Wherever I hang my sensor

8th September 2015
Phil Ling

Steve Rogerson looks at how sensors will play a leading part in the growth of smart home technology

Since the first TV remote control or VHS tape player, the number of gadgets in the home has been increasing, but now in the Internet of Things (IoT) era there is a growing momentum for more sophisticated devices in the home that are connected to each other and to the heating, cooling, lighting and security controls to create the so-called smart home. 

The vision is of a home that can predict its occupiers’ needs, be controlled remotely and interact in ways that were once the dream of science-fiction writers. But for this to become a reality, sensor technology has to play a major role, not just for detecting the temperature or whether a room is occupied, but who is occupying it and what is the state of their health. And these sensors need to operate on low power while at the same time communicating with a hub and each other.
For some companies, it seems little more needs to be done, as their existing sensors can easily be adapted for use in a smart home: “All the sensors that we use in consumer applications can be used in smart homes,” said Mohan Kannusamy, Product Marketing Manager for Vishay Semiconductor. “We have ambient light detectors and movement detectors. We have humidity detectors.”
But Sajol Goshal, Vice President of Strategic Development at AMS, formerly Austria Microsystems, believes the three key elements of sensor systems in smart homes are communications, the sensor hub and control systems to respond to what is being sensed, open windows, turn on lights and so on: “Everything has to be connected,” he said. “And it needs to be wireless. That is the most logical.”
The two key wireless technologies, he believes, will be Wifi and Bluetooth, followed by cellular, as all three are already on smartphones and some are on existing devices in the home. There is also Zigbee for mesh networks, but he thinks that when Bluetooth Mesh comes out next year this could be used instead.
The sensor hub will collect the information from the various sensors and carry out the necessary processing. While this will contain much of the intelligence in a smart home, Goshal believes it will be more important to have local intelligence at the sensors: “Otherwise you can get latency problems,” he said. “You need the light to come on as soon as you walk into the room. The statistical analysis can be done in the cloud and the sensors operate to local rules.”
The other problem will be ease of use. People do not want a home with so many gadgets that they need to read instruction manuals every time they want to turn on the lights. They also need to be easy to install: “Today, with many devices, you have to hire people to install them,” said Patrick Schuler, Marketing Manager with LEM. “We want things that people can do themselves, like smart plugs. Smart home systems can be cumbersome for people to put together.”

Occupant health
Perhaps one of the most exciting aspects of a smart home is how it can monitor the people within the home and adjust itself accordingly. “A wearable device could transmit body temperature to the air conditioner,” said Kannusamy. “This could use Bluetooth, Wifi or Zigbee.”
But more than that, there is the possibility of them monitoring the health of the occupants. Norwegian company Novelda, for example, has developed technology that can measure respiration even through walls.
“We need sensor technology that can give us more information about human beings,” said Kjetil Meisal, Novelda’s Product Marketing Manager. “Our device sends out an ultra wideband radio signal and we sample the reflections at a high frequency using rolling time domain technology. What we are missing is the signal processing. We have the knowledge, we just have to do the work.”
The technology can carry out respiration monitoring at up to 2.5m and the company has a proof of concept for up to 8m. Using radio signals is what gives it the ability to measure through building materials and duvets and blankets, so it can monitor respiration while people sleep.
These also have the added advantage over normal motion sensors for detecting if a room is occupied. If someone is sitting still or asleep, the motion sensor could decide the room is unoccupied and turn off the air conditioning or lighting, which would be annoying. But if it can detect breathing, then that problem is solved. This can extend beyond just detecting that someone is in a room, but where in the room they are; if there are multiple people in the room it could adjust the heating in different areas in the room depending on personal preferences. Smartphones can play a part in this, said Goshal: “You can have your profile in your smartphone, this can contain your environmental preferences. This is happening in cars so why not in the home?”

Smart meters
An essential part of any smart home is the power supply. Given that one of the main reasons people are looking at controlling the home is to reduce energy consumption, then linking that all with a smart meter is crucial. Though today smart meters are more about saving energy companies money, by allowing remote meter reading, in the future they could become the hub of a smart home. Thus, the first sensor in any smart home will be in the meter itself. Magnetic sensors are key here.
“Magnetic sensors can be used in smart meters for measuring the current,” said LJ Ristic, Vice President for Sensors at Crocus Technology. “They can also be used as a security device to protect them from tampering. These need to measure power consumption in real time so users can see what is being consumed when different devices are turned on and off.” However, to do this all the devices need to be compatible with the smart meter.
“Interoperability is a problem,” said Schuler. “If you want to measure your energy consumption by device you have to connect them altogether and make sure the devices talk to each other.” There are consortiums being set up but so far no unifying body for the whole industry.
There are two ways to look at power consumption. For some devices in a smart home, it is not crucial because there will be a mains supply, which is why there are those looking at putting hubs within lighting fixtures. But for many of the sensors, they will be remote from this hub and therefore need to consume as little power as possible. Householders will not want to be changing batteries at regular intervals and thus the consumption needs to be low enough so they can survive using energy harvesting.
“There are techniques to keep the power down,” said Ristic. “Sensors do not have to be on all the time, but can switch on and off. There are also aspects of the design for keeping power down.” However, many are looking at making the best use of the mains power. “In a home or office, the one thing that never moves is the light bulb,” said Goshal. “There is electricity in the light bulb socket so this can become the IoT hub. Other things can then connect to that.”
Will Tu, Director of Embedded Sector Marketing at ARM, said this was part of the trend to move sensor technology away from mobile phone criteria: “In mobiles it is important to have low power,” he said, “but in the smart home many of the devices are plugged in so there is not the same limitation of power. This means you can use the latest technologies.”
This, he said, gave the manufacturers a lot more options. For example, he said he knows of one company creating gas sensor technology using a Raspberry Pi platform, and this was not necessarily low power but could be an important safety system in a home. “Sensors could also be added to appliances that are already in the home,” he said. “I also think microphones will be the next big thing to allow a voice-based user interface. That has a lot of potential.”

One area where many sensors manufacturers will struggle in future smart home and other IoT applications is on the software side. “Software is a really critical piece of the equation and one that sensor companies are afraid of,” said Tu. “They have always stayed on the analogue side and not worried about linking with a processor. They will need to hire in new resources to handle that. They need to adopt a turnkey black box approach with all the software included.”
Smart homes are coming, bit by bit. There will be technology retrofitted into existing homes. There will be new builds that are smart from day one. Some of the technology is already with us; heating and air conditioning systems have been responding to temperature and humidity for years. But they will get smarter and there will be increased connectivity between them and other parts of the home. There will be robot cleaners and houses that watch us while we sleep. What they will all need though is sensing technology and thus smart homes are already looking like a boom market for sensor companies, and one that is set to continue growing.

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