智能家居是如何工作的？
How Smart Homes Work
BY MOLLY EDMONDS & NATHAN CHANDLER
When you're not home, nagging little doubts can start to crowd your mind. Did I turn the coffee maker off? Did I set the security alarm? Are the kids doing their homework or watching television?
With a smart home, you could quiet all of these worries with a quick glance at your smartphone or tablet. You could connect the devices and appliances in your home so they can communicate with each other and with you.
When you're not home, nagging little doubts can start to crowd your mind. Did I turn the coffee maker off? Did I set the security alarm? Are the kids doing their homework or watching television?
With a smart home, you could quiet all of these worries with a quick glance at your smartphone or tablet. You could connect the devices and appliances in your home so they can communicate with each other and with you.
Smart Home Software and Technology
Home automation has a long and fitful history. For many years, tech trends have come and gone, but one of the first companies to find success is still around.
The genesis of many smart home products was 1975, when a company in Scotland developed X10. X10 allows compatible products to talk to each other over the already existing electrical wires of a home. All the appliances and devices are receivers, and the means of controlling the system, such as remote controls or keypads, are transmitters. If you want to turn off a lamp in another room, the transmitter will issue a message in numerical code that includes the following:
An alert to the system that it's issuing a command,
An identifying unit number for the device that should receive the command and
A code that contains the actual command, such as "turn off."
All of this is designed to happen in less than a second, but X10 does have some limitations. Communicating over electrical lines is not always reliable because the lines get "noisy" from powering other devices. An X10 device could interpret electronic interference as a command and react, or it might not receive the command at all.
While X10 devices are still around, other technologies have emerged to compete for your home networking dollar. Instead of going through the power lines, many new systems use radio waves to communicate. That's how BlueTooth, WiFi and cell phone signals operate.
Two of the most prominent radio networks in home automation are ZigBee and Z-Wave. Both of these technologies are mesh networks, meaning there's more than one way for the message to get to its destination.
Z-Wave uses a Source Routing Algorithm to determine the fastest route for messages. Each Z-Wave device is embedded with a code, and when the device is plugged into the system, the network controller recognizes the code, determines its location and adds it to the network. When a command comes through, the controller uses the algorithm to determine how the message should be sent. Because this routing can take up a lot of memory on a network, Z-Wave has developed a hierarchy between devices: Some controllers initiate messages, and some are "slaves," which means they can only carry and respond to messages.
ZigBee's name illustrates the mesh networking concept because messages from the transmitter zigzag like bees, looking for the best path to the receiver. While Z-Wave uses a proprietary technology for operating its system, ZigBee's platform is based on the standard set by the Institute for Electrical and Electronics Engineers (IEEE) for wireless personal networks. This means any company can build a ZigBee-compatible product without paying licensing fees for the technology behind it, which may eventually give ZigBee an advantage in the marketplace. Like Z-Wave, ZigBee has fully functional devices (or those that route the message) and reduced function devices (or those that don't).
Using a wireless network provides more flexibility for placing devices, but like electrical lines, they might have interference. Insteon offers a way for your home network to communicate over both electrical wires and radio waves, making it a dual-mesh network. If the message isn't getting through on one platform, it will try the other. Instead of routing the message, an Insteon device will broadcast the message, and all devices pick up the message and broadcast it until the command is performed. The devices act like peers, as opposed to one serving as an instigator and another as a receptor. This means that the more Insteon devices that are installed on a network, the stronger the message will be.
Setting Up a Smart Home
X10, Insteon, ZigBee and Z-Wave provide only the fundamental technology, called protocols, for smart home communication. They've created alliances with electronics manufacturers who actually build the end-user devices. Here are some examples of smart home products and their functions.
Cameras will track your home's exterior even if it's pitch-black outside.
You can control a thermostat from your bed, the airport, anywhere your smartphone has a signal.
LED lights let you program color and brightness right from your smartphone.
Motion sensors will send an alert when there's motion around your house, and they can even tell the difference between pets and burglars.
Smartphone integration lets you turn lights and appliances on or off from your mobile device.
Door locks and garage doors can open automatically as your smartphone approaches.
Auto alerts from your security system will immediately go to your smartphone, so you instantly know if there's a problem at home.
