Switches: do not touch!
Please, do not touch! Because that doesn’t have to be the case at all. A new generation of switches for touchless switching has been developed for exactly this purpose.
Switching without touching means not contaminating the surface with potentially harmful germs, viruses or bacteria. How do these switches work and what are they capable of?
The recent pandemic has given a boost to a technology that was previously known only to insiders in specialised applications: touchless switches. This may sound confusing at first since we are used to pushing buttons where we usually hear or feel a solid click, and immediately know our input has been accepted successfully. This is what we call tactile feedback in the case of pushbuttons.
Other switch technologies such as capacitive or piezoelectric systems usually only provide optical feedback via a point or a ring illumination. Of course, it is also conceivable to add acoustic feedback to the switches. Illumination and a signal tone; that is rock solid then. Touchless switches do the same — feedback via illumination change.
Hygiene, hygiene and hygiene again — that has been the credo during a time of pandemic. Pathogens can spread easily and quickly, especially in places with a high frequency of visitors. Touching contact surfaces (eg, door handles) can transmit bacteria and viruses through smear infection. Not only in the healthcare sector, but also in public buildings, catering or food processing areas, the risk of spread is particularly high.
How does it work?
There are various technologies that can be used for touchless switching (see comparison table). The use of optical IR sensors and microwave sensors is widespread, and these two concepts also represent the two price points. To describe them all in detail would go beyond the scope of this article, but the basic principle of all these systems is similar to that of sonar. Instead of an acoustic signal, an optical signal is emitted, hits an object, is reflected and then detected. However, let’s take a closer look at one of these systems, which may be less well known.
Time of Flight
A technology that works very precisely and quickly is called Time of Flight (ToF). Time of Flight was introduced to the market in the 1980s. It is based on the pulse time of flight measurement of light.
Light is emitted by a transmitter and reflected by one or more objects. The reflected light beams are detected by a receiver and then the distance is determined. This technology enables highly precise settings.
Reliable and safe
False triggering can become a real problem depending on the application. Not exactly when cleaning the surface, even then the switch should not trigger of course, but perhaps in a hospital area; in use with automatic doors, where frail or severely injured people pass through. ToF is very reliable here.
Another advantage of ToF is its insensitivity to colours. It does not matter whether the sensor is approached with white, red or black gloves, this has no influence on the detection. The signal is always converted with the same speed and precision, whereas other optical sensor technologies often have difficulty distinguishing between light and dark objects. They respond to this with different reaction times, which can lead to inaccurate triggering of the switch.
Touchless switches are used wherever increased hygienic requirements for triggering door openings are demanded. These include hospitals with their operating room doors, laboratories and patient rooms.
Also in public restroom facilities — from the door opening to triggering the toilet flush and hand wash faucet — everything can be actuated without contact. In residential and care facilities, especially for people with limited mobility, they make life a lot easier.
An interesting application is also the door opening for service staff in the catering trade between the kitchen and guest zone, where both hands are often full. The same applies in hospitals when patients are moved from room to room through the doors.
Touchless switches offer very high reliability due to the absence of any moving parts. Due to their enclosed design resulting in high IP protection, they can be used outdoors without any problems.
A cool feature, which is rarely thought of at first, is the possible use as a light barrier. All you have to do is change the detection distance and you can open up countless new applications.
However, depending on the technology used, these switches can also have problems — like false triggering. For example, an insect flies directly along the sensor and triggers an impulse. Another example is when used outdoors, raindrops or snowflakes can get onto the sensor area, which can also lead to unwanted triggering.
In addition to false triggering, visually impaired people can neither recognise the distance to the switch nor whether it has been triggered if no acoustic feedback has been integrated in addition to the optical feedback.
Touchless switches form a new ‘species’, and the availability of different technologies means that we will have to consider their varying properties and select the one that is suitable to the application.
For more information on SCHURTER’s TTS touchless switch, visit https://www.schurter.com/en/datasheet/TTS.
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