A switch is a device that is used to make or break a circuit as and when required. Every electrical or electronic circuit needs at least one switch. Broadly speaking, a switch performs two main functions – closing its contacts in the ON state and opening its contacts in the OFF state.Types of Switches.
Switches can be categorised into two types:
1. Mechanical Switches:
These switches need to be operated physically for the ON/OFF action.
2. Electronic Switches:
These switches are controlled through semiconductor action and don’t need manual operation.
Types of Mechanical Switches.
Mechanical Switches can be further classified into different types. Some of the types of mechanical switches based on different factors are as below.
Number of Contacts:
- Single contact switches
- Multi-contact switches
- Manual switches
- Limit switches
- Process switches
Number of Poles & Throws:
- SPST (Single Pole Single Throw)
- SPDT (Single Pole Double Throw)
- DPDT (Double Pole Double Throw)
- DPST (Double Pole Single Throw)
Operation of the Switch:
- Push-button switches
- Toggle switches
- Rotary switches
Below, we will see some of the more popular mechanical switches in further details:
Push Button Switches
Push Button Switches are activated by manually pushing using a finger. The button, when pushed, activates or deactivates the switch. When released, the button comes back to its normal position. It has a spring mechanism inside, which helps operate the pressed and released states.
Toggle Switches are mechanical switches with a lever or mechanical handle for operation. They come with lever positions in the versions of SPST, SPDT, DPST, and DPDT. With different ratings and styles, they are widely used across different applications.
A Rocker Switch rocks ON and OFF on a pivot point. They are low-cost switches that are used across various consumer and household applications. They come in different sizes, features and styles.
Touch Switches are operated by just touching it. It is used for lamps or as a wall switch. Typically, touch switches are used on surfaces with metal exteriors
Slide Switches are mechanical switches that use a sliding mechanism to make or break a circuit. It is best used for small circuits. They stay in one state (ON or OFF) until the state is changed by sliding again.
Voltage Selector Switches
Voltage Selector Switches are used to select an internal circuit depending on the expected incoming voltage. They enable the user to tell which electrical equipment is to be used based on what the switch indicates. The switch helps the current to flow through the components that are meant to handle the voltage selected.
Refrigerator Switches are switches that are fixed to the refrigerator doors. They operate the light inside the refrigerator which is switched ON as the door opens and switched OFF when the door is closed. They come with both single pole and double pole options.
Types of Electronic Switches.
Electronic switches are also known as solid-state switches. This is because they do not have any moving parts or physical contacts. These switches are basically semiconductor switches and are used in systems using electrical motor drives or in HVAC systems.
Some of the Electronic Switches used today are:Power Diode:
Power diodes are built using p-type and n-type semiconductor materials to get a PN junction. When the diode is forward biased, it starts conducting (i.e. ON state). When it is reverse biased, it stops conducting (OFF state)MOSFET:
A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is commonly used in power electronics applications. It is a voltage-controlled device and has three terminals – drain, source, and gate. By controlling the gate to source voltage, the resistance between the drain and the source can be controlled. This resistance decides whether the switch is ON or OFF.SCR:
An SCR (Silicon Controlled Rectifier) is a unidirectional device with three terminals – anode, cathode, and gate. It is controlled by controlling the gate input and biasing the anode and cathode.
Some other switches electronic switches include:
- GTO (Gate Turn-off Thyristor),
- DIAC (Diode AC),
- TRIAC (Triode AC),
- IGBT (Insulated Gate Bipolar Transistor), etc.
Mechanical switches become an essential component in circuits and good quality switches are sought after. Bulgin manufactures a wide variety of switches which offer reliability.