Wemos D1 Mini Pro won't power on via VCC and GND pins, only powers on through micro USB

Hardware
1

I recently bought a Wemos D1 Mini Pro that would only power on if I plug the micro USB cable. When I try to power it on using the VCC and GND pin, it won’t power on. Curiously, when powered it on using micro USB, measuring the VCC pin gives me 5V.

I have another Wemos D1 Mini Pro and it wasn’t like this. You could power it from either micro USB or VCC pin. So are the other 5 Wemos’ that I have.

So is this Wemos defective?

1 Like
2

I’ve 2 d1 minis that have done the same. Not found a solution or reason yet.

3

I’ve seen mentioned a few places around the internet that some D1 minis can have weak and/or counterfeit voltage regulators. I wonder if that could be the cause?

4

Use your voltmeter and find out.

5

Sounds like they have a diode in series with VCC, and it is backwards.

6

I know this is old but a google search lead me here, if anyone else has this issue, it’s because the USB to serial IC draws power from the USB port directly, there’s a blocking diode preventing the 5v pin from reaching it, which is causing the enable pin to be low. I just removed the diode and bridged the pads (don’t need the USB port anymore).