C-Bus over fibre

Discussion in 'C-Bus Wired Hardware' started by znelbok, Apr 27, 2008.

  1. znelbok

    znelbok

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    I am installing a gate at the moment and I am thinking of putting a c-bus unit in the control panel there. The gate is about 100m cable length away and I was looking into the option of running fibre - one way to overcome lighting strikes, and for other reasons.

    Is there a way to get C-bus onto fibre. I know there would be no power available to the remote unit, but as long as it has a power supply built in or added tot he network then it should be no issue.

    I don't want to add two bridges as that seems a little pricey and I still need copper cable, which can make the system susceptible to lighting, That and it complicates the network just for one little four channel module (not to mention the monitoring of it via CQC).

    Maybe split a bridge in half and use the opto link, where now a fibre cable joints the two together (in my simplified world)?

    Mick
     
    znelbok, Apr 27, 2008
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  2. znelbok

    ashleigh Moderator

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    You can probably do what you suggest. There is no product available, though, so if you split a bridge, you'd still be looking at either buying 1 and butchering it, or buying 2 and butchering both.

    And then you need to rip out the opto-coupler and put a fibre tx/rx in instead. All possible, but not necessary cheap or easy.

    (And no warranty repairs available!!)

    C-Bus products are designed with fairly tight power budgets in mind, so the opto-coupler interfaces are usually run very light (thats a pun, geddit?), so not much current is run through the LED side. This might be a tight constraint. You better allow for no more than 1 to 1.5 mA being available there.
     
    ashleigh, Apr 27, 2008
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  3. znelbok

    znelbok

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    Thanks Ash

    I am not going to butcher a bridge.

    Is this something work putting on the wish list for you guys to look into. I must not be the only one who could use a c-bus over fibre connection.

    If the C-bus network was a 485 network then there would be plenty of fibre converters out there.

    Looks like I will stick with a copper connection and hope I don't blow anything.

    Can two wireless bridges be uses for a point to point connection?

    Mick
     
    znelbok, Apr 27, 2008
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  4. znelbok

    Don

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    bridge surgery

    Not that I've ever done it, but slicing a bridge in half and inserting an optical link does intrigue me. A few points for anyone that might want to try it:

    1) In all the Bridge PCB assemblies I've seen, you can easily see that there is a 5mm or wider strip with no copper. The two optocouplers span this distance. If you carefully desolder the optocouplers, you can saw the board in half at this point to get two half-bridges. Each half-bridge can operate independently.

    2) As Ashleigh states, there is only about 2mA to play with to drive the LEDs. The LED of each optocoupler is driven directly from a microcontroller port, and the limitation is on the port, not just the series resistor, so change the resistor to get more current will work for a small range, but you risk blowing up the port, which is of course not repairable.

    3) The signal going across the port is plain vanilla Asynchronous serial communications at 9600 baud; start bit, 8 data bits, stop bit as per usual. If you wanted to span a greater distance than the 5mm of optocoupler, you can source commercial rs232 - fibre - rs323 converters which should be able to use the signal directly from the micro as input. You will need to power the converter and since the C-Bus unit supply is limited to about 5mA, you will probably need an external supply. You need an ISOLATED power supply (NOT bonded to earth) to power the converters. If you don't use an isolated supply, C-Bus will get bonded to earth indirectly or directly, and communication reliability can be compromised.
     
    Don, Apr 28, 2008
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  5. znelbok

    rhamer

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    Not that I know, but I would have assumed this signal is TTL and not swinging RS232 signal levels.

    And whilst I realise that some PC's can read TTL signals on their RS232 ports, I would think you would need to run it through a MAX232 or similar first just to keep the RS232 to Fibre converter happy. This will invert the signal also so you may need a TTL inverter between the micro and the MAX232.

    Of course I'm just making all this up, so what we really need is someone with a couple of bridges to spare, a hacksaw, and a complete disregard for warranties :)

    Cheers

    Rohan
     
    rhamer, Apr 28, 2008
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  6. znelbok

    ashleigh Moderator

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    Yes you are right, it will need conversion to either RS-232 or RS-422 and thence to whatever the fibre needs.
     
    ashleigh, Apr 28, 2008
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  7. znelbok

    ashleigh Moderator

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    Only the product managers can put new products on the to-do list, and I'm not one of them. They do look in here now and again.

