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Chapter 4
Accessory and Cable Connections
Signal Connection Recommendations
This section contains detailed information about signal wiring including precautions and
guidelines for error-free operation.
General Connection Recommendations
Use the following guidelines when wiring signals and creating custom cables:
•
Keep all signals and their ground connections wired separately from the drive and encoder
signal connections. Wiring these signals near each other can cause faulty motion system
operation due to signal noise and crosstalk.
•
Use shielded cables with a low impedance connection to chassis ground to minimize noise
and signal crosstalk.
•
Use a separate power supply for the CompactRIO chassis and the NI 951x module(s) to
isolate the I/O from the controller.
•
Tie the V
sup
cable shield to chassis ground at the module side only.
•
Route wires along the machine frame to reduce high frequency noise.
•
Add clamp-on ferrites to cables to further reduce emissions.
•
Add a balun to the power cable to attenuate conducted and radiated emissions.
Caution
Do
not
exceed the maximum specifications on any input or output. Refer
to Appendix A,
, for more information.
Limit and Digital Input Connection Recommendations
Use the following additional recommendations when connecting limits and other digital inputs:
Caution
Failure to follow these guidelines may result in motion that stops at, but
then travels through, a limit, potentially damaging the motion system. Limits that are
wired incorrectly may prevent motion from occurring at all.
•
For the end of travel limits to function correctly, the forward limit must be located at the
forward or positive end of travel, and the reverse limit at the reverse or negative end
of travel.
•
Limit, home, and digital input signals are digitally filtered. Software configurable filters are
provided to filter or debounce the input signals. Use shorter filter periods for noise filtering
and longer filter periods to debounce the input.
