Wednesday, 17 October 2012

Home Automation Network

The first project, one that I've wanted to do for a long time, is a home automation network.  I look around the house and I see a bunch of systems that while useful by themselves, could be more useful if they were integrated and could communicate with each other.
For example - the security system uses IR sensors all around the house - wouldn't it be good if I could use them to tell if a room was unoccupied, so I could turn off the lights and save some electricity?
The plumbing 'network' knows when the kids have been in the shower for too long, wouldn't it be good to sound a warning, and then maybe even cut the hot water off if they go over some limit that I set?
The idea of the HA network (like many others before it) is to connect these systems together in a useful way, so that they can interact, and I can control them either automatically, or from anywhere in the house.
I have had some limited experience with using X10 to control some lights and applicances by remote control, and from the computer.  Unfortunately the 'WinPlus' line of X10 devices that I picked up from Bunnings, and also was given some stuff from a mate, seems to be particuarly dodgy - and every one of the X10/RF transceivers that I have has since failed.  While X10 itself is a fairly old technology, it should still be a little more reliable than this!
Commercial systems such as C-Bus cost an arm and a leg - and while I'm not ruling out the possible use of some C-bus components later in time, it is not a consideration at this point.
Switching into systems engineer mode for a while, I have the following high-level requirements
  • The network shall provide the capability to monitor environmental conditions (temperature, humidity, light level, air quality throughout the house
  • The network shall be capable of operating in degraded mode when some features are unavailable
  • The network shall be capable of being operated remotely
  • The network shall log routine and exceptional events for later review
  • The network shall provide control over sound (music/paging) throughout the house and outside areas
  • The network shall provide the following information to household members, by a wall mounted display, audio, or other means:
  • Environmental conditions (room temperature, outside temperature, weather forecast)
  • Users of the network shall have the capability to define time and/or date alarms for certain events during the day e.g. wakeup, bedtime, chores reminder (take the garbage out)
  • The network shall provide for control over lighting
  • The network shall provide for control over air conditioning (split system heating/cooling, and evaporative cooling)
  • Environmental control shall make recommendations on which system is most appropriate for the current environmental conditions, as well as advising on opening/closing windows/blinds where suitable.
  • The network shall provide basic control over room lighting - initial capability is for LED 'night lights'in rooms, to later expand to general room lighting.
  • The network shall be efficient - using a minimum of electrical power where possible
  • The network shall be cheap - using self-built devices where needed
  • The network shall be expandable
  • The network shall be reliable
  • The network shall be secure from external attack via wired or wireless means
  • The system shall be capable of being used with minimal training.

Next level down is design, and here are some design goals
  • Wired technology is still cheaper than wireless and also solves the problem of how to power everything and not be replacing batteries or putting things on charge all the time.
  • Wireless technology is suitable for low data rate period comms such as a remote temperature sensor, water tank level sensor, or for occasional remote control (eg wifi/bluetooth)
  • The main bus will use RS485 in a multi-drop mode, and ATMega 8-bit micro controllers for small nodes
  • The system will interface to the extant MRX multi-room audio system
  • The system will interface to the extant NX8 security system
  • The system will use the extant house file server/media centre/mp3 server for high level functions and storage
Thats all for now but I will try and turn this into a more structured document and make it available from here for anyone who is interested.

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