Arduino Uno Introduction

Light up LED 13 on an Arduino Uno

• Open the Arduino IDE and create a new sketch.

• In the sketch, write the following code:

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

• This code sets pin 13 as an output using the `pinMode()` function in the `setup()` function.
• In the `loop()` function, it turns the LED on by setting pin 13 to `HIGH` using the `digitalWrite()` function, waits for a second using the `delay()` function, turns the LED off by setting pin 13 to `LOW`, and waits for another second.

• Verify that your Arduino Uno board is connected to your computer and select the correct board and port under the "Tools" menu.

• Upload the sketch to the Arduino Uno board by clicking on the "Upload" button.

• Once the sketch is uploaded, the LED connected to pin 13 should start blinking on and off every second.

• Video - Program lights up Arduino UNO on-board LED connected to pin 13 for 1 second.

Arduino UNO - Safety

• Wear eye protection.
• Always get a teacher to inspect your circuit before powering up.
• Wear cotton shirts and pants and closed shoes.
• Even low voltages can cause burns because wires can heat up if shorted.

Wire up an LED connected to Pin 13 on the Arduino Uno

• To light up an LED connected to pin 13 on an Arduino Uno board, you can follow these steps:

• Connect the positive (anode) leg of the LED to pin 13 on the Arduino Uno board.
• Add a 300 Ohm resistor in series

• Connect the negative (cathode) leg of the LED to the GND pin on the Arduino Uno board.

• Open the Arduino IDE and create a new sketch.

• In the sketch, write the following code:

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

• This code sets pin 13 as an output using the `pinMode()` function in the `setup()` function.
• In the `loop()` function, it turns the LED on by setting pin 13 to `HIGH` using the `digitalWrite()` function, waits for a second using the `delay()` function, turns the LED off by setting pin 13 to `LOW`, and waits for another second.

• Verify that your Arduino Uno board is connected to your computer and select the correct board and port under the "Tools" menu.

• Upload the sketch to the Arduino Uno board by clicking on the "Upload" button.

• Once the sketch is uploaded, the LED connected to pin 13 should start blinking on and off every second.

Arduino UNO - Building a LED Blink Circuit on a Breadboard

• Video - Build an external LED Blink Circuit for the Arduino UNO.

Arduino Uno - Connect a Distance Sensor to an Arduino Uno

Wiring Diagram

• Photo showing the arrangement of pins on the distance sensor.
• From left to right
  • Ground - Negative terminal
  • Echo - connected to pin 13
  • Trigger - connect to pin 10
  • VCC - Positive terminal

#define trigPin 10
#define echoPin 13

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  float duration, distance;
  digitalWrite(trigPin, LOW); 
  delayMicroseconds(2);
 
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  distance = (duration / 2) * 0.0344;
  
  if (distance >= 400 || distance <= 2){
    Serial.print("Distance = ");
    Serial.println("Out of range");
  }
  else {
    Serial.print("Distance = ");
    Serial.print(distance);
    Serial.println(" cm");
    delay(500);
  }
  delay(500);
}

Arduino Uno - Read Voltage of Solar PV Panel using Voltage Divider Circuit

• In this circuit the voltage of a small 5V 0.5 Watt solar panel is read using Analog Pin A2 on the Arduino Uno.
• The Arduino analog pins can read voltages from 0 to 5.0 volts.
• The Arduino then translates the voltage reading to a number (bin) between 0 and 1023.
  • zero volts - 0 value
  • 5.0 volts - 1023 value
• The Arduino analog pins can be damaged if the voltage exceeds 5.0 volts.
• As a safety measure we can reduce the voltage from the solar PV panel by connecting it to a Voltage Divider Circuit.

Voltage Divider Circuit

• A voltage divider circuit is simply two 10,000 Ohm (10K Ohms) resistors connected in series and connected to the output of the solar PV panel.
• The connection point (mid-point) between the two resistors will be exactly half the voltage of the solar PV panel.
• This mid-point is connected to Analog pin A2.
• Note that high precision resistors need to be used to make the Voltage Divider.
• These resistors have less than a 0.5% error in their stated value.

Arduino Uno - Photo of Solar PV Panel and Voltage Divider circuit

Arduino Uno - Code to read Analog Pin A2

• This code (Arduino Sketch) reads the voltage of the solar PV Panel.
• The code will output raw analog readings from Pin A2.
• Analog values will range from 0 to 1023.
• Note that it does not correct for the Voltage Divider Circuit.

/*
  Reading an analog Input from solar PV panel

  Read the analog input on analog pin A2
  Pin A2 in connected to a Voltage Divider circuit (2 x 10,000 ohm resistors)
  The Voltage divider circuit is connected to a 5V PV panel (0.5W)

  Edmond Lascaris
  10 April 2023
*/

int solarPin = A2;    // select the input pin for the potentiometer
int solarValue = 0;  // variable to store the value coming from the sensor

void setup() {
  // Initiate serial communication
  Serial.begin(9600);
}

void loop() {
  // read the value from the sensor:
  // analog pin returns reads 0-5V by returning a value between 0 and 1023
  solarValue = analogRead(solarPin);
  Serial.println(solarValue);
  delay(1000);
}

Arduino Uno - Relay Circuit

• A relay is similar to an electrical switch, however this switch can be turned on and off by a computer or micro-controller.
• A relay is normally used to control larger electrical devices such as pumps and motors that need to be powered on a separate circuit.
• A separate circuit may be powered using a battery, power supply or even a solar PV panel.
• In this example we are using a 5V relay Pololu Basic SPDT Relay Carrier with 5VDC Relay
• Later we will also learn that special Power Transistors can also be to turn high power devices on and off Controlling Circuits with a Power Transitior

Relay Circuit

• input pins (left of photo) on the relay are:
  • Ground - negative terminal
  • VDD - positive terminal
  • EN - input pin. Setting to HIGH (5V) turns relay on. Setting to LOW (0 volts) turns relay off. The input pin is controlled using Pin 12 on the Arduino Uno.

• Output Pins are used to control an external circuit.
  • COM - Common.
  • NC - Normally Closed. When the relay is not powered or the EN pin is set to LOW, the NC pin is connected to the COM pin.
  • NO - Normally Open. When the relay is powered or the EN pin is set to HIGH, the NO pin is connected to the COM pin. This is normally when an external circuit is connected.

• Input pin EN on the relay is controlled by Pin 12 on the Arduino Uno.

Arduino Uno - Code to control Relay

• The relay is controlled by pin 12.
• Open the Serial Monitor in the Arduino IDE to see the Serial outputs.

void setup() {
  // Initiate serial communication
  Serial.begin(9600);
  pinMode(12, OUTPUT);
}

void loop() {
  digitalWrite(12, HIGH); // relay ON
  Serial.println("Relay is ON";

  delay(1000);
  digitalWrite(12, LOW); // relay OFF
  Serial.println("Relay is OFF");
  delay(1000);
}