Inexpensive PLC with some memory capacity?

friendlyfire · May 29, 2008

Hello,
Does anyone have any suggestions for a simple controller that can also handle a datalogging task? I have an application that requires basic control with four or so digital out, a few digital inputs, and a five or so analog in. Most of the analog in just needs to be recorded, although a couple of them feed back into the control loop.

The PLCs I've looked at don't have much memory capability and therefore won't do a good job on the data logging side. I could go with a cheap PLC plus a stand alone data logger, but there may be a requirement in future to hook everything to a SCADA system and then things will get messy!

I think I need around 100K of memory for saving the data by the way.

thanks
FF

Sergei Troizky · May 29, 2008

Omron CJ1H-CPU66H features 256KWords data memory.
For sure some other brands may have what you need as well.

Not clear though what to be considered inexpensive.
Omron is a good value usually.

scottmurphy · May 29, 2008

Omron CJ1H-CPU66H features 256KWords data memory.
For sure some other brands may have what you need as well.

This has truck loads of programming memory, if all you are wanting is to log data, then this could possibly be an overkill. For logging, you need memory areas to store your data, not programming memory.

Check this out, not sure of the pricing, could be what your after?
http://forums.mrplc.com/index.php?showtopic=12204&hl=

elevmike · May 29, 2008

PLCs are not very good dataloggers.

We use the AutomationDirect DL-06. It has about 7000+ 8 bit words of user memory.

However what type of data you need to log greatly effects how much you can log. For example if you want to log time stamped error events with the DL-06, that's not much memory:

Date = 3 words, (Day, month, year)
Time = 3 words, (Hour, Min, sec.)
Error code = 1 word. (lookup error code in manual)
That's 7 words per event. = Max 1000 events.

GeoffC · May 29, 2008

Modicon M340 has 8M of onboard configurable memory as standard

svn · May 30, 2008

Omron CP1L. Even the smallest model (8 DI + 6 DO) has 10K, 16 bit words data memory apart from 5 KSteps program memory. The 30 I/O model has 32K, 16 bit words data memory and 10Ksteps program memory. These are quite cheap. They have very good instruction set and supports Ladder, Function Blocks (Ladder and Structured Text).

SVN

Kelkoon · May 30, 2008

S7-200

Hi:

Siemens's S7-200 also has datalogging capacity. Ther is memory modules of 64 and 256kB.

Kelkoon

IAA · May 30, 2008

I would look at Red Lion. I use the Data Station Plus for Data Logging and I am pretty sure they have expandable I/O available for it. The DSP uses a CF card for storage, so memory wouldn't be a problem.

JesperMP · May 30, 2008

Is it to be installed in some remote location ?
Then it sounds like a classical "RTU" application, not "PLC".

friendlyfire · May 30, 2008

Hello, thank you for all the suggestions. I'll check some of them out. Note that it important that this memory is non voilatile. I do not want to lose all the logged data if the PLC loses power.

Jesper: I suppose it is a RTU application according to the definition I just looked at. I thought RTUs only acquire data and don't offer control capability. This said, I did a quick internet search for RTU products and I don't see any with control features. So, other than PLCs (and embedded controllers) what hardware would you suggest?
Scottmurphy: thanks for the suggestion re Omron. I'm calling the rep now about it.

I should also mentionthat I am seeking a solution around or under the $1000 price point, and prefer something IEC61131 compliant. I'm looking into the FP Sigma from Panasonic but I'm not sure if it fits the budget.

thanks again!

jgreenewv · May 30, 2008

Take a look at the Horner Electric XLE operator control stations:

http://www.heapg.com/Pages/Products/products_OCS_X_xle.html

You may need to add an expansion analog module, depending on the number you want to monitor. The XLE has a slot for an optional MicroSD card, and has instructions to write data to the card in CSV file format. It can also be programmed in either standard ladder, or in IEC61131. The price on this is pretty competitive to other options.

bkottaras · May 30, 2008

jgreenewv said:
Take a look at the Horner Electric XLE operator control stations:

http://www.heapg.com/Pages/Products/products_OCS_X_xle.html

You may need to add an expansion analog module, depending on the number you want to monitor. The XLE has a slot for an optional MicroSD card, and has instructions to write data to the card in CSV file format. It can also be programmed in either standard ladder, or in IEC61131. The price on this is pretty competitive to other options.

I 2nd the XLe from Horner.
The analog module can be added to it, no special networking options and such, just easy setup (Cscan Smart Stix) and you are up and running.
MicroSD as mentioned for logging all your data.
And it does come with 2 Analog Inputs/2 Analog Outputs (depends on the model).

PeterW · May 30, 2008

If your datalogging why not use a PC to read the data from a PLC and save in the PC.

Sergei Troizky · May 30, 2008

scottmurphy said:
This has truck loads of programming memory, if all you are wanting is to log data, then this could possibly be an overkill. For logging, you need memory areas to store your data, not programming memory.

Have you seen the CJ1H specs?
I said 256K DATA memory.

JesperMP · May 31, 2008

friendlyfire said:
Jesper: I suppose it is a RTU application according to the definition I just looked at. I thought RTUs only acquire data and don't offer control capability. This said, I did a quick internet search for RTU products and I don't see any with control features. So, other than PLCs (and embedded controllers) what hardware would you suggest?

I believe that it is quite common with at least some limited control capability. A typical application for an RTU is to sit in some remote location and control a well for example. If there is trouble it will send an SMS or email. And it is possible to connect to it and upload a weekly logfile.

A qick search found this vendor (look at the "intelligent" RTUs): http://www.iclinks.com/
They support all IEC61131-3 languages.

edit: also look at this vendor: http://www.sixnetio.com/html_files/products_and_groups/rtu_benefits.htm

I dont know pricing, like in all other aspects, I guess you get what you pay for.

Disclaimer: I dont work with RTUs.

Inexpensive PLC with some memory capacity?

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