Home automation, also referred to as smart home offers new applications and a not yet exploited degree of convenience. The market can still be considered to be in its infancy but it certainly comprises a large potential.
Todays home automation solutions are highly proprietary. They usually target a small number of problems like e. g., satisfying security needs or the control of a limited number of devices, usually all from the same manufacturer. They can only operate based on a particular infrastructure like non-standardized network and/or power supply cables. Thus, they are particularly suited for new buildings if home automation needs are considered in the design phase. Yet, they will be limited by the particular applications a manufacturer offers.
The proliferation of home-automation will certainly profit from easier installation. In some instances like historic buildings, cables may be no option at all. In any case, installing the infrastructure a posteriori is expensive and may not always be justified by the benefits. That is why we argue for wireless home automation.
However, we believe that the even more important aspect to making the smart home a success will be to offer a greater degree of freedom to the user when actually applying it to her home. Different users may have strongly varying use cases. Home automation should on one hand offer plug-and-play solutions for the most common scenarios while not limiting the user to adapt the system to local needs.
The success of the PC itself may be partly explained by its capability to solve problems. But another major aspect is, that it enables the user to apply his own creativity like making music, editing photos and videos etc. Many successful IT products like e. g., the Personal Digital Assistant (PDA) or the cell-phone bear this kind of duality. They are justified by their ability to solve a problem while at the same time attracting fascination for other reasons. We believe that we address both aspects with our idea of sensor network-based home automation.
In our vision of home-automation, cables are replaced by small and cheap sensor nodes. These nodes are autonomous computers including an all-purpose processor, memory and a transceiver for wireless communication. They perceive their environment by means of a number of sensors which can measure light, detect movement by a passive infrared sensor or sense vibrations of the device itself or the ground. They can even hear acoustic events and take pictures using a tiny CCD camera. The image below shows such a node we are using for our prototype.
The nodes are either powered by batteries and by solar energy if enough light is available. Sensor nodes have to be highly energy efficient. For this reason, their radio signal can only be received within a small range. Those small ranges suffice only because all sensors build a so-called wireless ad-hoc network in which information is forwarded to a central sink. Every node relies on its neighbor to forward its packet but it also provides this service to other nodes. This way, no infrastructure is needed. The sensor-network consumes the service it provides at the same time.
So far, we have only mentioned the sensors of the wireless smart home. But it must also be able to influence its environment using so-called actuators. In our prototype, every node is equipped with a consumer infrared transceiver to control all kinds of home-entertainment equipment. Simpler devices which can only be switched on and off are controlled using a special multiple plug that can activate electrical consumers via a standard Ethernet interface. Technically, an embedded board which acts a the home-automation center sends http-get requests to the multiple plug to power devices on demand. All home electronics which is operated by a remote control can be switch by the sensor nodes themselves.
The home-automation center is a small, disk- and fanless embedded computer based on a PowerPC 603 processor.
The embedded system runs an application which processes events signaled by the sensor network. The actual home automation solutions are implemented by linking events to actions in a very flexible way. An example might be the following:
IF ((detect_movement(sensor_living_room) == true)
AND (time > 18:00)
AND (time < 01:30))
THEN switch(light_1, 100%), switch(light_2, 50%)
The above scripting statement switches to a specific light configuration if someone is entering the living room between 18:00 and 01:30.
IF ((detect_movement(sensor_living_room) == true)
AND (time > 01:30)
AND (time < 05:00))
THEN switch(alarm, on)
However, if someone enters that same room
between 01:30 and 05:00 at night, it could be an intruder and a local
alarm is triggered.
These scripting lines can be used to 'invent' completely new applications based on the existing sensor nodes. A particular event or a set of events can trigger different actions in differing contexts. In the above example, movement is interpreted differently according to the current time.
Those definitions can either be defined by the user or they come as factory settings. One common application could be to save on energy by switching off lights and electronic equipment if all persons have left a room (e.g., no movement is perceived for more than 30 minutes – which is usually not even true for sleeping persons.). The electronic equipment can be controlled by sending the appropriate infrared signals to the devices. Simpler electronic devices are controlled by the Ethernet multi-plug. Thus, even if manufacturers do not cooperate, their devices can be included into the home automation solution.
Another application could be to equip the house cat with a small button-sized RFID-transmitter. When approaching the house, the cat-door is unlocked automatically or the owner is called by an audio signal. This could be implemented by a simple if-then scripting line.
A hearing-impaired person could add a constraint which switches on a spotlight if the telephone or the doorbell rings.
The two above mentioned applications have been chosen as an example because – surprisingly enough – they can already be bought separately off-the-shelf. But the examples shows that the scripting which combines arbitrary events and actions can be used to implement a vast amount of different ideas.
These ideas can come as factory settings, but they should also be freely definable by technology-avid users. In the best case, a community of smart home users could share home-automation ideas with one another like it is e. g., known from communities sharing their home-made music, videos, web-design templates or Java-script snippets.
Download Video: SensorRemote.wmv