Micro switches: a macro invention

"Micro switches, more famously termed as miniature snap-action switches are electric switches require very small amount of physical force for stimulation. They work on tipping-point mechanism, also called "over-center" mechanism that assures fast opening and closing of switch contacts and minimizes the risk of their burning or welding. Switching happens very consistently at specific and repeatable positions of the actuator, which is not necessarily true for other techniques. Unlike large switches, micro switches do not have hinge points and the motion is due to stressing of a thin metal strip, as a result of which, they are extremely reliable, operating for millions of cycles without failure. Whereas, large switches wear off quickly. Its highly efficient and meticulous design makes it durable up to 10 million cycles for heavy-duty models. Besides, it is also cost effective.

The most significant feature of micro switches is that a relatively small movement at the actuator button produces a relatively large movement at the electrical contacts and regardless of the speed of actuation, it happens at a very high speed. Very successful of the designs also exhibit a character known as hysteresis. It means that a small turnaround of the actuator is insufficient for reversing the contacts, i.e. the activation force is greater than the deactivation force. These are the two attributes that make it possible to achieve a clean and reliable interruption of the switched circuits.

These switches employ "butterfly contacts" which provide simultaneous switching of multiple circuits, self-cleaning contacts and have contact design which is resistant to vibration. These switches are used in special purpose applications where consistency and long life are critical and are useful in situations that require a fast opening or closing of a circuit, such as a mouse button or appliance setting.
These tiny little wonders invented by Peter McGall in the year 1932 in Freeport, are almost everywhere. Used, basically, to control and regulate devices, they are often placed in small places. A standard micro switch usually works with currents from 0.1A to 15A, and resists temperatures that are between -30 and 80 Celsius degrees.

One of the familiar types of switches is the mercury switch whose purpose is to allow or interrupt the flow of electric current in an electrical circuit. Common applications of micro switches include the door interlock on a microwave oven, leveling and safety switches in elevators, vending machines, and to detect paper jams or other faults in photocopiers. Micro switches are generally used in tamper switches on gate valves on fire sprinkler systems and other water pipe systems, where it is necessary to know if a valve has been opened or shut.

Other typical areas of application include security, medical, process controls, business machines, HVAC, material handling, vending, gaming, circuit breakers and household appliances.

But revolution occurred they started to use micro switches with speech output systems to help people with severe/profound intellectual or multiple disabilities in reducing their isolation and interacting with the surrounding world. An invention for a cause!"