3/23/2017 11:57 AM | |
Posts: 69 Rating: (0) |
hello k c das, thanks you for your answer. but with grafcet we need just too structure and didn't possible with cont ? |
3/23/2017 1:28 PM | |
Joined: 9/27/2006 Last visit: 9/27/2024 Posts: 12283 Rating: (2685)
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Hello norimane; Is this for a school project (so it does not really matter that you protect your equipment and the lives of the workers surrounding your machinery) or is this project a real-life industrial program? When you have machinery that you must protect and workers aroiund it, there is always the possibility of breakdown and danger to the personnel. This is where Machine Safety directives become important; one of the elements covered by Machine Safety directives is the E-stop. Have a look at this article discussing what E-Stop actually does in an industrial project (if you wish, look up Machine Safety on the web, there are many, many sources of information available): Emergency Stop - What's so confusing about that? Note the definition of the Emergency Stop in the article, and the various rules (american and european in this case) that apply to the use and implementation of the E-Stop sequence. Now look at the electrical circuits of the compressors you are working with; I know for having worked with them that the Atlas Copco compressors have terminals to which you are expected to connect either a E-Stop button (for local E-stop control) or a remote E-stop circuit controlled by a Failsafe relay or a FailSafe CPU. It would be expected that your Boge compressors also should make such contactys available too. When you have a portable compressor enclosure, you often have an integrated E-Stop button already connected to the E-Stop terminals of the compressor; he following describes what it is entended to do for an Atlas Copco portable compressor: EMERGENCY STOP The emergency stop button (2) is only to be used in emergency situations; not for stopping procedures. When an emergency stop button is pressed, power to all outputs is terminated, by the emergency stop itself (hardware) as well as by the software... To proceed operation the emergency stop button has to be unlocked and the alarm has to be acknowledged by pressing the enter button (3)... From: You must understand that when you use your S_Off instructions in Gafcet all you are doing is freezing the control sequence on the CPU. You are in no way removing power to the compressor actuators. If you compressor is surging, or a bearing is destroyed, or it is overhheating, stopping the control sequence does absolutely nothing to protect your equipment of the personnel working around it. An E-Stop circuit is designed (often) to remove power or apply brakes to an energized machine when a destructive fault is apparent. That is very different that blocking your sequencer in a fixed step. Imagine your car is on the highway, you see a truck blocking the road ahead of you, and all you have to stop your car is yelling "Woah!"; wouldn't you rather have good brakes you can apply boh feet on? Wouldn't that be a bit safer? Well, your S_Off signal is like yelling Woah! at your car in an emergency situation: it will not help you. In your case, I would start by finding where the emergency stop contacts are on each of your compressors, and determine whether you have the equipment ( e-stop buttons, Failsafe relays from Pilz, Siemens, A-B..., or FailSafe CPU and I/O) and knowledge to implement this type of E-stop control. This is not trivial. If you wish to have a look at what Siemens offers in terms of FailSafe controllers, you can examine the following Safety Integrated brochure, for starters: Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 3/23/2017 1:37:52 PM |
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This contribution was helpful to1 thankful Users |
3/23/2017 3:39 PM | |
Joined: 9/27/2006 Last visit: 9/27/2024 Posts: 12283 Rating: (2685)
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Hello norimane; Your S7-313c CPU is definetly not a F-CPU. Here is a link to the Siemens Product support site listing the available F-CPUs in the S7-300 family: For your sequence reset problem, here is a suggestion: let's say your compressors already have an E-stop button integrated in their control panel and you decide to use them for your project (in local E-Stop mode); you will need to add an auxiliary contact to the E-stop buttons (linked to an input of the PLC) so your CPU is made aware that one or more of these compressor E-stops have been activated. If you want to reset your sequencer if any of the compressors E-Stop button is activated, you can wire the auxillary signals in series. Then in every step of your control Grafcet you read the status of the E-Stop input signal and reset the Grafcet in case it is detected. One thing that might interest you, as most of the available information for this is in French: there is n way to generate (offline) a type of supervisory Grafcet to manage these kind if events in your project, such as an Emergency stop mode. It is calle "GEMMA" , or Gestion des Modes de Marche et Arrêts (in English, Management of Start and Stop Modes). It might not be usable for this project directly, since it would require some time to adapt your Grafcet to the Gemma analysis, but for future projects it may be possible. Here is a link to a GEMMA presentation: Le GEMMA, Guide d'Etude de Modes de Marche et d'Arret, GMMAHope this helps, Daniel Chartier |
Last edited by: dchartier at: 3/23/2017 3:40:44 PMLast edited by: dchartier at: 3/23/2017 4:41:13 PM |
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3/23/2017 4:08 PM | |
Posts: 69 Rating: (0) |
hello Dchartier, thank you very much ,I am very grateful for your help |
3/24/2017 12:55 PM | |
Posts: 69 Rating: (0) |
hello , i's me again :) please how i can do in step 7 horloge to : start compresseur every sunday night at: 22h00 and stop it on saturday at :22h00. thanks. |
3/24/2017 1:33 PM | |
Posts: 69 Rating: (0) |
hello Dchartier, for instance i have heur and minute and seconde of PLC , how can i compar it ? give me please exemple. |
3/24/2017 1:44 PM | |
Joined: 9/27/2006 Last visit: 9/27/2024 Posts: 12283 Rating: (2685)
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Hello norimane; It is time you started using the tools available on the forum to locate previous threads, manuals and FAQs discussing similar subjects. The easiest way nis to use the Site Explorer search box at the top right of this page. For example, searching for "Time compare Simatic Manager" would have loacted this thread, amongst many others: Look for more similar discussions if you need more information. Hope this helps, |
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