Recently I added a smart power strip to the TV/Amplifier setup in the
living room. My main aim was convenience - to make it easier to turn
everything off all at once. But I also wanted to see how much power I
could save by eliminating the parasitic power drain that a TV, amplifier
and two DVD players have when in the 'off' state.
The power strip I bought is the one featured to the right here and to
date I'm pretty happy with how it's working. The power strip has one
'blue' outlet that senses when a single device goes on or off and then
several 'green' outlets that switch accordingly. Initially I plugged the
amplifier into the sensing output and everything else into the green
outlets. That worked great and when the amplifier goes off so does the
TV, the DVD player and the DVD changer. Since the amplifier is a Denon
-CI model I can also control it remotely and since everything else
switches on and off with it I can remotely shut down the whole stack
from my home automation software.
The only problem with that approach is that in the 'off' mode the Denon
-CI still consumes about 5W whereas the TV consumes 0W when off. The TV
is one of the earliest HD TVs, a Panasonic Tau CRT TV so it's fairly
power hungry when on but it has a 'real' on/off switch so when it's off
there is no power draw at all. [Until recently the picture on that CRT
beat nearly every flat panel TV on the market, but with recent LED LCD
TVs I think I may finally be willing to part with it. It's old
technology, but still an awesome HD picture.] So now I have to chose
between remote power-off control and a 5W constant draw or no remote
control and 0W consumption.
When I purchased the smart power strip I was concerned that it might
itself have a phantom power drain equivalent to one of the other devices
but it appears to be relatively harmless consuming hardly any current
for itself.
The one adjustment you need to make on the smart power strip is to set
the sensitivity so it can turn on and off at the right point.
Overall, definitely a recommended buy on this one.
I've been working on home automation for over 15 years and I'm close to achieving my goal which is a house that understands where everyone is at all times, can predict where you are going next and can control lighting, heating and other systems without you having to do or say anything. That's a true "smart home".
An overview of the many sensors I've experimented with for home automation including my favorite under-floor strain gauge, through all the usual PIR, beam and contact sensors to some more esoteric devices like an 8x8 thermal camera.
One way to reduce the volume of sensor data is to remove redundant points. In a system with timestamped data recorded on an irregular interval we can achieve this by removing co-linear points.
Home automation systems need to respond to events in the real world. Sometimes it's an analog value, sometimes it's binary, rarely is it clean and not susceptible to problems. Let's discuss some of the ways to convert these inputs into actions.
Another super useful function for handling sensor data and converting to probabilities is the logistic function 1/(1+e^-x). Using this you can easily map values onto a 0.0-1.0 probability range.
In a home automation system we often want to convert a measurement into a probability. The ATAN curve is one of my favorite curves for this as it's easy to map overything onto a 0.0-1.0 range.
An if-this-then-that style rules machine is insufficient for lighting control. This state machine accomplishes 90% of the correct behavior for a light that is controlled automatically and manually in a home automation system.
