When we started this project, we thought we would have to place sensors everywhere, on every wall, behind every wall plate and peeking out of every corner. We hate things that sound so random and that suggest such inconsistencies, not to mention so many wiring runs. That, in turn, was a driving reason to reconsider. While some sensors might well have to stand alone, others could benefit from being in clusters.
We were inspired to rethink that approach when we learned about the Panasonic Grid-EYE, a component that can take 64 analog temperature readings (in an 8 x 8 grid). That led us to design a CAP (Ceiling Awareness Pod) that would go near the center of each ceiling to read the area's temperature map, measure the relative humidity and report the ambient light level, all of which would report to supervisory controllers over wired Ethernet. We since had to add one more sensor; you may like this story.
How big is a cell in an 8 x 8 temperature map? They can never all be equal but they come closest if the CAP is, as we said, near the center of the ceiling. Dead center of the ceiling is a position that tends to be occupied by a ceiling fan, so we wanted to establish a 3-in-a-row standard for the house, with a smoke alarm on one side of the ceiling fan and the CAP on the other, separated by a distance shorter than the fan blade. If the fan is running, it will have some effect on the readings of the array, but not a huge one.
There's a bigger problem if the fan should stop with its blade blocking the imaging window of the Grid-EYE, so we added one more component, pictured here. This is a Sharp IR (infrared) proximity detector, able to measure distances between roughly 8 inches and 6 feet, using triangulation, with an analog output proportional to distance. It can tell whether or not a fan blade is in the way. If it is, the controller can instruct an effector (relay) at the fan motor to briefly (0.2-0.3 seconds) apply power. Experimentation shows that this duration drives the blade about half of a blade width and if that is not enough to clear the blade, the sequence repeats. This sensor also tells the controller to ignore sensor readings until the fan blade clears.
We started there, then saw even more potential for the CAP. Here is a bulleted description of it in what we assume to be its locked and loaded configuration:
The house has 30 CAP positions. In addition to the obvious functions implicit in the above bullet points, programming (primarily using Python) within the Raspberry Pi performs several analyses:
We are making arrangements now that, if successful, will make the CAP a commercially available product (from one or more third parties) around the time of the debut media event for the house project.
Our project house has one very large (more than 28 feet deep) garage space with three single-width doors. Each space supports a line of 5 ultrasonic rangefinders pointing down from the ceiling. Starting at the door:
Each reading takes 40 ms or less, so activating each in turn allows 25 readings per second, 5 per sensor, and prevents mutual interference. There is enough raw information here to derive the status of the garage door, the status of the garage space, the presence or absence of something in that space and the direction of travel of both the garage door and the vehicle.
We're not done. A single-beam Lidar (like a radar but using the time of flight of laser light) at the back of each garage space provides a second source for some of the same information, plus some extras. It can report:
But we are still short of some significant information that yet one more sensor can provide.
We want to be able to recognize cars we know, cars that may belong in a garage space. And we also want to know whether their engines are running. Bluetooth 4.1 LE includes a Beacon service. We can equip each car with a beacon transmitter, hidden up and under the dash, that operates only when the engine has power. A beacon receiver can report every beacon it sees and, since each beacon is uniquely identified, identify which car is there. When a beacon presence disappears within minutes after appearing, it's an indication that the car has been turned off, and that is a signal that a moment later, if the garage door has not been closed, it should be.
Our project house is well up a hillside, meaning the driveway is over 400 feet long, so it will tend to take at least 10 seconds for even an aggressive driver to travel to the house from the street. By embedding sensors in what appear to be stone lamp posts, we can give both automation and occupants a head start.
Dual IR beam break pairs (half a pair shown in the picture) operating at different pulse frequencies and offset fore and aft of the lamp posts can not only alert us to the presence of a vehicle in the driveway but also tell us whether it's making an entry or an exit.
Adding another Bluetooth Beacon sensor (like we use in the garage) lets us identify whether a detected car is a known car; this helps our automation know what to do with garage doors and, as you will later see, other elements. .
We can bury a dual Inductive coil in the driveway when the concrete is poured as an additional way to detect the presence and direction of a vehicle.
