Quote:
Originally Posted by gtkid2002
Could you explain more as to what the T'd means?
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What I mean is, leave the switch connected the way it is, but strip some insulation off of the wire that connects the switch and its 'guino pin. Solder one lead of a resistor to that stripped off area. If you soldered the resistor on at a right angle to the wire, it should have a T shape, thus the term. Really it just means connecting to a wire without breaking the existing connection, also known as "tapping into" a wire.
Connect the remaining resistor lead to 5V+.
This will make the 'guino see 5V until the switch is pressed, at which point any power coming from the resistor or the 'guino itself will be shorted to ground through the switch. The resistor prevents this power flow from from becoming a true short by limiting the current. A 5K resistor limits current to 1 mA (see ohms law). You could use a higher value resistor to limit the current further, so long as the 'guino isn't sinking any significant current... Anything up to 100K would probably work, though I'm guessing really. Going to a lower value means more current would pass through the resistor and be dumped to ground (wasted) when the switch is pressed. There's no practical benefit to doing so, but you could go as low as 300 ohms before you start pushing the limits of a typical 1/8th watt resistor.