Micro switches are technically known as miniature snap-action switches. A micro switch is an electrical switch which is actuated using a tipping point mechanism that requires very little physical force to be applied.
How are micro switches constructed?
Most micro switches are made from a stiff strip of metal which is supported by a spring and will flip if enough force is applied to the switch button. When the force decreases below the tipping point limit the metal strip flips back. The activation force necessary is higher than the necessary deactivation force.
The fast moving of the strip of metal produces a clicking sound which will be familiar to most people from the clicking sounds of their PC mouse buttons.
A typical surface-mounted micro switch is only around 3mm by 3mm by 9mm. More information on micro switches are available online here.
What are the advantages of micro switches?
The main advantage of micro switches is that they are extremely reliable. Switching occurs reliably at repeatable and specific positions which cannot be said of many other types of switches. As they are often used in applications relating to safety mechanisms, the reliability of micro switches is extremely important.
Another big advantage of the micro switch is its durability. Even the less expensive switches can function for more than a million cycles whereas the more expensive heavy duty types can last for over 10 million cycles. Their durability is a natural result of their design.
Micro switches are also very inexpensive to purchase, especially in bought in bulk, which, when combined with their reliability and durability, makes them a very attractive option for the electronics market. As a result, micro switches are extremely popular and are a very common electronic component.
What are micro switches used for?
Micro switches are commonly used to detect paper jams in printers, in vending machines, as levelling and safety devices in lifts and as door interlocks in microwave ovens.
They are also used when we need to know whether a valve has been closed or opened such as with tamper switches on fire sprinkler systems.
They are a very widely used component and can be found in cars, industrial equipment, machinery and domestic appliances.
They are commonly used in control circuits but sometimes they can be found directly controlling lamps, solenoids, small electric motors or other components.
Specialised low-force micro switches are used to sense coins being entered into vending machines or a vane can be attached which allows a micro switch to detect air flow.
Micro switches can be operated directly by a mechanism of some kind or can be packaged as a part of a temperature, flow or pressure switch.
In conjunction with a motor driven cam a micro switch can be used as a timer mechanism. Or with rollers, plungers or levers, a micro switch can form a limit switch which can then be used to control electrically-driven machinery or machine tools.
Source: http://www.engineersgarage.com/insight/how-micro-switch-works.
Image credit : http://commons.wikimedia.org/wiki/File%3AMicroswitches.jpg
What is a micro switch and what are its uses?