TEChNOLOGY REVIEW > continued New components for the Human Machine Interface (HMI) The input unit is also fully sealed in


compliance with IP67, thereby preventing the penetration of fluid or dust into the inside of the device. Cleaning and disinfection of the control panel are also considerably easier than with other solutions. The issue of disinfection of switches


should also not be underestimated. Power switches are often hard to reach due to their placement on the side or back of devices, e.g. close to a cold-device connector. This makes them easier to miss in disinfection procedures than would be the case with front-mounted on and off switches. An elegant solution to this problem is


the use of antimicrobial rocker switches. These components look identical to standard switches but are effectively self-disinfecting. During injection moulding, the plastic granulate material used to make these switches is enriched with an additive that contains active silver ions when it hardens. By binding to single-cell organisms such as


Antimicrobial switches


bacteria and viruses, as well as fungi and yeasts, the silver ions inhibit cell metabolism, causing the germs to die relatively quickly. In addition to products developed


specifically for the medical industry, there are a number of electro-mechanical solutions


Double pole tactile switch


designed for other industries that are also very suitable for use in medical and laboratory equipment. For example, redundant buttons with switch contacts that close almost simultaneously can be used for electro- mechanical parking brakes. Due to material and manufacturing tolerances, the two poles of a switch can basically never work simultaneously. However, time thresholds are specified in data sheets, and both contacts must close within the defined period of time. This is the only way that a redundant contact can safely monitor a normally open contact. Another interesting component is a


push-button originally designed for use in white goods such as dishwashers – an SMT- compliant two-pole push-button modelled on a tact switch. This small push-button can switch up to 1A with 250 VAC. It also fits in perfectly both visually and in terms of feel among an array of tact switches on a front panel. This button can act as a power switch when used in combination with a relay circuit.


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focus magazine - issue 14


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