1769-HSC Reset with Micro 1500

I've got an issue with resetting a counter to 0 on a Micrologix 1500 with a 1769-HSC card. The preset is configured in the IO configuration for 0 and I set the soft preset bit (in this case O:2/81) but nothing happens.

The reset works perfectly when I first download the program but if I upload then download again it stops working. The customer has also rung me after a couple of days to say it's stopped working all by itself. The last time it stopped working I downloaded the original copy of the program and it worked fine, but this time I need a more permanent solution.

I do have the reset on a one shot so the first thing I'm going to try is removing that and holding it on for a while but they'll soon get sick of pushing a button for 20 seconds waiting for it to reset.

I've found a couple of things on the knowledgebase. Article 42716 talks about issue when the other counter is enabled but I'm sure it's not enabled.

Article 56789 says to go into the Input Config screen, check the box for the Reset Counters. Then go to the Counter Configuration tab and verify the value in the Preset. I can't find a Reset Counters box anywhere so I'm thinking that might refer to the compactlogix version and the value in the preset is 0.

I'm going back to site tomorrow to try a few things but I was wondering if anybody on here had some ideas of things to look for.

Cheers!

Article 56789 says to go into the Input Config screen, check the box for the Reset Counters. Then go to the Counter Configuration tab and verify the value in the Preset. I can't find a Reset Counters box anywhere so I'm thinking that might refer to the compactlogix version and the value in the preset is 0.

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I think you need to upload a copy of the Compact 1769 HSC User Manual, Rockwell Publication number 1769-UM006D-EN-P for the English version.
http://search.rockwellautomation.com/search?q=%221769-UM006%22&filter=0&btnG=Search&client=literature&output=xml_no_dtd&proxystylesheet=literature&oe=UTF-8&ie=UTF-8&hl=en&getfields=*&num=10&sort=date%3AD%3AL%3Ad1&ulang=en&entqrm=2&ud=1&exclude_apps=1&site=literature

Page 66 shows the HSC Configuration word, and that bit 1 of the HSC Configuration Word is the Counter Reset Bit (set to 0 to reset, normally = "1"). Your Reset button should cause that bit to be reset. When a Ctr Rst is done, I don't think that the value of the Preset in Configuration Words 10 and 11 should change. The Preset is the value that you want to count for each input (normally a "1"), so it should only be changed by the user and not by doing a Counter Reset.

To reset using RSLogix, there is a HSC Reset command, RAC (HSC Reset Accumulated Value). The counter also resets upon power cycling the module. It could be that your module is experiencing power blinks and resetting in the middle of operations.

When the module powers up, all output array and configuration array values are set to their default values. See page 66 in Chapter 4 or Appendix D on page 149 for default values. All input array values are cleared. None of the module data is retained through a power cycle. In effect, this means that power cycling clears the module with these results:
Stored counts are lost.

Faults and flags are cleared.
Outputs are off.​

The bus master will attempt to write program data to the output array and configuration array.​

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I thought I should report my findings here in case somebody else has the same issue. Hello future people!

So there was some weird stuff going on here. It seems that the issue was caused by the logic I had for retaining the count on a power cycle which I essentially copied from knowledgebase article 59434.

The whole thing worked beautifully but if the power was cycled the reset would stop working and I couldn't see any problems with the logic. What really threw me though was that it would work fine if the number in the counter was a negative before the power was cycled. It just didn't like positive numbers.

I removed all of the retention logic as it wasn't critical and probably not necessary - how can you guarantee that a machine isn't going to move more than 0.1mm when the power is off? - and now the reset works beautifully. I can only assume I was overwriting something I shouldn't have been somewhere but the machine is doing what the customer wants and I don't have the time to investigate further right now.

Thanks for listening.

Those KnowledgeBase articles are useful - if you have the same level of knowledge about the problem as the guy that wrote the article, so that you can understand all the ifs, ands, and buts of why it may not work for your particular situation.

...how can you guarantee that a machine isn't going to move more than 0.1mm when the power is off?

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I think that many machines could coast for 0.1mm before stopping or braking when the power goes off. If that was a requirement for using the Knowledgebase method, then you would have to know a lot about your machine before being able to use that method. I suppose the method was to save all the dozens of HSC parameters to non-volatile memory locations, then reload that data upon restart. If the power "bounced" - blinked off/on several times rapidly, then that method could lead to data errors in the HSC counter parameters.

Your efforts would probably be better spent putting the Micrologix 1500 HSC module on a small UPS power supply, so that it rides through power blinks and does not reset for each short power blink.