read acc. value 1746-HSCE with allen bradley 5/05 at hi speed conveyor

[feike2]

Can anyone tell me please if there is a way (exept an IMM instruction) to read the accumelated value (I:e.1) of the Hi speed counter 1746-HSCE immediately after a interrupt (STI or DII) occurs?
I hope somebody have more experiency with the high speed counter, because I need to read at hi conveyor speed.

Thanks a lot
Greetz

 

[rdrast]

Is there a reason you have an objection to IIM? or does it just not work?

 

[feike2]

I used an IMM instruction, but I think it doesn't work or it is still to slow.

 

[rdrast]

Why do you think it doesn't work? Use a temporary register, and in your interrupt, after the IIM, move the value into the temporary register. As long as there is a value, you can then inspect it outside of the interrupt routine. Clear the temp register, does a value return next interrupt?.

Can you read the accumulated count at all from anywhere?

And if it is too slow, well, not much you can do there. The I/O table is only updated at the beginning of the main (LAD-2) scan (or just before, I suppose, technically). If you MUST HAVE the current value of any input word, then you MUST use IIM to retrieve it.

 

[OkiePC]

1. What are you doing with the value in the program that requires such high speed? Are you sorting, turning on solenoids, stopping and starting the line?
2. Are your outputs that must respond to the counter in local I/O?
3. How fast is the conveyor running?
4. In a nutshell, what is the problem you're dealling with?

There is probably a way to accomplish whatever your trying to do without the IIM or STI. You said in an earlier post that your scan time was under ten ms. That should be fast enough for most applications I can think of. I have had similar applications in which I had to calculate the speed of the line and adjust operating "windows" so that my solenoids (on remote I/O) could be turned on early enough to control the drop arms that place product on the line within a few inches of each other. Answer the questions above and we can make good suggestions to help you get your problem behind you!

Paul Cunningham

 

[rdrast]

Paul just triggerred a thought in my feeble brain...

If you are trying to control an output in the interrupt based on the counter value, then you MUST also control the output with IOM. Simply using a normal output won't get to the physical output untill the processor does it's next housekeeping sweep.

 

[feike2]

I have products (width 4 cm) on a conveyor I have to detect the beginning and the end of the product with a photocell. At the beginning and the end of the product I have to save the acc. value of the hi speed counter, so I know how much pulses the product is. Conclusions of some tests I made:
Sometimes the product is about 400 pulses en the other time the product is 700 pulses. I need to have a more stabel result. My conveyor speed is about 120 meter/ min. Now I use a DII for the sensor and a IMM for the hi speed counter, greetz Feike

 

[feike2]

By the way, all I/O cards are local. Greetz Feike

 

[rdrast]

Hrm.

Maybe you would be better off using the counter module in a 'gated count' mode?

Toggle the 'Hold' bit off for the counter on the break of your photo-cell, then back on for the make on the photo-cell. After you have toggled it on, move the accumulated count somewhere (in the DII), and set another bit telling the main program that new data is available.

You may be pushing the limits of a SLC though.

 

[tom_stalcup]

On another note.... Some photocells aren't going to switch reliably at high speeds... You may want to pull up the tech sheet of the photocell, and make sure it can handle the job you are using it for.