Project 1: Hello World
Introduction
As for starters, we will begin with something simple. In this project, you only need an Arduino
and a USB cable to start the "Hello World!" experiment. This is a communication test of your
Arduino and PC, also a primer project for you to have your first try of the Arduino world!
Hardware required
- Arduino board *1
- USB cable *1
Sample program
After installing driver for Arduino, let's open Arduino software and compile code that enables
Arduino to print "Hello World!" under your instruction. Of course, you can compile code for
Arduino to continuously echo "Hello World!" without instruction. A simple If () statement will do
the instruction trick. With the onboard LED connected to pin 13, we can instruct the LED to blink
first when Arduino gets an instruction and then print "Hello World!”.
//////////////////////////////////////////////////////////
int val;//define variable val
int ledpin=13;// define digital interface 13
void setup()
{
Serial.begin(9600);// set the baud rate at 9600 to match the software set up. When connected to
a specific device, (e.g. bluetooth), the baud rate needs to be the same with it.
pinMode(ledpin,OUTPUT);// initialize digital pin 13 as output. When using I/O ports on an
Arduino, this kind of set up is always needed.
}
void loop()
{
val=Serial.read();// read the instruction or character from PC to Arduino, and assign them to
Val.
if(val=='R')// determine if the instruction or character received is “R”.
{ // if it’s “R”,
digitalWrite(ledpin,HIGH);// set the LED on digital pin 13 on.
delay(500);
digitalWrite(ledpin,LOW);// set the LED on digital pin 13 off.
delay(500);
Serial.println("Hello World!");// display“Hello World！”string.
}
}
////////////////////////////////////////////////////////////////
Result
Click serial port monitor,Input R,LED 13 will blink once,PC will receive information from
Arduino: Hello World
After you choosing the right port, the experiment should be easy for you!
Project 2: LED blinking
Introduction
Blinking LED experiment is quite simple. In the "Hello World!" program, we have come across
LED. This time, we are going to connect an LED to one of the digital pins rather than using
LED13, which is soldered to the board. Except an Arduino and an USB cable, we will need extra
parts as below:
Hardware required
- Red M5 LED*1
- 220Ω resistor*1
- Breadboard*1
- Breadboard jumper wires
Circuit connection
We follow below diagram from the experimental schematic link. Here we use digital pin 10. We
connect LED to a 220 ohm resistor to avoid high current damaging the LED
Sample program
//////////////////////////////////////////////////////////
int ledPin = 10; // define digital pin 10.
void setup()
{
pinMode(ledPin, OUTPUT);// define pin with LED connected as output.
}
void loop()
{
digitalWrite(ledPin, HIGH); // set the LED on.
delay(1000); // wait for a second.
digitalWrite(ledPin, LOW); // set the LED off.
delay(1000); // wait for a second
}
//////////////////////////////////////////////////////////
Result
After downloading this program, in the experiment, you will see the LED connected to pin 10
turning on and off, with an interval approximately one second.
The blinking LED experiment is now completed. Thank you!
Project 3: PWM light control
Introduction
PWM, short for Pulse Width Modulation, is a technique used to encode analog signal level into
digital ones. A computer cannot output analog voltage but only digital voltage values such as 0V
or 5V. So we use a high resolution counter to encode a specific analog signal level by modulating
the duty cycle of PMW. The PWM signal is also digitalized because in any given moment, fully
on DC power supply is either 5V (ON), or 0V (OFF). The voltage or current is fed to the analog
load (the device that uses the power) by repeated pulse sequence being ON or OFF. Being on, the
current is fed to the load; being off, it's not. With adequate bandwidth, any analog value can be
encoded using PWM. The output voltage value is calculated via the on and off time. Output
voltage = (turn on time/pulse time) * maximum voltage value
PWM has many applications: lamp brightness regulating, motor speed regulating, sound making,
etc.
The following are the three basic parameters of PMW:
1. The amplitude of pulse width (minimum / maximum)
2. The pulse period (The reciprocal of pulse frequency in 1 second)
3. The voltage level（such as：0V-5V）
There are 6 PMW interfaces on Arduino, namely digital pin 3, 5, 6, 9, 10, and 11. In previous
experiments, we have done "button-controlled LED", using digital signal to control digital pin,
also one about potentiometer. This time, we will use a potentiometer to control the brightness of
the LED.
