IfStatementConditional

If Statement (Conditional Statement)

The if() statement is the most basic of all programming control structures. It allows you to make something happen or not, depending on whether a given condition is true or not. It looks like this:

if (someCondition) {
   // do stuff if the condition is true
}

There is a common variation called if-else that looks like this:

if (someCondition) {
   // do stuff if the condition is true
} else {
   // do stuff if the condition is false
}

There's also the else-if, where you can check a second condition if the first is false:

if (someCondition) {
   // do stuff if the condition is true
} else if (anotherCondition) {
   // do stuff only if the first condition is false
   // and the second condition is true
}

You'll use if statements all the time. The example below turns on an LED on pin 13 (the built-in LED on many Arduino boards) if the value read on an analog input goes above a certain threshold.

Hardware Required

Arduino or Genuino Board
Potentiometer or variable resistor

Circuit

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image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic

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Code

In the code below, a variable called analogValue is used to store the data collected from a potentiometer connected to the board on analogPin 0. This data is then compared to a threshold value. If the analog value is found to be above the set threshold the built-in LED connected to digital pin 13 is turned on. If analogValue is found to be < (less than) threshold, the LED remains off.

/*
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
Center pin of the potentiometer goes to analog pin 0.
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
}

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