Cbus in a STAR configuration

[Charlie Crackle]

Have a job that has changing office layout. All lights stay in same place only the switches move. (and of course the programming changes)

To make this realy easy I was thinking of having a KRONE frame in the roof and running a totally star type network for all the switches. This way when only half the office changes I can disconnect just those switches easly and not effect the others and add new switches.

There will be just 1 run to the switch board with the 4 relay modules.

Has any one wired cbus in a perfect STAR like this ?? does it work ok.


If Bus is better

I was also thinking of just running a bus of CBUS around with lots of CAT 5 outlets. Just make the office partitions terminated with RJ45 Fly leads and then they can just be plugged into the bus at the closes RJ45 in the roof !


Charles

[ashleigh]

Should be Ok - just pay attention to total cable length.

The RJ patch leads sounds kinda neat!

[barry dawson]

Have a job that has changing office layout. All lights stay in same place only the switches move. (and of course the programming changes)

To make this realy easy I was thinking of having a KRONE frame in the roof and running a totally star type network for all the switches. This way when only half the office changes I can disconnect just those switches easly and not effect the others and add new switches.

There will be just 1 run to the switch board with the 4 relay modules.

Has any one wired cbus in a perfect STAR like this ?? does it work ok.


If Bus is better

I was also thinking of just running a bus of CBUS around with lots of CAT 5 outlets. Just make the office partitions terminated with RJ45 Fly leads and then they can just be plugged into the bus at the closes RJ45 in the roof !


Charles

We compleated an open plan Gov Office with C-Bus cable fitted off with shuttered surface mounted RJ45 jacks in the cieling space and flying leads from input devices.
This system was very flexable for the clients needs and worked well.
Note: we didnot double puch the c-bus cable in the jacks, we left a loop and striped off the outer sheath, and punched down with the cutter turned off.
This was a requirement in the spec, but we found it was trouble free and quick to fit off.

as for punching down in a krone frame i see no real problem but cable length.

[allgo]

Only possible problem with Krone termination apart from increased total length of cable is possible increase in volt drop. As it is only an insulation displacement connection (IDC) you dont get the same degree of contact between cables as you get with terminal blocks etc.

[Charlie Crackle]

My understanding is you get a better joint with insulation Displacement. Gas Free Contact joint.

Dont tell the Quick Connect Power Point department ! IDC is supposed to support 25Amps and more in fault conditions.

That why I thaught an IDC connector on the CBUS gear would be great

Charles

[Charlie Crackle]

allgo

My understanding is you get a better joint with insulation Displacement. Gas Free Contact joint.

Dont tell the Quick Connect Power Point department ! IDC is supposed to support 25Amps and more in fault conditions.

That why I thaught an IDC connector on the CBUS gear would be great

I agree the interface between an rj45 and socket would not be much good.


ashleigh

I did not think the cable length would really be a problem as we are now a star and voltage drop not such an issue. also every cbus item electricaly close even if the total cable was longer that the MAX (this wont be)






Charles

[UncleDick]

Charlie, Max total cable length is not only about volt drop it is also about cable capacitance, the 1km maximum is TOTAL cable that can be used not a limitation in length for volt drop (although volt drop is important and power supplies must be spread around in big networks to limit this see - http://www.clipsal.com/cis/pdf_files/CBus-Voltage-Calculation.pdf). The effect of capacitance is to 'soften' the edges of the data pulses that C-bus uses for comms. Because C-bus comms are relativly slow this capacitace does not become a problem until 1km with 1Gb/s eithernet the maximum run allowed with Cat 5 (e or Cat 6 or what ever the Datacomms boys are playing with these days) is 100m (90m to the wall plate + 10m to the PC).

[Charlie Crackle]

Now that makes more sense. I also now understand the Burdens (why they get less as the network get bigger). Thanks for clearing that up.


My understanding of ethernet cable length it is propagation Delay. (Hang over from the day of HUBS)
The computer waits the "propagation delay" for collisions before knowing is packet got through and I suppose "the propagation delay is related to capacitance" Not a problem these days with non blocking Full duplex switches.

Have a look at this picture. There should be no issues with a design like this ??

[UncleDick]

That layout looks fine Charlie