Switch basics for beginners (Guide, 2025)
You may be wondering why by pressing a button the fan or light turns on and off. This is all possible due to the switches. Switches are fundamental components in electronics.
The switches control the flow of electrons in a circuit. There are two primary states of switch: ON and OFF. When a switch is open, the circuit is broken, and no current flows. Conversely, when a switch is closed, the circuit is completed, allowing current to flow unhindered. Various types of switches are available and used for different applications.
This article will learn switch basics, their types, how they work, and why they are essential in electronics.
Switch basics
A switch is a crucial component that controls the flow of electric current within a circuit.
Like in your home, you press a button the appliances like fans, TVs, and phone chargers start working. This is because they have switches which are controlling the flow of current to the appliance.
These are used in the circuit for the same purpose to control the flow of current to specific parts.
In simple words,
The switch is an electronic and electrical component that controls the flow of current in a circuit.
It has two primary states: open (off) and closed (on). When a switch is open, it breaks the circuit, preventing the flow of current.
In an open state, the electrical contacts within the switch are physically separated, creating a gap that interrupts the path of the electric current.
Conversely, when a switch is closed, it completes the circuit, enabling the flow of current. In the closed position, the contacts within the switch come into contact, allowing the electric current to pass.
Electrical symbol
The electrical symbol of a switch is a graphical representation used to depict a switch in circuit diagrams or electrical schematics.
The electrical symbol of a switch depends upon the type of switch used in a circuit. There are various types of switches and each has a specific symbol.
The symbol given in the above circuit is most commonly used for switches in a circuit diagram.
There are other variations and specialized symbols for different types of switches, which will we discuss later in this article.
Types of switches
There are various types of switches but the two main types in the switches are divided: Mechanical and Electrical switches.
Let’s talk about these two types in detail.
Mechanical switches
Mechanical switches are a type of switch that rely on physical movement or mechanical action to control the flow of electric current.
These switches typically use physical contacts that make or break electrical connections when the button is pressed.
There are three main components of a mechanical switch, the contact, actuator, and springs.
The contacts are the crucial parts of a mechanical switch that physically touch or separate to complete or interrupt the electrical circuit.
The actuator is the part of the switch that initiates the mechanical action to open or close the contacts and the springs are to provide extra force for contact movement.
The mechanical switches are further divided into many different types.
1. Single pole single throw
This is the simplest type of switch, consisting of a single contact that can be either open or closed.
It has two terminals and is commonly used for basic on/off control. The switches in the home for turning light on and off are single pole single throw switches.
2. Single pole double throw (SPDT)
This switch has a single input terminal, and it can connect to one of two output terminals. It allows for toggling between two different circuits or positions.
One common application of an SPDT switch is in audio systems, where it is often used as a selector switch.
For instance, in a stereo amplifier, an SPDT switch can be employed to choose between different audio sources such as a CD player or radio.
3. Double pole single throw
This switch has two separate contacts that are simultaneously controlled by a single actuator. It can open or close two separate circuits simultaneously.
In simple terms, it has two isolated paths that can either be opened or closed simultaneously.
One common application of DPST switches is in the control of dual power sources or devices requiring a complete disconnection from both power lines.
4. Double pole double throw
A form of switch with two sets of contacts that may simultaneously control two different circuits is called a Double-Pole Double-Throw (DPDT) switch.
The switch has two positions on each pole, which enables it to connect to two distinct sets of terminals.
In electronic circuits, reversing a motor’s direction is a typical application for DPDT switches. In these situations, the user can successfully reverse the motor’s rotation by switching the polarity of the current passing through it by using the DPDT switch.
5. Push button
The most common type of switch used in electronic circuits is the push button. A momentary switch is pressed to make a connection and released to break it.
These switches are found in various devices for functions like power-on, reset, or doorbell activation.
6. Pressure switch
Pressure switches are devices that sense changes in pressure and use these changes to open or close an electrical circuit.
They are commonly employed in various industrial, commercial, and domestic applications where monitoring or controlling pressure is crucial.
One example of a pressure switch is found in water pumps used for well systems. In this context, the pressure switch is responsible for regulating the water pressure within the pump and tank system.
Once the pressure goes down from the set point the switch turns on the pump and when reaches the desired pressure it will turn off the pump.
7. Temperature switch
Temperature switches are devices designed to respond to changes in temperature and actuate a switch, opening or closing a circuit based on preset temperature thresholds.
These switches are essential where temperature control is crucial. One common example is the thermostat used in household heating and air conditioning systems.
When it senses the change in temperature from the set point it will turn on the air conditioner and when the room temperature reaches to desired temperature it will turn off the device.
8. Rotary switch
A rotary switch is a type of switch that operates by turning a spindle to different positions, each corresponding to a distinct circuit or function.
One common example of a rotary switch is the mode selector on a camera. In photography, the mode selector allows users to choose different shooting modes such as auto, manual, aperture priority, or shutter priority.
