NEX ROBOTICS SPARK V ATMEGA16 Hardware Manual page 30

Figure 3.25: White Line sensor calibration potentiometers
When the robot is not on a white line, amount of light reflected is less hence less leakage current
flows through the photo diode. In this case, the line sensor gives an output in the range of 3volts
to 5 volts. When the sensor is on a white line, more light gets reflected resulting in considerable
increase in the leakage current which causes voltage across the sensor to fall between 3 to 0.1V.
Sensor's sensitivity to the white and dark surface can be adjusted by controlling brightness of the
IR LED. This is done by adjusting potentiometer which is connected in the series of the IR LED.
Figure 3.25 shows the potentiometers used for white line sensor calibration. When potentiometer
is moved fully counterclockwise, IR LED's intensity will be maximum. Robot's sensors are
calibrated for optimal performance when robot is shipped from the factory.
White line Sensor
Left
Center
Right
Table 3.7 White line sensor connections with ADC of the ATMEGA16
Note:
Be very careful while selecting black surface for the line following. Black can be from ultraviolet
side or from the infrared side. If black is from the infrared side then for IR light it will be like
white surface as infrared black will reflect almost all the light. In such case it will be difficult for
the robot to differentiate between white and black surface.
© NEX Robotics Pvt. Ltd. and ERTS Lab IIT Bombay, INDIA
ADC channel number
ADC channel no. 3
ADC channel no. 4
ADC channel no. 5
Figure 3.26: White Line Sensor
SPARK V ATMEGA16 Hardware Manual
30