MicroLogix...reboot PLC from the HMI?

Skidood · Mar 27, 2019

Hi all, is there a way to reboot (simulating a power cycle) from the HMI?
I basically want to have the PLC perform the first pass scan (or fool it into thinking power has just been applied) without actually interrupting the power.
TIA.

James Mcquade · Mar 27, 2019

what is your application and what are you trying to accomplish?

james

Skidood · Mar 27, 2019

James, I was thinking about giving the operator a way to reboot the system without physically cycling power. In my application, it is a pain in the butt for the operator to access the control power switch if needed. And BTW this is not a machine with any moving parts nor is it in a factory setting. Its in a lab.

geniusintraining · Mar 27, 2019

Can you just make a 'new bit' that will do the same thing

Dravik · Mar 27, 2019

If you have a spare output, run the power for the PLC through a timer(set to some reasonable time frame to not kill your plc) that will reset when it gets an output.
Make the logic in the PLC set the output only when the HMI button is pressed or whatever, and have it 'reset' the timer.

Skidood · Mar 27, 2019

Thanks but I have no idea what you mean.

geniusintraining said:
Can you just make a 'new bit' that will do the same thing

Bit_Bucket_07 · Mar 27, 2019

Dravik said:
If you have a spare output, run the power for the PLC through a timer(set to some reasonable time frame to not kill your plc) that will reset when it gets an output.
Make the logic in the PLC set the output only when the HMI button is pressed or whatever, and have it 'reset' the timer.

That would do it, but I'd first want to look into the programming error that causes the system to need a reboot.

Skidood · Mar 27, 2019

Believe it or not, I have no spare outputs.

Dravik said:
If you have a spare output, run the power for the PLC through a timer(set to some reasonable time frame to not kill your plc) that will reset when it gets an output.
Make the logic in the PLC set the output only when the HMI button is pressed or whatever, and have it 'reset' the timer.

Aabeck · Mar 27, 2019

Skidood said:
Thanks but I have no idea what you mean.

When the HMI button is pressed turn on a "New First Scan" bit of your own with a OneShot.

Put XIO "New First Scan" on each line of your program with an OTE on it so that scan through will turn off all outputs.

Skidood · Mar 27, 2019

Agreed and I do agree that my idea may be a little "out there". Just something I was thinking about.

Bit_Bucket_07 said:
That would do it, but I'd first want to look into the programming error that causes the system to need a reboot.

Dravik · Mar 27, 2019

Bit_Bucket_07 said:
That would do it, but I'd first want to look into the programming error that causes the system to need a reboot.

Hey, sometimes you just want to power cycle things

James Mcquade · Mar 27, 2019

as Aabeck said, use this method.
BUT !!!
it doesn't matter if it's a machine or not, you MUST, I repeat MUST know the plc operation and what is going on.

you said this was not a machine and had no moving parts - ok.
this is in the lab - ok
What type lab? training lab or lab equipment?
is really doesn't matter. what DOES matter is that you need to know what the plc program does and how it's written.
are there any sequencers, latched in bits, latched bits to outputs, retentive timers...…
there are lots of things in a plc program that need to be addressed.

not slamming you and I do not know your level of expertise in programming,
i'm just trying to point out various things that need to be addressed in the program. this process will be useful in a programming career or in future applications.

james

geniusintraining · Mar 27, 2019

Skidood said:
Thanks but I have no idea what you mean.

See below

Aabeck said:
When the HMI button is pressed turn on a "New First Scan" bit of your own with a OneShot.

Put XIO "New First Scan" on each line of your program with an OTE on it so that scan through will turn off all outputs.

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)

Aabeck · Mar 27, 2019

Just remember as James said to go through your program and reset every TON & TOF timer, see if you need to reset a RTO, Reset any counter/DN bits, see if you need to reset the counter itself. Reset every OTE, and maybe unlatch certain OTLs. Reset sequencers.

Depending on how large the program is this may not be so simple.

OkiePC · Mar 27, 2019

Load a negative number in a timer preset. That'll shut 'er down.

Then maybe you can create a fault routine that fixes the timer and clears the fault...not sure if that would return the PLC to run mode.

I seem to recall a thread about this being possible with a limited number of PLCs maybe on a limited comms protocol....the A/B HMI was capable of altering the PLC run mode directly...

EDIT:
http://www.plctalk.net/qanda/showthread.php?t=75152

MicroLogix...reboot PLC from the HMI?

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