Its operating voltage is around 1.4V. So to protect it, a 10k resistor is placed before IR and is connected in forward biased. IR receiver is connected in reverse bias and a 15K resistor is placed between VCC and the receiver. Output is taken between resistor and IR receiver.

Line Following Robotic Vehicle Circuit Working:
Initially draw the path on the chart with black color.
Place the robot on the chart.
Now power the circuit.
Robot moves in the specified path.
When it moves out of path, sensors check it and automatically adjust the robot.




Working of IR Sensors:

The IR transmitter continuously transmits the IR rays.  When IR transmitter is on the black surface these rays were absorbed by the surface and when it is on white surface these rays were reflected. The IR receiver has maximum resistance when no IR rays are received and voltage from VCC flows through the resistor. At the output pin, voltage is approximately 5v.

As the intensity IR rays received by the receiver increases, resistance value decreases and reverse break down occurs .Thus voltage through the resistor is grounded. So, at the output pin, it will produce 0V.

Line Following Robot Circuit Applications:
This can be used in driver less car system with some added features like obstacle detection.
This can also be used in industrial and defense applications.
Limitations of Line Follower Robot:

Line follower robot requires 2-3 inches broad line.
It may not move properly if the black line drawn is of low intensity.
The IR sensors may sometimes absorb IR rays from surroundings also. As a result, robots may move in improper way.
Note: If anybody interested on more robotics projects, visit the page: Robotics Projects