Hardware Reference
In-Depth Information
Z-Wave is likely to be the better choice. On the other hand, if there's only a subset of devices, or you plan on
building your own then Zigbee is more likely to appeal. Especially given the Arduino XBee shield (
http://arduino.cc/
en/Main/ArduinoXbeeShield
) and its successor (
http://arduino.cc/en/Main/ArduinoWirelessShield
)
are still available.
Next, look at the physical space of your home. If, for example, you have lots of basement space or similar
situations that need multiple units to allow the RF to “see around corners,” then ZigBee is a better choice, because its
better bandwidth can facilitate more messages being repeated in order to get the signal to its destination. The caveat
here is if your traditional WiFi signal is unable to permeate the walls, then neither will ZigBee, as they operate on the
same frequency and there'll be even more lost bandwidth as both devices try to coexist.
C-Bus
Although there are several well-known protocols for appliance control, X10 and Z-Wave are better known, with
members of the knowledgeable public being aware of them, primarily because of their generally low barrier to entry.
Within the HA community, however, it is the ownership of a Clipsal C-Bus system, which becomes the goal.
6
About C-Bus
The C-Bus system was developed by an Australian company, Clipsal, as a means of controlling various light systems
remotely. Clipsal's original intention wasn't in the field of HA but in stadium lighting rigs and commercial arena
and conference centers. This meant the system had to support much longer cable runs than would be utilized in a
home setup and a larger address space. It succeeded on both counts, with cable lengths of 1km being possible with
100 appliances on a subnet—with each subnet being capable of connections to another six through basic bridges or
considerably more through the now available Ethernet bridges.
Differences Between X10 and C-Bus
C-Bus's primary difference is with its installation. Although X10 transmits its data along existing power cables, C-Bus
devices are controlled by utilizing a proprietary protocol that travels along a separate Cat-5 cable. Consequently, such
installations can be carried out only by qualified Clipsal-approved staff, pushing up the initial cost. However, once all
the cables have been laid, one achieves the benefit of a near-zero level of maintenance since the interconnects will
always exist and remain future-proof. It also provides two-way communication between the switch and a computer,
making it trivial to query the state of the light dimmer or appliance. Furthermore, because the signal speed is not
limited by the zero-crossings in the power line, all light changes happen instantaneously—a benefit that only those
with many years of experience with X10 systems can truly appreciate.
To lower this initial overhead, Clipsal has recently introduced a wireless version of C-Bus, which eliminates the
need for costly installations, so it is this subset of devices on which I'll concentrate. This optionally supports 128-bit
encryption of its data stream, making it more secure than an (unfiltered) X10 wireless solution, although it's still
hackable by the determined. Its wireless range is no better than the RF-X10 combinations covered previously, with
a 5 to 20 meter range according to material. Unfortunately, there is a maximum of 30 devices on a C-Bus wireless
subnet, making it less capable than an X10 system using two house codes. The generally adopted approach to C-Bus
installations is that a wired version is used for the initial house configuration, with wireless being added later as a
cheap upgrade path.
#"USISUSEDMOSTLYINTHE5NITED+INGDOMAND!USTRALIAWITHTHE53EQUIVALENTKNOWNAS3QUARE$#LIPSAL4HISISTOAVOID
CONFUSIONWITHASIMILARTECHNOLOGYCALLED#%"US%)!UTILIZINGTHECONSUMERELECTRONICSBUS#%"US
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