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Reading Information from SD Cards (.CSV)

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So I am working on a project creating a master/slave system and am trying to determine the best method for storing information that is going to collected via a cellular modem. I am at a stand still because I know the best way to probably store the information from 5 different sites is to write it directly to a .CSV file (seperate). Is there anyway to read the information from the SD card thru the PLC. I am not interested in having the customer having to open a software program to view it. 


I am open to other suggestions as well. I know I can store it in separate data tables and then dump the tables to the SD card but that will limit the amount of storage the unit can have.


Thoughts? Input?





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Our controllers do not have the ability to read information from an excel file or from another controllers SD card. For the end user the only method to obtain SD card data through a serial port we are currently able to recommend would be to use the SD card suite.


Is one PLC designated as the master and just being used as data collection form the multiple slave devices? Will all of them use the cellular modem? It is possible to use the Modbus Data Table functions to write information from one table to another which may allow for data gathering from multiple sites?

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One PLC will be designated as the Master used for data collection purposes (yes from multiple sites).

Each unit including the master will have a cellular modem.


As far as the Modbus data table functions go, I honestly haven't had a chance to do that play with that functionality yet. I was originally going to make the slaves (outgoing messages) begin with a site specific format of the message that allows the master the ability to know which unit was sending information to it (activate a bit because the message matches) and from there I will have integers from the site and store them directly into the data tables (FIFO) as well as writing an excel file for each site.


I am just worried about limiting the data that is visible thru the PLC to the point where it is isn't enough to satisfy the customer. There is no way to view information on the master's SD card thru the HMI? I'd like to use trends but it seems rather repetitive to eat memory in order turn data tables into vectors. Is there reason that this functionality wasn't build into SIs and just have the number of data points capped? To me a trend block that did the work that looked at the data tables or SD card would be very beneficial. 



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If you are using Modbus you would not need to use any specific message format as you would be manually connecting to the desired site. Once the information is retrieved it could absolutely be written to a data table. Sequencing would need to be worked out but it should be possible.


Do you just want to display information on each slave PLC's HMI or are you referring to viewing the information on the main PLC's HMI and viewing the remote PLC's SD card data? It is not possible to remotely view any SD card data from on PLC to another.


There is SD card trends which can pull up a previously created file, though this is limited to only the local PLC which houses the SD card.

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I suppose I didn't realize that I could use Modbus with the cellular modem. This is welcome news as it should make the retrieve of data easier.


I'm not worried about displaying any information on the slave PLCs HMI. I already have that taken into account with a data logging both to a .CSV as well as key point logging to the the data tables which I have already written the logic for retrieving data and displaying it using row registers for retrieval. 


Is is possible to in any way to view information from the SD card rather than from internal memory of the PLC? That is currently my main question. If I can pull a vector of information from the SD card I can do that with a register value to shift which data is pulled.


I haven't used trends before because I have mostly dealt with V130s and have written my slave PLC code accordingly. We finally have a customer who is ready to install a Master PLC (V1040) and add modems to all the units. I see added value for my customer to view trends on the screen rather than having to remove the SD card and use excel for analysis of the .CSV file.


To summarize, I would like to store recorded data onto a SD card rather than eat memory but I will need to retrieve the data.


I will hold off Modbus questions until I have the modems in hand and actually have the units spitting information at each other.

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