74*245 Motor Driver

H-Bridge Driver

Simple PWM Gen.

Handy Method Measuring RPM

Measuring RPM via Photo reflector

Introduction to Robotic

DC, Stepper,and Servo Motor

Microcontroller Tutorial

Computer Interface
Tutorial
.............more links

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Common problems and their solution
Q: I have got the photodetector and LED, both are transparent how do I know which one is which?
Ans: Just look from the top of both LEDs, a photodetector will have a black dot in the inside while an LED will be somewhat shiny from the inside. (Answer, Courtesy: NIT Trichy Lab Staff)

Q: My circuit wirks fine but it does not differentiate between black and white, it acts more as an object detection circuit?
Ans: This is perhaps the most common problem. You are using the IR LED with a very small resistance which has increased its power, just use a higher resisance. Good values are 470 ohm to 1K.

Q: All the circuit is good but nothing happens??
Ans: Make sure that in any case , LED light falls on top of the photodetector and not the side of the photodetector. For starters, take an LED photodetector pair and make them face each other top to top, connect them using the line follower circuit and check the output variation by putting a dark paper or something in between to disrupt the light. Later, tilt the pair such that a beam of light from LED will fall on top of the photodetector after reflecting off a piece of paper.

Remember, when using more than one such block ( the first figure ), instead of using seperate potentiometers (variable resistances) per block, directly connect the pointer part of the first block's variable resistance to the other block's comparator's positive port and tune it again.

The Last problem and perhaps the most important problem is that of motor speed control. We can always use a PWM generator using 555 but that is a fixed speed during the whole line follwing. For dynamic speed, we can use transistors but that is complex ( for beginners, according to me). Hence microcontroller based line followers are preferred because of their customizable features..

Any other questions can be asked in the comments section or in the forums. Happy Line following!! The next tutorial will be a microcontroller based Line Follower.

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