Industry insiders once hailed home automation as the proverbial “next big thing.” Who wouldn't be excited by such far-out possibilities as a refrigerator that could tell when your milk supply was running low and send a wireless message to your PDA to pick up another gallon? Once the “gee whiz” factor wore off, though, the impracticality of such systems placed into question the likelihood of their implementation. Yet the booming structured wiring industry and the popularity of wired home installations has made possible other less futuristic home automation applications like lighting, water, and access control. As the fifth installment in a 12-part series that will prepare electrical contractors to take the test to be certified as home technology integrators (HTI), this article will explain the design, component selection, and implementation of various automation systems that can work together to improve a home's comforts.
Automation systems use power line carrier technology to control several subsystems in one residence. The most common types of automation systems are X-10 and CEBus for controlling lighting systems, and RS-485 and RS-232 for HVAC applications.
X-10 systems send commands to individual devices by modulating the 60 Hz AC electrical waveform. X-10 sensors and switches can report their status back to the control program, allowing for complex conditional control sequences and status reports. Such a system requires no additional wiring and is largely software-based, but DIP switches may be necessary for additional control.
Consumer Electronic Bus (CEBus) is also a software-driven system that uses modulated household AC waveforms to control individual devices. Each device in a CEBus system must have a registered unique address so that it can be easily identified.
It's also important to note that household devices from vacuum cleaners to intercoms can interfere with both CEBus and X-10 technology.
RS-485 systems are based on an upgrade to the EIA/TIA RS-422 standard used to extend serial communications as far as 4,000 ft between two devices. Systems based on RS-422 carry a differential signal on a twisted-pair wire that rejects common mode noise. RS-485 systems, on the other hand, use either a 2-wire or 4-wire system, both of which also need a ground wire. Each device in a 2-wire system, including the transmitter of the main controller, is normally in the receive mode, so it must wait until the transmission is finished before responding. In a 4-wire system, each device is connected to the transmitter and receiver of the main controller and may respond only to commands addressed to it. The device can respond to any request immediately, even while receiving the request.
Whereas standard light switches and dimmers control lights in the room in which they're located, control systems can be set up to control lights anywhere in the house. Lighting control systems consist of five major components: the central control unit, receivers, motion sensors, user controls, and scene controls.
X-10 systems allow you to use an automation computer or a PC that runs home control software as the central control unit. The unit sends commands to receivers spread throughout the home to create lighting scenes and provide automatic on, off, and dim and brighten control for all lighting devices connected to the system. Lights can still be manually controlled from each individual control station.
Dimmers, switches, and receptacles are examples of receivers that carry out commands sent to them by the central control unit. The lighting devices can also be affixed with infrared receivers that can be wall-mounted or ceiling-mounted.
Motion detectors use ultrasonic sound transceivers or infrared change sensors to detect movement. The transmitter of one shouldn't directly face the receiver of another.
Traditional lighting user controls are hard-wired but can be supplemented by radio-frequency (RF) and infrared (IR) handheld controllers. Some touch panels can fit into a standard wall plate opening. Multiple lighting circuits may also be controlled by large multi-switch wall plates. Each switch, button, or slider controls one or more scenes, or pre-set combinations of lights and light levels. The scene controller can send commands for six scenes to as many as 20 scene-capable dimmers per circuit.
When planning a lighting control system, you must address its layout. Lighting control systems that use X-10 architecture don't require control-specific wiring or cabling. Each control has its own unique address. It's controlled by direct input switches or by automated software using wall switches or remote control devices.
Several control mechanisms, such as RS-485, use a home-run design, in which cables from each control module run directly back to the central computer's location. Other lighting control systems depend on a dedicated cable for passing messages.
In addition to lighting control, all major home automation architectures include control commands and remote activation modules that interface with furnaces, air-conditioners, and heat pumps. For example, dampers open and close to regulate airflow. Some are normally closed and must be powered to open, and some are normally open and must have power to close. On some systems, the dampers are set to open and close gradually.
