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Controlled Devices

Sensing Devices

I/O Interface Devices

Controllers

User Interfaces

System Network

Programming Computer

Components of an Automation System

The components of a home automation system can be broken down into several categories. Click on the menu on the left side of this page to see them.

Controlled Devices

Controlled devices include the tremendous range of equipment that a home automation system is capable of controlling. They include household appliances, door openers, power door locks, sprinkling systems, lighting systems, HVAC systems, audio/video systems, home theater equipment, power drapes, security systems, telephone systems, intercoms, messaging systems, information systems, and many other types of equipment. There are far too many types of devices to list here.

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Sensing Devices

Sensing devices can report values, such as temperature, humidity, light levels, sound levels, etc., or states (such as on, off, open, closed, etc.). The signals sent by sensors are converted into data that can be displayed to the user or used by a controller program to make informed decisions based on certain conditions. The signals can be converted at the sensor itself, if it has the appropriate circuitry, by an intermediate protocol converter (translater) or by the system controller. This data is a form of feedback.

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I/0 Interface Devices

I/O (input/output) interface devices provide the logical communication link between the controller(s) and the controlled devices in a system. They are the means of making various devices compatible with the physical and logical structure of the system. I/O interface devices may be separate equipment items, or they may be built in to a controlled device, in which case it would just be considered a feature of the controlled device rather than a separate equipment item.

Many equipment items that are typically part of home automation systems come with some kind of built-in industry-standard control interface. For example, VCRs, TVs, home theater, and audio equipment may have either infrared or serial interfaces, or both. Most use standardized protocols that allow remote controls from many manufacturers to interact with them.

Some controlled devices require optional or third party I/O interface devices that allow those devices to be integrated into the home automation system. Lighting equipment can be controlled with a variety of proprietary or third party dimmers or switches that have built-in I/O capabilities. Other equipment items that are less commonly used in home automation systems may require the use of "generic" I/O interface devices. As an example, to control a coffee maker, you would need some kind of generic on/off switch device with its own I/O interface. To control a reversible irrigation pump, you might need a two-relay device with its own I/O interface.

Most I/O interface devices provide one-way communications from the controller(s) to the controlled devices, although there are some types, such as RS-232 interfaces, which allow two-way communications. An example would be a smart thermostat with a built-in RS-232 interface.

An I/O interface device can serve several communications functions, including:

Converting analog signals to digital signals that can be used by the controller. This would, for example, convert the analog voltage from a thermocouple (temperature sensor) to a digital signal that could be used by the controller. Converting signals from the controller to a physical and logical form that can be received and understood by the controlled devices. Converting commands from the controller into a different set of commands that a controlled device understands. System interface devices have varying amount of built-in intelligence. For example, you might have a specialized I/O interface device that receives standardized commands from a central controller, translates those commands into a new set of commands that is understood by the device it is designed to control, and transmits those commands in the correct form and syntax to the device. This kind of "smart" device may sound like a combination of a controlled device and a controller, but it is more appropriate to call it an I/O interface device. Still another type of system interface device would be a dimmer. The dimmer would interpret the commands from the system and raise or lower lighting levels accordingly.

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Controllers

Controllers provide the intelligent control functions in a home automation system. They can range from a simple lamp timer unit to a smart keypad to a powerful computer. Controllers include any intelligent device capable of sending commands that are understood by the controlled devices.

The control functions may be contained in a single central controller, or there may be other controllers besides the central controller that have a limited subset of control functions.

All controllers must have sufficient data in order to control the controlled devices. Data can come from user input, sensor input, a timer, a control program, or some combination of these. To obtain user input, the system must have one or more user interfaces.

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User Interfaces

User interfaces allow the user to interact with the system by sending information to the controller or by presenting information to the user about the system. The form and capabilities vary widely. Depending on the system and the type of user interface, you could do any or all of the following:

Issue direct commands to the system (such as "turn on the kitchen lights"). Obtain feedback from the system (such as the temperature of the bedroom, via a thermostat). Program the controller to carry out certain functions automatically, based on time, sequence, or conditions. Some controllers may have an integral user interface (like the keyboard on a computer), or there may be remotely located user interfaces with varying degrees of built-in intelligence (such as wall-mounted or hand-held keypads or touch panels). A dumb keypad is only used as a remote user input for a controller. A smart keypad might function as a remote user interface for a controller, but also could have enough on-board intelligence to issue its own commands to certain controlled devices; hence it could function as both user interface and controller.

Similarly, a user interface device does not have to be entirely devoted to user input and/or feedback. For example, a keypad might incorporate a temperature sensor or a light dimmer and a microphone for use with an intercom system within the same physical enclosure.

A user interface may accept a variety of user input types. Keystrokes or button presses are the most common modes of entering data, but some systems may accept voice input or other forms of communication.

Not all controllers have a "user" interface. Some specialized controllers may simply use input from sensors (or other equipment), and programming to make intelligent decisions based on that input.

Typical user interface devices include:

Most high-level home automation systems are hybrid systems, using a variety of user interface devices, each suited to certain tasks. For example, some systems might allow you to carry out all control, programming, and feedback functions from a personal computer, but might limit the number of functions available from a hand-held remote control unit or a wall-mounted push-button LCD panel.

Don't confuse user interfaces with sensors. Even though there can be some overlap in function (both can accept "input" from a user), for the purposes of this discussion, a user interface is designed to provide a means of conscious, intentional interaction with the system. For example, a home automation system might use an infrared motion sensor to determine when you enter a room and automatically send the equivalent of a button press to turn on the room lights or to trigger a whole sequence of events, but it is something that happens automatically, without any conscious choice on the part of the user.

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System Network

The system network includes all of the controllers, sensors, wires, cables, RF (radio frequency) links, IR (infrared) links, adapters, connectors, junction boxes, dimmers, ballasts, power supplies, etc. that connect the various system components. This might sound like the simplest part of the system, but it can actually get quite complex. In many systems, this is the area that requires the most planning and can be the most labor-intensive part of a total system installation.

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Programming Computer

Some system controllers allow the user to program the system with the system's own user interface(s). Other systems require the use of a separate computer (typically a PC) to program the system controller. Still others may allow certain functions to be programmed with the system's own user interface(s), but require a separate computer to program the more advanced functions or change certain basic operating parameters.

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