Hi,

I'm Roy. I'm more of the hands-on tech with a screwdriver and not a programmer, so dumb down your answers a bit for me if you would...

I'm trying to add to the memory integers of a Unitronics V570 PLC so it can handle more sensory input from Ethernet Port. My company's programmer is asserting that the only thing that can be done is to add another PLC and break up the various inputs between them. I feel that there must be some kind of bigger memory chip or something I could add.

I know Allen Bradley has something for their PLC's but they've kinda priced themselves out of the running for the project I'm working on. The Unitronics system is so modular it seems they must have a snap-on memory expansion but I can't find one.

 

I'm not exactly in the PLC biz anymore, but I don't expect it would do any good if you did find such an animal. Why? because many PLCs do Ethernet as a convenience and because it's ubiquitous, not because they have high speed networking to do. Some even do Ethernet at exactly the same speed they do serial comms. And since they like to make their scan deadlines and it's difficult to predict how long networking may take, they are very conservative in how often they do it. Being rate limited, adding more nodes will very likely simply take longer to scan them all. I'm sure Lynn or somebody will correct me if I'm wrong, but more PLCs will probably be faster than bigger PLCs for this reason. And even if you made the PLC faster, the IO units tend to be incapable of handling back to back packets very fast.

Regards
cww

 

Hi Roy,

I'll be glad if you can send more details about the structure of the data you want to keep to [email protected]. This way you can get precise, professional answer.

In general:

In addition to "M" and "X" registers, you can keep data in Data Tables. They can be arranged as Excel sheets, which makes data operating very easy and intuitive. You have 120 Kbytes RAM (read/write) memory, dedicated to DT. This means more than 60,000 MI (16 bit registers) or 30,000 ML/DW/MF (32 bit registers).
You can store text in Data Tables too.

V570 supports SD card. The limit of data there depends on the card, but it's measured in Gigabytes. In practical level this means it's unlimited.

V570 supports normal, standard SD/SDHC cards - the same you have in your digital camera, smartphone, PDA...

 

Thanks for such a quick reply!

We have moved in the direction you and our programmer both suggested for this project and i believe our vendor has already brought the additional PLC and related parts to our cabinet builders. Not long now before the testing phase.

 

That was exactly my train of thought as well, but my programmer (reading over my shoulder) says that there is too much live feed that gets imported from Ethernet connection and exported to a website constantly to do this.

 

Thank you, this was my thought about it as well. Just plug in a bigger card...I can physically see the card right here and I know there are bigger ones, why doesn't that solve our issue? But our programmer says that's not what his issue is, he says there's 4000 memory integers that can't be expanded on and it's independent of that SD card for some reason. What we're doing is importing many temp readings through a VPN as well as some 4-20's hard wired into some ATC8's and based on that turning on 32 circuits.

 

You have 4095 16 bit signed, memory back up registers - MI, plus 512 fast 16 bit signed registers - XI. Do you want to tell me, that you have more than 4600 analog signals, which you want to distribute at real time?! I'm really curious to see your project and learn more about it.

SD card is something like Hard Disk in computers. It can hold huge amount of data (practically unlimited) in different ways, but it's relatively slow. In most of the cases even if you keep data in SD card, you need to transfer it first to registers (MI, XI, ML, XL, DW, XDW, MF...) and then to operate. The question here is how often you need to access the data? Again - more than 4600 registers at the same time on line?!

Another option to keep relatively big amount of data are Data Tables. There you have 120 kbytes RAM, which means another 60,000 registers. DT RAM memory is ways faster than SD and can be operated each scan. In addition - DT can be read by external application directly.

Please - send e-mail to [email protected] with more details about your project. I really don't believe you have more than 4600 values to share and have the impression there is a point of misunderstanding. I'm sure if I know more about your project and needs I'll be able to give you the right solution!