The designed robot is made to follow a line. The line could be white or black in Colour. These types of robots are mainly categorized into two, robots that follow the black line and the other type is robots that follow a white line. The major decision made by the robot is sensing the line to follow and running over it.
The concept that makes the basis of this robot is in relation to light, how light would behave when in contact with a white or black surface. Light falling on white surfaces are reflected, light falling on black surfaces are is reflected. The behavior, therefore, is fundamental to building robots that follow lines.
The robot to be designed in this project is Arduino based, making use of IR receivers and transmitters. These devices receive and send light respectively. The transmitter sends infrared light which would fall on the surface, either on a white or black surface. If the rays fall on a white surface greater percentage of it would be reflected back and received by the receiver that would generate changes in voltage. When the rays fall on black surfaces, the greater percentage would be absorbed with the very little amount being received by the receiver thereby no significant voltage changes would be generated.
This robot is Arduino based in that the sensing of a white surface leading so voltage changes produce an input to the Arduino but black surfaces would not produce such an input.
The arduino chosen was arduino pro mini whose advantage is the easy-to-use Arduino software that is quite flexible for advance and beginner applications. The software has the capability of running in Windows, Mac and Linux, key in robot programming. Other microcontrollers that may have been used include Phidgets, Parallax Basic Stamp, Handyboard and BX24. Most architects and designers have built interactive prototypes that are applied in music and art in the installation and experimentation f new instruments of music. Such features have made it possible for hobbyists, children, programmers and artists come up with inventions simply from following instructions available online. These other microcontrollers also exhibit the same advantages as the used Arduino microcontroller. The reasons for picking Arduino pro mini microcontroller include
The software is able to run on Mac, Linux and Windows operating systems.
Its board is less expensive if compared to the other named microcontrollers.
The IDE of Arduino software can be used by beginners for simple application as well as advance purposes. Similarly, the software can be used in teaching conveniently in the programming environment thereby making familiarization easier.
Other than experienced individuals in making Arduino circuits using it, the Arduino connection is that simple to allow relatively experienced individuals build properly functioning.
Combining the open source hardware, clear simple programming and Arduino’s cross-platform makes the Arduino selection a better choice in microcontrollers. Specifically selected Arduino is the Arduino pro mini that is smaller making it light and breadboard compatible. Burning the program requires FTDI burner.
Using the motor driver, L293D makes use of its 16 pins whereby, the pins are split into eight pins on every side both sides being dedicated to motor control. L293D has two H-Bridge that has the simplest controlling circuit utilizing low current rating.
These are the functions of all the pins of the motor driver;
Enables working of left side only when it is HIGH and turns off this side when otherwise.
It is INPUT 1 that allows a flow of current through output I when it is HIGH.
It is the OUTPUT 1 that is connected to a motor’s terminal.
These are ground pins.
It is OUTPUT 2 that is connected to a motor’s terminal.
It is The INPUT 2 that allows current flow through it when it is HIGH.
It is the VCC2 providing 5 V power source for use in the IC.
Allows functioning of the IC’s right side only when it is HIGH but turns the side off when LOW.
It is the INPUT 3 allowing current flow through it when HIGH.
It is the OUTPUT 3 allowing current flow through it when HIGH.
These are ground pins.
It is the OUTPUT 4 that is connected to a motor’s terminal.
It is the OUTPUT 4 allowing current flow through it when HIGH.
It is the VCC1 allowing voltage supply to the motor.
The two channels from the motor driver are for operating the chosen 2 motors. Having 2 pairs inbuilt Transistor Darlington as well as a separate supply of power pin that externally supplies the motors.
This is a sensor that composes of IR LED, LM358, potentiometer, LED and resistors. IR sensors are made to transmit infrared light with the photodiode receiving the transmitted light.
Its features include;
5V DC or 3.3V
OUT – output digital pin to be connected to the microcontroller’s input digital pin. In this scenario the Arduino pro mini microcontroller. Its output would be logic LOW if the object detects.
GND – It is the ground of the module also referred to as 0V.
VCC – This is the positive supply that is connected to an option +5V or +3.3V.
They are two in number one being red to indicate power on and another being green to show detection of an object.
Detects obstacle on a range of 2 to 10 cm.
