Switches and push buttons

Theory B: Push Button

DPST button and function

A double pole single throw push button micro switch (DPST) is a widely used button. Push button switches are often color coded to indicate their function.

Three methods to wire

1. External pullup or pulldown resistor: Use pinMode( Button_pin, INPUT); in the setup.
2. Internal resistor (20k-50k Ω): Use INPUT_PULLUP in setup pinMode( Button_pin, INPUT_PULLUP);. The default value is HIGH (1) and by pressing the button the state goes to LOW.
3. The bad method: Use pinMode( Button_pin, INPUT); in the setup without any resistors. The default value will float between 0V and 5V: there is no internal or external

voltage reference for the push button.