Forgive me for this really dumb question. I am an amateur in electronics, and im trying to wrap up my head around this question and im not able to do so. Need your help.

Im trying to power up a nodemcu using a 5v 1A power supply- I connected +ve to Vin and ground to ground. But i see that 5v is not enough to power up the nodemcu. So i removed the 5V and connected to a 9V battery, and again I find the same issue- the power is not enough. Knowing that i did something wrong - i measured the voltage across Vin and ground and find it to be around 2.5V when using the 5v source and around 2.5V when using the 9 V battery too.

Confused and thinking that my nodemcu is corrupted, i ordered a new one, and did the same. But i find that when i try to supply power using Vin, the voltage across the device- Vin and ground is around 2.5V for the newer device also. Obviously Im missing something.

Can anyone tell me what is it that Im doing wrong. Please tell me how to power a nodemcu without using a usb and only using a 5v source.

  • 9V -> Arduino -> VIN -> NodeMCU 5V = dead NodeMCU.
    – Majenko
    Feb 4, 2018 at 15:54
  • No. the NodeMCU works on USB power still. Its not dead. Feb 4, 2018 at 15:56
  • Then you're lucky that a 9V battery is one of the weakest batteries around, otherwise it would have killed the NodeMCU. It's the current you need to consider. The voltage is 5V and must always be 5V. If it seems "too weak", increasing the voltage is a very very bad idea.
    – Majenko
    Feb 4, 2018 at 15:57
  • The 5v power supply is 1A. So with that too, the NodeMCU doesnt work. Am I missing something here? Please help me. Feb 4, 2018 at 16:00
  • Did you connect the 5v to the Arduino barrel jack or the USB?
    – Majenko
    Feb 4, 2018 at 16:02

1 Answer 1


I have a NodeMCU Esp8266 v3 (Lolin) and it works fine conecting Vin and G to my cell phone power supply rated 5.1V, 1000mA. This develop board has a aprotective diode (the closest to Vin), if you have a Multimeter o multitester you can check it measurement continuity. If your diode is damaged the power applied to Vin never be enough to power up the nodemcu.


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