user80590: I read this answer https://arduino.stackexchange.com/a/51878 to a different, but related question. It seems like VIN on the NodeMCU is directly or via diode connected to the USB connector.

Image source: https://arduino.stackexchange.com/a/76119
I'm going to run my NodeMCU with a 5 V power supply connected to the USB connector. And I also need approximately 5 V for another part. So I was thinking of connecting it to VIN of the NodeMCU. So I don't want to power the NodeMCU from VIN, but I want to draw power from VIN for another part.
Is that a bad move or perfectly fine? And if it's okay, how do I find out the maximum current? Because I think the line from USB connector to VIN has some limits, so to not damage the board?

user4143: You cannot power items from the VIN pin of the NodeMCU V3.
The power circuit is like this:

simulate this circuit – Schematic created using CircuitLab
As you can see no current can flow out of the VIN pin because of diode D2.
You could, though, draw current out of the VU pin, though (situated at the top left of the board when the text is normally oriented) which is directly connected to the USB port's 5V pin.  How much current can you draw? Well, there's nothing in the circuit to limit it, so whatever the USB port that the board is connected to will provide (less enough to run the ESP8266 module).
If you want to draw 1A through the VU pin and the power supply is rated for 2A there should be no problem. The traces for the VU pin are reasonably chunky.
A better solution though would be to power the NodeMCU board and your external components through separate power feeds from the power supply - that way there can be no interference from the board.

80590: <p>I read this answer <a href="https://arduino.stackexchange.com/a/51878">https://arduino.stackexchange.com/a/51878</a> to a different, but related question. It seems like VIN on the NodeMCU is directly or via diode connected to the USB connector.</p>
<p><img src="https://i.stack.imgur.com/AW6ER.png" alt="" /></p>
<p>Image source: <a href="https://arduino.stackexchange.com/a/76119">https://arduino.stackexchange.com/a/76119</a></p>
<p>I'm going to run my NodeMCU with a 5 V power supply connected to the USB connector. And I also need approximately 5 V for another part. So I was thinking of connecting it to VIN of the NodeMCU. So I don't want to power the NodeMCU from VIN, but I want to draw power from VIN for another part.</p>
<p>Is that a bad move or perfectly fine? And if it's okay, how do I find out the maximum current? Because I think the line from USB connector to VIN has some limits, so to not damage the board?</p>
 4143: <p>You cannot power items from the VIN pin of the NodeMCU V3.</p>
<p>The power circuit is like this:</p>

<p><img src="https://i.stack.imgur.com/wXlJs.png" alt="schematic" /></p>

<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fwXlJs.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>
<p>As you can see no current can flow out of the VIN pin because of diode D2.</p>
<p>You could, though, draw current out of the VU pin, though (situated at the top left of the board when the text is normally oriented) which is directly connected to the USB port's 5V pin.  How much current can you draw? Well, there's nothing in the circuit to limit it, so whatever the USB port that the board is connected to will provide (less enough to run the ESP8266 module).</p>
<p>If you want to draw 1A through the VU pin and the power supply is rated for 2A there should be no problem. The traces for the VU pin are <em>reasonably</em> chunky.</p>
<p>A better solution though would be to power the NodeMCU board and your external components through separate power feeds from the power supply - that way there can be no interference from the board.</p>
