Momentary tactile pushbutton

Resistors are used to pull up or down the pin to which a switch is connected, to ensure that the pin never floats. (in this way it will allways be either HIGH or LOW, dependin on the switch status)

HJ

What would happen if I don't connect a resistor with the pushbutton?

There may be inconsistency in using the switch. Your device may be 'hung' between on and of or produce on when not pushed.

@hstaam

Posted by: @hstaam

There may be inconsistency in using the switch. Your device may be 'hung' between on and of or produce on when not pushed.

Quite true, but technically; it's more about the logic state of the GPIO itself... known as a "floating" pin, and this holds true for any device connected to a logic level pin.

@frogandtoad

I fully agree. I used the same word 'float' in my initial post.

HJ

@hstaam

Posted by: @hstaam

@frogandtoad

I fully agree. I used the same word 'float' in my initial post.

HJ

My apologies... I misread your original post 🙂

No need to apologise. 😀 

Why does the pushbutton float? Is it a characteristic property of it? Or is it that sometimes the contact might be made accidentally, even when not pressing the button?

I used the following sketch for switching on and off an LED. It uses a resistor with the pushbutton. Then, is it pull up resistor or pull down resistor?

This is the circuit diagram of the same.

Posted by: @sumanta

Why does the pushbutton float? Is it a characteristic property of it? Or is it that sometimes the contact might be made accidentally, even when not pressing the button?

No, it's not the button... it's all got to do with the logic level voltages supplied to the pin.

For digital pins to operate properly, the logic level voltages applied to them must fall within their specified ranges.  Without pull-up or pull-down resistors, the logic level cannot be properly determined, therefore is knows as a floating pin.

Posted by: @sumanta

I used the following sketch for switching on and off an LED. It uses a resistor with the pushbutton. Then, is it pull up resistor or pull down resistor?

You can check it for yourself with a Serial.print... statement in your setup function.

Learning to do this is a valuable debugging technique, and worth getting used to.

@frogandtoad Thank you so much for answering my question and for the proper explanation. I was struggling to understand this for a long time. Thanks again 😀 

@hstaam Many thanks to you too. 😀