10/10/2012 5:46 PM | |
Joined: 1/8/2012 Last visit: 8/21/2024 Posts: 17 Rating: (0) |
Yeah it's quite a mess this way and you are depended on "external" elements which I never like trusting. any how thanks for the help huggy_d1. |
10/10/2012 6:53 PM | |
Joined: 7/7/2010 Last visit: 10/18/2024 Posts: 15327 Rating: (2432)
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If you have a relay output s7-1200 plc, you can probably do this power/first scan run detection completely internally. I will say though, you might want to mess around with the input averaging (debouncer) vs edge detection on first scan to see how long it takes for the input to physically settle as it relates to the first plc scan. I think you could make it work out. If you do like we do, you put the plc on a ups, then detect loss of power upstream of the ups to stop running gracefully. Then on startup, the system state is more defined and you can actually force the plc to stop after a certain amount of time on loss of power. Maybe some of the suggestions can be made into a working solution. I'm still not sure though you couldn't just put a button on an HMI that the operator uses to confirm power outage or routine restart to make startup decisions for warm up purposes. The human element is more error prone than an external relay, but considerably more flexible. |
science guy |
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10/11/2012 1:55 PM | |
Joined: 1/8/2012 Last visit: 8/21/2024 Posts: 17 Rating: (0) |
Good idea, thank you. |
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