How Micro Switch Works
A micro switch, also known as miniature snap action switch, is a type of momentary contact switch used widely in automotive, industrial and medical instruments as sensor. The switch is termed as “micro” on the name of the company who first started manufacturing it commercially.Get more news about
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The actuator of these switches often has a hinged wheel placed above a push button. This switch is widely used in control system applications such as a door interlock, safety switches in elevators, vending machines etc. Having a diverse range of engineering applications, micro switches are available in various switch configurations, housing materials, actuator styles etc.
But what makes these switches to be called as “snap action” switches? How the momentary contact is managed by the switch? Is there a combination of spring or thin plastic fibers that allow such motion? Continue reading to reveal all the answers.
A conventional SPDT micro switch is shown in the image above. It is a blunt edged rectangular structure having three output contact strips denoting common (ground), open and closed state respectively.
Two diagonally opposite holes are dug in to provide easy mounting of the switch on surface. Similarly, holes at the terminals of output contact strips allow easy soldering with the wires. The plastic box can be made of polyester or phenolic plastic products.
Actuator assembly of the switch is a combination of a hinged wheel and a push button. The images above show the actuator assembly and its movement when switching state is changed.
Movement of Actuator: For this switch as the rest state of this switch is the normally connected position (NC) while the active state, i.e. the state when the actuator is pressed, is the normally open (NO) state of the switch.
The image above shows the NC or Normally Connected state of the switch. Here, the actuator is not pressed and hence, all other parts stay in their default rest state.
Tensile Metal Strip: The part taken out from the movable contact assembly is a metallic strip shaped like an inverted “U” that is stretched from its sides. This small tensile strip gives the restraining force to the movable contact, bringing it back to its rest state after force from actuator is removed. Working like a spring, this strip is responsible for the “snap” action of the micro switch.
The image above shows the actuator in the pressed state even there is no force upon it. This is due to no resilient force acting on the movable contact to bring it up and push the actuator to its rest state.