Many devices also come with built-in web servers that allow you to access their information online.
These products are available at home improvement stores, electronics stores, from installation technicians or online. Before buying, check to see what technology is associated with the product. Products using the same technology should work together despite different manufacturers, but connecting an X10 and a Z-Wave product requires a bridging device, and often, extreme patience and some technical skills on your part.
In designing a smart home, you can do as much or as little home automation as you want. For starters, it may be best to think of tasks you already routinely do and then find a way to automate them.
You could begin with a lighting starter kit and add on security devices later. If you want to start with a more expansive system with many features, it's a good idea to carefully design how the home will work, particularly if rewiring or renovation will be required. In addition, you'll want to strategically place the nodes of the wireless networks so that they have a good routing range.
About 60 percent of homebuilders who have installed home automation devices hired professional help [source: Regan]. If you're looking for a technician, check if they have CEA-CompTIA certification. This certification is the result of a partnership between the Consumer Electronics Association (CEA) and the Computing Technology Industry Association (CompTIA), and it represents proficiency in installing, maintaining and troubleshooting any vendor's home networking equipment.
The cost of a smart home varies depending on how smart the home is. One builder estimates that his clients spend between $10,000 and $250,000 for sophisticated systems [source: McKay]. If you build the smart home gradually, starting with a basic lighting system, it might only be a few hundred dollars. A more sophisticated system will be tens of thousands of dollars, and elements of home theater systems raise the cost of a system about 50 percent [source: Gloede].
Smart Home Benefits
Smart homes may make life easier and more convenient. Who wouldn't love being able to control lighting, entertainment and temperature from their couch? Whether you're at work or on vacation, the smart home will alert you to what's going on, and security systems can be built to provide an immense amount of help in an emergency. For example, not only would a resident be woken with notification of a fire alarm, the smart home would also unlock doors, dial the fire department and light the path to safety.
Here are a few more examples of cool smart home tricks:
Light a path for nighttime bathroom trips.
unlock your door automatically as you approach.
Feed your pets on a schedule with a preset amount of food.
Instantly create mood lighting for any occasion.
Program your television so that your children can watch only at certain times.
Warm the bedroom before you get out of bed so that it's nice and toasty when you get up.
Turn on the coffee maker from bed.
Smart homes also provide some energy efficiency savings. Because systems like Z-Wave and ZigBee put some devices at a reduced level of functionality, they can go to sleep and wake up when commands are given. Electric bills go down when lights are automatically turned off in empty rooms, and rooms can be heated or cooled based on who's there at any given moment. One homeowner boasted that her heating bill was about one-third less than a same-sized normal home [source: Kassim]. Some devices can track how much energy each appliance is using and command power hogs to use less.
Smart home technology promises tremendous benefits for elderly people living alone. A smart home could notify the resident when it's time to take medicine, alert the hospital if the resident falls and track how much the resident is eating. If an elderly person is a little forgetful, the smart home could perform tasks such as shutting off the water before a tub overflow or turning off the oven if the cook had wandered away. One builder estimates that a system like this could cost $20,000, which is less expensive than a full-time nursing home [source: Venkatesh]. It also allows adult children who might live elsewhere to participate in the care of their aging parent. Easy-to-control automated systems would provide similar benefits to those with disabilities or a limited range of movement.
Intelligent Products Galore
Home automation systems have struggled to find a mainstream audience, in part because they require a bit of technical savvy from their users. But these days, the fast proliferations of smartphones and tablets provide an easy way for even tech novices to communicate with home automation gadgets. And those gadgets are more numerous by the day.
The Nest thermostat comes with integrated WiFi so that you can control, schedule and monitor your home's temperatures, from the porch or from a taxi. Nest learns your behaviors and automatically adjusts its settings for maximum efficiency and comfort. It will tell you how much energy you're using, remind you to change your filters, and even alter its functions to account for the differences between, say, a heat pump or radiant heaters.
Philips' Hue lights offer some concert lighting effects right in your own home. Screw these LED bulbs into your regular fixtures, install the app to your phone or tablet, and then you can turn the lights on or off, brighten or dim them, or perhaps best of all, change the color. Then you can even program the lights to perform just about any combination of color and brightness, and control up to 50 lights on one bridge (which links the lights to your phone). The more lights you have the more fun it will be. But it will cost you -- a starter pack with three bulbs and a bridge goes for around $200.
