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Data log internal at PLC.

Created by: LSSchmidt at: 11/26/2014 11:43 AM (8 Replies)

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11/26/2014 11:43 AM	Rate (0)
LSSchmidt Posts: 14 Rating: (0)	Hello! I´m using a datalog to register 13 variables. This register is stored at SD card. However, i need create the same register internally at PLC, in other words, if the SD card is stolen, i can recover data from at least 3 days of the process. How can i create a data log internal at PLC? Any tips? Thanks! Best regards, Lucas Schmidt NBRtec.
LSSchmidt Posts: 14 Rating: (0)
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11/26/2014 1:36 PM	Rate (0)
eisenpferdreiter Posts: 1058 Rating: (93)	LSSchmidt Hello! I´m using a datalog to register 13 variables. This register is stored at SD card. However, i need create the same register internally at PLC, in other words, if the SD card is stolen, i can recover data from at least 3 days of the process. How can i create a data log internal at PLC? Any tips? Thanks! Best regards, Lucas Schmidt NBRtec. Hello LSSchmidt, this has been an issue here already. Look here: Data Logging - logged the data in CSV direct from PLC we want to do data logging from the PLC through two ports using data logging blocks in 1200 plc TIP: Sample program for Data Log with S7-1500 regards
eisenpferdreiter Posts: 1058 Rating: (93)
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11/26/2014 7:20 PM	Rate (0)
LSSchmidt Posts: 14 Rating: (0)	Thanks eisenpferdreiter for your tips. But i really cant find any thread about this case. My datalog is working fine, the problem is that i need a alternative to save data simultaneously at SD card (i´m doing it) and internal memory at PLC. I need 2 datalog. If a problem happen with SDcard (purposely by person responsible for the operation error), i need a way to rescue this information. Thanks.
LSSchmidt Posts: 14 Rating: (0)
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11/26/2014 9:41 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	Hi. The closest I can think of to do is to save the same data in a DB internal to the PLC. You will have to develop your own coding to keep track of the transactions. My first thoughts can be explained per example A global DB with the variables.. * FirstEntry : INT * LastEntry : INT * BlockSize : INT * Data : Array [1..size] of STRUCT - TimeStamp : {time of day} - Value : INT > BlockSize is less than size. > No valid readings when FirstEntry = LastEntry. > The LastEntry move to the next position on each read.. with foldover from size to 1. > Legal readings are only between FirstEntry and LastEntry markers (foldover!). > If the count of values between FirstEntry and LastEntry exceeds BlockSize, FirstEntry marker will also add one position (foldover!). > On each read Data[LastEntry].TimeStamp gets a new date and time value and Data[LastEntry].Value gets a new reading. > Data points beyond LastEntry to FirstEntry markers (foldover!) is ignored. Extraction of the data can be done by reading the DB with TIA. Else some extracting algorithm is needed to send all data points between FirstEntry and LastEntry markers. It is a bit of work, but it is possible to create the algorithm to mimic the data log function that uses the MMC. Helpful? w
William_B Posts: 5225 Rating: (1204)
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11/27/2014 2:22 PM	Rate (0)
LSSchmidt Posts: 14 Rating: (0)	William B. Hi. The closest I can think of to do is to save the same data in a DB internal to the PLC. You will have to develop your own coding to keep track of the transactions. My first thoughts can be explained per example A global DB with the variables.. * FirstEntry : INT * LastEntry : INT * BlockSize : INT * Data : Array [1..size] of STRUCT - TimeStamp : {time of day} - Value : INT > BlockSize is less than size. > No valid readings when FirstEntry = LastEntry. > The LastEntry move to the next position on each read.. with foldover from size to 1. > Legal readings are only between FirstEntry and LastEntry markers (foldover!). > If the count of values between FirstEntry and LastEntry exceeds BlockSize, FirstEntry marker will also add one position (foldover!). > On each read Data[LastEntry].TimeStamp gets a new date and time value and Data[LastEntry].Value gets a new reading. > Data points beyond LastEntry to FirstEntry markers (foldover!) is ignored. Extraction of the data can be done by reading the DB with TIA. Else some extracting algorithm is needed to send all data points between FirstEntry and LastEntry markers. It is a bit of work, but it is possible to create the algorithm to mimic the data log function that uses the MMC. Helpful? w Thank you William B. I´m testing how you explained. However the retentive variables are not enough... I´m worried. Attachment Load preview.JPG (302 Downloads)
