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Insight - How Rocker Switch Works

Written By: 

Abhimanyu Mathur
Image of Rocker Switch
 
Fig. 1: Image of Rocker Switch
 
Rocker switches arepopular among gadgets like computer printers, UPS, SMPS etc. Used solely for the purpose of shifting device operation from ON to OFF, rocker switches can be engaged or disengaged with a small force. Rocker switches are available in various types and sizes depending on the power requirements of the device they are used in. They often come with a light source mounted beneath the actuator to indicate the ON state.
Named on their motion like a rocker chair or a cradle, rocker switches present an interesting structure and internal assembly.Let’s find out the internal intricacies that enable the operation of the switch.
Rocker switches consist of stationary contact, movable contacts, springs and other mechanical parts to operate. When the switch is pressed from ON to OFF or vice versa, the spring movement tilts the movable contact to establish connection with the output contact. It is the movement of the actuator and the movable contact pin that have motion like a rocker or a cradle.
 
DPDT Rocker Switch and Layout of its Parts
 
Fig. 2: DPDT Rocker Switch and Layout of its Parts
 
The image above shows a simple DPDT rocker switch. The body is made from heat retardant polymer plastic with the contact legs at the bottom fabricated from metal. Circular cut sections are made on the contact for soldering or wiringthe switch with the circuit. The 0 and 1mark made on the actuator of the switch denote the OFF and ON position of the switch, respectively. Actuator is attached to the base with the help of small plastic latches extending out from side of the actuator.
 
Rocker Structure of Switch
 
Fig. 3: Rocker Structure of Switch
 
Actuator Movement: In a normal operation of the switch, two rocker motions can be observed out of which one is the actuator motion. The actuator is hinged around the center of the base through the latches and movement around them makes the actuator work like a rocker.

Internal Structure

(a) Base of Actuator---Inside View. (b) Spring Loaded Metal Contacts
 
Fig. 4: (a) Base of Actuator---Inside View. (b) Spring Loaded Metal Contacts
 
Base: The image shows the base and inside view of the actuator. The base holds the spring loaded metal contacts.
Actuator inside: There are two bulges on the inside of the actuator that aid in holding the actuator over the springs.
The arrangement of the base and spring is such that spring is neither in a perfectly relaxed state, nor it is compressed.
 
Image Showing Spring and Their Placement
 
Fig. 5: Image Showing Spring and Their Placement
 
Spring placement: The spring is placed over small metal protrudes over the metal plates. The springs are washed in dilute sulphuric acid so that oxides of iron are removed and they can be galvanized.
Extensions on the sideways of the metal contact enable easy placement.

Movable Contacts

(a) Top View of Moveable Metal Contact that has Extension to Hold Spring. (b) Bottom View of Movable Metal Contact
 
Fig. 6: (a) Top View of Moveable Metal Contact that has Extension to Hold Spring. (b) Bottom View of Movable Metal Contact
 
Movable Metal Contacts: The top and the bottom view of the movable contacts are shown in the image above. While the top structure has an extension for placing the spring, it also has a small pit which extends out as a bulge at the bottom of contact. This bulge establishes contact with the metal leg contacts whenever the switch is on.

Base

Layout of Base of Rocker Switch
 
Fig. 7: Layout of Base of Rocker Switch
 
Structure of Base: The image above shows the base of the rocker switch. This layer has moldings through which the output contact pins of the switch extend out. Towards the centre is the pivot over which the metal contacts rest when switch is off. This is the common contact point of the rocker switch and has two cut sections where side extensions of metal contacts are placed.
On the side is the output contact pointwith which the metal contacts establish connection when the switch is in “ON” state.
The base of the rocker switch holds the metal-spring contacts and provides frame for the actuator to get placed. Extensions of the metal legs are tightly placed between the moldings of base’s plastic so that mechanical impacts do not disturb the configuration of the switch. The contacts are well distanced through a thick wall that acts as an insulator.

Movement

Open State of Movable Metal Contact
 
Fig. 8: Open State of Movable Metal Contact
 
Movement of Movable Contact: The motion of the movable metal contact is like that of a rocker. In the open state as shown in the image above, the metal contacts rest on the pivot region and do not establish contact with the output contact point.
 
Closed State of Rocker Switch
 
Fig. 9: Closed State of Rocker Switch
 
Closed State: In the closed state, the metal contact tilts to establish connection with the output contact point of the switch.
In the whole switchingprocess, the task of the spring is to provide easy movement to the metal contact and hold it for the time switch in on or off state.
Rectangular Extensions: The plastic layer beneath the actuator has a rectangular extension which restricts the movement of the spring when it is at either of the switching state. In their absence, the spring can skid from its position of placement, thus disturbing the working of the switch.

 

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