Software for the 3€ China Espressif ESP8266 ESP-01 Relay Modul.
Inspired by the very good article in Elektor Magazine https://www.elektormagazine.de/news/eineinfacher2wlanschalterderfunktioniert
Just take the RelayBoard.ino file and compile and upload it with the Arduino IDE to the ESP-01 Board. Put the ESP-01 back in the Relay Module and start it up. The ESP-01 will open it's own WiFi network named "Relay-Modul". Go in this Network and open Browser at http://192.168.1.1 You will land on the StartPage. Go to Settings and enter all Data from your WiFi Network. It's easier when you set a static IP. Save it and wait 1 minute. Go back in your Network and open the URL to the IP you entered. http://yourIP Enjoy your IoT Relay.
PLEASE don't use the relay for 110V or 220V on power grid! Just for low voltage switching!
SetUp Arduino IDE for Espressif: https://m.heise.de/make/artikel/ESP-Boards-mit-der-Arduino-IDE-programmieren-4130861.html?seite=all
Module from Front View
Module from Side View
Start Page when view in Browser
Settings Page to edit parameters