Using Limit and Home Switches with My NI Ethernet Stepper Device

Updated Jun 5, 2018

Reported In

Hardware

  • ISM-7411
  • ISM-7412
  • ISM-7413
  • SMD-7613
  • SMD-7614
  • SMD-7615
  • SMD-7616
  • SMD-7620
  • SMD-7621

Driver

  • NI-Motion

Issue Details

I am using an NI Ethernet Stepper device with streaming commands over Ethernet. My motion system has limit and home switches, but I do not see these inputs on the device. Can I use limit and home switches with these products?

Solution

All NI Ethernet Stepper devices (SMD-76XX drives or ISM-741X motors) are compatible with limit and home switch inputs. The DC Stepper Motor Drives with Ethernet (SMD-7613-7616) have dedicated inputs for limit switches labeled CWLIMIT and CCWLIMIT. See page 21 in the SMD-761x product manual in the related links for connection information. 

For Integrated Stepper Motors (ISM-741x) and AC Stepper Motor Drives (SMD-762x) in streaming command mode, the Step and Direction digital inputs can be used for limit switches, and the Enable digital input can be used for a home switch. This behavior is enabled by default and is not configurable using the NI Stepper Configuration Utility. The diagrams below show the logic of the limit switch inputs, where a closed circuit denotes an active limit.
 

When a limit switch is enabled, the device will register the active limit and halt the axis. The Ethernet stepper device will flash its status LED according to which limit is active, and no further moves in the direction of the active limit switch will be enacted. At all times, the status of the limit switches can be monitored using the Read: Motion I/O method which can be accessed using an Invoke Node on the SoftMotion axis.

The logic of the home switch input is the same as the limit switches and is shown in the diagram below. The status of this input is exposed in the Read Motion I/O method in SoftMotion. Invoking a Home Reference Move will cause the Ethernet stepper device to travel between the limit switches until the input becomes active.
 

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