Apress - Smart Home Automation with Linux (2010)- P57 ppsx

CHAPTER 7 ■ CONTROL HUBS 263 Figure 7-7. A simple network configuration This allows you to reuse the router as a network switch and employ servers with only one network port, such as the majority of small low-power mini PCs on the market. If this configuration is too limiting, such as when you want to use Linux as the router itself, then you can adopt a configuration like the one shown in Figure 7-8. With this setup, you will need two network cards and a separate network switch. Figure 7-8. Using a Linux server to separate the two network domains CHAPTER 7 ■ CONTROL HUBS 264 In either case, you use a remote server, such as a colocated server or a virtual machine located in a data center, to accept and process all traffic thereby hiding the identity of your home machine. Figure 7-9. Using an external server Wiring Looms Whole-house audio and video with media accessible in every room can happen in one of two primary ways. The first is by using small PCs in each room, connected to the network to decode the audio locally. This is easier to upgrade and allows audio and video data to be streamed and controlled locally with very little effort. It is, however, expensive because of the hardware needed in each room. It is also inconvenient in those cases where you want to move between rooms while watching or listening since you have to manually restart it. 7 The cheapest way of distributing AV data is by running cables to each room. This involves a combination of amplifiers and switchers, as shown in Figure 7-10. 7 The software to manage this is currently minimal to nonexistent. CHAPTER 7 ■ CONTROL HUBS 265 Figure 7-10. A simple AV distribution network In all cases, the generic term of AV is used to refer to audio and/or video data, according to your needs. You will notice that distribution among the rooms upstairs is easier, since the cables can be run up into the attic, across the attic space in any haphazard manner you please, and down into the other rooms. Here there is a single set of AV cables running down the downstairs, giving full control to the living room. The primary limitation with this setup is the single AV channel coming from the Node0 server, meaning that any media not held on Node0 cannot be distributed or used elsewhere. The PVR, for example, can be controlled and viewed only in the living room. This is solved in Figure 7-11. CHAPTER 7 ■ CONTROL HUBS 266 Figure 7-11. Placing all the AV in Node0 In this environment, all the AV equipment is placed physically within Node0, making for short cable runs and easy-to-install IR transmitters. And there is still only a single AV cable to lay into each room wanting media. This is both a benefit, because the installation is much cheaper, and a hindrance, because only the same media can be experienced in each room. This is solved with a matrix switcher, shown in Figure 7-12, which allows any input to be sent to any room. Figure 7-12. The benefits of a matrix switcher Note that in all cases, the placement of the particular amplifiers will be determined by the amps themselves. Some provide two power outputs, allowing all speakers to be passive (that is, unpowered), while others provide only a line-out level requiring an additional amplifier (and therefore power socket) for each room in which they’re installed. CHAPTER 7 ■ CONTROL HUBS 267 Conclusion As you’ve seen with the example using the teakettle, there are comparatively few pieces of software needed to smartly automate a house. Once you can process incoming e-mails or text messages and issue an X10 command, then the task of “e-mailing your teakettle” becomes a simple matter of combining the two scripts in a trivial (almost banal!) fashion. The next level of interest is generated from the usability features and the specificity of function. Usability is something you can add only after living with the configuration for a while—having Festival use speech synthesis to say “the teakettle has boiled” is an easy technological change but is something so uniquely specific that only a geek living in the environment could actualize it with such effortless precision. Make the most of the opportunity. . all traffic thereby hiding the identity of your home machine. Figure 7-9 . Using an external server Wiring Looms Whole-house audio and video with media accessible in every room can happen. is too limiting, such as when you want to use Linux as the router itself, then you can adopt a configuration like the one shown in Figure 7-8 . With this setup, you will need two network cards. Figure 7-7 . A simple network configuration This allows you to reuse the router as a network switch and employ servers with only one network port, such as the majority of small low-power mini