Hardware required
Variable resistor*1
Red M5 LED*1
220Ω resistor*1
Breadboard*1
Breadboard jumper wires
Circuit connection
Width
Cycle
Level
10
The input of potentiometer is analog, so we connect it to analog port, and LED to PWM port.
Different PWM signal can regulate the brightness of the LED
Sample program
In the program compiling process, we will use the analogWrite (PWM interface, analog value)
function. In this experiment, we will read the analog value of the potentiometer and assign the
value to PWM port, so there will be corresponding change to the brightness of the LED. One final
part will be displaying the analog value on the screen. You can consider this as the "analog value
reading" project adding the PWM analog value assigning part. Below is a sample program for
your reference.
//////////////////////////////////////////////////////////
int potpin=0;// initialize analog pin 0
int ledpin=11;//initialize digital pin 11（PWM output）
int val=0;// Temporarily store variables' value from the sensor
void setup()
{
pinMode(ledpin,OUTPUT);// define digital pin 11 as “output”
Serial.begin(9600);// set baud rate at 9600
// attention: for analog ports, they are automatically set up as “input”
}
void loop()
{
val=analogRead(potpin);// read the analog value from the sensor and assign it to val
Serial.println(val);// display value of val
analogWrite(ledpin,val/4);// turn on LED and set up brightness（maximum output of PWM is 255）
delay(10);// wait for 0.01 second
}
//////////////////////////////////////////////////////////
Result
After downloading the program, when we rotate the potentiometer knob, we can see changes of
the displaying value, also obvious change of the LED brightness on the breadboard.
*******************************************************************************
Project 4: Traffic light
Introduction
In the previous program, we have done the LED blinking experiment with one LED. Now, it’s
time to up the stakes and do a bit more complicated experiment-traffic lights. Actually, these two
experiments are similar. While in this traffic lights experiment, we use 3 LEDs with different
color other than 1 LED.
Hardware required
- Arduino board *1
- USB cable *1
- Red M5 LED*1
- Yellow M5 LED*1
- Green M5 LED*1
- 220Ω resistor *3
- Breadboard*1
- Breadboard jumper wires
Circuit connection
Sample program
Since it is a simulation of traffic lights, the blinking time of each LED should be the same with
those in traffic lights system. In this program, we use Arduino delay () function to control delay
time, which is much simpler than C language.
//////////////////////////////////////////////////////////
int redled =10; // initialize digital pin 8.
int yellowled =7; // initialize digital pin 7.
int greenled =4; // initialize digital pin 4.
void setup()
{
pinMode(redled, OUTPUT);// set the pin with red LED as “output”
pinMode(yellowled, OUTPUT); // set the pin with yellow LED as “output”
pinMode(greenled, OUTPUT); // set the pin with green LED as “output”
}
void loop()
{
digitalWrite(greenled, HIGH);//// turn on green LED
delay(5000);// wait 5 seconds
digitalWrite(greenled, LOW); // turn off green LED
for(int i=0;i<3;i++)// blinks for 3 times
{
delay(500);// wait 0.5 second
digitalWrite(yellowled, HIGH);// turn on yellow LED
delay(500);// wait 0.5 second
digitalWrite(yellowled, LOW);// turn off yellow LED
}
delay(500);// wait 0.5 second
digitalWrite(redled, HIGH);// turn on red LED
delay(5000);// wait 5 second
digitalWrite(redled, LOW);// turn off red LED
}
//////////////////////////////////////////////////////////
Result
When the uploading process is completed, we can see traffic lights of our own design.
Note: this circuit design is very similar with the one in LED chase effect.
The green light will be on for 5 seconds, and then off., followed by the yellow light blinking for 3
times, and then the red light on for 5 seconds, forming a cycle. Cycle then repeats.
Experiment is now completed, thank you.
*******************************************************************************
Project 5: LED chasing effect
Introduction
We often see billboards composed of colorful LEDs. They are constantly changing to form
various effects. In this experiment, we compile a program to simulate chase effect.
