ESP32 3.3v Regulated External Power + USB

[cihanalak]

Hello friends,

I have a question about my project. I have a NodeMCU esp32s v1.1 board. I have to use 3.3v regulated power supply and usb simultaneously. Getting started page of devkitc says that dont use different power sources same time.

Will it be a problem?

Or if i modify usb cable to data only (with cutting 5v line of usb cable), will it work with programming board and serial communicaton?

Best Regards
Cihan Alak

[Spile2]

By accident I connected to usb whilst powered by vin 5v. Result was a non working esp32.

[cihanalak]

Yeah, i know the result with 5v vin +usb but cannot find a solution with 3.3v +usb. I tried to disconnect 3.3v rail on power regulator but mcu still powered from cp2102.

[cihanalak]

Hello,

I think i made a solution about +3.3V + USB connection.
I made a Normally Close Logic Mosfet switching circuit and connected 3.3v through it.
When usb is connected, It gets signal from ESP32 Vin pin and disconnect 3.3v power.
When usb is disconnected, Vin signal goes low and circuit connect 3.3v to ESP32.
At first try, when usb is disconnected, esp32 resetted because of mosfet's turn-on delay and rising time. I solved that with 470u decoupling capacitor.
*schematics is at attachment

NCMosfetSwitch.png (15.63 KiB) Viewed 5414 times

Now i can connect and disconnect usb when 3.3v power connected.

Best Regards
Cihan Alak