Vandal resistant switch

Vandal resistant switch

Vandal resistant switches (sometimes referred to as vandal proof switches) are electrical switches designed to be installed in a location and application where they may be subject to vandalism, harsh environmental conditions or simply operated very frequently and expected to survive. Pushbutton vandal resistant switches are manufactured by several companies. They are frequently constructed of stainless steel because of its durability and modern appearance. Such switches are often designed into panels that are also made of stainless steel, making them blend into the overall aesthetic design. The height of the button above/in front of the panel is often minimized to make it blend in better and more difficult to pry out.
Most, but not all vandal resistant switches are momentary types; that is to say they only open or close a circuit while being depressed and revert to their inactive state when the button is released. Piezoelectric vandal resistant switches usually fall into this category, but generally provide a pulse signal rather than staying continuously activated during the time pressure is applied, unlike their mechanical contact-based counterparts.
Latching (Push-on/push-off) type vandal resistant switches with mechanical contacts are also available, and are often used as the power switch for equipment that is used very frequently or subjected to abuse.

Applications

* Public interactive kiosks
* Elevators
* Call-in door switches
* Parking lot ticket machines
* Moderately extreme environments
* Food and food service equipment
* Medical electronics devices
* Heavy duty cleaning equipment
* Automobile dashboard controls
* Hobbyist-customized Personal Computers

Characteristics

Electrical Characteristics

Vandal resistant switches are often low-voltage, low current, so-called "signal" types intended to trigger a change in state, perhaps from "off" to "on" and vice-versa. The mechanical types often have gold-plated contacts that don't corrode to allow reliable low-power switching.cite web |title = General Electric Contact Materials | work = Electrical Contact Catalog (Material Catalog) | publisher = Tanaka Precious Metals | date = 2005 | url = http://www.tanaka-precious.com/catalog/material.html| accessdate = 2008-04-18 ]
A few types are capable of switching 120 or 220 Volt AC power at several Amperes. These types are better suited to on-off switching of the AC power to a device than the gold-plated contact switches. They often have silver or silver-plated contacts to handle the higher currents that they are specified to switch. Piezo switch types are another of the popular types of vandal resistant switches.

Mechanical Characteristics

Vandal resistant switches share a few general mechanical characteristics. They are made of durable materials such as machined brass or stainless steel, and often need to be water and dust resistant due to their environments. Some types are potted to make them waterproof. The International Electrotechnical Commission has produced a standard, IEC 60529, which categorizes products' degrees of protection from liquids and dust using IP codes. A DIN extension of the IEC standard, DIN 40050-9 further defines Degree of Protection IP 69K as being able to withstand high-pressure washing or steam cleaning. This capability is needed in some particular applications, such as dairy milking machines, and is provided by some manufacturers' products.

Illuminated (Indicator) Types

Vandal resistant switches (like some other types of switches) can incorporate indicator lights or LEDs to indicate circuit activation, deactivation or fault conditions. LEDs are used for this purpose in this style switch, being available in several colors and operating at low voltages. Single and ring-shaped groups of LEDs can thus show the current status of equipment or machines. In some products the LEDs can have two colors to show multiple status conditions, such as On(e.g. green)/Off(extinguished)/Fault(red).

Non-mechanical Types

Although mechanical contact-based switches are most commonly used for general purpose electrical switching, switches that have no moving parts are generally longer-lived. This is due to the fact that moving parts tend to wear, and wear-out occurs ar the end of a mechanical switch's life. Piezo and Capacitive switches are the two most popular non-mechanical switch types currently available.
One advantage they have over mechanical contact-based switches is that they have no moving parts to wear out. This makes them capable of lasting for tens of millions of operations. [http://www.electronicstalk.com/news/shu/shu123.html "Piezo switches are sealed to the highest levels"] ]

References


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