This has an onboard potentiometer that translates the detected range.
Detects approximately 35 degrees
Allows its ease incorporation onto a breadboard.
The IR module is easy to connect to all microcontroller types.
It has a dimension of 3.1 by 1.5 cm.
An addition of a voltage regulator would allow development of 5 V for an operation of Arduino, motor driver as well as the comparator to be implemented in the circuit. Including a battery voltage source of amount 9 V also enables powering of the circuit.
The robot’s design can be split into three sections; control section, sensor section and the driver section.
The sensors in the robot are a composition of a potentiometer, IR diodes, LED and op-amp comparator. The voltage is referenced at the terminal of the comparator using the potentiometer. Line sensing is done by the IR sensors that also provide voltage changes at the second terminal of the comparator. Both voltages at the first and second terminals of the comparator are compared by the comparator that later produces an output in the digital signal. This robot that was designed made use of two comparators for the two sensors. The comparator used was LM 358 possessing inbuilt op-amps with low noise (John-David, et al., 2011).
The line following process needs a point of control which is the Arduino pro mini. Comparator outputs would have a connection the Arduino pins 2 and 3 that are digital. The signals would then be read by the Arduino which send commands driving the line follower to the driver circuit (Richard, 2014).
Sections found in the driver sections include; 2 DC motors and motor driver. The motor driver drives the motors in the robot since the voltage supplied by the Arduino as well as the current would not be enough. These motor drivers then produce ample voltage and current to the motors. However, sending such voltages to the motors would firstly depend on the commands from the Arduino.
Once the robot senses a black line, the signal generated from comparator would be sent to the Arduino. The Arduino being the controller makes a command and sends it to the motor driver that would drive the robot’s motors in accordance with the output from the sensor (Richard, 2014).
The sensors used in this project are the right and left IR sensors. If both sensors sense a white surface then the motion produced is a forward movement.
In case the left sensor senses a black surface, the resulting motion would be to turn left.
In case the right sensor senses a black surface, the resulting robot’s movement would be turning right.
These movements would recur until both sensors sense white surfaces. If both surfaces are white, the robot moves forward.
Once both sensors sense black surfaces, the robot comes to a halt.
The complete diagram of the wired circuit is drawn above. The comparators’ output has a direct connection to the digital pins 2 and 3 of the Arduino. Input pins 7, 15, 2 and 10 from the motor driver are connected to the digital Arduino pins 5, 7, 4 and 6 respectively. A motor of the robot has a connection to the output pins 6 and 3 of the motor driver while the other motor being connected to out pins 14 and 1 of the same motor driver.
Firstly, the program defines the output and input pins before creating a loop that checks these inputs before sending outputs in accordance with the input signals to an output pin directed to the motor driver. In the checking process of the input signal, the “if” statements were used.
The statement has a total of four conditions that need to be read through using the Arduino as the robot follows the line. A total of two IR sensors were used in the project.
|
Input |
Output |
Robot Movement |
||||
|
Right Sensor |
Left Sensor |
Right Motor |
Left Motor |
|||
|
RS |
LS |
LM2 |
LLM1 |
RM2 |
RM1 |
|
|
0 |
0 |
0 |
0 |
0 |
0 |
Stop |
|
0 |
1 |
0 |
1 |
0 |
0 |
Turn Left |
|
1 |
0 |
0 |
0 |
0 |
1 |
Turn Right |
|
1 |
1 |
0 |
1 |
0 |
1 |
Move Forward |
The code of the Arduino is to be written in accordance with the above table.
Conclusion
The use and selection of Arduino pro mini were due to the ease of programming and its incorporation on a breadboard. It also was light with the use of less voltage for its operation. The other components used and connected as in the circuit diagram allowed the robot follow the line with detection from the IR modules. Caution was taken to make a program that only made use of the logic truth table for proper operation and robot movement.
Basu A, Intel Edison Projects (Packt Publishing Ltd 2017).
Grimmett R, Arduino Robotic Projects (reprint edn, Packt Publishing Ltd 2014).
Timmis H, Practical Arduino Engineering (illustrated edn, Apress 2011).
Warren J, Adams J and Molle H, Arduino Robotics (illustrated edn, Apress 2011).
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