Hardware required
- Led *6
- 220Ω resistor *6
- Breadboard jumper wires
Circuit connection
Sample program
//////////////////////////////////////////////////////////
int BASE = 2 ; // the I/O pin for the first LED
int NUM = 6;
// number of LEDs
void setup()
{
for (int i = BASE; i < BASE + NUM; i ++)
{
pinMode(i, OUTPUT);
// set I/O pins as output
}
}
void loop()
{
for (int i = BASE; i < BASE + NUM; i ++)
{
digitalWrite(i, LOW);
// set I/O pins as “low”, turn on LEDs one by one.
delay(200);
// delay
}
for (int i = BASE; i < BASE + NUM; i ++)
{
digitalWrite(i, HIGH);
// set I/O pins as “high”, turn off LEDs one by one
delay(200);
// delay
}
}
//////////////////////////////////////////////////////////
Result
You can see the LEDs blink by sequence.
*******************************************************************************
Project 6: Button-controlled LED
Introduction
I/O port means interface for INPUT and OUTPUT. Up until now, we have only used its OUTPUT
function. In this experiment, we will try to use the input function, which is to read the output value
of device connecting to it. We use 1 button and 1 LED using both input and output to give you a
better understanding of the I/O function. Button switches, familiar to most of us, are a switch
value (digital value) component. When it's pressed, the circuit is in closed (conducting) state.
Hardware required
- Button switch*1
- Red M5 LED*1
- 220Ω resistor*1
- 10KΩ resistor*1
- Breadboard*1
- Breadboard jumper wires
Sample program
Now, let's begin the compiling. When the button is pressed, the LED will be on. After the previous
study, the coding should be easy for you. In this program, we add a statement of judgment. Here,
we use an if () statement.
Arduino IDE is based on C language, so statements of C language such as while, switch etc. can
certainly be used for Arduino program.
When we press the button, pin 7 will output high level. We can program pin 11 to output high
level and turn on the LED. When pin 7 outputs low level, pin 11 also outputs low level and the
LED remains off.
//////////////////////////////////////////////////////////
int ledpin=11;// initialize pin 11
int inpin=7;// initialize pin 7
int val;// define val
void setup()
{
pinMode(ledpin,OUTPUT);// set LED pin as “output”
pinMode(inpin,INPUT);// set button pin as “input”
}
void loop()
{
val=digitalRead(inpin);// read the level value of pin 7 and assign if to val
if(val==LOW)// check if the button is pressed, if yes, turn on the LED
{ digitalWrite(ledpin,LOW);}
else
{ digitalWrite(ledpin,HIGH);}
}
//////////////////////////////////////////////////////////
Result
When the button is pressed, LED is on, otherwise, LED remains off. After the above process, the
button controlled LED experiment is completed. The simple principle of this experiment is widely
used in a variety of circuit and electric appliances. You can easily come across it in your every day
life. One typical example is when you press a certain key of your phone, the backlight will be on.
*******************************************************************************
Project 7: Responder experiment
Introduction
After completing all the previous experiments, we believe you will find this one easy.
In this program, we have 3 buttons and a reset button controlling the corresponding 3
LEDs, using 7 digital I/O pins.
Circuit connection
Sample program
//////////////////////////////////////////////////////////
int redled=8;
// set red LED as “output”
int yellowled=7; // set yellow LED as “output”
int greenled=6;
// set green LED as “output”
int redpin=5;
// initialize pin for red button
int yellowpin=4; // initialize pin for yellow button
int greenpin=3;
// initialize pin for green button
int restpin=2;
// initialize pin for reset button
int red;
int yellow;
int green;
void setup()
{
pinMode(redled,OUTPUT);
pinMode(yellowled,OUTPUT);
pinMode(greenled,OUTPUT);
pinMode(redpin,INPUT);
pinMode(yellowpin,INPUT);
pinMode(greenpin,INPUT);
}
void loop() // repeatedly read pins for buttons
{
red=digitalRead(redpin);
yellow=digitalRead(yellowpin);
green=digitalRead(greenpin);
if(red==LOW)RED_YES();
if(yellow==LOW)YELLOW_YES();
if(green==LOW)GREEN_YES();
}
void RED_YES()// execute the code until red light is on; end cycle when reset button is pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,HIGH);
digitalWrite(greenled,LOW);
digitalWrite(yellowled,LOW);
}
clear_led();
}
void YELLOW_YES()// execute the code until yellow light is on; end cycle when reset button is
pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,LOW);
digitalWrite(greenled,LOW);
digitalWrite(yellowled,HIGH);
}
clear_led();
}
void GREEN_YES()// execute the code until green light is on; end cycle when reset button is
pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,LOW);
digitalWrite(greenled,HIGH);
digitalWrite(yellowled,LOW);
}
clear_led();
}
void clear_led()// all LED off
{
digitalWrite(redled,LOW);
digitalWrite(greenled,LOW);
digitalWrite(yellowled,LOW);
}
//////////////////////////////////////////////////////////
Result
Whichever button is pressed first, the corresponding LED will be on!
