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line (pasting black line on the floor); you just need to make a distinct difference between the track and the
ground environment.
Black line tracking refers to the car drives along the black line on the white floor, it can know where to
drive according to the received reflected light due to the different light reflection coefficient on the black and
white floor.
White line tracking refers to the car drives along the white line on the black floor, it can know where to
drive according to the received reflected light due to the different light reflection coefficient on the white and
black floor.
In the "Hummer-Bot" car, we use the TCRT5000 sensor as tracing module, TCRT5000 infrared reflection
sensor is a photoelectric sensor which consists of an infrared emitting diode and an NPN infrared photoelectric
transistor. The detectable reflective distance is 1mm-25mm, the sensor is specially equipped with M3 fixed
installation holes, so it is easy to adjust the direction, it also has the 74HC14 Schmidt trigger inverter which
ensure the clean signal, the good wave shape and the strong driving ability. It can be applied to robot obstacle
avoidance, robot tracing (detecting black line in white background and detecting white line in black
background), which is the necessary sensor for tracing line robot and other occasions. The PCB size is
3.5cm*1cm, and the physical map is shown in Fig.3.2.16.
3.2.3.2 Working Principle
In the above, we talked about two patterns of tracing-the white line and the black line. In fact, either the
black line or the white line, we usually adopt the infrared detection method.
Infrared detection method means that different objects with different colors have the different infrared
reflection characteristics. The car launches the infrared to the ground continually during driving process, the
infrared receiving tube will be in a shutdown state and the output of the module is low level when the emitted
infrared is not reflected or the reflected infrared is not strong enough, and indicating diode will be off; when
the diffuse reflection occurred on a white floor, the intense reflected infrared will be received by the receiving
Figure .3.2.16 Physical Map of the Module
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