What are the pins for in this Relay module?
Typical relay module clone, they are all similar. Below schematic is per channel.

Keep in mind that RY-VCC (JD-VCC in the schematic) is for the Relay section, while VCC on the 4 pin connector is for the opto-isolated side.



https://arduinoinfo.mywikis.net/wiki/ArduinoPower for a full wiki on using these.