Not long before Christmas, as part of a new AV system, I installed an Acer Aspire Revo as a frontend for my now well established MythTV setup. This works great, but it did set me back a fair amount.
One thing that has been lacking since the first build of the rack is ventilation. With both sets of doors closed, the inside can get quite warm, especially when iron is turned on. Not any more though, having just completed the installation of 2 active ventilation zones, lighting and a low voltage power supply system complete with rack-mount control panel.
At the end of last year I tested the prototype of the matrix audio switcher, in the process blowing up part of the amplifier that powers the speakers in the living room. After investigating the damage, I found a great site to buy the replacement parts from. They arrived before Christmas, but I didn’t get around to installing them until recently.
The new transistors are exactly the same as the dead ones, so it was just a matter of unsoldering the old ones and replacing them. The nice chunky pads (compared to all the SMD boards I’m used to handling as computer parts) were lovely to work with, and the work was done in a matter of minutes. Minutes + £6 of parts = one big saving over a new amplifier and a lot of waste electronics. If only all devices were this easy to fault-find and fix.
With a fire extinguisher at the ready and my adrenaline gland just waiting to explode, I switched on the repaired circuit and ….. near silence, just the sound of the fan – it worked! Now that both channels are actually wired to something rather than one of them shorting out, the sound coming out is pretty good. In a few months the whole system should be up and running.
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:
- PIR (motion detector)
- Door contact
- Window contacts
Room specific sensors could be:
- Current meter
- Intruder alarm status (triggered/armed)
- Door bell
- 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…
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!
The test of the audio matrix switcher prototype has failed on two fronts:
- the multiplexers refused to work
- 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.
This project is intended to investigate the possibility of, and hopefully build if successful, a home-made externally-controllable matrix switcher with 8 inputs and 4 outputs using parts that cost a total of < £100 (excluding the external equipment such as amplifiers, speakers and cabling). The quality of the audio must be acceptable, but I'm not expecting it to be perfect - that's why the expensive matrix switchers exist. It just needs to serve the purposes of a small house. Continue reading “Audio Distribution System – Phase 1 – The prototype”