What is it?

This is a 4-channel Relay HAT designed for Raspberry Pi, also called "Relay DDL" (short for relay stack). It allows low-voltage signals from Raspberry Pi to safely control high-voltage devices, making it one of the most affordable and secure ways to build DIY smart home hardware. It connects directly to Raspberry Pi via GPIO and I2C, supports plug-and-play installation, and can be stacked up to 4 layers (16 relays).

Why did you make it?

We wanted to provide makers and developers with a simple, safe, and cost-effective way to control home appliances and electronic devices using Raspberry Pi.
From fans, fish tanks, classroom lighting, to laser toys for pets, this relay board makes automation projects easier and more creative.
By combining with cloud platforms like Tencent Cloud, Alibaba Cloud, or GIZWITS, users can even build IoT solutions directly at home.

What makes it special?

1. Fully programmable with multiple languages (C, Python, Java, Shell).
2. Direct control without coding using I2C commands.
3. Stackable design — up to 4 boards, total 16 relays.
4. GPIO expansion and multiple I2C addresses supported.
5. Relay status indicator LEDs for easy debugging.
6. Supports 3A 250V AC / 3A 30V DC.
7. Independent from Raspberry Pi hardware (I2C supported).
8. Compatible with Raspberry Pi, Banana Pi, ASUS Tinker Board, Orange Pi, and more.
9. Safe wiring design (NO/NC/Common) for reliable load control.
10. Official compatibility tested.

How to use it?

To get started, install the Raspbian system on your Raspberry Pi, connect it to the network, and enable SSH service using: sudo raspi-config

Then check the device base address with: i2cdetect -y 1 Normally, the address will be 0x10.

If the command is missing, install i2c-tools with:

sudo apt-get update sudo apt-get -y install i2c-tools

Once ready, you can control the relay directly from the command line. For example, to turn on the first relay: i2cset -y 1 0x10 0x01 0xff

• -y 1 → defines i2c bus (bus 1)
• 0x10 → base address of the relay board
• 0x01 → the first relay (0x02 = 2nd, 0x03 = 3rd, 0x04 = 4th)
• 0xff → turn relay ON (0x00 = OFF)

You can also write a shell script, make it executable, and run it:

chmod +x relay.sh ./relay.sh

The Relay HAT supports multiple programming languages. For example, in C:

gcc relay.c -lwiringPi -o relay ./relay

Or in Python (install smbus2 first): sudo pip3 install smbus2 Then:

chmod +x relay.py ./relay.py

With these methods, you can easily integrate the relay board with sensors and automation tasks—for example, turning on a fan when the temperature exceeds 25°C.