There are two stages to a heating and cooling system. Single-stage systems have one level of heating or cooling, and dual-stage systems have two levels of heating or cooling. Each stage of the heating and cooling system requires a control relay for proper operation, so the controlling system might need as many as four control relays for both heating and cooling.
HVAC sensors, commonly called thermostats, tend to be located in central airflow locations in non-automated residential settings. The thermostat controller is typically placed about 5 ft off the ground and away from environmental factors that could affect its temperature readings. Automated HVAC systems combine zoned airflow with programmable controllers to regulate temperature in the different rooms. The HVAC central automation control unit should be placed in the structured media center and connected using RS-232 architecture.
HVAC system devices communicate with a variety of four-, five-, and six-wire architectures. As with lighting control, HVAC control uses a home-run configuration that employs low-voltage cables to connect all devices in the system, such as sensors and thermostats. Thermostats can even be Ethernet-enabled, allowing Web browser control.
Water control systems are designed to save energy and protect homeowners by regulating temperature and flow at sinks, lavatories, and tubs. To accomplish these functions, control units that communicate with the hot water heater are placed at the point of application to provide water at pre-determined times and temperatures.
The most important configuration is the output water temperature at faucets. Water temperatures should typically be limited to 120° to reduce the chances of accidental scalding. However, when hotter water is required, the system can raise the water temperature. For example, under automated control, dishwashers can be scheduled to run late at night when it's safer to program the hot water heater for a higher temperature, then reset to the safer temperatures after the wash cycle is complete. Each faucet can also receive pre-determined and thermostatically controlled water.
Water systems typically communicate over two- or four-wire systems using RS-232. Control panels for spas and whirlpools must be located safely away from running water, typically near the lighting control for the spa area. Wireless remote control is a popular option for installations like spas and whirlpools because they offer a convenient, low-voltage solution.
One necessary addition found in standard plumbing is the electrical service required for the control electronics and valve actuation. You should check local electrical codes for requirements of electrical service in close proximity to running water and plan for ground fault circuit interrupters (GFCIs) as required. Article 680 of the NEC outlines the requirements that apply to the construction and installation of electrical wiring and equipment in or adjacent to pools, fountains, tubs, and spas.
Access systems will require entry activation devices like electrically operated strike plates for gates, doors, and garage doors. These entry control devices may be activated by standard keys, touch pads, magnetic identification keys, or remote-control units attached to the user's key chain.
Access control stations can be broken down into three categories. Locking mechanisms are usually located at the points of entrance to the building. Monitoring controls are located where users would like to get information on the residence. And function controls are usually located at the distribution panel.
Sensor switches used in access control systems are installed in normally closed (NC) or normally open (NO) configurations. The sensor switch contacts in an NC system are connected when the system is armed. In this configuration, the opening of an NC device will set off an alarm. If you're working with an NO system, the closing of a sensor switch contact will set off an alarm. A two-wire layout is sufficient when the only communications necessary is an “open” or “closed” signal. Closed-circuit television cameras (CCTV) are an exception to the two-wire communications rule because they require either coaxial video cable (RG-8) or Cat 5.
RF links have become popular as well, especially in retrofit or renovation installations. RF networking often makes use of the IEEE 802.11b wireless Ethernet standard, which designates the 2.4 GHz ISM (Industrial, Scientific, and Medical) band. There are, however, security issues to be considered when using wireless signals to deny access to the network by outsiders.
A host of other miscellaneous type control systems can be found in today's automated home. Home run cables are used to connect the rest of these miscellaneous devices, such as ceiling fan and window shade controls, to a central wiring closet. Some systems, such as the X-10, won't require any additional wiring, but it will be imperative to avoid electrical circuits with heavy motors and lighting ballast loads.
