C-Bus over fibre

Hi Mick

Dont know anything about fibre optics ...Looking briefly at the circuit wouldnt you need 2 fibres since the bridge is a 2 way device ??..........

Frank

 

Nope, a PCI doesn't understand what it speaks.

You also would have issues with the remote bits being another network, and it would all get messy.

As apposed to the mess you would create by sticking the Black & Decker 12" through a bridge

Cheers

Rohan

 

The other thing to consider here is the inter-bridge protocol used and whether it would be robust enough (error detection/correction and the like) to split the ends apart. Granted fiber is not prone to conventional noise though.

That is one advantage of using a commercial RSxxx to fibre converter, as it would probably wrap up the data somewhat.

Cheers

Rohan

 

A couple of those would go pretty close I would think.

You could do without the opto on the TX circuit though as the fibre its self will provide the isolation.

I have no idea why we're all devoting so much time to this, it's not like anybody is actually going to cut up a perfectly good bridge......... are they?

Cheers

Rohan

 

Yes and Yes. !

Ah yes but you don't what the power supply from the fibre circuit effecting the cbus. so I would leave it there. the bridges are CBUS powered.

Your would need two fibers to do it cheaply ! they are ways to send light both way down the same fibre but starts to get expensive

It is not the chip numbers, The Serial numbers !
THe bridge has 2 of them !

This would go very close to doing it.

How much are you willing to pay for a solution !

You could mount the complete solution in existing case. with a clever PCB design.

Pitty you probably can not buy the case on its own. for the second part of the bridge.

Charles

 

If you wanted to avoid the component level, you could always put a CNI at each end, buy a couple of copper ethernet to fibre ethernet convertors (10BaseT to 10FL, or 100BaseT to 100FX), and join the two networks over ethernet with the CNIs.

The distance you can achieve is mainly dependant on the type of fiber you use in that situation, 62.5u Multi-mode fiber will get you at least 200m, 50u MM fiber will get you at least 500m, and single-mode fiber run in duplex will get you at least a couple of kilometres.

Also, the copper to fiber convertors are pretty cheap second hand on ebay, especially the 10Mb ones, (cant see any reason to use 100Mb for a CBus link).

Darpa

 

How do you do this ??? two CNI can not talk to each other ?? (at the software level/bridge ???)

 

Why can't two CNI's pass msgs? Isn't that pretty much what the bridge is? - The transfer of messages via an optically isolated connection?

I would be keen to try though I only have 1 CNI.


What about using a barrier? Probably much cheaper than fibre!
Accepted by greater industry as an isolation method for field devices.


http://www.pepperl-fuchs.com/pa/interptop/k-system/default_e.html#3

http://www.pepperl-fuchs.com/pa/interptop/barriers/default_e.html

 

The zener barrier you linked to is for explosion protection in hazardous areas - not what I am concerned about here. If I have a hazardous area around the farm I am in bigger trouble as I have no dossier, not classification and not gear in place to deal with it - not to mention no money to pay for the extra protection.

I still think that a CNI or PCI with modded firmware is the easy solution - just needs someone to hijack the firmware and give it a go. There are many benefits from a CNI to CNI connections, 1 - Ethernet fiber converters are everywhere and 2 - you don't create a new network, it is still the same network.

CNI- CNI works great for me as I can then put a switch at the gate to bring back losts of signals (PLC, Cameras etc) as well.

If two CNI's will work then I can get a second one for a test to confirm it very easily.

Mick

 

Inter-bridge protocol is probably more robust than the serial protocol used by PC Interfaces. Every packet sent includes a checksum, and if the message is not received correctly, the packet will be re-transmitted. There is a lot of handshaking around the place to ensure that it all goes smoothly.

Bridges can do some things that you just can't achieve with PC interfaces (or CNIs), like automatically sending a duplicate of a message on one network to re-transmit on an adjacent or on some other network as required. Owing to the design of the bridge protocol, a bridge is twice as fast as a PC interface in converting C-Bus to serial and back again.

 

No, for the same reason you can't do it with a PCI (as they both talk the same language, just deliver it over a different medium)

Messages received from a PCI/CNI are not written in a format that another PCI would understand to be a message to be transmitted.

Cheers

Rohan

 

Again not having seen one of these, I thought it had a power supply, so in that case you would actually need a second opto on the RX leg as well.

