Experiment 9 Lab Manual
American International University- Bangladesh
Department of Electrical and Electronic Engineering
EEE4103: Microprocessor and Embedded Systems Laboratory
Title: Implementation of a motor control system using Arduino: Digital input, outputs, and PWM
Objective:
The objectives of this experiment are to get familiarized the students with the PWM signals
generated by the Arduino and the microcontroller-based DC motor’s speed control.
Theory and Methodology:
Microcontrollers and Arduino are digital devices; they cannot give analog output.
Microcontroller gives ZERO and ONE as output, where ZERO is logical LOW and ONE is logical
HIGH. In our case, we are using a 5 V as the logical HIGH of the Arduino and 0 V as the logical
LOW signal.
Digital output is good for digital devices but sometimes we need analog output. In such a case
the PWM is very useful. In the PWM, the output signal switches between zero and one, on a high
and fixed frequency. Pulse Width Modulation (PWM) is a technique by which the width of a pulse
is varied while keeping the frequency or time period of the wave constant. It is a method for
generating an analog signal using a digital source. A PWM signal consists of two main components
that define its behavior: a duty cycle and a frequency. Pulse Width Modulated signals with different
duty cycles are shown below:
Output Signal Of PWM
As shown in the above figure the ON time is T on and the OFF time is Toff. T is the sum of the Ton
and Toff, which is called the Period, i.e., Time period, T = T ON + TOFF. In the concept of PWM, T
is not varying, and the Ton and the Toff can vary, in this way when T on increases Toff decreases, and
vice-versa, but T remains fixed.
The duty cycle is a fraction of one Time period. The duty cycle is defined as the ratio of ON
pulse duration to the time period. The duty cycle is commonly expressed as a percentage or a
ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a formula, a
duty cycle may be expressed as:
T ON
D= ×100 %
T
Now, the moto r speed varies according to the duty cycle. Suppose the duty is zero, the motor
does not run, and when the duty cycle is 100 % the motor runs at its maximum speed. But this
concept is not always right because the motor starts running after giving some fixed voltage
which is called the threshold voltage.
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 1
Experiment 9 Lab Manual
Microcontroller and the Arduino can process signals and consumes almost 20 to 40 mA current,
but motors need high current and voltage, so we are using the transistor for driving the
motor. Transistor is connected in series with the motor and the transistor’s base is connected to
Arduino’s PWM pin through a resistance. The PWM signal is coming from Arduino and the
transistor works as a switch that short circuits the Emitter (E) and Collector (C) terminals when
the PWM signal is in a HIGH state and normally opens when the PWM signal is in a LOW
state. This process works continuously, and the motors run at the desired speed. The circuit is
given below:
H-Bridge DC Motor Control
To control the direction of rotation, we just need to inverse the direction of the current flow through
the motor, and the most common method of doing that is by using an H-Bridge. An H-Bridge
circuit contains four switching elements, transistors, or MOSFETs, with the motor at the center
forming an H-like configuration. By activating two switches at the same time, we can change
the direction of the current flow, thus changing the rotation direction of the motor. The figure
below is showing the current flow in one direction when one upper and one lower switches are
turned on.
So, if we combine these two methods, the PWM and H-Bridge, we can have complete control over
the DC motor. Many DC motor drivers have these features and the L298N is one of them.
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 2
Experiment 9 Lab Manual
L298N Driver
The L298N is a dual H-Bridge motor driver which allows speed and direction control of two
DC motors at the same time as given below. The module can drive DC motors that have voltages
between 5 and 35 V, with a peak current of up to 2 A.
Let’s take a closer look at the pinout of the L298N module and explain how it works. The module
has two screw terminal blocks for motors A and B, another screw terminal block for the ground
pin, the VCC for the motor, and a 5 V pin which can either be an input or output as shown below.
Next. are the logic control inputs. The Enable A and B pins are used to enable and control the speed
of the motor. If a jumper is present on this pin, the motor will be enabled and work at
maximum speed, and if we remove the jumper, we can connect a PWM input to this pin and
in that way control the speed of the motor. If we connect this pin to the ground, the motor will
be disabled.
