Here’s a design circuit for Line Following Robot sensor or surface scanner for robots is a
very simple, stamp-sized, short range (5-10mm) Infrared proximity detector
wired around a standard reflective opto-sensor CNY70(IC1). This is the figure
of the circuit;
How this circuit can work? IC1
contains an infrared LED and a phototransistor. The LED emit invisible infrared
light on the track and the phototransistor works as a receiver. Usually, black
colored surface reflects less light than white surface and more current will
flow through the phototransistor when it is above a white surface. When a
reflection is detected (IR light falls on the phototransistor) a current flows
through R2 to ground which generates a voltage drop at the base of T1 to make
it conduct. As a result, transistor T2 start conducting and the visual
indicator LED(D1) lights up. Capacitor C2 works as a mini buffer. After
construction and installation, the scanner needs to be calibrated. Initially
set P1 to its mechanical centre position and place the robot above the white
portion of the track.
Now slowly turn P1 to get
a good response from D1. After this, fine tune P1 to reduce false detection
caused by external light sources. Also ensure that the LED remains in off
condition when the sensor module is on the black area. Repeat the process until
the correct calibration is achieved. The red color LED (D1) is only a visual
indicator. You can add a suitable (5V) reed relay in parallel with D1-R4 wiring
after suitable alterations to brake/stop/redirect the robot. Similarly, the
High to low (H-L) transition at the collector of T2 can be used as a signal to
control the logic blocks of the robot. Resistor R1 determines the operating
current of the IRLED inside IC1. The sensing ability largely depends on the
reflective properties of the markings on the track and the strength of the
light output from IC1.
