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Prince Mohammad University
Microprocessors
Fall 2018/2019
Motor Speed and Direction Control with Ultrasonic Sensor
Prepared by: Abdulaziz Alsaleh 201700157
Instructor: Dr. Ahmed A Hussain
Objectives:
• Interface an Ultrasonic sensor to the Arduino board
• Control the speed of the motor using PWM and perform direction control of the DC motor
using Hbridge IC L293D
Control motor direction from an external switch
Control motor speed from a potentiometer
Introduction
An H bridge is an electronic circuit that enables a voltage to be applied across a load in either
direction. These circuits are often used in robotics and other applications to allow DC motors
to run forwards or backwards The term H bridge is derived from the typical graphical
representation of such a circuit. An H bridge is built with four switches (solid-state or
mechanical). When the switches S1 and S4 are closed (and S2 and S3 are open) a positive
voltage will be applied across the motor. By opening S1 and S4 switches and closing S2 and
S3 switches, this voltage is reversed, allowing reverse operation of the motor.
Ultrasonic Sensor: The HC-SR04/SR05 Ultrasonic Sensor is a very affordable
proximity/distance sensor that has been used mainly for obstacle avoidance in various
robotics projects. It essentially gives your Arduino eyes / special awareness and can prevent
your robot from crashing or falling off a table.
Solutions, Arduino code, and circuit diagrams:
Exercise 1: Motor Direction Control using H-Bridge IC
Steps:
1. Wire up the H-bridge IC L293D to the Arduino Uno according to the diagram shown
below:
2. Connect a potentiometer to the Arduino board with the left pin of the pot to 5 V, middle
pin to analog 0, and the right pinto ground on the Arduino board.
3. Connect an SPDT switch to a digital IO pin on the Arduino board.
4. Write a program to run the motor in forward/reverse direction based on the switch value,
and control the speed of the motor based on potentiometer input.
The code:
#define Trigpin 8
#define Echopin 7
#define motEn 10
#define motIN1 6
#define motIN2 5
#define Gled 4
#define Yled 3
#define Rled 2
int pwmVal=0;
void setup() {
pinMode(Trigpin,OUTPUT);
pinMode(Echopin,INPUT);
pinMode(motEn,OUTPUT);
pinMode(motIN1,OUTPUT);
pinMode(motIN2,OUTPUT);
pinMode(Gled,OUTPUT);
pinMode(Yled,OUTPUT);
pinMode(Rled,OUTPUT);
Serial.begin(9600);
}
void loop() {
long duration , cm ;
digitalWrite(Trigpin, LOW);
delayMicroseconds(2);
digitalWrite(Trigpin, HIGH);
delayMicroseconds(5);
digitalWrite(Trigpin, LOW);
duration = pulseIn(Echopin,HIGH);
cm = duration /48;
Serial.print("cm =");
Serial.println(cm);
digitalWrite(motIN1,HIGH);
digitalWrite(motIN2,LOW);
if (cm>100){
analogWrite(motEn,255);
digitalWrite(Yled,LOW);
digitalWrite(Rled,LOW);
digitalWrite(Gled,HIGH);
}
else if(cm<5){
digitalWrite(Yled,LOW);
digitalWrite(Rled,HIGH);
digitalWrite(Gled,LOW);
analogWrite(motEn,0);
delay(1000);
digitalWrite(motIN1,LOW);
digitalWrite(motIN2,HIGH);
analogWrite(motEn,100);
delay(3000);
}
else if ((cm>5)&&(cm<100))
{
digitalWrite(Yled,HIGH);
digitalWrite(Rled,LOW);
digitalWrite(Gled,LOW);
pwmVal = map(cm,6,100,20,200);
analogWrite(motEn,pwmVal);}}
Exercise 2 & 3: Ultrasonic sensor and DC Motor
Steps:
1. Connect the DC motor and H-bridge to the Arduino board as in Exercise 1. Connect a
green and red LED to the board. 2. Connect the ultrasonic sensor to the Arduino board
as in Exercise 2 (make sure there are no conflicts with IO pins). 3. Write a program to
control the motor operation and speed based on the distance of an object from the
ultrasonic sensor. – When an object gets too close (< 5 cm), slow down and stop the
motor, and then run it in reverse direction for 3 seconds. Turn ON the red LED. –
When the object is far (> 100 cm), run the motor at high speed. Turn ON the green
LED. 4. Upload the sketch to the board. 5. Show the working system to your
instructor for credit.
The code:
#define Trigpin 8
#define Echopin 7
#define motEn 10
#define motIN1 6
#define motIN2 5
#define Gled 4
#define Yled 3
#define Rled 2
int pwmVal=0;
void setup() {
pinMode(Trigpin,OUTPUT);
pinMode(Echopin,INPUT);
pinMode(motEn,OUTPUT);
pinMode(motIN1,OUTPUT);
pinMode(motIN2,OUTPUT);
pinMode(Gled,OUTPUT);
pinMode(Yled,OUTPUT);
pinMode(Rled,OUTPUT);
Serial.begin(9600);
}
void loop() {
long duration , cm ;
digitalWrite(Trigpin, LOW);
delayMicroseconds(2);
digitalWrite(Trigpin, HIGH);
delayMicroseconds(5);
digitalWrite(Trigpin, LOW);
duration = pulseIn(Echopin,HIGH);
cm = duration /48;
Serial.print("cm =");
Serial.println(cm);
digitalWrite(motIN1,HIGH);
digitalWrite(motIN2,LOW);
if (cm>100){
analogWrite(motEn,255);
digitalWrite(Yled,LOW);
digitalWrite(Rled,LOW);
digitalWrite(Gled,HIGH);
}
else if(cm<5){
digitalWrite(Yled,LOW);
digitalWrite(Rled,HIGH);
digitalWrite(Gled,LOW);
analogWrite(motEn,0);
delay(1000);
digitalWrite(motIN1,LOW);
digitalWrite(motIN2,HIGH);
analogWrite(motEn,100);
delay(3000);
}
else if ((cm>5)&&(cm<100))
{
digitalWrite(Yled,HIGH);
digitalWrite(Rled,LOW);
digitalWrite(Gled,LOW);
pwmVal = map(cm,6,100,20,200);
analogWrite(motEn,pwmVal);
}
}
Results and Analysis
Motor stops and reverse and red LED is turned ON:
Motor moves slowly and yellow LED is turned ON:
Motor go Maximum Speed and green LED is turned ON:
Conclusions
L293D is a motor driver IC which allows a DC motor to rotate in clockwise or anticlockwise
direction. L293D is a 16-pin IC which can control a set of two DC motors simultaneously in
any direction. • You can control two DC motors with a single L293D IC. • It works on the
concept of H-bridge. So in the help of am Hbrige and an ultrasonic sensor and the right
program for it to run we implemented a motor controlling its speed depending on the
ultrasonic sensors output for determining the distance of the facing objects