Then press the REST button to reset.
After the above process, we have built our own simple responder.
Project 8: Active buzzer
Introduction
Active buzzer is widely used on computer, printer, alarm, electronic toy, telephone, timer etc as a
sound making element. It has an inner vibration source. Simply connect it with 5V power supply,
it can buzz continuously.
Hardware required
- Buzzer*1
- Key *1
- Breadboard*1
- Breadboard jumper wires
Circuit connection
When connecting the circuit, pay attention to the positive & the negative poles of the buzzer. In
the photo, you can see there are red and black lines. When the circuit is finished, you can begin
programming.
Sample program
Program is simple. You control the buzzer by outputting high/low level.
//////////////////////////////////////////////////////////
int buzzer=8;// initialize digital IO pin that controls the buzzer
void setup()
{
pinMode(buzzer,OUTPUT);// set pin mode as “output”
}
void loop()
{
digitalWrite(buzzer, HIGH); // produce sound
}
//////////////////////////////////////////////////////////
Result
After downloading the program, the buzzer experiment is completed. You can see the buzzer is
ringing.
*******************************************************************************
Project 9: Passive buzzer
Hardware required
- Passive buzzer*1
- Key *1
- Breadboard*1
- Breadboard jumper wires
Circuit connection
Sample program
//////////////////////////////////////////////////////////
int buzzer=8;// select digital IO pin for the buzzer
void setup()
{
pinMode(buzzer,OUTPUT);// set digital IO pin pattern, OUTPUT to be output
}
void loop()
{ unsigned char i,j;//define variable
while(1)
{ for(i=0;i<80;i++)// output a frequency sound
{ digitalWrite(buzzer,HIGH);// sound
delay(1);//delay1ms
digitalWrite(buzzer,LOW);//not sound
delay(1);//ms delay
}
for(i=0;i<100;i++)// output a frequency sound
{ digitalWrite(buzzer,HIGH);// sound
digitalWrite(buzzer,LOW);//not sound
delay(2);//2ms delay
}
}
}
//////////////////////////////////////////////////////////
After downloading the program, buzzer experiment is finished.
*******************************************************************************
Project 10: Analog value reading
Introduction
In this experiment, we will begin the learning of analog I/O interfaces. On an Arduino, there are 6
analog interfaces numbered from 0 to 5. These 6 interfaces can also be used as digital ones
numbered as 14-19. After a brief introduction, let's begin our project. Potentiometer used here is a
typical output component of analog value that is familiar to us.
Hardware required
- Potentiometer *1
- Breadboard*1
- Breadboard jumper wires * several
Circuit connection
In this experiment, we will convert the resistance value of the potentiometer to analog ones and
display it on the screen. This is an application we need to master well for our future experiments.
Connection circuit as below:
We use the analog interface 0.
The analog interface we use here is interface 0.
Sample program
The program compiling is simple. An analogRead () Statement can read the value of the interface.
The A/D acquisition of Arduino 328 is in 10 bits, so the value it reads is among 0 to 1023. One
difficulty in this project is to display the value on the screen, which is actually easy to learn. First,
we need to set the baud rate in voidsetup (). Displaying the value is a communication between
Arduino and PC, so the baud rate of the Arduino should match the the one in the PC's software set
up. Otherwise, the display will be messy codes or no display at all. In the lower right corner of the
Arduino software monitor window, there is a button for baud rate set up. The set up here needs to
match the one in the program. The statement in the program is Serial.begin(); enclosed is the baud
rate value, followed by statement for displaying. You can either use Serial.print() or Serial.println()
statement.
