Cause I have a cheap-ass wall-wart! Its rated at 500mA, so this is the max output current right? If the load is less, it should supply less right?
This is true.
I read some where that the Arduino requires very little input current to drive Digital Inputs.
This is also true.
I figured I'd use a resistor from +5V to Gnd and then connect the Arduino input in parallel. Would this help as a sort of protection against over-current?
Suppose the device being read supplied 50V. What would the resistor do? Suppose the device was capable of supplying 500mA, but the Arduino was only drawing 10 mA. What would the resistor do?
should the Digital Outputs go through a resistor before being connected to the IC7447 inputs?
What does the data sheet for the IC7447 say? What would the resistor do?