I was looking for a transformer from 230v to 5v. Although I found multiple options, the price per unit seemed a little too expensive about €3.00. While that does not look too expensive per unit, remember we also need a switch and an ESP module for WiFi connectivity. So, as an alternative I looked into these Sonoff devices.


After learning that these are powered by ESP8266, I knew I can flash them to a custom firmware to get rid of the more complex software pre-installed (Chinese firmware).

So, the SonOff cost me  €4.55 with free postage from our friends in China.

The first thing I always do when purchasing from China is to flash the firmware. I don’t know what is pre-installed and well I prefer to have more control.

  1. Download new firmware from
  2. Upload firmware
  3. Upload code as normal via Arduino IDE

Remember you will need to solder those pins, I prefer a pin head

The four serial pins (3V3, Rx, Tx, GND, GPIO 14).

Looks like i may end up sticking with the Sonoff with my own coded software.

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