This question already has an answer here:
- A question on pull up resistors 1 answer
A.S. The question A question on pull up resistors answers only a part of my question as already mentioned in "EDIT" made shortly after this question was asked & answers here (below) are much detailed, in-context & easy to understand. Definitely not a duplicate; marking as duplicate for 2-3 points
I am reading a book on Arduino & I just do not understand the concept of push-up resistor, following is a quote from the book:
Why do we need the resistor R1? R1 guarantees that the Arduino’s digital input pin 7 is connected to a constant voltage of +5V whenever the push button is not pressed. If the push button is pressed, the signal on pin 7 drops to ground (GND), at the same time the Arduino’s +5V power is connected to GND, we avoid a shorted circuit by limiting the current that can flow from +5V to GND with a resistor (1 - 10 KΩ). Also, if there was no connection from pin 7 to +5V at all, the input pin would be “floating” whenever the pushbutton is not pressed. This means that it is connected neither to GND nor to +5V, picking up electrostatic noise leading to a false triggering of the input.
Another book called it Arduino's pull-up resistance because it pulls current towards 5V, which confuses me even more - how can a resistor increase voltage, shouldn't the voltage drop?
Edit - thanks to @Golaž for pointing to helpful material at A question on pull up resistors, in comments (this edit was inserted on Mar 30 at ~6).
So, what is this whole concept? And which term push-up/pull-up is correct?
Also, with reference to that circuit above -
- What is floating pin?
- How does R1 avoid a shorted circuit? Why does it count as short cicuit & not closed circuit. After all GND is a sink.
- Is a short circuit serious problem at mere 5V
I have already read:
- What are the mechanisms at work in a pull-up or pull-down resistor circuits with a push-buttons and a GPIO?
- Push-pull/open drain; pull-up/pull-down
But I still don't quite grasp it.