MELSEC Q & Ethernet

Hi,

i need some practical samples or advice of Melsec Q PLC and ethernet module usage. I want to exchange I/O states info between two Q01 PLC-s via ethernet. Have read manuals all day but haven't reach anywhere yet, IMHO it's far from simple (as i thought in the beginning).

Thanks,

Mardikas

IEC Developer or GX-Developer?

There are IEC-Developer function blocks for fixed buffer communication and also demo-programs for fixed buffer communication to GX-DEV. IEC-block are for example http://194.130.244.64/branch/de/service/source-cd/web/fb_e.php.

I only have used fixed-buffer communication between Q02 CPUs, but I was forced to modify those progs to GX-Dev. It works quite well, even with wireless lan.

You can find examples from Beijer Suomi, from here http://automation.beijer.fi/web/webbfiles.nsf/0/724661AB27D505E3C125701A0035C592?opendocument&LANG=FI

or http://automation.beijer.fi/web/webbfiles.nsf/0/54F2EDD12E97C6A6C1257082004F6B02?opendocument&LANG=FI

Tmu

GX IEC Developer 6.10

Thanks for the links, i will try them today.

Kiitos, Tmu

If you are only connecting Q series PLCs together, I would suggest that you use Melsecnet 10H instead of ethernet.

Melsecnet 10H doesn't require you to write any special program to send/receive messages. You only have to setup the network parameters.

Melsecnet 10H can be run on fibre-optic which allows for a ring topology and isn't affected by electromagnetic interference.

Melsecnet 10H offers better performance than ethernet.

Melsecnet 10H doesn't require additional hardware such as hubs, routers, etc.

I would only use ethernet for connecting Q series PLCs to PCs running applications such as SCADA.

I hope you haven't bought the ethernet modules already!

I will use also Citect SCADA

Can i use Ethernet between PLCs via fiber optics and media (TP-fiber) converters?

Why Melsecnet offers better performance over 100base Ethernet?

Yes, modules are bought and on my table I also managed to set up data exchange between PLCs.

Mardikas said:

Can i use Ethernet between PLCs via fiber optics and media (TP-fiber) converters?

Click to expand...

Yep. No problem.

Mardikas said:

I will use also Citect SCADA

Can i use Ethernet between PLCs via fiber optics and media (TP-fiber) converters?

Why Melsecnet offers better performance over 100base Ethernet?

Yes, modules are bought and on my table I also managed to set up data exchange between PLCs.

Click to expand...

If you look at the chart below you can see the difference in performance. Ethernet is the dark blue line, Melsecnet the light blue line. Melsecnet sends the data in a single block, ethernet will require the data to be sent in several smaller blocks hence ethernet will take longer.

Melsecnet is limited though, you have a maximum amount of data that can be sent. With Ethernet you can send more data than Melsecnet. The greater capacity of Ethernet makes it more suitable for SCADA because a large quantity of data is usually read from the PLC by the SCADA. Also most PCs have ethernet ports, but if you use Melsecnet you will need to add a PCI card to the PC.



This diagram came from Takebishi who make very good I/O drivers for Mitsubishi PLCs (Ethernet, Melsecnet and Serial).

Good luck with your project.

Kind regards

Alastair

(EDIT: Sorry the diagram is using Japanese on the X-axis, the X-axis shows the number of data points read from the PLC)

Melsecnet sends the data in a single block, ethernet will require the data to be sent in several smaller blocks hence ethernet will take longer.

Click to expand...

OT but,
Some networks (like ControlNet)have smaller blocks and are actually faster (not Mb/s), as "wasted space" in package is tiny compared to Ethernet

With Melsecnet cyclic communication (as opposed to transient comms) there are a fixed range of link addresses that are updated every time the network is "scanned". Every PLC connected to the network will receive the data of these link addresses every time the network is scanned. Even if the PLCs don't use these link addresses they are still updated in the communications module of the PLC. The network is configured so that each PLC can have exclusive write access to a specific area of the range of link addresses. So in the ladder program you only have to write to link address (e.g. as a coil or by a move instruction for example) you don't need to write a message instruction.

One way to think of it is this; The Melsecnet is a memory area, all connected PLCs may read from the memory area and each PLC has it's own range of address in the memory area to write to. The read/write access to the Melsecnet memory area is just the same as PLC internal memory, i.e. contacts and coils, move, copy, add, subtract, etc. etc.

The network scan time is deterministic too, the manual includes details on how to calculate it.

Melsecnet will have "wasted space" because you won't use all the available link addresses (I should say "don't" because it advisable to leave free space for later use). BUT, the performance, and ease of engineering, p***es all over ethernet for PLC to PLC communications.

Proprietry systems rule! ;-)

Clear

I ment that some networks have smaller amount of bytes in every package that are not for carrying "useful" data than other networks.

One question, #
you cannot pause the updating of data by stopping reciever CPU or can you?

Hundikoer said:

One question, #
you cannot pause the updating of data by stopping reciever CPU or can you?

Click to expand...

If the CPU of a PLC on the network is in stop (but power remains) the network will continue to function and data will continue to be updated.

If the power to a PLC is turned off, the communications module of that PLC will cease to function. If a fibre-optic ring network configuration is used, all other PLCs on the network can continue to send/receive data. The fibre-optic module has one input port and one output port. If two PLCs (lets call them A and B) on the network are powered down, a PLC connected between A and B cannot receive data if the PLC with the master communications module is on the other side of A and B. For example, if 12 PLCs are connected to a ring network (like the hour marks on a clock) and the master PLC is at 12 o'clock. If the PLCs at 3 and 9 o'clock are powered down, the PLCs at 4, 5, 6, 7 and 8 o'clock cannot send/receive data.

Can you guys help me to set up communication between Citect and Melsec Q (ethernet module is QJ71E71-100). Citect help seems to be outdated.

Have you tried Citec distributor?

Mardikas said:

Can you guys help me to set up communication between Citect and Melsec Q (ethernet module is QJ71E71-100). Citect help seems to be outdated.

Click to expand...

http://www.faweb.net/us/

from the link above you can download demo versions of OPC and DDE I/O servers that will allow you to interface the Q series PLCs with the Citect SCADA. The software manuals can also be download too. The manuals tell you exactly how to configure the Q series PLC for communication with a PC over ethernet (these settings should also work with a Citect I/O server).

(EDIT: could you take some screenshots of your PLCs' ethernet configuration in GX IEC Developer? These are the settings under network parameters. For an I/O server to be able to communicate with the PLC, these setting must be correct. If you can paste the screenshots to a new post in this thread, I can check it for you.)

Hundikoer said:

Have you tried Citec distributor?

Click to expand...

No. What can i do with it and where to get it from?