How to Connect NI 73xx Digital Outputs to Third Party Equipment Hardware: Motion Control>>Power Drives
Problem: When I connect digital outputs from the NI 73xx controllers through a Universal Motion Interface (UMI) in order to move a motor, disable a drive or trigger an event, the signal at the motion controller will change; however, my third party drive will not generate any of these actions. Why is this? Solution: By default the breakpoint, inhibit and step & direction output signals on the NI 73xx controllers are configured as 'open collector.' Open collector means that the controller can sink a fairly large amount of current but only source very little. A very popular way to provide optical isolation for the digital inputs on many third party amplifiers is by means of an optocoupler. In order to operate properly, an optocoupler requires that the signal that will switch its state provide enough current to do so. In a scenario where the two previous circumstances are present the effect may sometimes be that the NI 73xx controller sends out a breakpoint, inhibit or step & direction signal and the third party equipment will not see any transition at all. The drive will produce no response to the command. In order to properly connect the inhibit, step, and direction lines, please refer to this Developer Zone Tutorial: How to connect the 73xx inhibit and command signal outputs to third party drives. The breakpoint outputs on the 733x and 734x controllers are also open collector. On the 735x however, the breakpoint output signals may be configured either as open collector or totem pole by selecting their mode in Measurement and Automation Explorer by following these steps:
2. Under Devices and Interfaces Locate your 735x series controller. 3. Expand Default 7350 settings. 4. Expand Axis X (where X is the desired axis). 5. Click on Compare and Capture Settings. 6. Under Position Breakpoints, select either Open Collector or Totem Pole. 7. Click Save and then Initialize.
If you are using open collector mode breakpoints, the connections to optocoupled trigger inputs on third-party equipment should follow the same rules described in section 1 of the tutorial for all open collector signals. If you are using totem pole mode breakpoints, then these connections should follow the same rules described in section 2 of the tutorial for all totem pole signals. Related Links: Developer Zone Tutorial: How to connect the 73xx inhibit and command signal outputs to third party drives Product Manuals: Getting Started with NI-Motion for NI 73xx Motion Controllers Product Manuals: National Instruments 7330 User Manual and Specifications Product Manuals: National Instruments 7340 User Manual and Specifications Product Manuals: NI 7350 User Manual and Specifications Attachments:
Report Date: 09/04/2003 Last Updated: 09/22/2008 Document ID: 313C8EOV |
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