In this note, we are going to know about a topic called “What is a Relay Module? and Its Function and Uses. Welcome to Poly Notes Hub, a leading destination for engineering notes.
Author Name: Arun Paul.
What is a Relay Module?
A relay module is an electrical component that functions as a switch, allowing low-power signals (such as those from a microcontroller) to control high-voltage or high-current devices such as lights, motors, or household appliances. It serves as a link between logic-level electronics and electrical devices that require more voltage or current to function.
Important Functions of Relay Module
The primary functions of a relay module are electrical isolation and switching control. When a tiny input voltage (usually 5V or 3.3V) is applied to the module, an electromagnetic coil inside the relay is activated, causing an internal switch to open or close. This technique enables:
- High-voltage devices can be turned on and off using a low-voltage control signal.
- Protecting the regulating circuit from electrical spikes and overload.
- Offering safe and automated switching of AC or DC devices.
Key Components of Relay Module and Its Terminals
Here, we have listed some key components used in the construction of the relay module. Also, in the picture below, we have shown the terminals of the relay module that are used to connect with the microcontroller or any device to get operation from it.
- Relay (Electromagnetic switch)
- Optocoupler (For isolation)
- Transistor (For driving the relay)
- Flyback Diode (To suppress voltage spikes)
- LED Indicator (To show status)
- Screw Terminals (For output connection)
This is the circuit diagram of a relay module. In this circuit, we have shown that how all the components are connected in the relay module PCB
📌 Noted: The output connections on the screw terminals are NC (Normally Closed), COM (Common), and NO (Normally Open). The transistor is used here for switching the circuit from NC to NO. There are two LEDs or light emitting diodes in the module, one is RED (Power LED) and another is GREEN (Switching Indicating LED).
Types of Relay Module
There are various types of relay module –
In the above picture, we have shown 5 types of relay modules, from which you will get an idea about relay modules.
- 1 Channel Relay Module – A 1-channel relay module has a single relay on its PCB. It is used to regulate a single electrical equipment. It’s ideal for simple tasks such as turning on and off a light or fan.
- 2 Channel Relay Module – This type of relay module has two relays on the PCB and it is used to control two separated devices on a single time.
- 3 Channel Relay Module – Control 3 separate devices.
- 4 Channel Relay Module – Control 4 separate devices.
- 8 Channel Relay Module – Control 8 separate devices.
There are other types of relay modules based on the number of relays attached to the PCB.
Common Uses of Relay Module
There are various applications or uses of relay module –
- Used in home automation.
- Used in industrial control panels.
- Used in college and school projects or robotics.
- Used in security systems, automobiles, and many other applications.