Since Wemos D1 mini's I/O pins are 3.3V and it didn't switch on the relay when HIGH signal was given to the input pin of the relay module. Then I changed the trigger position to LOW in my relay board and observed that it could be driven from the low level trigger successfully.
Is that safe to use Low level trigger? (I want to avoid switching on the relay accidently on the occasions such as Loss off power to microcontroller side , When microcontroller is booting up etc.)
Your illustration shows the 12 V version but you refer to the 5 V version.
That suggests you had the module wired wrongly in some way. There is no reason it will not work as either a high or low level trigger device.
The correct wiring is to connect the DC + and - to your 5 V supply. Not 3.3 V.
Remove the jumper. Connect the "Com" pin to 3.3 V on your ESP module for low level trigger, ground for high level trigger. Connect the "IN" terminal to your ESP output pin. Incidentally, it does not matter if you swap these two; the "Com" pin and the "IN" terminal.
Yes as you said I hooked up the wiring correctly. The relay module and the board is directly connected to a 5V 1A source. It worked well with Arduino Nano .
For Wemos D1 mini it doesn't work. So my guess was 3.3V signal from ESP module I/O pin wasn't enough to activate the transistor on the Relay Module.
