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Topic: Daisy chain input buttons (Read 913 times) previous topic - next topic

edgeman

Hi all,

I'm (still) putting my home automation solution together, and my electrician, who will be running all the cables, has said that CBUS is easier to cable because it is daisy-chained, whereas at the moment in my design all my CAT5e cables come back to the switchboard (and then the Arduino), so each light switch will have it's own cable going back to the Arduino.

I like the sound of daisy chaining, it seems like a neater solution, but I honestly have no idea how to approach that. I *think* I need to put a small circuit behind each light switch (which is not a problem), just like the CBUS switches, the purpose of the circuit will be to uniquely identify that particular switch. And this would have to be flexible enough to accommodate up to 6 switches on the one wall switch (i.e. 6 gang). The small circuit would also need to be able to communicate, sending the status for each switch to the Arduino, so that the Arduino can then switch on / off the solid state relays as per the programming.

Any guidance / thoughts on this would be very welcome!

Thanks in advance ;-)

Nick Gammon

Do you mean CAN bus?

http://en.wikipedia.org/wiki/Canbus
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

0AlphaOmega

#2
Jan 26, 2013, 10:34 am Last Edit: Jan 26, 2013, 10:42 am by 0AlphaOmega Reason: 1
daisy-chain = addressable

Do you want addressable switches/devices or discreet?

A hub-centric system is more robust

It is cbus Nick - many protocols grew out of early HA development - I developed one based on a chip-set from Cherry (IIRC). client pulled out ;(

For whom does the clock pulse? It pulses for you!

kDodman

If you daisy chain then one point of failure brings everything past it down.

Nick Gammon

OK, well to save other people doing what I had to do, here is the link:

http://en.wikipedia.org/wiki/C-Bus_%28protocol%29
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

Nick Gammon


I *think* I need to put a small circuit behind each light switch (which is not a problem), just like the CBUS switches, the purpose of the circuit will be to uniquely identify that particular switch.


Are you going to use CBUS, or just using that as an illustration of the general idea?
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

edgeman

Hi there, just using CBUS as the idea, not using any CBUS components / switches / etc.

After thinking it over I tend to agree that a hub-spoke (star) topology is probably more robust.

However I did come across the following in my searches, which looks like it would do the trick, in terms of giving every switch a unique ID: http://pdfserv.maximintegrated.com/en/ds/DS2401.pdf. Have not yet figured out how to link that up to the Arduino, may order a couple and have a look, they seem relatively inexpensive.

edgeman


If you daisy chain then one point of failure brings everything past it down.

A very good point, I think perhaps the electrician just doesn't want to run all those CAT5e cables. From a cost perspective the CAT5e is pretty cheap. Might run it myself to save the hassle, and stick with the centralised topology.

After thinking about it, a daisy-chained topology would be like the old coax-based 10base-2 networks, where a faulty or incorrectly attached terminator would bring down the entire network. Not my idea of robustness :-)

Nick Gammon

I think a single cable run through the building should be OK, per se. After all, the cable won't fail.

If you use a balanced electrical protocol (ie. RS485) then you could send out commands via that, and any listening devices could respond.

This might be slightly off-topic, but whatever:

http://www.gammon.com.au/forum/?id=11428
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

edgeman



If you use a balanced electrical protocol (ie. RS485) then you could send out commands via that, and any listening devices could respond.



Awesome, thanks for the info, I'll check it out :-)

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