The title does not tell the entire story. I have successfully powered my WeMos by supplying 5vdc to the 5v pin. My power source is 12v battery so I am using a buck converter to drop the voltage to 5v. All is well so far. However, I need to trigger 12vdc relays so I am using a ULN2803 Darlington IC to drive the relays.
I am using the same 12v battery source. This is where my problem seems to be. Everything works if I power the WeMos via USB but if I unplug USB and apply 5vdc to the 5v pin. I fry the WeMos if I leave it connected for more than a few seconds.
If I remove the yellow 5V connection in the lower left and connect USB, everything works. This is my first WeMos project and I'm not great at electronics so I may have everything wrong here. :-\
How can I use a single 12VDC power source to both power the WeMos and drive 12VDC relays?