As the user rotates the switch it will set to the desired function you want.
Electrical switches
The electrical switches as the name suggests are the type of switches that are controlled by electrical charges or current. They can be either electro-mechanical or semiconductor-based.
They are also divided into some other types. Let’s discuss these.
1. Relays
Relays are electro-mechanical switches. They use a coil that produces a magnet field when current passes through it.
This magnetic field attracts or repels fixed-type magnets connected to the switch to operate different devices.
Relays used for controlling high-power devices with low-power signals are commonly found in industrial and automation systems.
2. Bipolar transistor
The bipolar transistor is also used as a switch in various circuits. The transistor has three operating regions.
The active region is not used while the transistor is used as a switch. The transistor is mainly operated in saturation and cut-off regions to operate as a switch.
In saturation, the transistor is fully on and it is fully off in the cut-off region which makes it a valuable option for switching.
Why do we use switches?
Switches are essential components in electrical and electronic systems, serving a variety of purposes that are crucial for the control and operation of devices.
There are various vital uses of switches in today’s world. Here’s a detailed explanation of why switches are used.
1. Control of electrical current
Switches allow users to control the flow of electrical current in a circuit. By opening or closing the circuit, switches determine whether electricity can reach a device or component.
For example, The amount of current that goes to the lightbulb in your house is managed by a light switch. When the switch is turned on, the circuit is completed and power can reach the lightbulb, lighting the room.
2. Power ON/OFF functionality
To turn the device ON and OFF the switches are used. This is a basic yet crucial function in various electronic systems.
Just like the power button on a computer or the on/off switch on household appliances like televisions and washing machines.
3. User interface interaction
Switches serve as the interface between users and electronic devices, allowing users to interact with and control the behavior of the system.
The buttons on a TV remote control, allow users to change channels, adjust volume, or turn the TV on/off is one of the examples of user interface interaction.
4. Mode selection
Electronic gadgets include switches to allow users to choose between various operating modes or settings, giving them a greater degree of functionality.
A washing machine might have a switch to select different wash cycles (normal, delicate, etc.) or a camera with a mode dial for selecting shooting modes (auto, manual, etc.).
5. Safety and emergency stop
Switches are integral to safety systems, providing a quick way to disconnect power in emergencies or stop the operation of machinery.
Emergency stop buttons in industrial settings or safety switches on power tools to quickly cut off power.
6. Automatic control
In automatic control systems, switches are used to enable or disable specific functions according to established requirements.
Thermostats in heating systems that, depending on the temperature setting, employ a switch to turn the heating element on or off.
These are some reasons that make switches an important tool in various electrical and electronic applications.
Switch ratings
Switch ratings define the electrical characteristics a switch can handle safely. These ratings help in selecting the right switch for any application.
The swtich ratings include:
- Current rating
- Voltage rating
- Power rating
- Mechanical rating
Voltage rating (maximum voltage the switch can operate without arcing), current rating (maximum current it can carry without overheating), and power rating (maximum power it can handle, combining voltage and current). Exceeding these ratings can damage the switch or lead to failure.
If you want to learn more about swtich ratings check our article:
Testing of switch
We can also test the switch to check whether it is functional or not. A digital multimeter will be very helpful for testing switches.
Here I will provide you with step-by-step guidelines on how you can test your switch using a multimeter.
- First, you have to grab the switch which you want for the test.
- Turn on the multimeter and set it to the continuity mode, if this mode is not available set it to the resistance mode.
- If you have a two-terminal switch, there are only two connections. These are commonly labeled as “COM” (Common) and “NO” (Normally Open). Sometimes, there might be symbols (like “o” for common and “>” for normally open).
- Connect one probe to the COM terminal and the other to the NO terminal.
- If the switch is good and in closed mode, the multimeter will produce a beep in continuity mode, and in resistance mode it will show low resistance.
- Move the switch to the open position and test for continuity again. There should be no continuity or no beep. In the open position, the resistance will be high.
This same process can used for three terminal switches. By following these steps, you can effectively test any switch to determine if it is functioning correctly.
If the switch fails any of these tests or exhibits signs of damage, it may need to be replaced.
If you want to learn more about switch testing, check out our article:
Conclusion
Switch plays a crucial role in controlling different parts of a circuit.
A switch is a device that is used to control the flow of electric current. It is commonly used to turn a circuit on or off, allowing or interrupting the flow of electricity.
There are various types of switches but two main types are mechanical and electrical switches. These types are further divided into many other types.
Switches are used for various functions in a circuit. Some functions of switches are the following
- Control of electrical current
- Power on/off functionality
- Mode selection
- User interface interaction
- Safety and emergency stop
- Automatic control
The testing of switches is also very important to know whether the switch is good or bad. The multimeter in continuity or resistance mode be used to test a switch.
This was all about the switches, I hope it will be helpful.
Thank you…
Other useful posts:
