A micro switch, also called miniature snap action switch, is a kind of momentary contact switch used broadly in automotive, industrial and medical instruments as a sensor. The switch is termed as “micro” on the name of the company who first started manufacturing it commercially.
The actuator of those switches often has a hinged wheel positioned above a push button. This switch is widely utilized in control system functions similar to a door interlock, safety switches in elevators, merchandising machines and so on. Having a diverse range of engineering functions, micro switches can be found in varied switch configurations, housing materials, actuator kinds etc.
But what makes these switches to be referred to as “snap action” switches? How the momentary contact is managed by the switch? Is there a mixture of spring or thin plastic fibers that allow such movement? Continue reading to reveal all the solutions.
A typical SPDT micro switch is proven in the picture above. It is a blunt edged rectangular structure having three output contact strips denoting widespread (ground), open and closed state respectively.
Two diagonally reverse holes are dug in to offer simple mounting of the activate surface. Similarly, holes at the terminals of output contact strips permit easy soldering with the wires. The plastic field can be manufactured from polyester or phenolic plastic products.
Actuator Assembly
Actuator meeting of the switch is a mixture of a hinged wheel and a push button.
Movement of Actuator: For this switch as the rest state of this switch is the usually linked position (NC) whereas the active state, i.e. the state when the actuator is pressed, is the normally open (NO) state of the switch.
ON and OFF State
The NC or Normally Connected state of the switch. The actuator just isn't pressed and hence, all different parts stay of their default rest state.Let’s find out the internal assembly of the switch that responds to the actuator force and modifications the state of the switch.
Internal Structure Assembly: On opening the plastic casing of the switch, the different parts of the interior construction of the switch could be seen. It is a simple assembly, comprising of:
- Two stationary contacts for NC and NO place.
- One movable contact meeting.
Movable Contact Assembly
Tensile Metal Strip: The part taken out from the movable contact assembly is a metallic strip formed like an inverted “U” that's stretched from its sides. This small tensile strip offers the restraining force to the movable contact, bringing it again to its relaxation state after pressure from the actuator is removed. Working like a spring, this strip is answerable for the “snap” action of the micro switch.
The image above reveals the actuator in the pressed state even if there is no pressure upon it. This is because of no resilient pressure performing on the movable contact to deliver it up and push the actuator to its relaxation state.
The image above reveals the actuator in the pressed state even if there is no pressure upon it. This is because of no resilient pressure performing on the movable contact to deliver it up and push the actuator to its relaxation state.
Parts clung to Ground Contact Strip: The rest of the mechanical meeting of the movable contact has been taken out from the plastic base in the picture above. The components are:
- Contact strip serving as frequent (floor). (Labeled as part A)
- A bent strip placed beneath the actuator meeting.(Labeled as half B)
- A dive board shaped movable contact. (Labeled as part C)
- Common Contact Strip
Common Contact Strip: The picture above reveals a stair shaped ground contact strip which additionally holds the remainder of the elements of the movable contact meeting. The higher a part of the contact is fastened between the moldings on the plastic base while the decrease part emerges out as a contact strip.
Bent Strip: The bent strip positioned beneath the actuator meeting has been proven within the picture above. One finish of this strip is positioned inside a minimize section of the ground contact strip and the opposite end of this strip is placed in a cut part of the movable contact.
The task of this strip is to switch the force exerted by the actuator to the movable contact which then strikes and makes connections with the NO contact of the switch.
As quickly as the force from the actuator is released, the movable contact comes at rest state as a result of resilient force of the tensile strip and this strip forces the actuator back to its rest state.
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