Arduino boards and the like are great for lighting up an LED or sending signals, but when you want to work with more powerful devices, you’ll need additional hardware. Relays are one way to control extra juice, and while slower than transistor-based options, their simple design using actual magnetically-controlled switches makes them easy to understand and implement.
If you need to control a multitude of relays, the 16 Channel I2C Electromagnetic Relay Module IoT by KRIDA Electronics could be a great solution. As per its name, this board features 16 relays, which can be controlled by a single I2C signal. As shown in the video below, an Arduino Uno can click all 16 of these devices on or off, indicated by LEDs next to each one.
Relays used here are rated at 10 amps, and should be good for 10 million operations. You can hear the device clicking away in the video below, along with their indicator LEDs to display which relays are active. For a faster, less-clicky version you might be better served with this 8-channel solid-state relay (SSR) device, which we featured in 2019. There’s also a 16-channel SSR version if you so prefer.
