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Unread December 10th, 2019, 05:10 PM   #16
James Mcquade
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JaxGTO,
i'm not a logix 5000 expert. what happens when someone uses 20 or 30 of this always on bits to debug the program and get it running. he forgets / doesn't correct the logic because it's 2 am. then a year later, Bubba modifies the program on the weekend during a maintenance day without telling anyone he turned off the bit or does it by accident. Monday morning, the machine doesn't run and everyone is in a state of panic?
this is why we put the always on / off rung as the first line of the plc code.
james
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Unread December 10th, 2019, 06:44 PM   #17
janner_10
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Quote:
Originally Posted by JaxGTO View Post
I just create a BOOL tag called AlwaysOn. Edit the Properties and make it Read only and a Constant. No logic needed.
This. KISS
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Unread December 10th, 2019, 06:58 PM   #18
Aabeck
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Quote:
Originally Posted by janner_10 View Post
This. KISS
The only problem with that is when Bubba'a online and he toggles the TRUE bit off it will stay off. Always make sure on the first rung to turn it back on. And force the status of the AFI bit off.
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Unread December 10th, 2019, 07:15 PM   #19
dmroeder
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Quote:
Originally Posted by Aabeck View Post
The only problem with that is when Bubba'a online and he toggles the TRUE bit off it will stay off. Always make sure on the first rung to turn it back on. And force the status of the AFI bit off.

When it is set to constant, it cannot be toggled from a rung in the ladder window. However it can be changed from the tag database
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Unread December 10th, 2019, 08:46 PM   #20
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Quote:
Originally Posted by Aabeck View Post
The only problem with that is when Bubba'a online and he toggles the TRUE bit off it will stay off. Always make sure on the first rung to turn it back on. And force the status of the AFI bit off.
if it’s ever changed, major fault the controller. if an “always true” expression isn’t always so, then the PLC shouldn’t also be in an undefined state.
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Unread December 11th, 2019, 12:49 AM   #21
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Originally Posted by dmroeder View Post
When it is set to constant, it cannot be toggled from a rung in the ladder window. However it can be changed from the tag database
How?
Open tag properties, untick constant (only offline mode?), Hit ok, toggle bit, download? Or is there another way?

Seems as difficult as inserting a rung with "otu always_on" halfway through the code.

For both, don't let your cats play with your code.
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Unread December 11th, 2019, 07:52 AM   #22
Aabeck
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Originally Posted by AustralIan View Post
For both, don't let your cats play with your code.
Don't underestimate Bubba.

Even with an IQ of 73 he has 7 working hours online all 3rd shift, unsupervised!
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Unread December 11th, 2019, 08:17 AM   #23
Rson
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I always create an "ALWAYS OFF" Boolean.

Then just use a NC contact from it.
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Unread December 11th, 2019, 11:04 AM   #24
dmroeder
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Quote:
Originally Posted by AustralIan View Post
How?
Open tag properties, untick constant (only offline mode?), Hit ok, toggle bit, download? Or is there another way?

Seems as difficult as inserting a rung with "otu always_on" halfway through the code.

For both, don't let your cats play with your code.

I understand your point, someone can always work around it. My point was more to show that a bit that is set to constant can simply be set to 1 from controller tags.


You don't need to download to change the constant property, right click, edit properties, uncheck. Although at that point, Bubba's gonna do what Bubba's gonna do, so I'm with you there.
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Unread December 11th, 2019, 03:37 PM   #25
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Originally Posted by dmroeder View Post
Although at that point, Bubba's gonna do what Bubba's gonna do, so I'm with you there.
I have thought further on this. Perhaps we are misnaming the "always_on" bit. "Please_leave_on"? "I_put_games_in_Routine_14_please_play_around_ther e"? "I_dare_you_to_leave_me_on"?

Curiously, does "XIC TRUE" work? or "XIC 1"?
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Unread December 11th, 2019, 03:46 PM   #26
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Originally Posted by AustralIan View Post
I have thought further on this. Perhaps we are misnaming the "always_on" bit. "Please_leave_on"? "I_put_games_in_Routine_14_please_play_around_ther e"? "I_dare_you_to_leave_me_on"?

Curiously, does "XIC TRUE" work? or "XIC 1"?

XIC 1 will not work, XIC TRUE will work if there is a tag named TRUE. It's not a built in constant or anything like that, although that would be neat.
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Unread December 11th, 2019, 03:51 PM   #27
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Quote:
Originally Posted by AustralIan View Post
I have thought further on this. Perhaps we are misnaming the "always_on" bit. "Please_leave_on"? "I_put_games_in_Routine_14_please_play_around_ther e"? "I_dare_you_to_leave_me_on"?

Curiously, does "XIC TRUE" work? or "XIC 1"?
'Bubba_P**s_Off' is probably best.
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Unread December 12th, 2019, 04:50 PM   #28
defcon.klaxon
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Do you need more than one "always-on" bit? You can also use a NOP instruction.
No not with what I'm currently doing.
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Unread December 13th, 2019, 06:14 AM   #29
daba
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If you are using this as an input parameter to an AOI, which it sounds like you are doing (from post #4), then you don't need a tag, just put literal "1" where you would put the always-on tag for the AOI instances that need the parameter to be ON, and "0" for instances where you need it OFF.
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Last edited by daba; December 13th, 2019 at 06:28 AM.
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