Fire Bird V ATMEGA2560 Hardware Manual
3.12 White Line Sensor:
White line sensors are used for detecting white line on the ground surface. White lines are used
to give robot sense of localization. White line sensor consists of a highly directional photo
transistor for line sensing and bright red LED for the illumination. Due to the directional nature
of the photo diode it does not get affected with ambient light unless it is very bright.
Figure 3.39: White line sensor
Figure 3.40: White Line sensor
When the robot is not on a white line, amount of light reflected is less, hence less leakage current
flows through the photo transistor. In this case, the line sensor gives an output in the range of 2V
to 3.3V. 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 2 to 0.1V.
Power to the red LEDs of white line sensor is controlled PG5 of ATMEGA2560 microcontroller
to extend robot’s battery life. Switching action of the power control circuit is exactly same as
power switching circuit of IR proximity sensors as discussed in section 3.11. Line sensors can be
permanently turned on by inserting jumper in the Jumper J1-4. For more information refer to
figure 3.35 and table 3.11.
Figure 3.41a shows schematic of the whiteline sensor module on the main board and figure 3.42
shows location of potentiometers for the white line sensor calibration. Standard Fire Bird V robot
has 3 channel white line sensor module. It can also be seamlessly upgraded to 7 channel white
line sensor module using the same connector. Main board has potentiomenters for 7 ch white line
sensors. For more information regarding upgrade, refer to the application note in the application
notes section in the documentation CD.
Important:
Standard Fire Bird V robot is shipped with 3 potentiomentrs for 3 channel white line sensor
module. Additional 4 potentiomenters can be readly soldered on the main board. Figure 3.42
shows all seven potentiomenters but robot is shipped with only 3 potentiomentrs for left, centre
and right side white line sensor.
© NEX Robotics Pvt. Ltd. and ERTS Lab, CSE, IIT Bombay, INDIA 49
