count down time clock in plc5

[James Mcquade]

hi all,

i have 16 lines here and almost all are identical.
each has a steel seam belt to transport product on.
each belt stretches and must be shortened every 2 or 3 days by cutting the seam and 30 ft off the belt.

i was given a task to track the belt seam and i have it working. when the line stops, the tracking system pauses.

now they want me to incorporate a count down timer into the wonderware 7 hmi to help eliminate the operators reading a chart (which is fairly accurate) until you take into consideration any belt stoppages.

i searched the site but was unsble to find what i need.
the plc is a plc 5/40 or bigger.

any help would be much appreciated.

thanks in advance,
james

 

[jstolaruk]

Do you need PLC5 help? or Wonderware help? Can you be more concise?

 

[James Mcquade]

i have the position tracking program working.

i need help with the plc portion since i'm new to wonderware 7.0
i can compute the estimated time in the plc in hours and minutes, but how would you be able to relate this time to a clock, say 12 hours from now?

regards,
james

 

[dmargineau]

Within a PLC5 system the Status data file contains the CPU internally running clock which's decimal values will be stored within Memory Address S:21 (Hours), S:22 (Minutes) and S:23 (seconds).
You could "snap-shot" the three respective values at the time Line Start and Line Stop events occur and then "relate" these values to your "countdown timer".

 

[James Mcquade]

dmargineau,
thanks for that information.

that points me in a good direction and i can do it in the plc.

how would i do it with wonderware 7.0?

i ask because they may not like the plc solution.

regards,
james

 

[OkiePC]

now they want me to incorporate a count down timer into the wonderware 7 hmi to help eliminate the operators reading a chart (which is fairly accurate) until you take into consideration any belt stoppages.
---
thanks in advance,
james

Sounds like an application where you'd be better served by an encoder. Even an absolute with cheap digital inputs, as long as you could capture the delta D at PLC5 scan rates to keep your tracking logic accurate to the the encoder resolution no matter what happens to the conveyor. Ideally, you bring this in from a tail roller so you can also prove the drive train and conveyor are still connected. It can eliminate the chart and a lot of hassling in code. Ramping into exact position becomes a peace of pi.

I have a sorting system where the cheapskates balked at the encoder costs so I did it with hand measurements and time. I used a SLC5/04 and it STI routine and scaled measured motion per 10ms including accel and decel rates in my math with good results. It still requires photocell for precise triggering of diverters and wouldn't work with too many stops and starts being experienced by a single piece in transit.

 

[dmargineau]

dmargineau,
thanks for that information.

that points me in a good direction and i can do it in the plc.

how would i do it with wonderware 7.0?

i ask because they may not like the plc solution.

regards,
james

James,

I don't know what Wonderware product is integrated with the PLC5.
Is it a stand-alone InTouch HMI application? A distributed one? SCADA? Historian?
Any/all the above are information products, designed to "connect" with automation platforms and "process" the received data (SCADA), create a user interface with an automated system (InTouch HMI), or create a "storage" database (Historian).
I am pretty sure you could accomplish the at hand task on the Wonderware side, however, the PLC5 will provide the easiest, most efficient and accurate way to establish a time relationship between the production lines operational state since all the required information is already there; IMHO, sending "raw" data to a different platform and processing it there would be an unnecessary "extra" step.

 

[James Mcquade]

OkiePC,

That's what i told them. use an encoder and track the belt that way. several years ago they tried that and when the belt tore or hung, they destroyed the encoder.

You have given me an idea though about using an encoder on the main drive shaft away from the belt.

Thanks!
james

 

[OkiePC]

OkiePC,

That's what i told them. use an encoder and track the belt that way. several years ago they tried that and when the belt tore or hung, they destroyed the encoder.

You have given me an idea though about using an encoder on the main drive shaft away from the belt.

Thanks!
james

Give them both. When the encoder failure is detected, switch over to a timed calculation and try to minimize stoppages until it is fixed...best of both worlds...One of the green tire conveyors I programmed this way actually ran for who knows how long since it was early upstream and rarely paused and the HMI with the fault was up on the catwalk. It had to un-sort tires randomly dropped from known fixed locations in spaces on the belt. The encoder had seized and was just a shell of dust when they found the roller bearing also gone when bb's starting pinging off the floor and the wobble and screeching finally became unbearable.

That way you can disclaim accuracy with multiple stops in "sensorless mode" and all they have to do to cure it is add the encoder, reset the faults, and prove you right.