What is pull up and pull down resistor?
1 answer(s)
An input pin, like on an Arduino, can sometimes be 'floating'. This means it is not HIGH and it is not LOW. It is just undecided and can give you weird errors. Pull-up and pull-down resistors fix this problem. They give the pin a default state.
A pull-up resistor connects the pin to your power source (like 5V). This makes the pin's normal state HIGH. When you press a button, for example, it connects the pin to ground and it reads LOW.
A pull-down resistor is the opposite. It connects the pin to ground, so its default state is LOW. They just make sure your inputs are reliable and not floating around.