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Contactless switching comes of age with the IoT
Stephan Menze, product sales manager Analog & Sensors, Rutronik, talks about some of the developing technologies within the Internet of Things
T
he huge breadth of devices and applications forecast to make up the Internet of Things is challenging designers on a number of fronts. It is a highly competitive sector and the pressure is on to deliver ‘winning’ designs. Challenges vary depending on the application with things such as battery life, portability, functionality, connectivity and convenience being common threads. As a trend this is leading us towards a future with billions of highly sophisticated and very small devices with which we need to interact. And, therein lies one of the greatest challenges of the IoT and the future in general. Traditionally we have interacted with our technology through pushing buttons or typing on a keyboard and while there have been successful small products (such as the Casio Databank watch from the mid-1980s) that used this approach, the functionality and need for convenience in modern devices requires a better solution. One method that has been developed with some success is voice recognition. With the advent of better microphones this is now becoming a viable option, although issues such as background noise remain – and catering for multiple languages and
regional accents will always be a challenge. Touch gestures have also allowed
control of sophisticated devices, but they also have some drawbacks in that they require a relatively large touch surface to allow ‘pinch’ and ‘rotate’ gestures to be performed properly. While this technology is suitable for tablets, laptops and trackpads it is really not viable for ultra- small wearable devices where there is no space (or power) for a sensitive surface of a suitable size.
Contactless gesture control offers a number of advantages including being language-independent and is rapidly gathering a lot of attention as a viable method of interacting with smart devices. As there is no need to physically touch the device this technology works with devices of all sizes. It is also useful in in-car automotive applications where, as long as the gesture is in approximately the right place, the driver does not have to take their eyes off the road to find a small button. Finally, in the food and medical sectors, the ‘non-touch’ approach is considered to be very hygienic. While contactless gesture control provides the convenient operation that users and
consumers seek, implementation does require engineers to select the right device for their application and to be mindful of a few considerations when designing. With gesture recognition, any movement within the ‘active area’ can be interpreted as a gesture. So, to prevent accidental deployment it is important to consider the aperture carefully to ensure that the gesture sensor sees only the required area. By controlling the size of the active area, the unwanted effects of extraneous light sources can also be mitigated. Range is another consideration, product designers need to consider how far from the sensor a valid gesture can be made, detected and interpreted. In general, smaller aperture angles give greater distances although the light sensitivity of
the detector also has a significant role to play in this. Optical lenses can also be added in front of the sensor to adjust the field of view, although this adds complexity, size and cost to the solution. UV / sunlight filters are available to mitigate the effects of strong sunlight in outdoor applications – including the interior of vehicles. It is important to protect the sensor against contamination from dirt and dust. Special infrared transparent glass makes a good solution here – the main consideration is that the IREDs will be shining through the same piece of glass, so there may be some internal reflection which will need to be adjusted for by internally calibrating the sensor. The final consideration for the designer is selecting the best sensor device for the application. One of the latest devices to reach the market is the VCNL4035X01 proximity and ambient light sensor (ALS) from Vishay that is available from Rutronik. The advanced device integrates a proximity sensor (PS), ALS, multiplexer and a driver for up to three external IREDs / LEDs into a single 4.0mm x 2.36mm x 0.75mm surface mount package. Also incorporated into the package is signal conditioning and an I2C interface. The high resolution PS offers a 12-bit or 16-bit option and the ALS delivers 16-bit resolution for ambient light, allowing the sensor to recognise gestures in demanding conditions – especially due to the excellent background light cancellation. By not incorporating the emitters in the package, designers are free to configure the sensing zone to meet the application requirements. While the sensor is ideal for smart home, wearable and industrial applications, its 105°C operating temperature and AEC-Q100 approval ensure that the device is a good choice for demanding automotive applications, especially as in-built temperature compensation keeps the output stable over a wide temperature range.
www.rutronik.com www.cieonline.co.uk Components in Electronics March 2018 25
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