The 3v pin on nodemcu gives different voltages

Edit: grammer

Hello, I’m new to NodeMCU board. I connected a simple LED + 330 Ohm resistor between GND and 3V, and the 3V pin read -1.86 V. But when I connected a potentiometer between GND and 3V, with the middle tap at A0, the 3V pin seems to output 3.3V just fine. Why is this?

Although I’m new to this, I’m also an electrical engineering undergrad. Please let me know things I should.

how did you connect it exactly and how/where did you measure the voltage?

Sure it was 330 ohm ?

So according to the pinout diagram, I connected the LED and resistor between the GND and 3V below TX.

It was about 326 Ohms.

What your saying is very confusing unless you are not using ground as reference. Why not post a schematic, since your an engineering undergrad you should have the tools available and skilled in using them. It sounds like the LED is very bright and probably RED in color. Put your little finger on the 3V regulator and count to 10 slowly, if you cannot keep it there you have a definite overload.

Please upload a picture of your setup with your leads to show exactly how/where you’re measuring voltage.


Untitled Diagram(1)

The LED didn’t turn on, as expected.

To verify, when you have no LED, there’s 3.3V? What happens when you put the leads on the other way, +1.8V? And what happens if you connect the LED backwards?

I just tried and it’s working as expected

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Strangely, now it seems everything is fine. That seemed most peculiar.

Well, thank you everyone. There must have been an error on my part, or maybe the NodeMCU does this sporadically.

Also its my first time posting so please don’t be harsh.

I probably would say the error is on the way you wired or tested.

The NodeMCU 3.3V is probably straight out of the big regulator you see in the middle of your board which is probably used as well for the ESP12E

The AMS1117 is a cheap copy of the LM1117 which can output Current of more than 1A. So driving a LED should be fine.

No, it does not :exclamation:
Perhaps you measured the voltage over the led in reverse, or your multimeter is bad, or it was connected in a different way than you thought.
When you use a breadboard, then it can have bad contacts. Jumper wires can be broken. Check the wiring and every connection and you should be fine :smiley:

Reverse your meter leads.

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