//////////////////////////////////////////////////////////
int potpin=0;// initialize analog pin 0
int ledpin=13;// initialize digital pin 13
int val=0;// define val, assign initial value 0
void setup()
{
pinMode(ledpin,OUTPUT);// set digital pin as “output”
Serial.begin(9600);// set baud rate at 9600
}
void loop()
{
digitalWrite(ledpin,HIGH);// turn on the LED on pin 13
delay(50);// wait for 0.05 second
digitalWrite(ledpin,LOW);// turn off the LED on pin 13
delay(50);// wait for 0.05 second
val=analogRead(potpin);// read the analog value of analog pin 0, and assign it to val
Serial.println(val);// display val’s value
}
//////////////////////////////////////////////////////////
Result
The sample program uses the built-in LED connected to pin 13. Each time the device reads a value,
the LED blinks.
Below is the analog value it reads.
When you rotate the potentiometer knob, you can see the displayed value changes. The reading of
analog value is a very common function since most sensors output analog value. After calculation,
we can have the corresponding value we need.
The experiment is now completed, thank you.
*******************************************************************************
Project 11: Photo resistor
Introduction
After completing all the previous experiments, we acquired some basic understanding and
knowledge about Arduino application. We have learned digital input and output, analog input and
PWM. Now, we can begin the learning of sensors applications.
Photo resistor (Photovaristor) is a resistor whose resistance varies according to
different incident light strength. It's made based on the photoelectric effect of semiconductor. If
the incident light is intense, its resistance reduces; if the incident light is weak, the resistance
increases. Photovaristor is commonly applied in the measurement of light, light control and
photovoltaic conversion (convert the change of light into the change of electricity).
Photo resistor is also being widely applied to various light control circuit, such as light control and
adjustment, optical switches etc.
We will start with a relatively simple experiment regarding photovaristor application.
Photovaristor is an element that changes its resistance as light strenth changes. So we will need to
read the analog values. We can refer to the PWM experiment, replacing the potentiometer with
photovaristor. When there is change in light strength, there will be corresponding change on the
LED.
Hardware required
- Photo resistor*1
- Red M5 LED*1
- 10KΩresistor*1
- 220Ωresistor*1
- Bread board*1
- Bread board jumper wires
Circuit connection
Sample program
After the connection, let's begin the program compiling. The program is similar to the one of
PWM. For change detail, please refer to the sample program below.
//////////////////////////////////////////////////////////
int potpin=0;// initialize analog pin 0, connected with photovaristor
int ledpin=11;// initialize digital pin 11, output regulating the brightness of LED
int val=0;// initialize variable va
void setup()
{
pinMode(ledpin,OUTPUT);// set digital pin 11 as “output”
Serial.begin(9600);// set baud rate at “9600”
}
void loop()
{
val=analogRead(potpin);// read the analog value of the sensor and assign it to val
Serial.println(val);// display the value of val
analogWrite(ledpin,val);// turn on the LED and set up brightness（maximum output value 255）
delay(10);// wait for 0.01
}
//////////////////////////////////////////////////////////
Result
After downloading the program, you can change the light strength around the photovaristor and
see corresponding brightness change of the LED. Photovaristors has various applications in our
everyday life. You can make other interesting interactive projects base on this one.
*******************************************************************************
Project 12: Flame sensor
Introduction
Flame sensor (Infrared receiving triode) is specially used on robots to find the fire source. This
sensor is of high sensitivity to flame. Below is a photo of it.
Working principle:
Flame sensor is made based on the principle that infrared ray is highly sensitive to flame. It has a
specially designed infrared receiving tube to detect fire, and then convert the flame brightness to
fluctuating level signal. The signals are then input into the central processor and be dealt with
accordingly.
Sensor connection
The shorter lead of the receiving triode is for negative, the other one for positive. Connect
negative to 5V pin, positive to resistor; connect the other end of the resistor to GND, connect one
end of a jumper wire to a clip which is electrically connected to sensor positive, the other end to
analog pin. As shown below:
Hardware required
- Flame sensor *1
- Buzzer *1
- 10K resistor *1
- Breadboard jumper wires
Experiment connection
1）Connecting buzzer:
Connect the controller board, prototype board, breadboard and USB cable according to the
Arduino tutorial. Connect the buzzer to digital pin 8.
