ML 1200 - High Speed Speed Counter issue

[FONT=Arial, sans-serif]I am having an issue with either the Encoder – an Encoder Products [FONT=Arial TUR, sans-serif]25T-40SG-0500NV1RPP-SMJ-S3[/FONT][FONT=Arial TUR, sans-serif] or the High Speed Counter on a ML 1200.[/FONT][/FONT]
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[FONT=Arial TUR, sans-serif]The encoder is installed with Count B on I:0/0, Count A on I:0/1 and the Z reset on I:0/2.[/FONT]

[FONT=Arial TUR, sans-serif]It is a 500 pulse / revolution encoder running at approx 1 second per revolution. Not very fast at all.[/FONT]
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[FONT=Arial TUR, sans-serif]The HSC is set to Mode 7. (Count both directions with the reset pulse). The Embedded I/0 Configuration is set so the input filters for Inputs 0 + 1 and 2 + 3 are set to 25 micro seconds.[/FONT]
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[FONT=Arial TUR, sans-serif]When I talk to the folks at Encoder Products they act like they never heard of a Micrologix processor before.[/FONT]

[FONT=Arial TUR, sans-serif]I have an earlier set up on a similar machine and had a problem with the Z pulse being high and going low for the reset pulse. They said that I had it wired wrong or something was up with the “Counter” I was using. They did rewire the Encoder for the Z Not signal and it worked. They said that the Open Collector wasn’t as hardy as a Push Pull output, so I ordered this Encoder with the Push Pull out put. Occasionally it works, but it is totally random.[/FONT]

[FONT=Arial, sans-serif]What could I be missing?[/FONT]

I will be more clear as to my specific problem.


The reset pulse randomly works to resets the counter. The count should not go over 500, it seems to randomly work after several revolutions. The counts appear to be working and when the reset does work it does occur at the proper position.

I have this line in the main Program to get a value in N:34 so I can display it on the Panel View.

MOV HSC:0.acc N:34

I added this line to see when the HSC wound be over 500, I would use b/199 to turn on a light.

GEQ HSC:0.acc 501 – OTE b/199

The counter wound never reset and the program faulted after the value in the HSC maxed out.

I modified the line to use N:34 instead of looking right at the HSC

GEQ N:34 501 – OTE b/199

Now I am back with the random resets, maybe once every few revolutions.

http://www.youtube.com/watch?v=23N39uJRtdM

A quick video from my phone. Maybe this can help.

Never having worked with the HS inputs on a ML1500, your symptoms seem nearly like they are scan time dependedant. Are you capable of backing off the speed to see if say a 2 seconds per revolution rate helps. What does AB publish as the minimum "on time" or max freq for you the Z channel?

Damian,

The High Speed Counter is hard wired with special inputs that are rated to count up to 20 khz. I am running at .5 khz.

I agree that there is something with the logic. What intrigues me is that I just did the same thing, to a sister machine and it worked. I was reusing the same program.

I checked the reset voltage and when stopped at the right spot, I measure 23 volts. Also the A & B counts are working as they should. I am using the Power Supply built in the ML 1200 to run the encoder. All the other Inputs and Outputs are on a separate Power Supply.

Mark,
I do understand that the counting of the A&B phases is not scan dependant and is meant to operate at high frequency. What I am getting at is (at least on many others have used), the logic for resetting that count is not always scan independant and thus needs to be taken care of in the ladder. Usually what happens is there is some sort of flag that is set (like a registration input) that stays on to let you know that your Z-pulse occured. This way if your Z-pulse On time is too short for the SCAN to detect reliably you can still know that it happened. Normally then you would just simply perform your logic, reset the flag, and then wait for the flag to trip again.

I'm only speaking of how I've seen it done on other products. So I may be out to lunch with reagrds to how the ML1200 handles it.

Mark, Another thought just looking at manual. You selected mode 7. This shows the function being a reset and hold.

The hold being allocated to
I1:0.0/3

If you left this floating, it is possible this input is "holding" intermittently on you. Just throwing out a dart.

Damian,

There is no connection to I:0/3 – “The Hold input”

After spending the morning on the phone with Rockwell, it is the Encoder, the Cable or the Processor.

I am using a standard 889D-F5AC cable about 4 feet long. It is a 22ga 5 conductor cable. I’m going to try separating out the gray wire from the cable. This should help protect the Z signal from disappearing …