First, I need a 3-way switch, ON, OFF, AUTO. I'm not sure how they work with adruino.
You can do that with a "center-off"(on-off-on) toggle switch ([u]example[/u]), or a rotary switch. The toggle switch I linked to is a double-pole (6 connection) switch. You can use a single-pole double-throw (3-connections) center-off switch, or ignore the 3 extra terminals on a double-throw switch.
You can find rotary switches with adjustable stops, so you can adjust the number of positions, in case you can't find the "right" 3-position rotary switch.
With a center-off switch, you can use two Arduino inputs and you'll have 3 states*... Input "A" can be on, or input "B" can be on, or both inputs can be off. You can use [u]if-statements[/u] in your sketch to take different actions depending on the switch/input states.
[u]This example[/u] shows you how to connect a switch an read the state. Most likely, "on" will mean that you are grounding an input and reading zero.
I also am looking for a 2-way switch, ON and OFF. Basically the same thing, I need to determine the position of the switch.
Any-old SPST (single-pole-single-throw) switch will work for that.
- With 2 inputs, there are actually 4 possible states. But, with this type of switch, there is no way to turn-on both inputs at the same time.