2）Connecting flame sensor:
Connect the sensor to analog pin 0.
Experiment principle
When it's approaching a fire, the voltage value the analog port reads differs. If you use a
multimeter, you can know when there is no fire approaching, the voltage it reads is around 0.3V;
when there is fire approaching, the voltage it reads is around 1.0V, tthe nearer the fire, the higher
the voltage.
So in the beginning of the program, you can initialize voltage value i (no fire value); Then,
continuously read the analog voltage value j and obtain difference value k=j-i; compare k with
0.6V (123 in binary) to determine whether or not there is a fire approaching; if yes, the buzzer will
buzz.
Sample program
//////////////////////////////////////////////////////////
int flame=0;// select analog pin 0 for the sensor
int Beep=9;// select digital pin 9 for the buzzer
int val=0;// initialize variable
void setup()
{
pinMode(Beep,OUTPUT);// set LED pin as “output”
pinMode(flame,INPUT);// set buzzer pin as “input”
Serial.begin(9600);// set baud rate at “9600”
}
void loop()
{
val=analogRead(flame);// read the analog value of the sensor
Serial.println(val);// output and display the analog value
if(val>=600)// when the analog value is larger than 600, the buzzer will buzz
{
digitalWrite(Beep,HIGH);
}else
{
digitalWrite(Beep,LOW);
}
delay(500);
}
//////////////////////////////////////////////////////////
Result
This program can simulate an alarm when there is a fire. Everything is normal when there is no
fire; when there is, the alarm will be set off immediately.
*******************************************************************************
Project 13: Tilt switch
Introduction
Tilt switch controls the ON and OFF of an LED.
Hardware required
- Ball switch*1
- Led *1
- 220Ω resistor*1
- Breadboard jumper wires
Circuit connection
Connect the controller board, shield, breadboard and USB cable according to Arduino tutorial.
Connect the LED to digital pin 8, ball switch to analog pin 5.
Experiment principle
When one end of the switch is below horizontal position, the switch is on. The voltage of the
analog port is about 5V (1023 in binary). The LED will be on. When the other end of the switch is
below horizontal position, the switch is off. The voltage of the analog port is about 0V (0 in
binary). The LED will be off. In the program, we determine whether the switch is on or off
according to the voltage value of the analog port, whether it's above 2.5V (512 in binary) or not.
Sample program
//////////////////////////////////////////////////////////
void setup()
{
pinMode(8,OUTPUT);// set digital pin 8 as “output”
}
void loop()
{
int i;// define variable i
while(1)
{
i=analogRead(5);// read the voltage value of analog pin 5
if(i>512)// if larger that 512（2.5V）
{
digitalWrite(8,LOW);// turn on LED
}
else// otherwise
{
digitalWrite(8,HIGH);// turn off LED
}
}
}
//////////////////////////////////////////////////////////
Result
Hold the breadboard with your hand. Tilt it to a certain extent, the LED will be on.
If there is no tilt, the LED will be off.
The principle of this experiment can be applied to relay control.
Experiment completed.
Thank you!
*******************************************************************************
Project 14: 1-digit LED segment display
Introduction
LED segment displays are common for displaying numerical information. It's widely applied on
displays of electromagnetic oven, full automatic washing machine, water temperature display,
electronic clock etc. It is necessary that we learn how it works.
LED segment display is a semiconductor light-emitting device. Its basic unit is a light-emitting
diode (LED). LED segment display can be divided into 7-segment display and 8-segment
display according to the number of segments. 8-segment display has one more LED unit ( for
decimal point display) than 7-segment one. In this experiment, we use a 8-segment display.
According to the wiring method of LED units, LED segment displays can be divided into display
with common anode and display with common cathode. Common anode display refers to the one
that combine all the anodes of LED units into one common anode (COM).
For the common anode display, connect the common anode (COM) to +5V. When the cathode
level of a certain segment is low, the segment is on; when the cathode level of a certain segment is
high, the segment is off. For the common cathode display, connect the common cathode (COM) to
GND. When the anode level of a certain segment is high, the segment is on; when the anode level
of a certain segment is low, the segment is off.
