- Fri Oct 23, 2020 2:41 pm
A NodeMCU should work OK from 5V up on the external Vin. It feeds the regulator just like the USB (with an isolation schottky). Although some NodeMCU may be able to tolerate higher voltages that will because they have a higher voltage capacitor fitted. It is still not a good idea to feed a linear regulator with a higher voltage than necessary as it causes excessive heat and will drain the battery faster.
If you are having to use a higher voltage then I would suspect that there is something wrong with the boost converter particularly around whether it can supply the peak current requirements of the NodeMCU which can go up to 500mA.
As I said feeding this from 5V may be better idea if this can give a decent current. It will also probably work direct from the battery at least when well charged. The on board regulator fitted is not the best from a drop out viewpoint so that would limit how far the battery voltage can fall.
A SG90 servo should only draw about 300mA when running. This should not cause any difficulty even on the same rail as the NodeMCU. I have several servo applications using MG90 (metal gear equivalent) and they power the servos from same supply with just simple decoupling.