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 3
Experiment 9 Lab Manual
Next, the Input 1 and Input 2 pins are used for controlling the direction of rotation of motor A, and
inputs 3 and 4 for motor B. Using these pins, we can control the switches of the H-Bridge inside the
L298N IC. If input 1 is LOW and input 2 is HIGH, the motor will move forward. If input 1 is
HIGH and input 2 is LOW, the motor will move backward. When both inputs are the same,
either LOW or HIGH the motor will stop. The same applies to inputs 3 and 4 and motor B.
Arduino and L298N
Now, let’s make a circuit to control the speed of the motor using a potentiometer and change
the rotation direction using a push button. Here’s the circuit’s schematic diagram. You need to
connect a push button switch at pin 2 of the Arduino with this circuit.
Components List
L298N Driver
12 V High Torque DC Motor
Arduino Board
Potentiometer
A DC power supply
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 4
Experiment 9 Lab Manual
Breadboard and Jumper Wires
Program to be written in ArduinoIDE:
int in1 = 8; //Declaring where our module is wired
int in2 = 9;
int ConA = 10;// Don't forget this is a PWM DI/DO
int speed1;
void setup() {
Serial.begin(9600);
pinMode(2, INPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}
void TurnMotorA(){ //A function to control the direction and speed
if (digitalRead(2) == LOW){
digitalWrite(in1, LOW); //Switch between these HIGH and LOW states to change direction
digitalWrite(in2, HIGH);
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
analogWrite(ConA, PWMvalue);// To activate the DC motor
}
else if (digitalRead(2) == HIGH){
digitalWrite(in1, HIGH); //Switch between these HIGH and LOW states to change direction
digitalWrite(in2, LOW);
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
analogWrite(ConA, PWMvalue);// To activate the DC motor
}
}
void loop() {
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
Serial.print("Digital Value = ");
Serial.print(PWMvalue); //print digital value on serial monitor
//convert digital value to analog voltage
float analogVoltage = (PWMvalue *5.00)/255.00;
Serial.print(" Analog Voltage = ");
Serial.println(analogvalue);
TurnMotorA(); // function that keeps looping to run the motor continuously
//you can add another one with a different direction or stop
}
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 5
Experiment 9 Lab Manual
Alternative version:
int in1 = 8; //Declaring where our module is wired
int in2 = 9;
int ConA = 10;// Don't forget this is a PWM DI/DO
int speed1;
void setup() {
Serial.begin(9600);
pinMode(2, INPUT);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
}
void TurnMotorA1(){ //A function to control the direction and speed in one direction
digitalWrite(in1, LOW); //Switch between these HIGH and LOW states to change direction
digitalWrite(in2, HIGH);
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
analogWrite(ConA, PWMvalue);// To activate the DC motor
}
void TurnMotorA2(){ //A function to control the direction and speed in another direction
digitalWrite(in1, HIGH); //Switch between these HIGH and LOW states to change direction
digitalWrite(in2, LOW);
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
analogWrite(ConA, PWMvalue);// To activate the DC motor
}
void loop() {
float analogvalue = analogRead(A0); // declaring and reading an analog voltage value from the pin
int PWMvalue = map(analogvalue, 0, 1023, 0, 255); // mapping the analog readings to change
// range from 0-1023 to 0-255 to divide the value by 4 to get a PWM value
Serial.print("Digital Value = ");
Serial.print(PWMvalue); //print digital value on serial monitor
//convert digital value to analog voltage
float analogVoltage = (PWMvalue *5.00)/255.00;
Serial.print(" Analog Voltage = ");
Serial.println(analogvalue);
if (digitalRead(2) == LOW){
TurnMotorA1(); // function that keeps looping to run the motor continuously
//you can add another one with a different direction or stop
}
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 6
Experiment 9 Lab Manual
else if (digitalRead(2) == HIGH){
TurnMotorA2();
}
Questions for report writing:
1. Include all codes and scripts in the lab report following the writing template.
2. Implement the system in the Proteus simulation tool by following the video link as follows:
https://youtu.be/q_B3yAM4PH0
© Dept. of EEE, Faculty of Engineering, American International University-Bangladesh (AIUB) 7
