Looking for practical Arduino projects? This guide shows how to control a relay from your smartphone using an Arduino Uno — either via Bluetooth or Wi-Fi.

The Uno R4 chip (pictured) that Arduino debuted today is the new top-end option in its Uno series of microcontroller boards. The series is the company’s most popular product line.

Using a USB-C phone with Power Delivery is ideal here, as it allows the phone to be powered while also communicating with the Arduino over USB. The RemoteXY app is built specifically for this purpose.