B4R Question D1 R2 Ext Power


Well-Known Member
Licensed User
I have a WeMos D1 R2 that I am using again after a few years.


Using B4R 2.51 I'm seeing some strange stuff - sometimes it does not run, then all of a sudden works as expected; log output has garbage characters, then suddenly works; sending UDP I get random resets.

One guess is the the USB on my laptop is not providing enough power.

I seem to remember from years ago that I had an external power supply connected to the board (at circled connector).

I cannot find any manual or documentation online to confirm this is a power connector. I don't trust my memory enough to risk frying the board.

Can anyone confirm this is a power connector and providing external power may help with the errors I am seeing.




Well-Known Member
Licensed User
Just connected my board to a 5V power supply. Works fine.
Thanks. Right now I have mine connected to the USB of the laptop to get power (5 V) and serial.

Did you mean you connected to an external 5 V power supply to the connector circled in red above or do you have it similarly just connected to USB for serial and power?

I previously had a problem with a board that it was sometimes a little flaky if I didn't have a strong power supply - I think my laptop only provides the minimum amount of power. But, I don't remember whether it was this D1 R2 or some other board.



Active Member
Licensed User
The Wemos D1 R2 features an on-board switching power supply which allows you to power the board from a power supply up to 12V.
(Attention: the Wemos is a 3.3V device. If you connect it to 5V digital sensors or devices you will need a logic level converter.)
USB 2.0 ports are current limited. In some cases, when using only USB power and WIFI on the Wemos is on and sensors or other devices
are connected, the Wemos is not working correctly.


Licensed User
Try this....take a brush...dip in Petrol/ methyl alcohol...clean the usb connectors of your pc and D1 board...and also usb data cable connectors...such kind of problem is due to dust...on usb connectors..