Tape Detection / Line Following
Line Sensors:
Once we locked on onto the loading zone and approached the center vertical line on the playing field, we used line sensors to the T.
The line sensors were positioned at the center front of the bottom base, on variable-height mounts. We found that positioning the sensors 2-3 millimeters above the playing field gave the most accurate readings. Adding an opaque plastic skirt around the front of the robot reduced fluctuations in light levels throughout the day and allowed line-detecting thresholds to remain appropriate in changing light conditions. Although hysteresis was built into the initial code used to line follow, the circuit was not noisy enough to warrant making an upper and lower threshold for light levels. Instead, there was a single threshold value and a reading above this signaled that the sensor was over black tape, and a value below this indicated that the sensor was not above black tape.
Once we locked on onto the loading zone and approached the center vertical line on the playing field, we used line sensors to the T.
The line sensors were positioned at the center front of the bottom base, on variable-height mounts. We found that positioning the sensors 2-3 millimeters above the playing field gave the most accurate readings. Adding an opaque plastic skirt around the front of the robot reduced fluctuations in light levels throughout the day and allowed line-detecting thresholds to remain appropriate in changing light conditions. Although hysteresis was built into the initial code used to line follow, the circuit was not noisy enough to warrant making an upper and lower threshold for light levels. Instead, there was a single threshold value and a reading above this signaled that the sensor was over black tape, and a value below this indicated that the sensor was not above black tape.
Parts Required:
3 - Line Sensors (OPB704WZ)
3 - Resistors
3 - Op-Amps (LM 324D)
3 - Line Sensors (OPB704WZ)
3 - Resistors
3 - Op-Amps (LM 324D)
In the photos below, placement and mounting of the line sensors is shown as the plastic skirt is being attached to the base.
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Circuit Diagram:
A trans-resistive circuit (diagram pictured below) improved the accuracy our readings gave while on and off the tape. The excellent functionality of this circuit was integral in the success of our robots line following ability.
A trans-resistive circuit (diagram pictured below) improved the accuracy our readings gave while on and off the tape. The excellent functionality of this circuit was integral in the success of our robots line following ability.
