Electronic – a pull up and pull down


Can some one explain this terminology please I think I understand it but not completely sure.

I think pull down is where you place a resistor between +V and the other component and pull up is where you place the resistor between 0v and the component.

If I am completely wrong then let me know!

Best Answer

It's the other way around.

Pull up is where you place a resistor between a signal and +V, pull down is pulling it to ground.

Image of pull up pull down.
(from http://roguescience.org/wordpress/?page_id=11)

Here, you can see that when the switch is open, in the pullup scenario the input pin will read high, but for pull down it will read low.