Pull-up or pull-down resistors for switch?

John Abshier

I vaguely remember reading about reason to pick one or the other.· Alas, I don't remember which it was or the reason.· The PE Kit uses pull downs.· The PPDB uses pull ups.

John Abshier

Mike Green

In most cases it doesn't matter. Pullups are better if you're using a "home-made" switch like a contact "whisker" since the contact is made to ground and the other side of the switch is current limited by the pullup. You won't accidentally short circuit your power supply if there's an accidental contact to ground.

mctrivia

pull up is to vdd, pull goes to vss. 10k is the standard value but any value for 300 to 1M will usually work.

If your switch goes between input and vss use pull up
if your switch goes between input and vdd use pull down.

if your input goes through a switch to another input(matrix configuration) use pull ups for active low inputs and pull downs for active high inputs.

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