PaulRB:
MrMark:
I'd recommend against providing 3.3V directly from the step down converter as this makes the wiring and performance of the step down converter more critical than would be with using the Wemos on-board regulator.Can you explain in more detail please?
The ESP8266 uses a few tens of milliamps in normal operation, but when the radio is transmitting, the current consumption is much higher. I've seen brief current spike measurements on the order of 300 mA. Thus if the power supply is not robust there may be voltage sag at the ESP MCU which cause it to crash. This is a common problem with persons using the bare ESP modules (e.g. ESP-01) and much less a problem with persons using regulated power on module devices (e.g. NodeMCU or Wemos D1). It's also a fairly obscure pitfall and difficult to see without measurement equipment most hobbyists don't have on hand.
The potential issue with an off-board regulator is that the relatively high (compared to circuit board traces) resistance and inductance of the wires bringing in regulated power can cause significant voltage drops when the current spikes. That's not to say that off-board regulation can't be made to work, but enough people have experienced issues with ESP modules that it's a hazard best avoided unless there's a compelling reason to go there, particularly the electronics novice.