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S7-1212 program execution problem

Created by: Dado_BiH at: 5/15/2014 11:12 AM (5 Replies)

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5/15/2014 11:12 AM	Rate (0)
Dado_BiH Posts: 5 Rating: (0)	Hi, I recently wrote program for bending cycle on the machine. Program is executed in steps. Now I have following problem. When I start machine after power off, sequence is not executed correctly, some steps are omited. Every other start and stop of the sequence works fine until next power off. I windwr is it necessary ro reset counters and timers at the begining of the program (OB 100) and can someone help me with this program?
Dado_BiH Posts: 5 Rating: (0)
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5/15/2014 11:54 AM	Rate (0)
kriipc Silver Member Joined: 4/11/2011 Last visit: 10/7/2024 Posts: 132 Rating: (7)	Use First Scan bit for this.
	I'm just a human. Mistakes are allowed. Sorry for my english. Only 3 months of training and manuals :)
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5/15/2014 1:22 PM	Rate (0)
Dado_BiH Posts: 5 Rating: (0)	THX I will tra this.
Dado_BiH Posts: 5 Rating: (0)
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5/15/2014 11:06 PM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Hi, Create a Startup OB: Go to ceate a block. Go to "OB" Ask for "STARTUP" OB.. normally OB100. Whatever you wish to execute in the first scan can be coded inside that OB100. w
William_B Posts: 5225 Rating: (1197)
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5/16/2014 3:53 AM	Rate (1)
BhaPraJ Silver Member Joined: 1/28/2012 Last visit: 7/23/2024 Posts: 519 Rating: (83)	[quote user="Dado_BiH"]Hi, I recently wrote program for bending cycle on the machine. Program is executed in steps. Now I have following problem. When I start machine after power off, sequence is not executed correctly, some steps are omited. Every other start and stop of the sequence works fine until next power off. I windwr is it necessary ro reset counters and timers at the begining of the program (OB 100) and can someone help me with this program? Not required to reset timer or counter. But check whether any bit remained set after power on. In such case reset those bits in OB 100 or unmark these bits from retentive range.
	Regards, BhaPraJ
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This contribution was helpful to 1 thankful Users Thangabali

5/16/2014 6:31 AM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Pranav J. Bhagat Not required to reset timer or counter. But check whether any bit remained set after power on. In such case reset those bits in OB 100 or unmark these bits from retentive range. Okay.. I'll byte (bite).. [pause] [smile] @Dado_BiH: Please check the structures of the datablocks you are using. Check if these are set to be retentive or not. Please make a choice if you wish them to have memory or not. Consider my advise -> [serious] Recovery from power outage is one of the things most programmers ignore or do not impliment correctly. Now you know how much of a problem it can cause. Think about what routine you can develop that will "recover" or "reset" your sequencing after a power outage. Have that new routine be triggered indirectly by OB100, which you now know of. Be careful to develop a routine that is safe! [very serious] The problem with OB100 is that it does not distinguish between power outage and you placing the PLC in RUN mode after extensive changes. You can detect this condition. After you have done your recovery, set a "sure" bit. This "sure" bit indicates you can trust the positioning. This bit is also not retentive. After a power outage this bit looses its own state. So.. you execute the recovery routine only after you see "sure" = FALSE or when the user requests a system reset. A variation on the theme is to not write a automatic routine. You can have the user assist you by making manual movements available to him/her. The "loop-in-alarm" function of the alarms on a current generation Siemens panel, can make this happen for you. [Nice function to use for this.] Utilising your panel is beyond the scope of this thread. To find out more about "loop-in-alarm", you can enquire from "Visualization/WinCC (TIA)" section of this forum. I hope these commentary are of value to you. Please do not hesitate to ask detailed questions (even in a new thread). WithIn this month our forum friends will be most willing to help. [smile] Good luck. w
William_B Posts: 5225 Rating: (1197)	Last edited by: William B. at: 5/16/2014 6:38 AM better the readability.
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