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Topic: Getting 5V output from NodeMCU v3 (Read 321 times) previous topic - next topic

obuw

Hello all,

I'm trying to get a 5V output from my nodemcu v3 module for a sensor (which unfortunately doesn't work with 3.3V).

I have done a bit of digging, and found out that unfortunately the v3 version specifically doesn't let you to draw power from the VIN pin.

I'm already powering the nodemcu through the usb port, so I have 5V right there, but I can't access it!  :smiley-cry:


The easiest/cheapest solution I can think of is to add an extra usb connector, and power both the board and the sensor through that. But that seems so... inefficient...

Can't I somehow solder a pin somewhere on the nodemcu, or maybe use a voltage multiplier, to get a workable voltage? The sensor works fine with about 4.2V so I don't even need a full 5V.

Semtex9

#1
Oct 08, 2020, 08:31 pm Last Edit: Oct 08, 2020, 08:35 pm by Semtex9
OK, Vin goes to regulator and you can put 20V on it, is there a Vu pin, it should rout to usb 5V on the board? google the pinout...

obuw

There is indeed a VU pin, and yes! It has 5V! Thanks!

By the way, you can't put 20V to the VIN from what I have read. It can supposedly accept up to 20V but I've heard reports of boards frying with as little as 12V. The safe range for VIN seems to be 5-10V.

Grumpy_Mike

Quote
but I've heard reports of boards frying with as little as 12V
That is because they are cheap rip off clones with only a 12V rated capacitor, instead of 16V.

The common ratings for capacitors are 6.5V, 12V, 16V, 24V and 48V. And you should never run them any higher than 80% of the rated voltage.

Semtex9

Yup i wouldn't recommend going near max, just what I got from a 1 min google search...

Paul__B

#5
Oct 08, 2020, 11:39 pm Last Edit: Oct 08, 2020, 11:40 pm by Paul__B
OK, Vin goes to regulator and you can put 20V on it, is there a Vu pin, it should rout to usb 5V on the board? google the pinout...
No you can not!  :smiley-eek:

There is a (Schottky) diode feeding "VDD5V" from "VDDUSB" on the above schematic but the CH340 USB interface chip is supplied by "VDDUSB", so guess what happens when you provide more than 6 V to this terminal?  :smiley-roll:

Semtex9

#6
Oct 09, 2020, 01:43 pm Last Edit: Oct 09, 2020, 01:54 pm by Semtex9
There is a (Schottky) diode feeding "VDD5V" from "VDDUSB" on the above schematic but the CH340 USB interface chip is supplied by "VDDUSB", so guess what happens when you provide more than 6 V to this terminal?  :smiley-roll:
If Vin routs to Vdd5V schottky blocks it from 5Vusb line, usb chip dosent work, and it goes to 3.3v regulator powering the rest of the board, but fries the CH340G at more then 6.5V you mean to say? stupid board should power CH340G from 5Vusb, like it does with the other one... Much safer
I red that Vin pin can take more voltage looking at a bogus pinout image, sorry

Paul__B

I read that Vin pin can take more voltage looking at a bogus pinout image, sorry
Please cite that pinout/ schematic so we know the problem.

Semtex9

#8
Oct 09, 2020, 02:07 pm Last Edit: Oct 09, 2020, 02:14 pm by Semtex9
https://www.theengineeringprojects.com/2018/10/introduction-to-nodemcu-v3.html
These guys say: There is a candid difference between Vin and VU where former is the regulated voltage that may stand somewhere between 7 to 12 V while later is the power voltage for USB that must be kept around 5 V.

But there was an image that said Vin regulated input up to 20V
https://i.pinimg.com/originals/73/9f/9f/739f9f89055e789d4aa515bccd9d8f63.png
oh that's a slightly different board...

raschemmel

#9
Oct 09, 2020, 08:50 pm Last Edit: Oct 09, 2020, 08:53 pm by raschemmel
SN74LVC245A

Quote
Inputs can be driven from either 3.3-V or 5-Vdevices. This feature allows the use of this device as a translator in a mixed 3.3-V/5-V system environment.

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