Adjacent to one lamp post and right at the street, our mailbox includes cameras and proximity sensors.
Do you think of a light switch as a sensor? Ours is nothing but a sensor, meaning there are several ways to rethink light switches. The Eaton decorator switch at the right is a momentary switch, meaning its contacts remain closed only for as long as you push on the rocker. It may look fancy but electrically, it might as well be a doorbell button.
We have enough automation sensors (for ambient light levels, for detecting where people are or are not present and where they are heading and more) that we could fully automate lighting everywhere to make lighting control by occupants unnecessary (as Cisco recently accomplished at a new data center) but that would be a mistake. People never want to feel like they have no control and a house without a light switch could create that toehold for resentment.
But this simple-looking switch can offer more than you might guess at first glance.
Obviously, to meet user expectations, just a tap will turn the lights from on to off or off to on, immediately (more or less; it might take a quarter of a second). Press on it for more than a second and it will work like a dimmer making the lights brighter or less bright, always beginning in the direction opposite the direction of its last usage..
Can you say, “A thou - sand - one”? Press and hold it during “A thou” (longer than a quarter second, roughly a half second), then tap twice after “sand” and “one” to temporarily put it into a command mode. The room speaker will sound a single tone. In the next 3 seconds, tap it once to tell the automation to now consider the room occupied, twice to consider it vacant or maybe 3 times to indicate the presence of an intruder or some other appropriate peril to get the house to respond by silently placing a prerecorded voice call to 911. You could also, of course, substitute a recorded gag to play over the local speaker; maybe, “This house will self-destruct” or “Pathogen released - begin quarantine.
So most of the time, the light switch seems to just work as a light switch, but any time you need it to, it can become an automation interface.
We should acknowledge that each Ecovent motorized vent register includes temperature and pressure sensors that are interpreted by the Ecovent hub; that automation subsystem is largely self-contained and we make no other use of that sensor data. We will also have an indoor barometric sensor; comparisons of indoor and outdoor air pressure can allow us to vent the house when oncoming low pressure is likely to cause even minimal inflation of the building envelope; this can help extend the life of initially soft materials like putty, caulk or glue, that are used in construction.
Is a smoke alarm a sensor? Several current models offer ways to communicate with various current-generation home control protocols, but they never quite make it easy. Phooey on that. In some residential, many multi-family, some commercial and many industrial environments, the companies behind many of the smoke alarm brands familiar to you also offer AC wire-in smoke (or smoke and CO combination) alarms that interconnect with each other so that a fire detected at any one location can also trigger alerts at dozens of others. An interconnectable system can also include a small accessory that's significant to us: an SPDT (single-pole, double-throw) electromechanical relay. An Arduino can easily take advantage of either its normally open or normally closed dry contact to alert our automation.
A wind sensor outdoors can allow us to pause irrigation (lawn and garden sprinkling) systems when the spray would just get blown away; it also lets us turn off outdoor-exposed ceiling fans when a nice breeze renders their contribution unnecessary. Soil moisture sensing can help husband watering times, as can weather information.
We hope to implement a self-contained weather station with a wireless link to our controllers; we are also planning access to macro weather data through APIs to various professional online weather resources that offer micro-forecasts, some with precision down to two decimal places in latitude and longitude (essentially, a single address). This can also let us tailor irrigation scheduling based on expected rainfall, heat and other factors.
Surveillance cameras ringing the house monitor significant pixel shifts within otherwise still images to alert the system to motion anywhere around the house.
And the septic system can send a notification in the critical event of high levels, indicating a need for fast field intervention.
No matter how we try to set up our classifications, a few outliers always remain. For example, our sensor in the range hood over the kitchen cook top that directly controls when its vent fans turn on and off.
And we should probably mention a disconnected sensor, the camera in the drone that has several jobs to do. During construction, for example, we are using it to help document the build.
Once the house is up, we will use it to patrol the gutters, its video able to minimize the number of trips up the ladder we ever need to take to clear them. And in the event of a major storm, we will similarly use it to patrol just inside the property line to spot such signs of damage as fallen trees or standing water.
© Copyright 2016 Newstips, Lord Martin Winston and J2J Corporation; all rights reserved
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