Types of Switches
A switch is an electronic device employed to make or break an electric circuit either automatically or manually. Its working principle is based on the ON/OFF mechanism. Electrical or electronic circuits employ various types of switches to trigger or control the circuits. The connections of the circuit a switch makes determine its type. The types of connections a switch can make depend on its essential components like pole and throw; these also define differences in switch contact.
What are poles and throws?
Poles and throws are two essential components of a switch. The number of circuits a switch can control is defined as its poles, while the number of positions a switch can adopt is defined as throws.
In a single-throw switch, there is only one pair of contacts, such as close or open. In contrast, double-throw light switches contain a contact that can connect to two additional contacts. Electric current travels between the switch’s two terminals when the switch is turned on. Electric current does not flow between the switch’s two terminals if the switch is off.
Types of Switches
There are four main types of switches— single pole single throw, single pole double throw, double pole single throw, or double pole double throw.
SPST (Single Pole Single Throw)
This type of switch is a simple ON and OFF switch. It is employed for breaking or connecting the circuit between two terminals. This switch is used to give a power supply to the owl circuit. Below is the representation of an SPST switch.
The use of this switch is in the light switch represented in the picture below. It is sometimes also referred to as a toggle switch. It has an input and an output. This light switch controls one wire, and a single connection is established by it. As it is an ON and OFF switch, when the switch in the below circuit is closed on set as ON, electric current flows between the two terminals, and there is blinking in the bulb in the circuit. On the other hand, when the switch is open or OFF, there is no current flow between the two terminals.
SPDT or Single Pole Double Throw Switch
These types of light switches have three terminals. Of these three terminals, one of the terminals is employed as an input, while the remaining two are employed as output terminals. One out of the two terminals is joined to a common terminal. Apart from the other terminals, only the COM terminal is used in the SPDT types of light switch. For instance, COM and A or B and COM can be used.
These types of switches are mainly used in a three-way circuit to turn a light bulb ON or OFF from two different locations, like from the bottom or top of a staircase. When switch A is closed in the circuit below, electric current flows between the terminals. However, only light A glows while light B is OFF. If switch B is closed, electric current will flow via the terminals, and only light B will light up while light A will be OFF. Both the circuits here will be controlled by a single source or way.
DPST (Double Pole, Single Throw)
This switch comprises two poles, meaning two identical switches are included in it that lie side by side. A single toggle operates this switch, meaning that the regulation of two discrete circuits is carried out at the same time via a single push.
The application of this switch is in turning two circuits ON/OFF. It comprises four terminals— two inputs and two outputs. The main function of this switch is in regulating 240V appliances, which requires both supply voltages to be ON, while an unbiased wire can stay connected at all times. If this switch is turned ON, current flows through the two circuits. If it is turned OFF, no current flows in the circuits.
This type of switches is used to turn on and off two circuits. Its four terminals are home to two inputs and two outputs. The major function of this switch is to regulate 240V appliances, therefore both supply voltages must be activated while allowing an unbiased wire to be connected continuously. If this switch is switched ON, the two circuits are linked. If it is turned OFF, there is no current flowing through the circuits.
DPDT (Double Pole Double Throw)
This type of switches equals two SPDT switches combinedly, meaning two separate circuits connect each circuit’s two inputs to one of two outputs. The position of the switch regulates the number of ways, and each contact can be routed from the two contacts.
If this switch is in ON-OFF-ON or ON-ON mode, it functions as two discrete SPDT switches managed by a similar actuator. Only two loads can be ON at one time. These types of electrical switches can be employed in any application that requires a closed and open wiring system.
Modeling the railroad is the best example of this type of switch. In this model, small scaled trains and railways, bridges and cars are used. The system can be switched at all times because of the close permit, while extra pieces can be triggered through the relay or switched ON because of the open permit. Imagine if in a circuit A, B, and C are connections from the switch’s one pole while D, E, and F are connections from another pole, the connections E and B are mutual in all the poles.
If there is an entry of +Vs at connection B and the switch is attached to the top, connection A then becomes positively charged, and the motor rotates in a single direction. If we set the switch to the lowest position, there is an inversion of the power supply, and the connection D becomes positively charged. The motor rotates in the opposite direction. The power supply in the middle position is not connected to the motor and does not cause its rotation. These types of electrical switches are mostly employed in motor controllers where we need to invert the speed of that motor.
Toggle Switch
A toggle switch can be handled manually with the help of a mechanical lever, handle, or rocking mechanism. Their application is mainly as light control switches. Most of them are available in two or more lever positions in SPST, SPDT, DPDT, and DPST versions. They can be used for switching small as well as high currents and are available in a diverse range of sizes, ratings, and ratings which can be chosen based on the application. Any level of their position can represent ON, but the download position is usually the ON position.
Characteristics of a Switch
Before closing the topic, let us have a look at some important characteristics of different types of electrical switches:
- Pole and throw are the two most important characteristics of a switch. While a pole represents a contact connection, a pole represents a contact-to-contact connection. A switch is described by the number of poles and throws it constitutes.
- Single and Double are some standard numbers of throws and poles. The number is often used directly if the number of throws or poles is more than two. For instance, a switch with three poles and six throws is represented as 3P6T.
- The action of a switch is also an important characteristic. It can either be latched or momentary. Push buttons are momentary switches that are used while making momentary contact. On the other hand, latched switches keep on maintaining contact until it is forcefully moved to the other direction.
Conclusion
We hope this blog makes you familiar with what a switch is, the different types of light switches, different types of keyboard switches, types of switches and their applications. You will also have acquired some basic knowledge about how it works and what its characteristics are. As switches are fundamental to the working of electronic devices and circuits, having fundamental knowledge related to their types and working principles is important.
Frequently Asked Questions (FAQs)
1. What are limited types of keyboard switches?
Limit types of keyboard switches are the types of light switches that work in the presence of certain objects or moving parts of a machine rather than by human hand operation.
2. What is the function of float switches?
Float switches are commonly used to control AC and DC motor pumps depending on the water or liquid in a sump or a tank. This switch starts working when the floating object goes downwards or upwards depending on the water level in a tank; because of this float movement of chain assembly or rod and its counterweight results in the opening or closing of the electrical contacts. The Mercury bulb switch is another type of float that does not comprise any float chain or rod arrangement.
3. What are flow switches used for?
Flow switches are types of light switches that are applied mainly to detect the movement of the airflow or liquid in a duct or a pipe. A snap action performs the construction of the airflow switch. This type of micro switch is attached to a metal arm to which a thin metallic or plastic piece is attached.
