Limit And Home Inputs - National Instruments UMI-7774 User Manual

Chapter 3 Connecting the UMI-7774/7772 to Drives and Other Devices
National Instruments UMI-7774/7772 User Manual
Pass-Through Signaling on Encoders and Limits
Some drives have pass-through signaling on encoders and limits. If the
drive has the pass-through feature, ensure that the drive does not filter the
encoder or limit signals because this could reduce achievable closed-loop
performance and stability for the system. If the drive does not have
pass-through signaling for encoders and limits or if you choose not to use
the pass-through signaling, you can connect the UMI-7774/7772 to the
encoders and limits directly. If you are using Hall effect sensors for
brushless motors and also are using a National Instruments motion
controller with sinusoidal commutation, connect to these sensors either
directly or through the drive.

Limit and Home Inputs

The UMI-7774/7772 has connections available for forward limit, reverse
limit, and home sensors or switches. The limit sensors or switches are
typically located at physical ends of travel. The home sensor or switch can
be located at any reference position within the range of travel.
The limits and home inputs are sinking inputs on the UMI-7774/7772 and
are optically isolated. A sinking input is an input terminal that can sink
current by providing a path to a supply common or ground. You can wire
this type of input to a sourcing output device. A sourcing output device can
source current by providing a path to a supply source. PNP sensors are
examples of sourcing output devices. The interface circuit is the same for
the forward limits, reverse limits, and home inputs. As shown in
Figure 3-16, you can wire a sourcing output device, such as a PNP sensor,
to the limit or home inputs. You can use the isolated power (V
isolated common (C
iso
the limit home sensor.
Refer to the Voltage Considerations for the UMI-7774/7772
voltage information that applies to the limit and home switches and sensors.
) signals provided on the control connector to power
3-20
) and
iso
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