Abstract:

This Line follower Robot or buggiee is self powered, Heart of our robo is intel’most power family of microcontroller 8051,we are using, at89c2051microcontroller IC2. IC33 is ld293 motor driver ic which drives two nos motors M1 and M2..IC1 is 7805 ,5v regulator ic.

Circuit operation:
We have fixed INFRA RED sensors on fore side on the robo. The principle of sensors is that black colour will normally observe the light where other colours will normally reflects the lights light source is fixed down ward D1 and D3 are infra red leds and D2 and D4 are photo diodes reflected light will fall on the photodiode . IR l.e.d. D1 has series resistor R8 limiting the current to 40mA.

This is near the maximum for the l.e.d., producing a high level of illumination. The radiation reflected back from the surface is detected by IR photodiode D2. This is reverse-biased so only a weak leakage current flows.The current passes through a high resistance (R9 plus preset Potentiometer There are two sensors, each comprising an infra-red (IR) l.e.d. and an infrared pho todiode.

The l.e.d. is directed down onto the surface over which the vehicle is travelling. The photodiode receives the reflected radiation. The sensor gives a low logic output when the surface is black or dark- coloured, and a high output when the surface is white or light- coloured.

The reason for using infra-red is to avoid interference from ambient light. No problems were found when operating in bright indoor daylight, or in low-level incandescent illumination.The sensors are used to detect lines painted in black on a white background. Theoretically, it is possible to operate the sensors in the reverse direction, by chang ing the program so that they respond to white lines on a black background.

This was the original intention, but an unexpect ed problem was encountered some black cardboard is not black, or at least, it is not black in infra-red light.Two different batches of black card were tried, purchased from the same stationers. They both looked equally black to the eye; one did not reflect IR, but the other reflect- ed it very strongly. The robot was unable to detect a white strip on the reflecting black background. So it was decided to use white (or light-coloured) fluorescent or metallic card as the background and paint the paths IC5 is nand gate ic 4011 to reverse the logic before it is given to p3.3 and p3.4 of the microcontroller as left and right sensor input.