Many communicable diseases, such as viruses and bacterial infections, are transmitted by direct contact with a person who has the disease or with something that person touched. Avoiding contact is an obvious way to prevent spreading diseases. Touch-free sensors allow many frequently accessed functions in restrooms, such as automatic hands-free urinal and toilet flush, hands-free soap, water and paper towel dispensing and touch-free drying stations. While almost expecting this type of automatic , touch-free sensing today in public places such as airport terminals, hospitals and cruise ships, the technology for an “Automatic Cleaning-liquid Dispensing Device” was only granted a patent in 1991 – slightly over 25 years ago. Another common non-contact sensing product is a sanitizing fluid dispenser frequently found on cruise ships and other high-traffic publics locations such as casinos, fitness clubs, and office lobbies.
The type of touch-free sensing technologies used in these products can include microwave, ultrasonic, photoelectric and passive infrared (body heat activated) techniques. Perhaps the simplest and most cost-effective approach is the photoelectric technique, that uses infrared (IR) light with a wavelength typically in the range of 850 nm. With no hands present, no light from the emitter is reflected back to the collector. When a hand is present, the IR light bounces back to the collector and the sensed pulse can be used to trigger actuation from a pump or motor to achieve the desired hands-free actuation.
A frequently seen touch-free hand sanitizer dispenser is powered by three C-size batteries.