If you remember the article I did on the
single smart relay switch, there is now an expanded version of this board that is also based on the ESP8266 WiFi module but packs even more extra cool features such as DC power connectivity, four relays with optoisolators, 3.3V regulator, USB to UART converter, NodeMCU header for connecting OLED displays, as well as an LED for GPIO LED test.
The functionality of the single-way relay switch was already great for controlling light bulbs remotely via an android phone. But now, with the
four-way relay switch board you can connect even more sensors to the board and control four light bulbs at the same time.
The four relay board also features a 100-230V /5V AC/DC power supply to connect the board directly to mains electricity, two headers for connecting digital sensors, as well as a USB to UART converter onboard for programming the ESP8266 to your liking.
By the way, it's not just light-bulbs you can control. You'll also be able to create a WiFi smart power strip with four sockets and four two-way switches to control different appliances in parallel with each other, so you can turn on one appliance without having to turn on the others.