Is freezing logic in a Click PLC possible?

Hi all, student newbie here.

Was curious if there was anyway to stop logic from running during break times? Like all physical and software inputs stop functioning for a certain period of time based on the PLC's internal clock. (off from 0915-0930). No input from operators, just repeats itself daily.

Is this possible?

I am not that familiar with Click software but if you could put all the logic in a subroutine, maybe the internal clock could switch off and on the subroutine at the desired times. Another possibility is to add a bit in each rung that was controlled by the internal clock. Probably using the 1st method would be easier to understand.

Doesn't sound like the best idea. It probably would be better to build a timer or RTC logic into your logic that would "inhibit" outputs from being true.

Not sure with the click and the real time clock, but you could build your routines to be called off the state of the clock if the click allows it or a timer, if time is between x then instruct to call routines.

Don't ever stop logic from executing. Ever.*

If you have an output turned on, and then you stop scanning that rung, the output won't turn off just because its rung stopped being scanned. The only way for the output to be turned off is if some code is executed that turns it off - like a reset coil, or a regular coil that has no "power flow" into it.

So if you suddenly stop executing code, the machine won't stop - it'll just hold exactly the state it's in, whatever that is.

You should instead program a controlled shutdown at the required times, and inhibit any restarts.

*OK, there are a few reasons to do this, but not many good ones, and if you're a student, they probably won't really be applicable to anything you're doing.

You can use the real time clock and stop the execution of a subroutine.
Click PLC Program Control Instructions:
http://accautomation.ca/click-plc-program-control-instructions/
https://www.youtube.com/watch?v=uJZyfF-bKdA&feature=youtu.be
The program will always be scanning the program.

Regards,

Do not confuse the running of the PLC program with the operation of the machine. It is true that the machine will stop when the PLC stops, but that's not the best way to bring the machine to a safe, controlled, repeatable, stopped condition. It is also advisable to keep the PLC running while the machine is stopped so you can restart in a safe, controlled, repeatable manner.

Just stopping execution of a subroutine will not stop the machine. If an output is "on" it will remain "on", until instructed to turn "off". I made this mistake once, just once.

Stop Button.............? usually mounted in proximity to the Start Button.

Just curious if it was applicable.

Sorry I'll go back to my corner now.

John Morris said:

Stop Button.............? usually mounted in proximity to the Start Button.

Just curious if it was applicable.

Sorry I'll go back to my corner now.

Click to expand...

Idea! Wire a solenoid to a spare output with a plunger that presses the stop button. Then have that output stay on for the duration of the break time

I do something like you are talking about for lighting displays but not for machinery.

Based on the clock/calendar I enable an Active bit that calls subroutines for lighting control. But I make sure to scan through each subroutine turning off all outputs and setting a Skip Bit if Active is OFF.

When Active is OFF and Skip Bit is ON I don't call that subroutine, when Active comes back on the subroutine is called and at the end of the first scan through it Skip Bit is turned off.

Wow, it has been a while since I've been here. I didn't know so many people responded. I had no idea what a "subroutine" was, now I'm an expert at it. Was able to use the RTC for my needs, however be aware of daylight savings time! My ladder is nice and neat too.

Special thanks to Garry and his website, it was super helpful with no nonsense.

quietman187 said:

Wow, it has been a while since I've been here. I didn't know so many people responded. I had no idea what a "subroutine" was, now I'm an expert at it. Was able to use the RTC for my needs, however be aware of daylight savings time! My ladder is nice and neat too.

Special thanks to Garry and his website, it was super helpful with no nonsense.

Click to expand...

I'm glad that you got it going. Thanks for your comments of the website.

Regards,
Garry

Unless the rules have changed, you cannot do what you are suggestion.
the automatic stopping / starting of a machine based on the time of day is not allowed. My 2 cents on this.

if i'm wrong, you must do the following
Look at NEC 70 electrical code.
NFPA 79 - electrical standard for industrial machinery.
Do a complete risk assessment involving guarding, safety door interlocks, loading / unloading, safety alert indication lights, machine starting horns.

this involves your local osha guy (I think), safety, management, engineering, maintenance, and operators.

if you can ask what if, you better have an answer !!
every possible situation you can think of MUST be addressed.
to me, you are just asking for an accident to happen !!

I suggest a cycle stop button to stop the machine after the current cycle is complete.
a cycle start button to resume the auto cycle.

if I am wrong, someone please point it out.

james