Chapter 3
Signal Connections
©
National Instruments Corporation
3-9
NI 951x User Manual
Motion I/O Signals
Limit and Home Inputs
The following inputs are available for limit and home functionality on the
NI 951x modules:
•
Forward Limit Input
•
Reverse Limit Input
•
Home Input
These inputs are typically connected to limit switches located at physical
ends of travel and/or at a specific home position. When enabled, an active
transition on the Forward Limit, Reverse Limit, or Home input causes
motion on the associated axis to stop. The stop mode is user-configurable
in software. Refer to the
NI SoftMotion Module
book of the
LabVIEW Help
for information about the available stop modes.
The Forward Limit, Reverse Limit, and Home inputs are digitally filtered
and have programmable filter frequencies. Active limit and home signals
should remain active to prevent motion from proceeding further into the
limit. Pulsed limit signals stop motion, but they do not prevent further
motion in that direction if another move is started.
Forward Limit, Reverse Limit, and Home inputs are not required for basic
motion control. These inputs are part of a system solution for complete
motion control.
Caution
National Instruments recommends using limits for personal safety, as well as to
protect the motion system.
Limit and Home Input Circuit
You can use software to enable and disable Forward Limit, Reverse Limit,
and Home inputs and to configure the active state of the signals to on or off.
You can also configure the Forward Limit, Reverse Limit, and Home input
circuits for current sinking or sourcing output devices.
Tip
Refer to the
Signal Connection Recommendations
section of Chapter 4,
Accessory
and Cable Connections
, for additional wiring and cabling recommendations.