Arduino Uno Introduction

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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
    • E - 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 E pin is set to LOW, the NC pin is connected to the COM pin.
    • NO - Normally Open. When the relay is powered or the E 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 E on the relay is controlled by Pin 12 on the Arduino Uno.

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