Whilst pondering over what sensors I could put around the house, I ventured upon the idea of having a ’sensor box’ per room. This would be based upon something like the Netiom xAP, which would connect various sensors to the house’s IP network. Some of the sensors in each room would be different. Here are some examples of the sensors that would be common to all of the rooms:

• Temperature
• PIR (motion detector)
• Door contact
• Window contacts
• Light

Room specific sensors could be:

Entrance hall:

• Current meter
• Intruder alarm status (triggered/armed)
• Door bell

Kitchen:

• Back door bolt contact
• Oven/hob state

Each of these nodes can then be queried, via the xAP protocol in this case. Temperature could be recorded, although at present our combi-boiler would probably not allow for remote control. Motion detection and door contacts can be used to determine which rooms are occupied, and along with the window sensors could be used as a secondary security system. The light sensors would be used to control the house lights.

Having one single ‘node’ to talk to would do away with having lots of independent sensors that would probably all communicate differently. Thanks to having picture rail throughout most of the house, there won’t be a problem with hiding the wiring. I’m not sure how big the boxes would be, but I dont think they would be massive. I just need to find the money to build a prototype.

Here’s a video I’ve put together about some of my projects. Sorry about the wobblyness and wonkyness - I’m not sure where I’ve put my tripod.

Today I took a look at the damage caused by last weekend’s test of the matrix switcher prototype. I suspect that the cause of the bangs was actually a short because in my haste to test I’d only connected one channel to a speaker and left the other with bare ends - oops!

Removing the case revealed that the damage appears to be limited to two transistors on one of the channels. I’m not the only person who’s tried to fix this model of amplifier so a quick search for the numbers written on the remaining transistors revealed the information I needed to order some replacements. The parts have been ordered, so will hopefuly arrive before Christmas, although delivery times recently seem really slow.

Now I just need to remember where I left my soldering iron…

In the same way that the saying “you’ve got to spend money to make money” works, sometimes it’s also necessary to spend energy to save energy. An automated home may have more gadgetry than normal homes, but if set up correctly these little power-consumers can help to save energy. While the debate about whether the apparent global warming trend is the result of our actions, it can’t hurt to try to reduce energy use (or rather, conversion) as much as possible.

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MythTV, as previously mentioned, is an open-source project that provides a client/server based media centre solution. One of the parts I like most about it is the ability to have multiple ‘recorder’ backends anywhere on the network, and all recordings are combined into one listing. You can also watch live TV through any of the backends on the network. You can also listen to music, watch videos in pretty much any format, play DVDs, watch/listen to internet streams etc.

I’m going to exploit the distributed nature of MythTV by setting up a network of backends and frontends in our house. Here’s a diagram (click for larger version):

Currently the master backend is set up in the living room, connected to the TV via a VGA cable, and the slave backend is set up in the cabinet in my bedroom. Until the new tuner card I’ve ordered arrives, the only tuners sit in the computer in my room. However the client/server basis for MythTV means that the computer in the living room can connect to the card in my room and use it for watching live TV or recording from.

I also have a single Hauppauge Media MVP. This lovely bit of kit is a thin-client that is intended to be used with it’s own Windows-based software. However, the mvpmc project provides a way to get a far better client onto the little box which can connect to a MythTV backend. So not only can MythTV be enjoyed via a standard computer, but also a small set-top-box. The main advantages of using a Media MVP box are that it is silent, so suitable for quiet rooms, and it consumes very little power.

Eventually there will be at least one more Media MVP and another PC-based front-end in the kitchen and dining room respectively.

As more of my sub-projects get completed, there is going to be a need to control the various systems. There are loads of IR/RF remotes around designed to handle all sorts of HA/AV equipment. However, since I’m building my systems I’m going to need a more flexible and easily customisable way of controlling them. As soon as Apple announced the iPod Touch I knew that I had found what I was after. To me it’s not the music-related stuff on the iPod that’s important, it’s the combination of WiFi and Safari. All I would have to do is set up a PHP/ASP.Net etc. based web site that can communicate with all the systems, then access it through an iPod.

Possible systems to control include:

• Selecting audio sources and where to play them in the house
• Scheduling recordings on the MythTV distributed A/V system
• Controlling the lights
• Monitoring the security cameras
• Setting reminder alarms (announced)
• Running photo slideshows around the house
• Building shopping lists

To complement the iPod there will be several touch-screen terminals around the house which will give the same control, but in known locations so that the improvised remote doesn’t have to be carried around everywhere (and argued over).

I might mock-up some interface designs to give an idea of how I intend the system to work. Stay tuned!

