Apress - Smart Home Automation with Linux (2010)- P29 pps

CHAPTER 4 ■ HOME IS HOME 118 Having a primary server generally requires it to remain switched on 24/7. Centralizing the tasks to a single location and unifying all the services onto a single machine means that only the Node0 machine requires protection from power outages (via a UPS) or theft (via a strong lock). Indeed, the data most at risk is usually on stand-alone laptops, so I’ll cover backup plans for them later too. Determining the Best Room Even the humblest of abodes has several locations suitable as Node0. Most people choose the closet under the stairs (since it’s central and therefore requires less wiring), but there’s more to it than that! In fact, while reading the next section, you are expected to mentally move the server from one room to another as each problem or solution presents itself. Furthermore, in some cases, it’s not physically possible to find one room that can solve all of the particular problems, in which case you may have to drop the offending feature or use a second server in a separate location. Lawful Considerations Laws vary according to country and change over time, so it is important to take the necessary advice and acquire any permissions before work is begun. In reality, this affects very few people, such as those who are building new structures on their land (such as sun rooms) or amending buildings that have been granted “graded” or “listed” status. Necessary Considerations The necessary considerations in this section cover the limits of particular pieces of hardware and their interconnects. Since the main server will need full unfettered access to all your equipment, these considerations are of primary importance. X10 signals can dissipate and get swallowed whole by various devices placed around the house, as mentioned in Chapter 1. Moving the Computer-X10 gateway (CM11) to another socket can change its reach quite considerably, so a lot of testing is necessary. Alas, it might not be possible to place the device in any single location that allows the messages to make a complete circuit in both directions around the house. This would subsequently require two servers or two gateways. Ethernet over Power (EoP; not to be confused with Power of Ethernet) is one way of adding two-way networking capabilities using the existing power lines, in the same way that X10 introduces appliance control. Like X10, it is at the mercy of other devices on the power line, so should parts of your home become inaccessible to WiFi, this approach should be tested also. Broadband and cable modems can often enter the house only at a number of predetermined points, thereby limiting the rooms available. It is, however, rarely necessary to have your server connected locally to the modem unless your Linux machine is acting as the gateway to the rest of your home. In most cases, a good router can effectively separate the internal and external network traffic with enough control to make the use of a full-blown PC unnecessary. WiFi signals, like X10, dissipate. Furthermore, since the frequency band used is common to many other protocols, this can cause the connection quality to worsen considerably or disappear altogether. These devices include some wireless access points (such as the United Kingdom’s BT Homehub), wireless phones, TV senders, and microwave ovens. Furthermore, since they travel through the air, they’re more susceptible to external influences outside of your control, such as neighbors. You can limit the effect of these other devices by doing the following: CHAPTER 4 ■ HOME IS HOME 119 • Switching the WiFi channel. Depending on the country, WiFi is split into either 14 (Japan) or 13 (everywhere else) distinct frequency bands with each channel occupying a group of 4 or 5 of these bands. This places channels at midpoints at channels 1, 6, and 11 (for the United States) and 1, 5, 9, and 13 in most other places. • Adding more WiFi base stations to minimize the distance necessary for each signal to travel. When setting this up, set all units to the same SSID, and connect to the same section of wired Ethernet • Switching to wired versions of the offending devices. To determine the offending device, simply turn them off in sequence, and/or point a spectrum analyzer in each direction to determine the source of the transmissions. • Jamming the signal of the offending device (particularly if it originates from someone else). • Using directional transmitters. When using AV distribution to introduce whole house audio, the cable that powers speakers or amplifiers from the main server can affect the location of the server, since every meter of cable increases the chance of external noise affecting the quality of the audio. Also, since this is an analog signal, it will become less powerful if it has to travel farther. Good-quality cable can minimize this. Cat5 cable is the best method of getting fast Ethernet throughout the house because it is not susceptible to the external factors of WiFi or EoP. However, you will need to ensure that you can effectively reach the majority of the house from your Node0 location. Concrete and structural