Thursday, September 20, 2007

Home Automation

Did you ever see programmes on the television in the 1980s and 1990s like Tomorrows World and some science fiction series? The prediction was that by the early 21st century our homes would be automated to make our lives easier. By easier I mean you wouldn't need to use a light switch to turn the lights on. After you left the room the lights would turn off automatically.

The basic concept of home automation is that your house would 'think' and know what you were doing and how you needed it to respond to any events.

Before I gave the situation any thought I assumed it would be very easy to make it happen. Burglar alarms have successfully detected movement for years. It should be easy to switch a light on instead of setting of an alarm! Right?

Well no. In an outbuilding or garden this solution would probably be enough. Someone walks into the shed at night and the lights comes on. 5 minutes later the light would go off, because the person has got the item they wanted and gone away. If movement is detected in front of your house it is nice to have a super-powerful floodlight turn on for a minute so any prospective intruder is exposed.

Now lets complicate things a bit and set up a system in a bathroom. There are two options for a sensor. One that detects the door opening, or one that detects movement in the room (please no puns). So you enter the bathroom and it is easy for it to decide it needs to put the light on. How long do you wait before switching the light off? Is the person washing their hands for 30 seconds or having 30 minutes in the bath? The movement detector isn't a very good system here. You could have a movement detector in the hall so it knows you moved in the bathroom then moved in the hall. Success you think! Problem is the computer doesn't know who moved if there is more than one person in the house.

In the lounge the problem gets worse. There is the same issue about a lack of movement. Have you gone to the pub, or are you talking or reading? But think about turning the light on. You are settled down to a good movie in the dark, and you reach on the table to pick up your drink. The system may detect the movement and turn the light on just when you didn't want it to!

One could get round this issue with more intelligence. The processing unit needs to have numerous modes. One for watching the tele when it does not turn the light on if you move. One for if you need a bath so the bathroom light doesn't time out. But hang on, now I have a switch to control the system and tame the intelligence. That means the switch behaviour wouldn't be as predictable as when it just turned a light on and off. You have to think even more 'I am about to watch the tele so I need to set the automation to TV mode'.

So you have paid £hundreds for an intelligent system. You have to think a lot more about how to use it AND you still have to control it manually.

What I havn't mentioned is the installation. All the components of the automation system need to be powered and linked together. Running special cables to all lights and sensors would be a big job. There are wireless options that use radio or mains wiring to communicate, but most of these only do one way communication. The processor will send a signal saying bathroom light on and assume it got there. To be reliable it needs to wait for a reply saying the light has been turned on, and if this is not received it must resend its instruction.

My last point is latency. I walk into the kitchen. The movement sensor picks me up when I cross its zones. It tells the computer there is movement. The computer thinks what time it is, has the sun set and what mode am I in. It decides if it needs to turn the light on and sends the signal. The light then comes on with a cool soft fade-up. Problem is by the time this is done you have got your beer out the fridge in the dark and are walking back to the lounge.

Don't get me wrong it is extremely cool to bring someone home after a lucky night in the pub and all the house lights fade on as you enter each room. You can amaze your friends by texting the system from the street to turn a light on. But it does not work. It doesn't save any hassle. It will probably save some electricity but is it worth it for the inconvenience of the lights going off three times during your evening meal?

When everybody has an embedded electronic chip in their body the system will be able to get a bit smarter and would probably work well. In the meantime assuming you don't want all your family to be chipped steer clear! You would have to wait years to save enough electricity to make a return on the investment!


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