Today I discovered two new libraries/applications:

• Festival (text-to-speech engine)
• PulseAudio (distributed cross-platform feature-packed sound daemon)

This has opened up a whole new realm of possibilities. Rather than paying out £400+ for an A/V matrix switcher, PulseAudio may allow everything to be done through a combination of software and soundcards. If I understand it correctly, the audio sources could be anywhere in the house (via a nearby networked computer with soundcard) and the sinks (amps, speakers, recorders etc.) can be elsewhere in the house (also connected to a nearby computer). The network carries the audio over IP and PulseAudio does all the funky stuff.

Combine this with the text-to-speech features of festival and you’d also have a talking house. This isn’t a new idea - many home-brew home automators have added TTS facilities to their houses - but it’s an interesting one. While it wouldn’t be used for frequent announcements, urgent announcements could be broadcast. If I can get the alarm system connected to the network, it could shout out messages to intruders. If a CO or smoke detector is triggered, the voice system could relay the message to all rooms in the house.

A little over two weeks ago I ordered a new computer from EfficientPC. They appear to be the only independent business selling true linux-based machines. Anyway, what I was after was a box that could run MythTV reliably but quietly (since it will be in the living room).

At our previous house I tried to set up Boron as the machine for this job, since we had the space under the TV (though I had to take a jigsaw to the back of the cabinet) and it was the only suitable machine for the job at the time. Our huge and heavy CRT (now retired to the master bedroom) has component input, so I tried several DVI to component converters that supposedly worked on the Radeon 9600 that sits inside Boron. As these things always go, it didn’t work. So now that we have a TFT TV with VGA input, I have another chance to get a fully-functional media server set up.

This new machine is pretty much silent - certainly quiet enough to sit in the living room, behind the TV (it’s also very slim). I’ve also discovered that it’s pretty nippy, sporting an Intel Core 2 Duo E2140 with just 512MB of DDR2 (since there doesnt need to be a huge amount of RAM for a media centre - processing power is more important). The 500 GB drive should give a few hundred hours of recording capacity. It has been called Sodium, because I try to go for things that are orangey with the Ubunto machines - sodium lamps shine orange - and it will be the ‘Master Backend’ server for MythTV. Boron will be a slave server, and there will be various front-ends around the house.

I found out after ordering this new Asus Camulus-based computer that EfficientPC is run by a single person, so service is not speedy. He is apparently struggling to keep up with demand, so emails often go unanswered. I am not bothered by this, and the quality of the product is pretty good. This guy makes sure that the hardware that he provides works with Ubuntu, which provides more peace-of-mind than if I would have ordered the parts myself then found out that they don’t work under linux.

The only problem, other than breaking a PSU, is that the PCI DVB-T tuner cards that I have will not fit inside the Isis case. I’ve ordered a Nova-T 500 dual tuner card to compensate (along side the replacement PSU and another 500 GB drive). The beauty of MythTV is that it will allow me to use all of the cards in separate machines, combined into one set of recordings that can be watched through any of the MythTV front-ends in the house. So that’s 4 tuners allowing 4 shows to be recorded simultaneously. Eventually this may be expanded to include satellite tuners because we have a very weak digital signal around here. More on the specifics of MythTV and how it’s being set up in our house soon.

There will be photos shortly, once I’ve got the system fully set up.

I’m not having a very good week when it comes to breaking stuff. While removing two tuner cards from boron for the fantastic new pc for the living room (details coming soon) I decided to blow some of the dust away with a can of compressed air. It certainly did the job, but when I plugged the power back in nothing happened. I suspect that when I cleaned out the power supply, the very cold air coming from the can (since gasses cool as they expand) caused one of the components to experience thermal shock thus causing it to fail. So a new power supply is on order, and I’m hoping it will arrive tomorrow though I’ve not had a despatch notice from Dabs yet. In the meantime I’ve found an old PSU that used to be inside aluminium, but was replaced because it sounds like it’s arcing, so to avoid a fire caused by that PSU boron is currently switched off.

Moral of the story: don’t air-dust warm components.

The test of the audio matrix switcher prototype has failed on two fronts:

1. the multiplexers refused to work
2. the amplifier exploded

Of the two problems, the second is clearly the worst because it’s cost me a £50 amplifier. It may be repairable (sounded and smells like a capacitor exploding) but I’m not going to assume that it is. Since the multiplexer didn’t work as I had hoped, another approach to the audio routing needs to be sought. I’ve contemplated buying a commercial product, and a quick look on eBay finds some A/V switchers with RS232 support for £350-£500. Getting one of these would have the advantage of being able to route video signals too. Of course the disadvantage is that it will be significantly more expensive than I had planned on. Remember, on top of the cost of the switcher will be the cost of 4 stereo rack-mountable amplifiers at about £50 each.

So not a great end to an otherwise highly productive weekend. I have managed to get more of the rack cabinet finished (added the locks), tidied up a bit and got mvpmc working.