Line Follower Robot Tutorial

March 20th, 2008 by Robot Technology | 79 Comments | Filed in Electronics, Mechanics, Microcontroller, Programming, Robotics Tutorial, Sensors, Software

Line Follower ROBOT

Plermjai Inchuay, plermjai@loxinfo.co.th

Award winner from VingPeaw Competition 2543, the robot built with 2051, L293D, and four IR sensors. Simple circuit and platform, quick tracking and easy-understand program using C language.

Line Follower Robot design

I designed my robot, which use two motors control rear wheels and the single front wheel is free. It has 4-infrared sensors on the bottom for detect black tracking tape, when the sensors detected black color, output of comparator, LM324 is low logic and the other the output is high. Microcontroller AT89C2051 and H-Bridge driver L293D were used to control direction and speed of motor.

line follower robot circuit

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Photo Detectors

March 20th, 2008 by Robot Technology | No Comments | Filed in Robotics Articles, Sensors

Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:

photo sensor

Most optical detectors are quantum devices in which an individual photon produces a discrete effect.

  • Chemical detectors, such as photographic plates, in which a silver halide molecule is split into an atom of metallic silver and a halogen atom. The photographic developer causes adjacent molecules to split similarly.
  • Photoresistors or Light Dependent Resistors (LDR) which change resistance according to light intensity
  • Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated
  • Photodiodes which can operate in photovoltaic mode or photoconductive mode
  • Photomultiplier tubes containing a photocathode which emits electrons when illuminated, the electrons are then amplified by a chain of dynodes.
  • Phototubes containing a photocathode which emits electrons when illuminated and in general behaves as a photoresistor.

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The Difference Between Stepper Motors, Servos, and RC Servos

March 20th, 2008 by Robot Technology | 1 Comment | Filed in Electronics, Mechanics, Robotics Tutorial

robotics motors

Stepper motors:
A stepper motor’s shaft has permanet magnets attached to it. Around the body of the motor is a series of coils that create a magnetic field that interacts with the permanet magnets. When these coils are turned on and off the magnetic field causes the rotor to move. As the coils are turned on and off in sequence the motor will rotate forward or reverse. This sequence is called the phase pattern and there are several types of patterns that will cause the motor to turn. Common types are full-double phase, full-single phase, and half step. To make a stepper motor rotate, you must constantly turn on and off the coils. If you simply energize one coil the motor will just jump to that position and stay there resisting change. This energized coil pulls full current even though the motor is not turning. The stepper motor will generate a lot of heat at standstill. The ability to stay put at one position rigidly is often an advantage of stepper motors. The torque at standstill is called the holding torque.

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Voltage Comparator

March 20th, 2008 by Robot Technology | 3 Comments | Filed in Electronics, Robotics Tutorial

In electronics, a comparator is a device which compares two voltages or currents and switches its output to indicate which is larger. More generally, the term is also used to refer to a device that compares two items of data. Output voltage will “switch” whenever the input voltage (at the inverting input) reaches the reference voltage Vref (at the non-inverting input). It is very useful for comparing signals and working with sensors

Simple comparator shown below:

Note that R2 and R1 form a voltage divider. Use a potentiometer in place of R2 for an adjustable reference voltage.

Comparator cicuits can be built with opamps, but there are also comparator ICs with large slew rates and short propagation delays – good for high speed switching.

A dedicated voltage comparator will generally be faster than a general-purpose op-amp pressed into service as a comparator. A dedicated voltage comparator may also contain additional features such as an accurate, internal voltage reference, an adjustable hysteresis and a clock gated input.

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Line Follower Sensor

March 20th, 2008 by Robot Technology | 4 Comments | Filed in Sensors

The circuit diagram for the Line Follow Sensor board is shown below:

The board is connected directly to the Light IO board via PL4.

This circuit is very simple. +5V is applied via PL4 pin 4 to the circuit, and 0V is connected to pin 1 of PL4. When power has been applied, which is controlled by the processor1 board, Infra-Red LEDs D1 and D2 will emit Infra-Red light. If you

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