Line follower Robot / Buggie
One of my friend
working for B.H.E.L asked me once ,can you design a control circuit for the
truck so that the truck can be operated without driver on the road.Thay had lot
of trouble with the local union ,and some times drivers do not perform the way
they are expected.Their requirement was to convey a raw material from point a
to point b in a circular fashion. Road reserved only for this purpose.
One truck normally
takes 150 trips in a day and they want to increase this frequency. There was
lot of trouble with designing realtime due to so many factors,but I kept in
mind when my student friend asked me to design for them, I worked on the
project and this is the presentation.
This 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.
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.
This low logic
detection confirms that the robo is not on the black road if the robo is out of
the black road this logic will become low and it indicates off-road. Depending
upon the left or right sensor robo will move towards right or left direction in
order to stay on road out put from both the sensors shoul be high when the robo
is on the road.