micrologix 1000

[bucks7756]

I have an application where I need to track parts entering an exiting a machine. There is a photoeye at the entrance and a photoeye at the exit. Once a part enters the machine it has a certain time to exit the machine or the machine needs to be shut off. The problem that I am having is that there can be multiple parts inside the machine at once which will require multiple timers. Does anybody have any advise on how to keep track of this in RSLogix? Any help will be appreciated.

 

[hillimonster]

why don't you compare the rate of parts going in to the rate of the parts going out? If the ingoing rate is 1 part per second, the outgoing rate should get to one part per second (after an initial transit time). If the rate out goes down to 1/2 part per second, then one is missing. I don't think it can be instant feedback, in that you would have to miss a part out, with some tolerance in time, before you know for sure one is mising. Also if there is wide variability in rate this would take more consideration.

 

[jonesy29847]

I would set up any array of timers and shift, actually MOV, the accumulated values every time a part enters.

You have to shift the last accumulated value first, assuming a 3 part capacity timer[1] (process) would shift into timer[2], then timer[0] would shift into timer[1] and so on to suit.

Once the shift is complete you can then look at the accumulated values an see if any are over limit.

If you have ST programming capibility the check routine could index through the array and return 1 if any value is over limit.

Be sure the shift is triggered from a oneshot, and you reset timer[0].

 

[jlobito]

I did something similar to this a while back for a washer. I wasn't real concerned with how long the parts were in there, just that there wasn't a pile-up inside. I set up a counter that was incremented by parts feeding in and decremented by parts exiting. If the counter ever got higher than the max number I wanted in there, I generated an alarm and shut down the infeed.