Introduction
What is a line follower?
Line follower is a machine that can follow a path. The path can be visible like a black
line on a white surface (or vice-versa) or it can be invisible like a magnetic field.
Why build a line follower?
Sensing a line and maneuvering the robot to stay on course, while constantly correcting
wrong moves using feedback mechanism forms a simple yet effective closed loop
system. As a programmer you get an opportunity to ‘teach’ the robot how to follow the
line thus giving it a human-like property of responding to stimuli.
Practical applications of a line follower : Automated cars running on roads with
embedded magnets; guidance system for industrial robots moving on shop floor etc.
Prerequisites:
Knowledge of basic digital and analog electronics.
(A course on Digital Design and Electronic Devices & Circuits would be helpful)
C Programming
Sheer interest, an innovative brain and perseverance!
Background:
I started with building a parallel port based robot which could be controlled
manually by a keyboard. On the robot side was an arrangement of relays connected to
parallel port pins via opto-couplers.
The next version was a true computer controlled line follower. It had sensors
connected to the status pins of the parallel port. A program running on the computer
polled the status register of the parallel port hundreds of times every second and sent
control signals accordingly through the data pins.
The drawbacks of using a personal computer were soon clear –
It’s difficult to control speed of motors
As cable length increases signal strength decreases and latency increases.
A long multi core cable for parallel data transfer is expensive.
The robot is not portable if you use a desktop PC.
The obvious next step was to build an onboard control circuit; the options – a
hardwired logic circuit or a uC. Since I had no knowledge of uC at that time, I
implemented a hardwired logic circuit using multiplexers. It basically mapped input from
four sensors to four outputs for the motor driver according to a truth table. Though it
worked fine, it could show no intelligence – like coming back on line after losing it, or
doing something special when say the line ended. To get around this problem and add
some cool features, using a microcontroller was the best option