Centralized vs. Distributed Control
The control and intelligence of a home automation system does NOT have
to be totally centralized. On the contrary, even the most sophisticated
home automation systems take advantage of "smart" equipment whenever practical.
For example, a programmable VCR has built-in intelligence that a home automation
system can access by sending it standardized commands via an infrared or
Besides taking advantage of the preprogrammed intelligent functions
of certain connected devices, some home automation systems might allow
you to send additional commands to those devices to override or modify
their preprogrammed functions. This type of capability expands the role
of the home automation system to include what could be called "intelligence
Of course, there are many equipment items that have no intelligence
of their own whatsoever. These devices, such as lamps, rely totally on
the intelligence of the home automation system controller(s) for any automated
Whenever practical, home automation systems should have at least one
central controller, such as a personal computer or a dedicated system computer,
where all control functions and programming features are available (with
the exception of certain intelligent device functions that can only be
programmed at the device itself). If this were the only controller in the
system, the system could be described as totally centralized.
However, for user convenience you will usually want to distribute some
of the control and intelligence. For example, you could install control
keypads in several rooms. These keypads could be "smart" keypads that provide
a subset of the central controller's capabilities, or they could be "dumb"
keypads that function only as a user interface for the central controller.
They could also be a combination of the two, with enough on-board intelligence
to provide certain basic functions and still function as a user interface
to the central controller for handling more complex tasks. They could also
provide certain backup functions if the central controller broke down.
Another example of distributed control would be the use of an intelligent
thermostat. Even if you could program the heating and air conditioning
system from a central location, it would still be convenient for a user
to be able to override the settings from the central controller and change
thermostat temperature by simply pressing a button at the thermostat, rather
than going through a sequence of keystrokes at a generic control keypad
or having to walk into another room or start a computer program to make
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Real-Time vs. Programmed Control
Control commands can be sent directly by the user (real-time control) or
by a software or firmware program running on a controller (programmed control).
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In its simplest form, a home automation system allows you to execute real-time
commands to control equipment in your home. For example, a simple home
automation system might allow you to touch a few buttons on a wall-mounted
panel to lower the lights, close the drapes, turn up the audio volume,
and lock the front door.
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The next step up in home automation systems allows you to program events
to take place at scheduled times or in certain sequences. For example,
you could program a system so that at a specific time the living room lights
would dim, the blinds would close, and the television would switch on and
tune in a specific program.
A control program can be a custom software program written especially
for you, a pre-written program that you cannot change, or a pre-written
program that allows you to change various operating parameters, allowing
flexibility without requiring you to be a programmer.
The program may be run from a disk or CD, or it may be programmed into
a chip in the controller. Some controllers may use both types.
To add even more power to home automation systems, some systems allow
you to program events to take place when certain conditions are satisfied.
To do this, you need system components that can provide feedback to the
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