Aim:The main objective of this project is to build a line follower robot without the use of microcontroller.This type of robot is used to follow a black line against a white background or a white line against a black background.
IR sensors are used in this project.The sensors emit IR radiations in the forward direction and when the black line is not detected the IR radiations emitted by the proximity sensor are reflected back to the IR sensor and the the sensor gets switched off due to which the control input to the L239D IC is off and motor gets switched off due to this and the wheels connected to the motor also switches off.
Explanation of the circuit working:
The IC used here is L239D. The output of the IR sensors are connected to the pin numbers 2 and 15 which are the control inputs to the motors. As discussed earlier the sensor emits IR radiations in the forward direction and when an black line is not detected the IR radiation is reflected back to the sensor and this switches off the sensor and this in turn switches off the motors and the wheels. A single battery is used to power on the L293D IC.
Working of the IR sensor:
An IR proximity sensor works by applying a voltage to a pair of IR light emitting diodes (LED’s) which in turn, emit infrared light. This light propagates through the air and once it hits an object it is reflected back towards the sensor. If the object is close, the reflected light will be stronger than if the object is further away. The sensing unit (for this experiment a Sharp IS471FE will be used), in the form of an integrated circuit (IC), detects the reflected infrared light, and if its intensity is strong enough, the circuit becomes active. When the sensing unit becomes active, it sends a corresponding signal to the output terminal which can then be used to activate any number of devices. For the purpose of this exercise, a small green LED will turn on when the sensor becomes active.