Micrologix 1100/1500 Datalogging

[CnMEngineering]

Hi Guys,
New to this forum.
I am in selection phase for a Data-logging project. Requirement is given below.
Data should be stored in battery backed memory. One record size contains 6 signed 16-bit integers (including relative-time-stamp saved as UINT). I want to be able to save at-least 10,000 records.
Data will be later retrieved through modbus rtu by a user application developed on labview running over a PC and connected to multiple such Units.

I was thinking of using Micrologix 1500 or 1100, since they have sufficient memory and modbus as well. But now that I started looking at the programming manuals I cant seem to find a way to access the datalogging memory through ladder logic, furthermore it looks like it can not be accessed over modbus either. Can you guys help me out find a way to transfer the logged data over modbus?
If any further clarifications are required let me know.

Thanks in advance

Anas
wwww.pakplc.com

 

[rootboy]

Hi Guys,
New to this forum.

Welcome!

...6 signed 16-bit integers (including relative-time-stamp saved as UINT). I want to be able to save at-least 10,000 records...

Ok, so you need at least 120K of memory.

I was thinking of using Micrologix 1500 or 1100, since they have sufficient memory and modbus as well. wwww.pakplc.com

1764-MM3RTC‡ MicroLogix 1500 16 KB Memory Module with recipe data storage and Real-Time Clock Well, the 1100 does at least. The 1500 doesn't seem to have the memory for what you want to do.

And it looks like you would have to use the Rockwell utility to get at your data:

http://www.patchn.com/index.php?option=com_content&view=article&id=166

 

[CnMEngineering]

Thank you for the reply, I know about the data retrieval tool as well as the DF1 command syntax given in manual, however I would like to get the data through modbus as this unit will be installed in an existing network.
(Little background
we developed three datalogging units for a client and developed user interface on Labview for uploading of data, drawing graphs, reporting, and modifying data logging variables. The PLC used before has a problem of slow analog response. The manual states it is 25ms but it really is around 160ms. To get rid of this problem we selected AB as its input response is pretty fast compared to our existing PLC.)
So bottom line is that I want to avoid major changes in interface software. Also if I use the data retrieval utility it will change the whole communication protocol to DF1.
I'm really stumped, why cant there be a way to access PLC memory through ladder logic. This seems pretty absurd. Maybe I'm missing something.

 

[rootboy]

Thank you for the reply, I know about the data retrieval tool as well as the DF1 command syntax given in manual, however I would like to get the data through modbus as this unit will be installed in an existing network.

Anytime!

(Little background
we developed three datalogging units for a client and developed user interface on Labview for uploading of data, drawing graphs, reporting, and modifying data logging variables. The PLC used before has a problem of slow analog response. The manual states it is 25ms but it really is around 160ms. To get rid of this problem we selected AB as its input response is pretty fast compared to our existing PLC.)
So bottom line is that I want to avoid major changes in interface software. Also if I use the data retrieval utility it will change the whole communication protocol to DF1.
I'm really stumped, why cant there be a way to access PLC memory through ladder logic. This seems pretty absurd. Maybe I'm missing something.

No, you're probably not missing anything. And I agree, the way that you have to retrieve the data from these "DataLogger" memory modules is a bit Klunky at best.

Hmmm, hmmm, ... I guess that it goes without saying that you want to be able to run these things for long periods of time without having the PLC hooked up live to Modbus?

If you can make the PLC the Modbus master, and have it initiate a transfer when it's data table is full (and then zero out the data table for the next group of data), that might work.

 

[CnMEngineering]

Thank you rootboy for the help. Im now thinking of logging data to a locally connected HMI, and make it behave like a modbus slave which seems pretty straight forward.
BR
Anas
www.pakplc.com

 

[rootboy]

That sounds better. I'd make the PLC the master, and have it spit out data whenever there is a change.