PULL UP RESISTANCE

Importance and Working of Pull-Up Resistors in Arduino Uno with Push Button Input

Introduction:

In this write-up, we will explore the importance and working of pull-up resistors in the context of Arduino Uno. We will specifically focus on a scenario where a push button is connected to pin number 7 of the Arduino Uno, and the output of the button press is observed in the Serial Monitor. We will discuss the significance of pull-up resistors, their role in providing a stable input state, and how they ensure reliable button detection.

Importance of Pull-Up Resistors:

Pull-up resistors play a crucial role in digital circuits, especially when using push buttons or switches as inputs. When a push button is not pressed, it essentially creates an open circuit. In this state, the input pin of the Arduino is left floating, and it can randomly detect HIGH or LOW states due to electrical noise or interference.

The pull-up resistor provides a defined path for current flow when the button is not pressed. It "pulls up" the voltage at the input pin to a HIGH state, ensuring a stable reference voltage and preventing the input from floating. This ensures reliable and predictable readings when the button is not actively pressed.

Working of Pull-Up Resistors with Push Button and Arduino Uno:

To understand the working of pull-up resistors with a push button in Arduino Uno, follow these steps:

1. Hardware Setup:

   • Connect one leg of the push button to digital pin 7 on the Arduino Uno.

   • Connect the other leg of the push button to the ground (GND) pin on the Arduino Uno.

   • Add a pull-up resistor between digital pin 7 and the 5V pin on the Arduino Uno.

2. Sketch Implementation:

   • In the Arduino IDE, write a sketch that sets up pin 7 as INPUT_PULLUP. This enables the built-in pull-up resistor feature of the Arduino Uno.

   • Create a loop that continuously checks the state of pin 7 using digitalRead() function.

   • If the button is pressed, pin 7 will read LOW, and you can perform desired actions or send signals accordingly.

   • To observe the output, use the Serial Monitor to print the button state or any other relevant information.

Working Principle:

When the push button is not pressed, the pull-up resistor connected between digital pin 7 and 5V provides a path for current flow, pulling the pin voltage to a HIGH state (logical 1). This stable HIGH state indicates that the button is not pressed.

When the push button is pressed, it creates a direct connection between digital pin 7 and GND, overriding the pull-up resistor's effect. The pin voltage is then pulled to a LOW state (logical 0), indicating the button press.

By reading the state of pin 7 using digitalRead(), you can detect button presses and perform appropriate actions in your code. The use of pull-up resistors ensures accurate and reliable button detection, even in the absence of active button presses.

Conclusion:

Pull-up resistors are essential components in digital circuits, particularly when using push buttons as inputs in Arduino Uno projects. They provide a stable reference voltage and prevent the input pin from floating, ensuring reliable button detection. By configuring the pin as INPUT_PULLUP and connecting the appropriate pull-up resistor, you can accurately detect button presses and incorporate them into your Arduino programs. Using the Serial Monitor, you can observe the output and verify the functionality of your push button circuit. Understanding the importance and working of pull-up resistors enhances the reliability and performance of your Arduino projects involving button inputs.

Code:

void setup() {  

  pinMode(7,INPUT);

  Serial.begin(9600);

}

void loop() {

  int pullup = digitalRead(7);  

  Serial.print("Value at Pin 7= ");

  Serial.println(pullup);  

  delay(1000);

}

Output:

Value at Pin 7= 1  // when push Button is not Pressed

Value at Pin 7= 1  // when push Button is not Pressed

Value at Pin 7= 1  // when push Button is not Pressed

Value at Pin 7= 0  // when push Button is Pressed

Value at Pin 7= 0  // when push Button is Pressed

Value at Pin 7= 0  // when push Button is Pressed