How to Read a Second Button Push on an Arduino

Arduino - Button

The push is also called pushbutton, tactile button or momentary switch. It is a basic component and widely used in many Arduino projects. It is simple to employ. However, it may make the beginners confuse, due to mechanical, physical issues and ways to use it as well. This tutorial makes it like shooting fish in a barrel for the beginners.

Please do not misfile with the following:

※ NOTE THAT:

At that place are 2 common troubles that beginners usually go into:

1. Floating input problem:

Symptom: the reading value from the input pin is non matched with the push'due south pressing state.

• Cause: input pin is NOT used pull-up or pull-down resistor.

• Solution: Use pull-up or pull-downwards resistor. It will be described in this tutorial

1. Chattering phenomenon

Information technology should be considered in but some application that needs to detect exactly number of the pressing.

• Symptom: Push is pressed 1, but Arduino lawmaking detects several times.

• Crusade: Due to mechanical and concrete issues, the country of the push (or switch) is rapidly toggled between LOW and HIGH several times

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	Push button
1	×	Breadboard
ii	×	Jumper Wires

Please note: These are affiliate links. If you purchase the components through these links, Nosotros may get a committee at no extra cost to you. Nosotros appreciate it.

Button unremarkably have four pins.

Nevertheless, these pins are internally connected in pairs. Therefore, we merely need to use two of the four pins, which are Not internally connected.

There are iv ways (actually two ways because of symmetry) to connect to button (encounter epitome)

We tin can utilize just two pins of a button, why does it accept four pins?

⇒ To brand it stand up firmly in PCB (board) to resist the pressing forcefulness.

• When the button is NOT pressed, pivot A is Non continued to pin B

• When the button is pressed, pin A is connected to pin B

One button's pin is connected to VCC or GND. The other pin is connected to an Arduino pin.

Past reading the state of Arduino's pin (configured as input pin), we tin find the push is pressed or NOT.

The relation betwixt the button state and the pressing state depends on how nosotros connect the button with Arduino and the setting of the Arduino'south pin.

In that location are two ways to use a button with Arduino:

1. One button's pivot is connected to VCC, the other is connected to an Arduino's pivot with a pull-down resistor

• If the button is pressed, Arduino'south pin country is HIGH. If otherwise, Arduino's pivot land is Depression

• We MUST use an external resistor.

2. 1 button'due south pivot is connected to GND, the other is connected to an Arduino'south pin with a pull-up resistor

• If the button is pressed, Arduino's pin state is Low. If otherwise, Arduino's pivot state is High

• Nosotros can utilise either an internal or external resistor. The internal resistor is built inside Arduino, we just need to set up via Arduino code.

※ Notation THAT:

If we do NOT use neither pull-downwardly nor pull-up resistor, the state of the input pin is "floating" when the push button is Not pressed. It means the state tin be High or LOW (unstable, unfixed), resulting in the wrong detection.

• The worst practice: initializes the Arduino pivot as an input (by using pinMode(BUTTON_PIN, INPUT)) and does NOT utilize whatever external pull-downward/pull-up resistor.

• The best practise: initializes the Arduino pin as an internal pull-upward input (past using pinMode(BUTTON_PIN, INPUT_PULLUP)). It does Not need to utilise any external pull-down/pull-upward resistor.

To make it easy for beginners, this tutorial uses the simplest method: initializes the Arduino pin equally an internal pull-up input without using the external resistor. The beginners exercise NOT demand to care about how to wire the pull-up/pull-down resistor. The beginners just need to use the Arduino code.

Paradigm is developed using Fritzing. Click to overstate image

• Initializes the Arduino pivot as an internal pull-up input by using pinMode() office. For case, pivot 7:



pinMode(7, INPUT_PULLUP);

• Reads the state of the Arduino pivot by using digitalRead() function.



int buttonState = digitalRead(BUTTON_PIN);

※ Notation THAT:

At that place are 2 wide-used apply cases:

• The first: If the input state is HIGH, practice something. If the input land is LOW, do some other thing in reverse.

• The second: If the input land is changed from Low to Loftier (or HIGH to Low), practise something.

Depending on the application, nosotros choose one of them. For instance, in case of using a button to command an LED:

• If we want the LED to exist ON when the button is pressed and OFF when the push is NOT pressed, we SHOULD utilise the kickoff use case.

• If we desire the LED to be toggle betwixt ON and OFF each time nosotros press the push, nosotros SHOULD use the second utilize case.



const int BUTTON_PIN = 7; int lastState = HIGH; int currentState; void setup() { Serial.begin(9600); pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { currentState = digitalRead(BUTTON_PIN); if(lastState == Depression && currentState == HIGH) Serial.println("The country changed from Low to High"); lastState = currentState; }

• Connect Arduino to PC via USB cablevision

• Open Arduino IDE, select the right lath and port

• Copy the below code and open with Arduino IDE



const int BUTTON_PIN = 7; void setup() { Series.begin(9600); pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { int buttonState = digitalRead(BUTTON_PIN); Serial.println(buttonState); }

• Click Upload push on Arduino IDE to upload code to Arduino



• Open Serial Monitor

• Press and release the button several time

• See the result on Series Monitor:

1 is High, 0 is Depression.

Read the line-by-line explanation in comment lines of code!

Let's change the code to observe the press and release events

• Modify the lawmaking as beneath



const int BUTTON_PIN = vii; int lastState = LOW; int currentState; void setup() { Serial.begin(9600); pinMode(BUTTON_PIN, INPUT_PULLUP); } void loop() { currentState = digitalRead(BUTTON_PIN); if(lastState == HIGH && currentState == Low) Serial.println("The button is pressed"); else if(lastState == LOW && currentState == HIGH) Series.println("The button is released"); lastState = currentState; }

• Click Upload push button on Arduino IDE to upload code to Arduino



• Open Serial Monitor

• Press the button and then release

• See the event on Serial Monitor

The button is pressed The push button is released

※ Notation THAT:

Even you pressed and released the button only in one case, the output in Series Monitor may show several pressed and release events. This is the normal behavior of the button. This behavior is called the "chattering phenomenon". You tin acquire more in Arduino - Button Debounce tutorial.

※ NOTE THAT:

To arrive much easier for beginners, especially when using multiple buttons, we created a library, called ezButton. You can learn about ezButton library here.

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• Turn on LED when button is pressed and turn off LED when button is Non pressed.

• Toggle LED between ON and OFF each time the button is pressed.

When should and should Non we use a pull-down/pull-upward resistor for an input pin?

• If the sensor has either closed (connected to VCC or GND) or open up (NOT continued to anything) states, yous need a pull-up or pull-down resistor to make these states get ii states: LOW and HIGH. For example, push-push, switch, magnetic contact switch (door sensor)...

• If the sensor has two divers voltage levels (Low and HIGH), you do NOT need a pull-upwards or pull-down resistor. For example, motion sensor, touch sensor ...

About electronic products accept a reset push. Additionally, the button also keeps other functionalities in many products.

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Source: https://arduinogetstarted.com/tutorials/arduino-button

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