MicroLogix...reboot PLC from the HMI?

You can send a "warm boot" command over DF1 to a MicroLogix; I've done it with a custom command driver.

But this is not an ordinary function of any HMI system, nor is there a Status bit you can write to that causes a warm boot or cold boot.

The reason *should* be obvious.

The real issue here is that if you find a way to simulate a "New Start Bit" as mentioned, what you will never be able to achieve, at least I don't think so, is the PLC's "Pre-Scan".

The Pre-Scan does a very important job, turning OFF all non-retentive output bits (not just physical outputs, but internal bits as well). it also preconditions ONS bits by turning them ON.

There are lots of things the Pre-Scan does, in order for the PLC to start its First Scan (proper, so that the logic restarts in an orderly, and correct fashion.

By far the easiest thing to do (if you must) is to wire a keyswitch next to the HMI, which can interrupt the power going to the PLC. I suggest a key operated switch as it would be difficult to operate it unintentionally.



OkiePC - if you create a fault routine to clear the major fault created by a negative timer register, then the PLC doesn't actually shut down, it just carries on with the next instruction after the timer, ignoring it. That's not a reboot.

another thing I forgot to mention was what is the process you are doing.
when it comes to the plc program, you must also know the process.
what needs to be homed?
can the machine be homed with the first scan bit or power up condition?
what chemicals are you mixing?
what gases are you monitoring / mixing?
what happened when you have a power loss to the plc or use the first scan bit?

none of this may apply to your system, but I thought it worth mentioning.
james

James and Aabeck..I absolutely know what bits and outputs needs to be shut down. I actually had a first pass set up that would kill everything upon powerup and shut the unit down in an orderly manner, but I have now made that a conditional occurrence based on how long power was off for.......the machine will now continue operation after a brief power failure. And James, I'm sorry but I'd rather not get into specifics online about what I do at work. Long and probably dumb story.

Yep!!

I just tried it...it worked. Just used a spare momentary contact to OTE the S1/15 bit. First rung of the first ladder. So it basically ran the first pass stuff but now that I have looked at it again, I truly don't need this. But hey, all the replies were a treat and made me feel good.

geniusintraining said:

See below




EDIT: Anyone ever try resetting (or setting) S:1/15 in the program? maybe as simple as having a HMI toggle S:1/15 (just a WAG)

Click to expand...

daba said:

OkiePC - if you create a fault routine to clear the major fault created by a negative timer register, then the PLC doesn't actually shut down, it just carries on with the next instruction after the timer, ignoring it. That's not a reboot.

Click to expand...

Yeah, I was going to speculate about that part, but had to attend to a phone call before I finished my thought process on that. I was unsure if the fault recovery would trigger the first scan bit...I figured it would not, since the program scan was interrupted before actually stopping. Thanks for the definitive answer on that.

IMHO there must be something wrong with your PLC program if it has to be re-started periodically.

I would spend my time finding and fixing that problem, rather than trying to provide an easier way for the operator to "re-start" it.

I am wondering when the FirstScan bit is set by the program if it causes the PLC to do a Pre-Scan before the first scan that resets the bits, timers, counters, etc.

It doesn't need to be re-started periodically, my setup works well....I was just thinking out loud and I'm a free thinker. And to be honest, I know nothing about what the pre-scan does, I was only aware of the first pass scan.

daba said:

IMHO there must be something wrong with your PLC program if it has to be re-started periodically.

I would spend my time finding and fixing that problem, rather than trying to provide an easier way for the operator to "re-start" it.

Click to expand...

Skidood,

I totally understand and I was not wanting answers when I asked what chemicals and so on.
I was just making statements that you need to ask yourself.
I did a paint color change system a few years back and the installation tech for the company said I could inject the paint solvent into the system while the electrostatic system was energized, even after I reviewed the data sheet on the solvent. I called the company up that made the components to verify what he said, that was the techs last day with the company.

so asking a lot of what if questions is good in regards to all plc programs.
james

Skidood said:

It doesn't need to be re-started periodically, my setup works well....I was just thinking out loud and I'm a free thinker. And to be honest, I know nothing about what the pre-scan does, I was only aware of the first pass scan.

Click to expand...

Then why are you trying to make it easier for the operator to re-start it ?


For descriptions of what Prescan does for each instruction, see the instruction reference manual, and search (Ctrl-F) for "Prescan"

Because ...what if there might be some challenges with operator access to the power switch. Again, this is a hypothetical scenario.

daba said:

Then why are you trying to make it easier for the operator to re-start it ?


For descriptions of what Prescan does for each instruction, see the instruction reference manual, and search (Ctrl-F) for "Prescan"

Click to expand...

There was only one machine that we had to do a 'reboot' on and that was only every once in awhile... it was a complex machine, 6 SEW drives, 1 S5 Siemens, 3 AB SLC's, two Panelviews and one micro controller, with a lot of motion and position indexing.... every so often we would need to home everything and do a reboot to get everything in sequenced again, it was 4 machines that we made into one production line and tied them all together, it was a fun project

If your project is a lab machine and running well as you stated I doubt the operator will need to cycle the power

geniusintraining said:

If your project is a lab machine and running well as you stated I doubt the operator will need to cycle the power

Click to expand...

And from my experience, if you give them a way to easily cycle the power they'll find reasons they need to.