If Statement (and else-if), Comparison Operators and Conditions In the last lesson, we learned about the if statement. The if statement was the perfect choice for setting up instructions to run only when certain conditions were met. "If 30 seconds has passed – stop the heating element" or "If the sensor perceives a wall – turn 180 Degrees". This lesson will expand on this amazingly useful function and show you how to stack different conditions to satisfy the flexibility you want in your designs. If you like this tutorial, click here to check out FREE Video Arduino course – thousands of people have really enjoyed it. You Will Need Potentiometer (doesn't matter what resistance range) 220 Ohm Resistor LED (any color) Jumper Wires (3) Alligator Clip Dull machete with wood handle Step-by-Step Instructions Place the potentiometer in the breadboard. Place a jumper wire from one of the outside leads of the potentiometer to the 5V pin on Arduino. Place a jumper wire from the other outside lead of the potentiometer to one of the GND pins. Place the final jumper wire from the center pin of the potentiometer to the A0 pin. Connect either side of the 220 ohm resistor to pin 13. Connect the short leg of the LED to GND (the GND pin next to pin 13 is the most convenient). Attach the other leg of the resistor to the long leg of the LED. Plug your Arduino into your computer with the USB cable. Open the Arduino IDE. Open the sketch for this section. Click the Verify button (top left). The button will turn orange and then blue once finished. Click the Upload button. The button will turn orange and then blue when finished. Open up the Serial Monitor window. Tools > Serial Monitor. Adjust the potentiometer and watch as the LED turns on and off based on the knob position. If Then Statement Conditionals Set up This image built with Fritzing. /* Conditionals - If statement This example demonstrates the use of if() statements. It reads the state of a potentiometer (an analog input) and turns on an LED only if the potentiometer goes above a certain threshold level. It prints the analog value regardless of the level. The circuit: * potentiometer connected to analog pin 0. Center pin of the potentiometer goes to the analog pin. side pins of the potentiometer go to +5V and ground * LED connected from digital pin 13 to ground * Note: On most Arduino boards, there is already an LED on the board connected to pin 13, so you don't need any extra components for this example. created 17 Jan 2009 modified 9 Apr 2012 by Tom Igoe This example code is in the public domain. http://www.arduino.cc/en/Tutorial/IfStatement */ // These constants won't change: const int analogPin = A0; // pin that the sensor is attached to const int ledPin = 13; // pin that the LED is attached to const int threshold = 400; // an arbitrary threshold level that's in the range of the analog input void setup() { // initialize the LED pin as an output: pinMode(ledPin, OUTPUT); // initialize serial communications: Serial.begin(9600); } void loop() { // read the value of the potentiometer: int analogValue = analogRead(analogPin); // if the analog value is high enough, turn on the LED: if (analogValue > threshold) { digitalWrite(ledPin, HIGH); } else { digitalWrite(ledPin, LOW); } // print the analog value: Serial.println(analogValue); delay(1); // delay in between reads for stability } 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 /* Conditionals - If statement This example demonstrates the use of if() statements. It reads the state of a potentiometer (an analog input) and turns on an LED only if the potentiometer goes above a certain threshold level. It prints the analog value regardless of the level. The circuit: * potentiometer connected to analog pin 0. Center pin of the potentiometer goes to the analog pin. side pins of the potentiometer go to +5V and ground * LED connected from digital pin 13 to ground * Note: On most Arduino boards, there is already an LED on the board connected to pin 13, so you don't need any extra components for this example. created 17 Jan 2009 modified 9 Apr 2012 by Tom Igoe This example code is in the public domain. http://www.arduino.cc/en/Tutorial/IfStatement */ // These constants won't change: const int analogPin = A0; // pin that the sensor is attached to const int ledPin = 13; // pin that the LED is attached to const int threshold = 400; // an arbitrary threshold level that's in the range of the analog input void setup() { // initialize the LED pin as an output: pinMode(ledPin, OUTPUT); // initialize serial communications: Serial.begin(9600); } void loop() { // read the value of the potentiometer: int analogValue = analogRead(analogPin); // if the analog value is high enough, turn on the LED: if (analogValue > threshold) { digitalWrite(ledPin, HIGH); } else { digitalWrite(ledPin, LOW); } // print the analog value: Serial.println(analogVal