Efficiency and Fun
Belkin markets its WeMo home automation switches specifically to smartphone users. For about $100, you'll receive a smart WeMo switch and a motion detector. Plug the switch into an electrical outlet, and then plug a device, such as a lamp, heater or coffee pot into the switch. Pair the switch with your smartphone using Belkin's app, and then you can control the switch remotely, letting you, for example, turn a light on or off from 1,000 miles away (or just from your cozy bed).
Home automation isn't always about pricey products. Some of the most useful smart home tools are actually free.
The WeMo is one of many products compatible with IFTTT (IF Then, Then That), which is a free Internet service that lets you automate an endless number of processes. For example, with IFTTT (which rhymes with gift), you could create a so-called "recipe" that automatically posts Twitter tweets to Facebook if they contain a specific hashtag or keyword in them. Or you could schedule a text message to yourself as a reminder to call your grandma.
IFTTT is basically just a simple way to create triggers that result in specific actions, and it works with WeMo. For instance, you could set up a WeMo motion detector in your bedroom, and when it sees that you're up for the morning, it will trigger the coffee pot in the kitchen.
The potential for these kinds of "if x, then y" type of actions is limited only by your imagination. Of course, it takes some time to set up all of these fun actions. And that brings up one of the biggest challenges of home automation products.
Many smart home products use their own proprietary apps. In short, you could install dozens of home automation gadgets and their associated apps, and then slowly drown in frustration as you try to control all of them.
The Revolv is a $299 WiFi hub that connects to all of your other wireless home automation products. Revolv attempts to unify all of your home automation gear under one app, and also helps you build pre-programmed capabilities, all in the name of realizing a truly automated home.
Once connected, you control all of your gadgets from the central Revolv app. Revolv currently works best with Z-Wave, Insteon and WiFi products, and it's available only for iPhone users. However, the company plans to expand to hundreds of other products and to add Android compatibility, too. You'll find similar consolidation hubs from companies such as Insteon and SmartThings.
Smart Home Challenges
A smart home probably sounds like a nightmare to those people not comfortable with computers. Those who routinely fumble around with a remote control just trying to change the TV channel might have stopped reading by now.
One of the primary mental blocks of installing a smart home system is balancing the complexity of the system against the usability of the system. If it's downright exasperating, then it's actually making your life harder instead of easier. When planning the system, it's important to consider a few factors:
What kinds of components are part of the system? Are they basic, such a light dimmer, or more imposing, like an alarm system or a video camera?
How intuitive will the system be to a non-user?
Is the device actually fulfilling a need or is it just a fancy and potentially frustrating toy?
How many people will be required to use the system?
Who will know how to operate the system? Who will know how to maintain the system and address failures?
How easy is it to make changes to the interface? For example, if your house is programmed to wake you up at 7 a.m., how will you let it know that you're away overnight on business or sleeping in on a Saturday?
For these reasons, it may be easier to start with a very basic home network and expand as enhancements are needed or desired. Like many new technologies, smart homes require a significant investment in both cash and time to keep up, so if you're short on either, you may want to stick with your "dumb" old house.
Before you buy, check product reviews and avoid those that draw the ire of users. There are plenty of products making sky-high promises that fall flat in the real world. And if you're a smartphone user, strongly consider products that come with an equally well-reviewed smartphone app. Some apps are so unwieldy or convoluted that they cause more headaches than they relieve.
Smart homes also come with some security concerns. Hackers who find a way to access the network may have the ability to turn off alarm systems and lights, leaving the home vulnerable to a break-in. They could also cause mischief like turning devices on and off rapidly, which could ruin some electronics or -- in an extreme case -- possibly cause a fire.
Consumer electronics manufacturers are ramping up their product lines in the hope that home automation finally hits the mainstream. Thanks to smartphones and tablets, and the many home automation apps that are now available, there's a chance the trend will catch on ... but a full-on Jetson's-style home may still be years or decades off.
That's because, in spite of so many technological advances, there's still no standard system for automating all of these gadgets. Without such a standard, many consumers are left wondering if they're spending hundreds or thousands of dollars on products that will wind up obsolete or unusable in a short time.