Wireless EtherCat

bestbier

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Join Date
Jun 2008
Location
Cape Town
Posts
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Hi

I am planning a project that needs remote IO station that is wireless. This station will have only 8 I/O and 2 VSD controlled via the bus. Range between transmitter and receiver is 5m - 25m with some large metal objects.

I was thinking about running EtherCat with Beckhoff PLC, IO & VSD with 2 industrial WLAN routers in bridge mode but cannot find any info that it will work.

Speed is not critical - I have done this previously with 3 brick style PLCs and RS232.

Maybe I can use another bus? Ethernet/EthernetIP/???

I would prefer, if possible, a solution that is transparent and does not require special programming.

Thanks
Bestbier
 
Hi Bestbier. EtherCAT has strict latency requirements, and thus is not well suited for a wireless link.

You could still use Beckhoff, the model BK9000 runs Modbus TCP, which you could then run over the wireless link, Modbus TCP it is much more forgiving of connection latency, since it runs on TCP/IP.
 
Hi Steve

Thanks for the info.

Just a question. My only experience is with Profibus and there the PLC handled the communication - You change the bit and words and at the end of the cycle the bus values are updated. When using ModbusTCP do you have to handle communication with fuction blocks in your program or is it done automatically?

Best regards,
Bestbier
 
Hi Steve

For Modbus TCP probably the Beckhoff CX8090.

I started thinking and since I need a Profibus drop to connect to a X-Ray machine - why don't I just run everything on Profibus. There are radio availible. And as far as I know all profibus data exchange is cyclic, so you just have to make sure that cycle interval is longer than the time it takes update the bus.

Best regards,
Bestbier
 
Hi bestbier, I agree that if you need profibus, a profibus radio would make sense. I don't have any experience with profibus radios, so I'll leave that to others with more experience.

You may want to start another discussion thread with "Profibus Radio" in the title to get more feedback about that.
 
Hi Steve

I spoke to a Profibus radio supplier today and one problem is that although the busspeed can be up to 12Mbps the actual airspeed is only 19.2kbps. He suggested just plain Ethernet - so I will look into that and then maybe start a new thread.

Best regards,
Bestbier
 
I have heard of optical links for profibus. They will of course need a free line of sight. has anyone used anything liket this? It might be a solution.
 
I will contact my local Schildknecht supplier and find out more info.

I am currently thinking of a spring cable reel from Wampfler - Speed of 500kbps.
 
Hello Again, bestbier. If you are thinking about a cable reel, then you could re-consider EtherCAT, EtherCAT requires Category 5 rated Ethernet cable, which I think you can get on a cable reel?
 
Hi Steve

I have looked at Wampfler cable reels - I use their products for the electrical supply. Their standard products can only handle data at 500kbps. Everything I read about Ethercat says 100Mbps. I am trying to find out if they can do heigher speeds.
 
Originally posted by bestbier:

I spoke to a Profibus radio supplier today and one problem is that although the busspeed can be up to 12Mbps the actual airspeed is only 19.2kbps.
Click to expand...

I don't know if this is really an issue. Most of the devices like this that I have seen are bridges. The device will buffer data between the physical bus and the radio transmission. So you can have an asynchronous relationship between the data on the physical link and the data going over air.

If the device you are looking at is simply modulating the physical bus signal to a radio signal then you are limited. If it is buffering the data you probably don't have an issue.

Keith
 
Thanks for the info Keith.

I am going to contact the local Schildknecht Dataeagle (they seam to be the best choice for Profibus) distributor on Monday to find out some more details.
 

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