Cheers

Rohan

 

One thing that could be a problem with this approach is network timing. Sometimes dedicated multi drop networks like the C-Bus one use timing as part of the packet framing. It can also be used to determine which module speaks when and the like. I have no idea if C-Bus does such a thing, but it might.

If you wrap these messages up for transmission using TCP/IP then you loose control of the timing, as delivering the message then becomes the responsibility of the TCP protocol. You could use another protocol like UDP or something else, but the point I'm getting to is, there is a bit more involved than what it seems on the surface.

If you were going to do it this way using 2 CNI's, then I would think the simplest approach would be to have a program running on a networked PC that can see both CNI's and translate the messages between them. Of course saying this is simple is an understatement as anybody who has seen the full C-Bus protocol would attest.

But it could be easier than destroying a bridge? especially if you already have a PC running 24x7.

Cheers

Rohan

 

If there was an app that could do it then its a possibility, but I don't like relying on a PC for a hardware system like this (Yes CQC could do it, and the latency that would be introduced would be acceptable for my particular install, buts its a PC doing the work and I don't like it). Wrap all that up into a c-bus unit and I'm happy.

For speed etc, it not an issue if it is a little slower. The amount of traffic would be minimal.

But I understand that a solution, if it were to be followed up should b scalable to any size network.

I must say I have thoroughly enjoyed this thread with the lateral thinking that has been required. Its branched of into the unknown nicely

Mick

 

Would it be possible at all to get a two C-bus networks connected together over Ethernet (via two CNI's).

What would be needed - custom firmware in the CNI?

Latency would not be an issue, a 1 second delay in the light coming on is not an issue. Just as long as the networks are in sync and data is getting through ( a slow connection is better than no connection).

Mick

 

As Darpa mentioned re fibre the distances can be even greater on the fibre. We worked with a lot of MMOF and SMOF networks in the past and the max distance was 2km with consideration to the following table and single mode was even up to 70km depending on the wavelength source and data transfer rate. I belive the CNI is only 10meg so distance is easliy achievable and with the lowering cost of fibre convertors this method is very flexible.

Maximum Cable Distance For Ethernet:*

Ethernet Standards (IEEE) Data Rate Cable Fiber Type Maximum Distance (IEEE)
Ethernet (10Base-FL) 10 Mbps 50?m or 62.5?m Multimode @ 850nm 2km
Fast Ethernet (100Base-FX) 100 Mbps 50?m or 62.5?m Multimode @ 1300nm 2km
Fast Ethernet (100Base-SX) 100 Mbps 50?m or 62.5?m Multimode @ 850nm 300m
Gigabit Ethernet (1000Base-SX) 1000 Mbps 50?m Multimode @ 850nm 550m
Gigabit Ethernet (1000Base-SX) 1000 Mbps 62.5?m Multimode @ 850nm 220m
Gigabit Ethernet (1000Base-LX) 1000 Mbps 50?m or 62.5?m Multimode @ 1300nm 550m
Gigabit Ethernet (1000Base-LX) 1000 Mbps 9?m Singlemode @1310nm 5km
Gigabit Ethernet (1000Base-LH) 1000 Mbps 9?m Singlemode @1550nm 70km

 

Thanks Nathan

I am looking at a wireless option now. Hence the request for a C-bus to Ethernet to Ethernet request. So far I can get a wireless Ethernet connection into handle everything but C-Bus - unless I can get it working between two CNI's.

Using the fibre is still the second option, but still places me in the same position re C-Bus and still wanting a C-Bus Ethernet bridge.

It actually works out a lot more economical to use wireless, even with some of the extra hardware required. I am not a wireless fan, but in this case it is an acceptable solution. The wireless bridge that has been nominated for the task has extra security features to make even more suitable for the task at hand.

Mick

 

Well that is good news, but I wont be holding my breath - it will happen when it happens

I'd be happy with

C-bus -> Ethernet -> C-bus

Mick

 

Long distance C-Bus

C-Bus can very easily be converted to fibre using a very simple ethernet to fibre converter. These converters are easily found at many wholesalers, and data cabling companies i.e Pacific datacomm, Alloys International etc.
You then simply require two converters - one to fibre, one from fibre into 2 CNI's - one at each end.

If the costs associated with running fibre is excessive, and you have line of sight, you can consider using a wireless microwave link.
These are very cost effective, and available through places like Alloys International in Melbourne.

Seen here
http://www.networkvideoproducts.com...uct.aspx?cat=Wireless+(Bridges+/+Access+Point)