Home automation concepts and CAN Bus Home automation

Edit: Since then, much has passed, cheap 802.11 chips and solutions (such as esp8266 or the esp32), cheaper products for mostly any use, both in wall and in the electrical panel. So information here is not up to date and not much relevant.

===========

I Recently started researching home automation options for personal use. And I found that, in general, you have basically 2 approaches in 2 categories when talking about standard relaying/lighting control which is usually most of the required endpoints.

Data transmission: I define this as the communication used by smart switches(I,E. just a simple sensor), to either a central smart hub or to a relay module (tasked with actually switching the load).
They can be roughly categorized into 2 groups:

• Wired, technologies like C-BUS, KNX-TP, X10, HAPCAN(see below)
• Wireless: Wifi 802.11 based smart plugs/switches, KNX-RF, Z-Wave, ZigBee

Most of the information above I found through wiki

Power transmission: I define this as the manner of which power (on off) is transmitted to the consumer (light switch):

• Central: I.E. All of the smart consumer are routed into an electrical box and relay in the junction box carry voltage to the load.
• Distributed: The relaying occurs in different places through the house, usually on the power outlet (such as most of the "Smart power outlet" of WiFi ones) or the existing wall switch (some of the Z-Wave wall switch and `in wall relays`).

This guy explains gives a little bit of background on this

Like with everything, there are advantages and disadvantages, for some reason I only see disatvantages in most of the :

• Wireless WiFi band technologies 2.4Ghz (ZigBee also in that range) - In today's environment there sometimes of tens of WiFi network around us, which causes interference you should not necessarily dismiss.
• WiFi specifically is an overkill for simple things like relay module or a simple sensor/switch.
• Z-Wave is fairly good solution, but not all modules can be found in all authorized frequency ranges. That means you cannot use all modules anywhere, plus different frequency modules are not compatible, plus in some countries (like mine) the allowed frequency range is such that there are almost no modules to choose from, let alone central hubs (Like Vera for example)
• KNX-TP Is proprietary and extending it / creating a custom module is basically, not possible..
• X10 - I Have heard it has many reliability issues and if I recall well even read stories where a neighbor X10 device switched on a device in a person house. Security - this is basically a bus shared with your neighbors. I Dislike the idea.
• C-BUS: Again, looks mostly proprietary and relatively low accessibility bus and closed system.
• Ethernet - I do not want to mix my high speed network with the low speed. If this would be the choice, it would have to be separated with the home network.
• Advantage: Existing PoE solution
• Disadvantage, Cannot use Ethernet Bus topology. wires, again would be needed to route to a central location. Although Ethernet is actually a BUS, it is only possible with coaxial cable which then renders PoE not possible.

So what are the needs I see? First for the data transmission I wish for:

• A low speed, reliable, tolerant and Collision-detectable bus with relatively cheaply and accessible hardware
• Option to carry sensor/module power (somewhere from 5-24v) to the endpoints in order not to have a transformer in the module.
• In so that I can implement less common controllers, TV control IR blaster, RGB led strip, alarm/motion sensors, etc.

One of the hardware wire protocols I'm familiarized with is CAN bus/protocol. If you don't know, CAN is a relatively simple, differential(I.E less affected by noise), 2 wire(no ground required) bus+protocol, usually transmitted over Twisted-Pair, used in every car made since the 80's.

CAN bus can be carried over a pair in CAT5/6 STP/UTP Cable, That leaves 3 more pairs that can be used to carry power GND and power voltage.

HAPCAN Is such an open solution, They've made everything open, including hardware schematics and software, Also, interacting with the bus is easy as connecting a CAN-enabled microcontroller to it. (Such as the Teensy 3.1/3.2, that has build-in can controller) or a CAN module to any microcontroller, Also PC's could be interfaced with CAN-USB adapters available for purchase.

This is an interesting project, I still have one issue with it, although different modules are decentralized, The switching and power transmission is done in the electrical box, this means that all High mains-supply voltage smart-consumer, should be wired independently to the electrical box. Which overheads in electrical box room and tens of meters of wiring.

BTW, Some of the above technologies also requires wiring mains back to electrical box for each 

KNX and ZigBee (sometimes, depends on the module).