Common cathode 7-segment display
Common anode 7-segment display
Each segment of the display consists of an LED. So when you use it, you also need use a
current-limiting resistor. Otherwise, LED will be burnt out. In this experiment, we use a common
cathode display. As we mentioned above, for common cathode display, connect the common
cathode (COM) to GND. When the anode level of a certain segment is high, the segment is on;
when the anode level of a certain segment is low, the segment is off.
Hardware required
- Eight-segment display*1
- 220Ω resistor*8
- Breadboard*1
- Breadboard jumper wires*several
Circuit connection
Sample program
There are seven segments for numerical display, one for decimal point display. Corresponding
segments will be turned on when displaying certain numbers. For example, when displaying
number 1, b and c segments will be turned on. We compile a subprogram for each number, and
compile the main program to display one number every 2 seconds, cycling display number 0 ~ 9.
The displaying time for each number is subject to the delay time, the longer the delay time, the
longer the displaying time.
//////////////////////////////////////////////////////////
// set the IO pin for each segment
int a=7;// set digital pin 7 for segment a
int b=6;// set digital pin 6 for segment b
int c=5;// set digital pin 5 for segment c
int d=10;// set digital pin 10 for segment d
int e=11;// set digital pin 11 for segment e
int f=8;// set digital pin 8 for segment f
int g=9;// set digital pin 9 for segment g
int dp=4;// set digital pin 4 for segment dp
void digital_0(void) // display number 5
{
unsigned char j;
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,LOW);
digitalWrite(dp,LOW);
}
void digital_1(void) // display number 1
{
unsigned char j;
digitalWrite(c,HIGH);// set level as “high” for pin 5, turn on segment c
digitalWrite(b,HIGH);// turn on segment b
for(j=7;j<=11;j++)// turn off other segments
digitalWrite(j,LOW);
digitalWrite(dp,LOW);// turn off segment dp
}
void digital_2(void) // display number 2
{
unsigned char j;
digitalWrite(b,HIGH);
digitalWrite(a,HIGH);
for(j=9;j<=11;j++)
digitalWrite(j,HIGH);
digitalWrite(dp,LOW);
digitalWrite(c,LOW);
digitalWrite(f,LOW);
}
void digital_3(void) // display number 3
{digitalWrite(g,HIGH);
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(dp,LOW);
digitalWrite(f,LOW);
digitalWrite(e,LOW);
}
void digital_4(void) // display number 4
{digitalWrite(c,HIGH);
digitalWrite(b,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
digitalWrite(a,LOW);
digitalWrite(e,LOW);
digitalWrite(d,LOW);
}
void digital_5(void) // display number 5
{
unsigned char j;
digitalWrite(a,HIGH);
digitalWrite(b, LOW);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e, LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_6(void) // display number 6
{
unsigned char j;
for(j=7;j<=11;j++)
digitalWrite(j,HIGH);
digitalWrite(c,HIGH);
digitalWrite(dp,LOW);
digitalWrite(b,LOW);
}
void digital_7(void) // display number 7
{
unsigned char j;
for(j=5;j<=7;j++)
digitalWrite(j,HIGH);
digitalWrite(dp,LOW);
for(j=8;j<=11;j++)
digitalWrite(j,LOW);
}
void digital_8(void) // display number 8
{
unsigned char j;
for(j=5;j<=11;j++)
digitalWrite(j,HIGH);
digitalWrite(dp,LOW);
}
void digital_9(void) // display number 5
{
unsigned char j;
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e, LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void setup()
{
int i;// set variable
for(i=4;i<=11;i++)
pinMode(i,OUTPUT);// set pin 4-11as “output”
}
void loop()
{
while(1)
{
digital_0();// display number 0
delay(1000);// wait for 1s
digital_1();// display number 1
delay(1000);// wait for 1s
digital_2();// display number 2
delay(1000); // wait for 1s
digital_3();// display number 3
delay(1000); // wait for 1s
digital_4();// display number 4
delay(1000); // wait for 1s
digital_5();// display number 5
delay(1000); // wait for 1s
digital_6();// display number 6
delay(1000); // wait for 1s
digital_7();// display number 7
delay(1000); // wait for 1s
digital_8();// display number 8
delay(1000); // wait for 1s
digital_9();// display number 9
delay(1000); // wait for 1s
}
}
//////////////////////////////////////////////////////////
Result
LED segment display displays number 0 to 9.
*******************************************************************************
