Single-channel Relay HAT Expansion Board

Product Overview

This product is a single-channel relay Raspberry Pi expansion board, compatible with Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B, STM32, ESP32, Arduino, and more. It features onboard optocoupler isolation and level-shifting circuits, making it compatible with 3.3V and 5V systems.

Product Features

Power Supply Voltage: 3.3V/5V
Relay Load Capacity: NO: 10A 250VAC/28VDC; NO/NC 5A 250VAC
Relay Operation Indicator LED: Allows easy monitoring of relay status
Optocoupler Isolation Circuit: Strong anti-interference capability, stable operation
Open-source Example Programs: Provided for Raspberry Pi and Arduino development boards

Product Specifications

Dimensions	45mm (Length) * 28mm (Width)
Weight	100g (Net Weight: 21g)
Power Supply Voltage	3.3V/5V
Optocoupler	LTV-357T-B-IN
Trigger Level	Low-level Trigger

Usage

The relay control pin DRV is triggered by a low level. When the VCC supply voltage is 3.3V and the DRV pin's logic level is 0V and 3.3V, the VIO switch can be set to the VCC or 3V3 position. If the VCC supply voltage is 5V and the DRV pin's logic level is 0V and 3.3V, the VIO switch should also be set to the 3V3 position. However, if the logic level is 0V and 5V, the VIO switch should be set to the VCC position. The corresponding states of the switch for different VCC and DRV pin drive voltages are shown in Table 2-1 below:

VCC Voltage	DRV Signal Level	VIO Switch Position
3.3V	0～3.3V	VCC/3V3
5V	0～5V	VCC
5V	0～3.3V	3V3

Module Resources Overview

The resource overview is shown in the diagram below:

1. Power Indicator LED

2. Relay

3. Relay Output Terminals

4. Relay Working Indicator LED: The LED is on when the relay's normally open (NO) terminal is closed and the normally closed (NC) terminal is open. The LED is off when the NO terminal is open and the NC terminal is closed.

5. Relay Control Signal Level Selection Switch: Can be set to VCC or 3V3

6. PH2.0 1x3P Connector

7. 2.54mm 1x3P Pin Header

Relay Wiring Diagram is as follows:

Raspberry Pi Platform Example Program Usage

The example code is available in two versions: one for the WiringPi library and one for the Lgpio library. The Bullseye system uses the WiringPi library, while the Bookworm system uses the Lgpio library.

Wiring Definition

In the Raspberry Pi mainboard, the example program for the Bookworm system uses BCM numbering for pin definitions, while the Bullseye system uses WiringPi numbering. The pin wiring definitions for the Raspberry Pi mainboard are as shown in the table below:

Table 2-2 Relay HAT and Raspberry Pi Interface Definitions
Expansion Board Interface	Pin Function	BCM numbering	WiringPi numbering
VCC	3.3V	3.3V	3.3V
GND	GND	GND	GND
DRV	Relay Trigger Pin	26	P25

WiringPi Library Installation

sudo apt-get install wiringpi
wget https://project-downloads.drogon.net/wiringpi-latest.deb #

Raspberry Pi 4B Version Upgrade

sudo dpkg -i wiringpi-latest.deb
gpio -v #

If version 2.52 appears, it indicates that the installation was successful.

# For the Bullseye branch system, use the following commands:

git clone https://github.com/WiringPi/WiringPi
cd WiringPi
. /build
gpio -v #

# Running gpio -v should display version 2.70. If it does not, it indicates that the installation is incorrect.

If you encounter the error "ImportError: No module named 'wiringpi'" when running Python example programs, use the following command:

# For Python 2.x version

pip install wiringpi

# For Python 3.x version

pip3 install wiringpi

Note: If the installation fails, you can try the following compilation and installation steps:

git clone --recursive https://github.com/WiringPi/WiringPi-Python.git

Note: The --recursive option automatically pulls submodules; otherwise, you will need to download them manually.

Navigate to the downloaded WiringPi-Python folder and enter the following commands to compile and install:

# For Python 2.x version

sudo python setup.py install

# For Python 3.x version

sudo python3 setup.py install

If you encounter the following error:

If you encounter the error, enter the command sudo apt install swig to install SWIG. After installation, run sudo python3 setup.py install to compile and install. If you see similar information, it indicates that the installation was successful.

Lgpio Library Installation

For the Bookworm system, the example program uses the Lgpio library. The installation command for this library is as follows:

wget https://github.com/joan2937/lg/archive/master.zip
unzip master.zip
cd lg-master
make
sudo make install

Run Example Program

Python:

Enter the Python directory:

cd /home/pi/raspberry-pi/relay-lgpio/python

cd /home/pi/raspberry-pi/relay-wiringpi/python

Execute：

sudo python3 relay.py

Enter the C directory:

cd /home/pi/raspberry-pi/relay-lgpio/c

cd /home/pi/raspberry-pi/relay-wiringpi/c

Execute：

sudo make clean
sudo make
sudo ./main

Arduino Platform Example Program Usage

Wiring Definition

The wiring definitions for connecting the module to the Arduino UNO mainboard are shown in the table below:

Table 2-3 Module and Arduino Pin Definitions
Pin Interface	Arduino UNO
VCC	5V
GND	GND
DRV	D7

Run Example Program

After wiring according to Table 2-3, open the project file demo codes\Arduino\relay.ino using the Arduino IDE. Then, select Arduino Uno in Tools -> Board and the corresponding port in Tools -> Port. Click Verify to check for errors, and if verification is successful, upload the code to the Arduino Uno. Observe the relay status.

Resources

Datasheet

Technical Support

Technical Support and Product Notes