# Resistors A "pull-down" resistor goes between digital pin and ground. Then put the button between voltage and the digital pin. The resistor pulls the pin down unless the button is pressed (connecting voltage). A "pull-up" resistor is like "pull-down", but swap the ground and supply nodes. All else being equal, it seems to me it would save power if we use pull-down. How to select the resistance: resistor should be "1/10 less than the input impedance of the digital pin" (does this mean 90% of the input impedance?) (or 10kOhm if you can't be bothered).