Signal Wire Length

[EricVanWyk]

How familiar with circuits are you? From the questions, you may have current vs voltage confused.

Originally Posted by Ewilliams2006

From the Control System's manual:

• 5V/3A buck power supply for DSC circuitry with excess power available at the GPIO and I2C headers

Does this mean the DSC will source 3A to a nearly shorted connection, such as a depressed limit switch? What does "excess power" mean?

It means that it will reliably source 5V at up to 3A. If you draw more than 3A, the overcurrent protection will trip and temporarily shutdown the supply.

A limit switch has an effective resistance of 10kOhms when wired correctly, because of the 10k pullup resistor on the DSC. The effective impedence of the cRIO module's pin is very high.

Originally Posted by Ewilliams2006

Does the "Input current" mean that the module itself limits the input current to ±250 μA, or that is the maximum input current allowed into the module?

If a pin is set to an input and you apply between 0V and 5V, up to 250uA may flow. It is effectively stating the pin's impedance.

Originally Posted by Ewilliams2006

Finally, would adding a bypass capacitor across the ground and signal pins help reduce noise?

I'd stick it across the power lines myself.