My project is Charging Battery via Solar and Piezoelectric sensor while also getting the Realtime Voltage of the Battery, Capacitor, and Solar.

I want to use Vin as the source to get 5V because ESP8266 NodeMCU only has 3.3V output.

As the diagram shows, can it power 3 Voltage sensors and 2 Relays? or should i use an external power source?

Ps: The solar is the 'normally closed'

enter image description here

  • I don't see how your layout would work, as there + terminal of your battery isn't really connected to anything except the voltage sensor.
    – PMF
    Commented Jan 10 at 11:36

1 Answer 1


Vin is for powering the ESP via the onboard voltage regulator which converts Vin to 3.3V for the ESP. It's not a source of 5V unless connected via USB.

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