How to save energy through lighting control with home automation
Over the years as I've advanced my home automation system I've gained a
good picture as to how power is used within a home and number one on the
list of energy hogs is home lighting. Maybe in a small house this would
be different but in America houses tend to be large and they have lots
of lights and those lights are left on for long periods of time.
In addition to replacing some light bulbs with compact fluorescents and
some with LED lights (Cree LED's only since I don't like flickery-blue
light) the house also strives to shut down the lights in any area of the
home that's not occupied. It aggressively shuts down lights in rooms
that have had no motion in them for a while and if it detects someone
leaving it looks for more opportunities to shut off lights sooner.
Another unexpected saving that you can make with home automation is to
run your incandescent lights at less than 100% brightness. Since most
home automation controlled light switches are dimmable it's easy to set
them to come on at 90% or less. Based on the time of day my house will
use different lighting levels - just 20% if you head to the bathroom
late at night, 60% early evening while there's still natural light and
90% for 'full-on'. Not only does this save energy but it prolongs the
life of the light bulbs themselves dramatically. Couple with running at
less than 100%, the soft-start that most smart light switches offer
provides less thermal shock on the filament and it runs cooler. And
since it takes energy to make light bulbs, and it's tiresome to go
around changing them all the time, this is one saving that pays multiple
dividends.
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.