LSSchmidt Posts: 14 Rating: (0)
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11/27/2014 5:32 PM	Rate (0)
William_B Posts: 5225 Rating: (1204)	LSSchmidt Thank you William B. I´m testing how you explained. However the retentive variables are not enough... I´m worried. Good to have your feedback. I understand that the S7-1200 now has a battery add-in card (SB = signal board). Maybe this can help to keep the memory from being wiped clean of values. I can not tell if this will work, but it is worth looking into. Another option is to see how you can reduce the memory used. The time stamp takes up too much space. And may it is not needed to record each one. What if you record only "first" and/or "last" and know at what frequency the values are updated. The problem comes in when there is a power outage which interrupts the "frequency". You could find another way to construct a time stamp that does not use all the information. For example "year" and "month" could be coded with a smaller number; counting each month since January 2014 for example. Time may only require a shorter format. Think "before the Y2K scare". Some clever compression tricks might be used, especially when you are not using the full range of the numbers being recorded. Extracting the data is going to be a challenge. It is not dead easy, but still possible. Helpful? w
William_B Posts: 5225 Rating: (1204)
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11/27/2014 6:02 PM	Rate (0)
LSSchmidt Posts: 14 Rating: (0)	William B. LSSchmidt Thank you William B. I´m testing how you explained. However the retentive variables are not enough... I´m worried. Good to have your feedback. I understand that the S7-1200 now has a battery add-in card (SB = signal board). Maybe this can help to keep the memory from being wiped clean of values. I can not tell if this will work, but it is worth looking into. Another option is to see how you can reduce the memory used. The time stamp takes up too much space. And may it is not needed to record each one. What if you record only "first" and/or "last" and know at what frequency the values are updated. The problem comes in when there is a power outage which interrupts the "frequency". You could find another way to construct a time stamp that does not use all the information. For example "year" and "month" could be coded with a smaller number; counting each month since January 2014 for example. Time may only require a shorter format. Think "before the Y2K scare". Some clever compression tricks might be used, especially when you are not using the full range of the numbers being recorded. Extracting the data is going to be a challenge. It is not dead easy, but still possible. Helpful? w Thanks again, i'll verify. Another option to my aplication is create only a internal datalog, without SD card. Accessing data only using the webserver. It´s possible? Thanks!
LSSchmidt Posts: 14 Rating: (0)
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11/27/2014 7:50 PM	Rate (1)
William_B Posts: 5225 Rating: (1204)	LSSchmidt Thanks again, i'll verify. Another option to my aplication is create only a internal datalog, without SD card. Accessing data only using the webserver. It´s possible? Thanks! ..well if I was in your position.. * record the data on the MCC card * secure the PLC in a mechanical way to make it difficult to remove the MMC card. (locking the cabinet is possible but not suggested, I'm thinking of a special bracket ) * hook up the PLC to a Wi-Fi router * access the web server of the PLC via the Wi-Fi link * downloading the CSV file through the Wi-Fi w
William_B Posts: 5225 Rating: (1204)	Last edited by: William B. at: 11/27/2014 8:17 PM quoting corrected
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11/27/2014 8:08 PM	Rate (0)
LSSchmidt Posts: 14 Rating: (0)	William B. LSSchmidt Thanks again, i'll verify. Another option to my aplication is create only a internal datalog, without SD card. Accessing data only using the webserver. It´s possible? Thanks! ..well if I was in your position.. * record the data on the MCC card * secure the PLC in a mechanical way to make it difficult to remove the MMC card. (locking the cabinet is possible but not suggested, I'm thinking of a special bracket ) * hook up the PLC to a Wi-Fi router * access the web server of the PLC via the Wi-Fi link * downloading the CSV file through the Wi-Fi w Thanks for your effort to help me!
LSSchmidt Posts: 14 Rating: (0)
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