    Yes, though it would be quite painful to set up, it would probably work provided the distance between them is not too great. You would need to use the "forward to remote network" function on the WIRED sides and design your topology carefully. They are not designed for this, and getting the same house code into both will require the use of another wireless unit. I'm not sure how it will perform but you could give it a go. I've heard of more peculiar things being done with wireless devices :)
     
    ashleigh, Apr 28, 2008
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  8. znelbok

    znelbok

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    No, just the money to spare and a love of electronics. With the cost of bridges I wont be donating mine for science - although the challenge sounds tempting.
     
    znelbok, Apr 28, 2008
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  9. znelbok

    znelbok

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    So... if the bridge is basically a serial connection between the two networks, then what about two PCI's communicating to each other with a fibre converter at each end? That is basically the bridge idea with out the new network required. (may not be that cost effective either)

    Speed is not a big issue, it will only have a single unit, maybe two at most (apart from the PCI)

    I already have a couple of self healing redundant fibre converters (232, 422 or 485) and a spare PCI so it may not cost me that much if I go that path.

    Or a CNI - Cu network - fibre network - Cu network - CNI i.e. use a CNI instead of the PCI in the above example and the network as the medium in the middle (dedicated network with only the PCI's and a crossover connection, no switch). This means I buy 1 CNI as I have one already for toolkit to use.



    Mick
     
    Last edited by a moderator: Apr 28, 2008
    znelbok, Apr 28, 2008
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  10. znelbok

    Charlie Crackle

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    Cut Here !

    Cut Here !!!!!
     

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    Charlie Crackle, Apr 28, 2008
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  11. znelbok

    rhamer

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    Won't work, the serial side of a PCI talks a different lingo to the C-Bus side and one PCI is not designed to understand another. You would need to put some device in the middle to translate RX to TX and vice versa.

    Same with the CNI

    The bridge would be the best place to do it.

    Cheers

    Rohan
     
    rhamer, Apr 28, 2008
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  12. znelbok

    znelbok

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    Come on Charlie - your almost there - go on do it, you know you want to :p
     
    znelbok, Apr 29, 2008
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  13. znelbok

    znelbok

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    Gotta ask - I thought maybe with a new bit of firmware it might, seeing as the bridge is using "serial" to make the connection.
     
    znelbok, Apr 29, 2008
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  14. znelbok

    Charlie Crackle

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    Still Pondering this one... (too may other work pressures)

    I was thinking.... still to keep the Opto Couplers (just add two more) that way I can power the transmitters with out cbus bonding (grounding) issues.

    Dont see any point using RS232 to Fibre back to rs232 converters should be able to drive some fibre transmitters. just a very large GAP opto coupler.

    Charles
     
    Last edited by a moderator: Apr 29, 2008
    Charlie Crackle, Apr 29, 2008
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  15. znelbok

    rhamer

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    I think I've missed something obvious.

    Not having ever seen a bridge with it's clothes off before, are the 2 sides of the bridge identical?

    So we only need to cut one in half?

    BTW why did you blank out the chip numbers?

    Cheers

    Rohan
     
    rhamer, Apr 29, 2008
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  16. znelbok

    ashleigh Moderator

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    The bridges talk inter-bridge protocol between them. It might be over a serial link, but it has nothing to do with what comes out of your PCI.
     
    ashleigh, Apr 29, 2008
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  17. znelbok

    JasonCox

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    haven't tried it - but wouldn't two PCI's with a null modem cable crossover and fibre converters work?
     
    JasonCox, Apr 29, 2008
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  18. znelbok

    znelbok

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    But could the PCI/CNI have firmware written to do the job to allow comms (serial) between two networks (yes it is a bridge then, but at least I could get it on fiber or Ethernet)

    So it looks like a dissected bridge is still the best option.

    Can casings be purchased that are empty?
     
    znelbok, Apr 29, 2008
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  19. znelbok

    znelbok

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    I know next to nothing about electronics, but I found this. Its a midi interface that has a f/o converter. (not interested in the MIDI aspect, more the concept of the conversion to fiber)

    http://www.wb5mrn.com/midi/midixtnd.pdf

    In it is a optocoupler (which converts the midi to TTL) and then some circuitry to the fiber LED. Can something like this be added on to each half of the bridge to get the extension. Apparently we already have TTL so everything after the opto is potentially a solution (I think)

    Mick
     
    znelbok, Apr 29, 2008
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  20. znelbok

    Don

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    The bridge is in fact two identical circuits mounted on the same board.

    Some bridges might have different positioning for each of the two LEDs which can be mounted to indicate communication activity, but you will find the circuit connections identical

    There is beauty in symmetry :)
     
    Don, Apr 29, 2008
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