PLC connectivity

Hi all. I want to connect two PLC machinery over the internet. Is there a way to do that by using ADSL connection?

Thank you.

Manolis.

If you can get an ethernet card for the PLC on each end then you should be able to communicate over the internet. I highly recomend you get a point-to-point VPN connected between the two sites, then use a private IP on each PLC (10.x.x.x or 192.168.x.x).

Also keep in mind that the internet is VERY VERY VERY slow regardless of connection when compared to tradtional PLC communications.

ADSL is going to appear slow because while it can be high bandwidth it is variable bit rate. You may get 512kbps average throughput, but that is an average for a reason, the graph of data over time is really ugly (trust me).

A T-1, DS-0, or ISDN line will actually serve you better because they are constant bit rate connections. I've found a 64kbps ISDN line is better to work with than a 2Mbps cable modem or 1.5Mbps DSL connection. In the PLC world its not about high bandwidth, its about constant bandwidth...

manolis said:

Hi all. I want to connect two PLC machinery over the internet. Is there a way to do that by using ADSL connection?

Thank you.

Manolis.

Click to expand...

Manolis, There is so many ways to do this that the best advice would be to contact your sales rep. and ask him/her(sure!) what he has to offer and how it is done in your region with his brand.

Never done this myself, (so anybody step in and correct me), but as I understand it, you'll need an ECOM card/module (for each plc), a router, and a hub (if more then one plc). From what I understand the router will make the VPN connection (fixed IP), then the PLCs will be set up with private IP addresses. Hmm sounds like some work.

Let us know how it turns out.

PLC / Internet

The easy and cheapest and easiest is

Get a cheap P3 computer, 128mb Ram 10GB Hard drive
Basic VGA graphics etc.
Load a Red Hat version of Linux. (6.0 or 7.0)
Install a program called "squid". It is a caching proxy server.
Install two network cards.
One card is for your local or PLC network. Address 192.168.x.x Plug
this into your local hub. All HMI and workstations can access the
internet from here.
The other card is for the internet connection. This IP address will
be assigned by your ISP Via a program called Pump or BootP. DHCP.
Plug this into your ASDL, Cable, or what ever service you use.

Squid is very secure, and can be set up so tight that the other
network is invisible to all hacker probes. It takes some reading
and time to set up right. It is free. Ask the forums if you need
Help, they can show you some short-cuts. Only your remote machine
will be able to access the PLC network

Total cost of this system $680.00 Cdn.

There are other ways, like a router, but these are not that secure.
There are routers that also work as firewalls. Some are quite reasonable. Cost determins the features you get. Youll have to spend about $1100.00 Cdn for a reasonable unit. Do not use a home designed router for this application.

It all depends on the time you want to spend on the project. Money may also be a factor.
Something to think about Cheers.
Bruce

Bad news Mike.

elevmike said:

Never done this myself, (so anybody step in and correct me), but as I understand it, you'll need an ECOM card/module (for each plc), a router, and a hub (if more then one plc).

Click to expand...

The ECOM modules do not use a TCP/IP stack. AD sends raw E-NET packets between their PLCs so AD packets aren't routable. That is how AD gets very good E-NET performance, their E-NET is very lean and mean. Other than the AD part you are on the money. I would also use a VPN. It is true that communications will not be as fast if the PLCs were local but who needs to coordinate I/O in two remote locations?

I would investigate Bruce99's Linux idea too.

Reply

Peter, Bruce, ElevMike, Pierre, Marksji,
thank you all for your postings. What I'll do, is try out the ISDN connection first and then the LINUX solution. I'll let you know of the outcome (hope it'll work!).