Maintenance bit ?

I need to put a bit into the logic to throw a fault every 90 days to have maintenance done to a machine with rs logix any help on this ?

Remember that "RSLogix" has versions for the PLC-5, the SLC-500/MicroLogix family, and ControlLogix. Which controller are you using ?

Since you're looking at resolution monitored in Days, an easy approach would be to use a counter that increments every time the Real Time Clock comes around to a selected time of day (like midnight, or noon, or 7 AM). Once that counter reaches 90, set the Maintenance Required bit.

Are you actually going to set a "fault" bit that will prevent the machine from being used until maintenance man does his job ?

What would happen if there was no-one available at that time ?

Would it not be better to set a bit that "calls" for maintenance after, say, 85 days, and then shut the machine down if that maintenance is not performed after, say, another 10 days.

And who is going to reset the fault bit that you carefully program to come on after xxx days ?

Do you see where I'm leading to with this...?

Also, does the machine run 24/7 ? A simple timer, or Ken's idea, will accrue time whether the machine is running or not. You might like to look at the "Retentive Timer" RTO, which you can enable only when the machine is running. if you had this timer time for one-hour (3600 seconds), you can use a counter to count hours (90 days is 2160 hours).

another edit : You might also need to consider that a machine might need maintenance if it has NOT been run for a period of time, prior to it being started up.

plc electrician,

a word of caution on what you propose.

setting a bit every 90 days for maintenance is one thing.
i may misunderstand your definition of a fault bit, but to fault / stop the machine after 90 days until maintenance is done is a different story.

programming this bit without work instructions in place and without anyone knowing how to reset this bit is asking for big trouble. it is pointing a gun right at you.


regards,
james

A simple counter will do the trick.

Each time the hour becomes 0 (between 12 midnight and 1 am) the counter upcounts. Since the counter is transitional it only counts once at the start of the midnight hour and doesn't count again until the next midnight.

--+---------------+---------+----------------+-

  |EQU            |         |COUNTER     C5:0|

  |Source A   HOUR|         |PRESET        30|

  |Source B      0|         |ACC            0|

  +---------------+         +----------------+

The source of your HOUR value will depend on what PLC you are using, that is why the other forum members have requested this information.

Thanks Ken I am using a micrologix.

Daba
You brought up some very good points. The machine is a baler so its not as if we would shut down a facility. I like the 85 day warning before the fault as this would kick things in gear. Its mainly that it needs to be done and its not getting done on schedule causing other issues. The machine runs 24/5 but I believe Kens idea of a retentive timer is a good move. We have to consider this carefully before actually implementing it . I appreciate all the advice.

James Mcquade said:

plc electrician,

a word of caution on what you propose.

setting a bit every 90 days for maintenance is one thing.
i may misunderstand your definition of a fault bit, but to fault / stop the machine after 90 days until maintenance is done is a different story.

programming this bit without work instructions in place and without anyone knowing how to reset this bit is asking for big trouble. it is pointing a gun right at you.


regards,
james

Click to expand...

James It would be set up in advance and training set up on how to reset this before it was just thown in there. We are just trying to make sure this machine is maintained and not left to run . Recently spent a ton on repairs due to lack of maintenance. It is only a baler but I agree it should be thought out before we just throw logic in. But we have a trained maintenance electrician on each shift who could reset this.

I would consider giving the operator a timed reset button.
reset for X hours and allow running on. prevent the button from being bridged or held on.
so long as it becomes a headache for the operator - he/she will call maintenance