walls have to be considered since it might not be possible to run cables through them. You will also want to have as few network switches as possible en route between server and clients, so the loft or attic might not be the best solution, particularly if you plan on streaming a lot of video to the TV room downstairs. Power is a necessary evil of the system, so any room must have enough power (and be connected to suitable fuses) to allow several hundred watts to be drawn. This is more of an issue for older houses. Negative Effects Computers, even Linux-based ones, aren’t immune to everything, and some rooms are naturally more hostile to electronics than others. Kitchens, conservatories, cellars, and utility rooms are more prone to moisture and humidity than elsewhere. The moisture can cause untold damage to a machine when (not if!) it gets inside the PC case and reacts with the electronics. It should be noted that although humidity isn’t a particular problem for the machine in itself, it will make it sticky, causing it to become a magnet for dust particles that in turn can clog up one of the PC’s fans (there are usually three on most desktop machines: CPU, PSU, and graphics card). The dust can also settle in the various gaps between circuit boards, such as the PCI/AGP cards, making them inoperable. Furthermore, the dust can carry moisture, which, in combination with that present in the water vapor, can cause the various components to rust and degrade, leading to short circuits and general damage. Relative humidity of 45 to 60 percent is generally accepted to be a suitable range, which can be measured with a hygrometer. CHAPTER 4 ■ HOME IS HOME 120 ■ Note Problems with humidity also occur when there are brusque changes in temperature, such as when a machine is brought in from the cold. In this case, leave it to naturally reach room temperature before switching on. Temperature can affect computers to the same detriment as moisture but in different ways. Although most machines can survive cold temperatures (certainly colder than most humans would be happy living in!), they are not as happy with hot temperatures—as the number of fans present will testify—and computers will often automatically shut down if the onboard temperature sensors exceed their limits. This can often eliminate the utility room, and sometimes the loft or attic, as a suitable location. Since the only moving parts in a PC (other than the fans) are the hard disks, it can be necessary to consider their operating temperature. This can vary between drives but is around the 5- to 55-degree Celsius range. Human Considerations The computer is moving into your living space, not vice versa, so once you know the physical limits of your chosen location, you can consider the lifestyle impact of a machine living there. The antisocial elements of PC behavior include noise, lights, and heat. The noise from a standard desktop PC comes from its various fans and the clicking and whirring of the hard disk. Although the fans produce a constant hum that soon disappears into the ambient background noise of your home, the disks make noise occasionally and can be more annoying. If you are used to sleeping in the same room as a PC, then you will appreciate that the fan often becomes a comforting bedfellow, whereby it later becomes difficult to sleep without its companionship. The noise from a hard disk, although slight, has an interesting dual property. Although you (or your partner) might be disturbed by the noises coming from a hard disk somewhere within the house, it can provide a very good audible alert system should you suddenly hear the (normally) quiet hard disks suddenly fire up in the middle of the night. As you’ll see later when looking at server types, some machines are fanless (thereby eliminating most of the noise), and some can work from solid-state devices instead of hard disks (which eliminate all noise). Naturally, the positioning and/or soundproofing of Node0 might make the concept of noise a moot (mute?) point! The lights on most PCs are the simplest form of output interface available. The standard front plate contains lights for power and hard disk activity, while the reverse has the equivalent for network activity, along with the other visible light sources on the motherboard shining through the rear cooling holes. There are similar lights on external hard disks, modems, and routers. The former lights give Node0 a distinct glow of cyber-cool (usually since more technology comes with blue LEDs nowadays!), while the latter creates an annoying flicker that, in the dead of night, is visible in the next room. Although all of these lights can be hidden by black tape, it is usually preferable to hide the units inside a box, cupboard, or drawer so that the diagnostics lights can be reviewed when needed. In addition to being affected by heat, computers (particularly desktop ones) produce heat. And having one on 24/7 can raise the room temperature by 1 or 2 degrees. You will consequently have to consider the other home heating elements and consider whether placing Node0 on the ground floor of CHAPTER 4 ■ HOME IS HOME 121 your house and