With the help of handheld remote control units, these miscellaneous control systems allow users to do things like control the flame intensity of their gas-powered fireplaces without leaving the comfort of their chair. Fireplace controls can also be made part of an overall home automation panel and set as part of overall “scenes” defined by the home technology integrator (HTI) that combine lighting levels, fireplace intensity, water fountain activity, and shade extension. When considered as part of overall room control, fireplace controls should be incorporated into full-house control panels located at room entrances or, increasingly, in wireless remote-control units.
Ceiling fan controls have also moved beyond the simple wall switch. They may be either wall-mounted or handheld. Hand-held fan remote units tend to be simple, with few controls beyond those for the fan speed and any lighting that may be built into the fan.
Window shades may be controlled individually or as part of lighting scenes designed to better facilitate movie or television viewing. Shade controls can also be used to help maintain a cool temperature in the house by shutting out the sun. Windows in many new homes will be installed high in the ceiling for light, and electronic controls will operate the shades. These systems are controlled through a combination of wall-mounted switches, keypads, and handheld remote control devices.
Individual remote control units and wall switches may work well if there is a single fan, or if the homeowner hasn't decided on full-house automation. For more involved or complete home automation situations, the sheer number of controls can become unwieldy if they aren't combined into a single system.
Pulling it all together.
The central home automation system can eliminate remotes and allow users to combine several systems into a whole-house solution. Configuration of miscellaneous systems in the automated home often means coordinating their activities with lighting levels, water activity, or access control. Proper sequencing of controlled actions is crucial to avoid conflicting combinations, such as a room monitored by an infrared security sensor and heated by a fireplace that radiates varying levels of infrared energy into the room. Much of the configuration work on these systems involves integration that ensures the command set required by one device will be understood by another.
As the number of systems placed under total control grows, it becomes more important for you to ensure that one component isn't affected by unintentional interference from another. Care must also be taken when electric motors or lights with ballasts, such as fluorescent or halogen lamps, are placed in a circuit with controlled devices.
Testing the system and creating documentation.
When the installation is complete, test each subsystem and then the entire system. In the case of lights, make sure that every level, from “off” to “fully powered,” is tested. Test access system components to ensure that each sensor and contact provides the expected input, in the expected manner, when it's activated. This level of testing is especially important for HVAC controls, where incorrect control input can cause damage to compressors and dampers; and for access systems, in which incorrect input can threaten the safety of the residents or result in fines from excessive false alarms.
A key piece of a complete documentation kit is a plan view of the system that provides a visual of how all the components are connected (Fig. 1). In addition, a signal flow diagram will help you document how the devices communicate.
A complete plan for the layout of all equipment used in an automation system is also required. It will be necessary for any local Code-mandated inspections. Any complete plan must begin with a description of all symbols that adhere as closely as possible to accepted architectural standards, and it must include accurate scale renderings of the space with the placement of each component. All relevant architectural details must be shown. The equipment placement diagram or blueprint is the place to note any special structural or electrical requirements for installation.
Organize and provide all commands and functions, all necessary user intervention to correct malfunctions, block diagrams, blueprints, and manufacturer literature on each component.
Today's homes may not be equipped with all of the home automation gadgets and gizmos once predicted, but more homeowners are hiring HTIs to install a selection of such systems in their homes. By future-proofing their homes with structured wiring or using power-line carrier technology, they can enjoy the benefits of a home automation system…and create work for you in the process.
Dusthimer is publisher of Cisco Learning Institute Press, York, Pa.
Sidebar: Who Wants to Be an HTI?
Electrical contractors can now become certified as home technology integrators (HTI). CompTIA, in conjunction with the Internet Home Alliance and a cornerstone committee of Fortune 1,000 companies, has developed a two-exam certification process. The material in this 12-part series is part of a 50-hr training program designed to prepare individuals to take the HTI+ certification exam. Throughout the year, the articles in this series will include excerpts from the HTI+ training program developed by the Cisco Learning Institute along with industry partners Leviton Manufacturing, HAI, Premise, Interlogic, and Bluevolt. This program will prepare electrical contractors and their employees to capitalize on this new and financially rewarding segment of the field.