Raspberry Pi - Smart Home Automation with Linux and Raspberry Pi - page 272

question of having more space on your desk, it's a question of being able to automate devices that otherwise would
become to cumbersome to use if there was a full-size machine connected to it. Similarly, having one this cheap means
that you can experiment more and automate more (and more esoteric) devices.

Obvious Benefits
Despite my comments in the preceding paragraph, being small and cheap does have its benefits. The size allows us
to connect it to other devices and in other places. Surprisingly, an Raspberry Pi can fit into a light switch! Because
the plan for HA is to remove old manual technology, such as the light switch, this means that you can reuse the hole
where the switch once was for a Raspberry Pi and some additional add-ons. This is especially true for peripherals
such as webcams, 1 which are dumb pieces of technology that require complex software drivers to work. If you were
so inclined, you could use SimpleCV add face recognition to the switch by your den, or study, and limit access in this
way! Or, with the addition of a small screen, you could turn the switch into a conferencing or VOIP terminal.

N For those with more money, replacing each wall switch with an iPod Touch or Android tablet can achieve the
same effect!

Note

It is also worth considering that the Raspberry Pi is easier and cheaper to hack than any existing gadget off the shelf.
In the past, developers would spend months reversing engineering a $35 gadget just so they could add one feature or get
it to run some version of Linux or BSD. Now, with the Raspberry Pi costing the same amount, there is little need to do this
work because a Raspberry Pi can become that gadget through minimal hardware, and a prominence of software-software
that is mostly already available and released under an open source license.

Towards Full Local Control
The cost of a Raspberry Pi means that it's no longer unreasonable to have one (or two) computers in every room in the
house. What's more, because it is more powerful than an Arduino, it can be used as both a media streamer and a control
system, particularly as it runs Linux, and therefore capable of using all the traditional Linux software for these tasks.
As already noted, the Raspberry Pi can fit inside a light switch so you can replace the “hard” switch, through
which current flows to control the light, with a “soft” switch. In the HA context, this means that the switch doesn't
(directly) control the current flow. Instead, the switch is connected to the Raspberry Pi, which in turn sends the open/
close message to Node0. Node0 picks up this message, interprets it, and sends an appropriate control signal to the
light. If the light is on X10, or a Hue bulb, then the commands we've already seen can control the light. However, you
can also implement a similar system yourself by connecting the GPIO of the Raspberry Pi to a relay, which in turn
controls the existing circuit with the light bulb. The circuit in Figure 8-2 is of use here, although more details of the
Raspberry Pi GPIO interface will be discussed later.

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