LINE FOLLOWING ROBOT

The sensor module has two LED-LDR sensor pair mounted on it (Minimum two is required. You can use any number). The LED or light emitting diode is a semiconductor light source which we will be using. I had used a 5mm white LED for my project. Also, LDR or Light dependent resistor is used here as a Light sensor.
 It senses the reflected light; i.e light transmitted by the LED and reflected from the surface. 
If the surface is white, LDR will detect the light. In case the sensor is placed over black surface, LDR cannot detect any light, as the black surface has absorbed all the light.


Components :
High power LED (5mm) - 2 to 4
LDR's -2 to 4
Preset 20k -2 to 4
220 Ohm Resistors -2 to 4
L293d -1
Geared motors -2
Chassis
4.8V Li-ion rechargeable battery
Burg strip, 2 pin relimat & other secondary stuff..

CIRCUIT DIAGRAM

The Left sensor-pair is connected to the left Motor and Right sensor-pair is connected to the right Motor. Notice that the sensor (Either left or right), from which the arrow is pointing outwards is our white LED (transmitter) which emits white light and the one on which arrow is pointed to is LDR or Light dependent resistor (Receiver). This LDR detects the amount of light that will get reflected from the surface, depending on whether the surface is white or black-line.

Working principle:

Our 9th grade science book has taught us that, when light falls on white surface, it gets reflected. When it falls on black surface (or any dark surface) light gets completely absorbed by it. How is this concept applied here? The sensor module has two LED-LDR sensor pair mounted on it (Minimum two is required. You can use any number). The LED or light emitting diode is a semiconductor light source which we will be using. I had used a 5mm white LED for my project. Also, LDR or Light dependent resistor is used here as a Light sensor. It senses the reflected light; i.e light transmitted by the LED and reflected from the surface. If the surface is white, LDR will detect the light. In case the sensor is placed over black surface, LDR cannot detect any light, as the black surface has absorbed all the light.

How Robot follows Line:
(Here I have used two LED-LDR sensor pair instead of four)

Please try to understand that the Left sensor-pair is connected to the left Motor and Right sensor-pair is connected to the right Motor. Notice that the sensor (Either left or right), from which the arrow is pointing outwards is our white LED (transmitter) which emits white light and the one on which arrow is pointed to is LDR or Light dependent resistor (Receiver). This LDR detects the amount of light that will get reflected from the surface, depending on whether the surface is white or black-line.