Posted by : AVINASH CHAKRAVARTHI Wednesday, 2 October 2013

it really nice experience to make line follower to this weekend .
we can make it either by  using micro controller or with out micro controller.
first we will see without making microcontroller :-
steps involving to make this:
we should make ir transmitter and reciever.
(black colour strip is good observer of IR where  white colour is good reflector.)

so,when line follower robot passes over the black strip the light fallen from IR transmitter is not reflected back and when it passes over the white surface IR transmitter receives the signal.

when passes over black surface ir signal absorbed
so, ir RX doesn't receives any signal and viceversa .
assume that we attached the two pair of IR sensors placed in front of the robot .see the below set of conditions.
sensors are connected to the pin 1 and voltage divider is attached to the pin 2 whose voltage is maintained at 2.5 v
we use comparator ,where pin 1 is attached to the out put of the ir receiver and pin 2 is attached to the votage divider.

when the voltage of the sensor is above the 2.5v the output is 5v and when the voltage is less than 2.5v the output will be 0v.

case 1:-

when it passes over the black surface the IR  RX gets 0v .which is connected to the pin 1 of the comparator
so output will be 0v
case 2:-
when it passes over the white surface the IR RX gets >2.5 and <5. so the output of the comparator will be high .

To be more accuracy we will use 3 set of  IR pairs whose receiver ends are connected to comparator which intern connected to logic gates to obtain the below table.

say A is left sensor B is center sensor C is right sensor.

lets us consider the case L+:
k=map for the case L+

from the table,  L+=A'(B'C+BC)+A'(BC+BC')+BC
circut diagram for the case L+:

similarly for the case L-,R+,R-.we can obtain the circuit diagram.

to drive the motors we will use l293d ic (which is like h-bridge):-

the outputs of L-,L+,R-,R+ is connected to pin 4,5,6,7 respectively.and 12v supply is given to l293d.

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