Maximum counts

RickParrot · Dec 14, 2016

I am designing a system that will count thousands of inputs in 1 second. 2304 to be exact. I will break this up between 16 regular counters(144 counts each). I don't want to buy a HSC card. The program is in a Micrologix 1400 and will be using the regular inputs on the processor. The program will be 14 kbites. I've looked at the PDF manuals, but I am still foggy about how many counts a regular counter can count in 1 second. Your thoughts?

Steve Bailey · Dec 14, 2016

You will need to use a Micrologix1400 with DC inputs and configure one of the inputs as a high speed counter. You can configure up to six high sped counters capable of handling 100 kHz count frequency.
You can't do the task with input points driving CTU instructions. At 2304 counts per second you get a count every 434 microseconds. Assuming a square wave pulse that's 217 microseconds on, 217 microseconds off. The Micrologix1400 isn't capable of that fast a scan time.

Sergei Troizky · Dec 14, 2016

A regular counter counts Off-to-On transitions of the condition.
In other words, the condition must be scanned Off to be counted on its transition to On.
By theory, for guaranteed detection of physical input transitions, the PLC scan frequency must be twice the signal maximum frequency.

It's unclear, however, what you mean by "thousands of inputs".
Micrologix 1400 cannot have thousands of physical inputs.

RickParrot · Dec 14, 2016

The inputs are coming in from a rotating disk under a scanner. There are 16 tracks on the disk, so I HAVE to use 16 counters to count the pulses on the disk. If I purchase HSC cards, I believe there are only 2 HSC counters on each card. I would have to buy 8 cards right?
Also, the Kbite size is actually 80(looking at wrong ladder). I forgot about the scan to OFF and another scan back to ON!
I think that is why I am not catching all of them.

James Mcquade · Dec 14, 2016

since you have 16 regular inputs, is this a paper or rotary drum type sequencer
with optical inputs?

also, what part of Iowa are you located?

james

RickParrot · Dec 14, 2016

I have lived in Waterloo and Waukon, but now am in Wisconsin.

Optic pixels are on disc. Although I agree a drum would have been more efficient.

James Mcquade · Dec 14, 2016

Look at the device and disk, we have had an instance in which dirt built up in the disk and on the optical sensor preventing signals from getting through.
james

RickParrot · Dec 14, 2016

Thank you for your info. I am just gonna have to slow the disc way down. 80 Kbite program will be scanned once every 12.5 mSeconds. With a transition from OFF and another Scan back ON, that is 25 mSeconds/count! In just one second, a regular counter can only tract 40 counts per second.
Right?

shooter · Dec 14, 2016

yes rick correct.
arduino can count much faster
or use cmos counters in hardware

Sergei Troizky · Dec 17, 2016

With enough inputs on the main unit, I would use selectable timer interrupt with immediate input refresh.
This would also eliminate problems caused by scantime variations, including longer scans during online edit.

shooter · Dec 18, 2016

is there a code on these discs like a gray code?

RickParrot · Dec 23, 2016

The disc isnt formatted in Grey Code, but could be. One critical thing I failed to mention in this thread is that these thousands of inputs don't have to be scanned in "single file". They can and will be coming in packets of 32 until they hit a partial.
The disc can show an update to 32 counters in one scan. With 32 inputs coming in/per scan, it changes every thing.
I have a 129Kbyte program running right now on a ML1200 with a scan time of 14,700 microseconds.
Even with a scan time of 28,000 microseconds to update these counters, I can update these counters 35 times in 1 second.

Maximum counts

RickParrot

Member

Steve Bailey

Lifetime Supporting Member + Moderator

Sergei Troizky

Member

RickParrot

Member

James Mcquade

Member

RickParrot

Member

James Mcquade

Member

RickParrot

Member

shooter

Member

Sergei Troizky

Member

shooter

Member

RickParrot

Member

Similar Topics