Issue #156 | Aug. 1, 2008 | by Cees Links

Sense and control networks are an important part of our lives. They are all around us – in our homes, offices and factories, and in our cars.

We are all familiar with certain types of sensors and their associated networks and controls, such as temperature and light sensors, motion sensors, carbon monoxide sensors, etc. Municipalities are using sensors as parking monitors to indicate empty spaces. Cities use sensors to control traffic lights and maximize the flow of vehicles during rush hours.

Big and small, sensors are everywhere. However, a sensor by itself cannot do much.

It needs a controller to actually complete an action. For example, the thermostats in our living rooms are a combination of a sensor and a controller, switching the heater of our central heating system on or off; powering up the air conditioner.

Redefining sensors – the quiet revolution in your hand

Motion sensors switch on a lamp when motion is detected. These kinds of sensors can be considered as actuators. In that “sense,” every switch, whether a light-switch in our home or on the car dashboard, actually functions as an actuator. It can be described as a type of sensor.
Yes, it requires human interaction; but it is responding to the environment – in this case a push that toggles the switch from one state to another. Whether responding to a change in temperature; monitoring the weight in a parking slot; or responding to a manual tug that turns off the lights, these are all sensors because a response to a condition activates an action.

So what is missing?

The network. In some situations, the switch or sensor is adjacent to the controller. In other cases, the sensor might be across the room, across the street or even across an ocean from its controller.

Until recently, sensor networks were usually wired for both connectivity and power. They needed wires to talk to the controller, and to pass the collected data from controller to sensor. The sensors needed power to operate and stay awake. More wires.

One solution is using sensors powered by batteries. That eliminates cable issues but poses a new problem. Sooner or later, batteries run out of power and must be replaced or recharged. Replacing batteries for tens, hundreds or even thousands of sensors in a building is a nightmare.

Fortunately, we are beginning to see low power sensors and actuators that can use energy harvesting or allow for decades of battery life. Solving that problem begins to enable maintenance free sensor networks.

You still have the cables for the network. The network needs to be connected and it needs to be powered. Wireless technologies like Wi-Fi and Bluetooth can effectively eliminate network wiring; but they require a lot of power. With a little bit of discipline and forethought, one can keep a laptop, a cell phone or a Bluetooth headset charged, but it is not easy.

However, with the recent arrival of the IEEE 802.15.4 radio standard (ZigBee), wireless sensor networks that require very little power are now starting to enter the marketplace. By combining ZigBee based networks that are very power efficient with clever software that minimizes energy requirements, it is now possible to build virtually maintenance free networks that do not require power lines or even batteries. The new generation of ZigBee based networks are so power-efficient that they can function without batteries, operating off of energy harvesting units that transform solar radiation, kinetic movement, temperature differentials or vibration, into enough power to run a sensor as well as its network.

“Maintenance free wireless control networks” are a part of the quiet revolution that is going to help redefine what a sensor is.

Cars with their sensors and actuators are a precursor to this revolution. The expectation is that many of the conveniences commonly found in our vehicles will migrate into our homes, like central door locking or climate control per seat.

The new control center
The dashboard in a car has a central control function and is an essential part of the “car network”. In our homes we have the equivalent of this “dashboard”. Although it is still relatively primitive, it is the common “remote control”, used for controlling television or audio equipment – although there are already remote controls that can do much more than that.

Most of today’s remote controls are not part of a true connected network; they are a wireless (infra-red) extension of a piece of equipment. The consequence is that bewildering array of remote controls floating around in the living room.

It has taken a few years, but within the last month or so, the world’s consumer electronics companies are getting a wake-up call, and have decided to work together to establish an interface standard that works on top of IEEE 802.15.4. This will allow different remote controls to start interacting with different brands and types of equipment.

This is a big step forward. There will be less remote controls in the home and one remote will support other types of gear as well, more like a dashboard. The new ZigBee based remote control, packed with sensors, and switches acting as sensors, could control the house: locking and unlocking doors; starting the coffeemaker; changing the room temperature and lighting in the upstairs bathroom; and maybe even turning on and modulating the temperature of the bathwater itself.

An innocuous piece of electronics called a remote control is now becoming the center of the home sense and control networks. Full circle: from remote sensor to dashboard.

Cees Links is CEO of GreenPeak Technologies, a Dutch company innovating green, ultra-low power wireless communication technology. GreenPeak Technologies - Ultra Low Power Wireless Control Networks

Editor's note: Happy birthday, Jerry. Still rockin’.