allowing the heat to rise 1 can provide any reasonable savings on your bills. The downside of this excess heat is that it might get very uncomfortable to work on the machines in Node0 if they’re in an enclosed space that is heating up by the second. Consequently, install only low-energy or fluorescent lights here to prevent it from heating up any further when you’re working on it. Primary Options Given the previous possibilities, most people will consider one of the following rooms: • Living room: By being physical close to the TV and primary stereo system, the living room provides good access for all the media elements of an HA installation. This eliminates the need for IR transmitters and a lot of extra cabling. It’s easily accessible if you plan on using physical DVDs, and if the server is connected directly to the TV and stereo, you get the highest-possible-quality AV. On the downside, however, having your server here can be intrusive to family life (particularly when you are tweaking physical connectors), and you can’t use any server that needs a fan since the noise will often obscure the quieter music and dialogue in films and TV dramas. • Bedroom: This is the first and last place you spend each day, so having the machine on hand, displaying news, videos, e-mails, and so on, can be highly optimal, if slightly unnerving at times. It also has many of the benefits of the living room, since the (master) bedroom is normally home to the second most important TV in the house. Consequently, it can suffer the same problems with noise, in addition to those associated with randomly blinking lights in the night and increased heat. 2 • Under the stairs: This is nicely hidden from view and enclosed, meaning that most noise and light pollution is hidden and therefore acceptable. It is also central to the house, meaning you have shorter cables for the wired protocols (Cat5, X10, audio, and so on) and less chance of interference for the wireless ones. However, in most cases it is difficult to see how and where to get cables (especially power) into and out of the cupboard under the stairs without it being obvious. Additionally, it is usually a very small space, making it prone to temperature rises and difficult to work in—for both the machine and for you when carrying out Node0 maintenance. 1 Technically, hot air is less dense, causing it to rise. 2 It is often recommended that the bedroom be around 2 degrees cooler than other rooms in the house to help your body get to sleep easier. CHAPTER 4 ■ HOME IS HOME 122 • Loft or attic: This is a nice, hidden, and secure location that is highly unlikely to be burgled! It’s also very easy to drop cables into all rooms on the upper floor. (But conversely, it’s less easy for those rooms on the ground floor, unless you decide to run a large trunking all the way down through the ground floor’s ceiling.) As mentioned earlier, getting a suitable amount of power to the loft might be tricky, as could temperature control. Building the Rack The equipment found in a home automation rack is wide and varied and consequently doesn’t usually come in the correct form factor (of pizza-box-sized units) to fit into a rack. But although you might not use a rack in the traditional sense, you should consider some kind of stacking mechanism for your equipment. After all, you should be able to access every piece of kit on an individual basis, because you won’t want to unplug and slide out the router, modem, and switch just to plug in some new toy in the USB socket on the back of the PC! ■ Note You can ensure good access by not filling the entire Node0 space with technology. This also ensures there’s space left for new kit as you acquire them. If you have access to a nearby kitchen DIY store, you can sometimes find drawers and cupboards that can swing through 90 degrees as the door is opened, which can be misappropriated as a good rack mount. Alternatively, if there is a partition wall between the Node0 room and the next, you could mount an access hatch (similar to a kitchen-serving hatch) between the two. For the theatrical readers, you could hide this behind a painting with a secret hinge! The equipment typically found in a Node0 rack includes the following: • Modem • Router • Wireless router • Home alarm system • Phone exchange • Network switch • Main server PC (low power 24/7) • Media server PC (loaded with TV capture cards) • Monitor, keyboard, and mouse (connected to servers through KVM switch) • External hard drives (easier to replace/upgrade than internal and less likely to head crash) . generally accepted to be a suitable range, which can be measured with a hygrometer. CHAPTER 4 ■ HOME IS HOME 120 ■ Note Problems with humidity also occur when there are brusque changes in temperature,. Building the Rack The equipment found in a home automation rack is wide and varied and consequently doesn’t usually come in the correct form factor (of pizza-box-sized units) to fit into a rack. But. modem unless your Linux machine is acting as the gateway to the rest of your home. In most cases, a good router can effectively separate the internal and external network traffic with enough control