Wemos d1 mini pro will not connect when powered via 5v pin

I have a wemos d1 mini pro that the works fine if plugged in to the serial cable port(mini usb). Connects and I can access it with no issue. However, if I connect it via 5v to the 5v and ground pins, the blue light will flash on and off, but it never connects? Is this not an input pin? If it is not which pin can you power it with?


what is the 5V source?

Hi @neketege88
to make it easier to help, post a schematic of your project.
It can be done by free hand.
Do not use fritizing image, which is not schematic.

RV mineirin

Definitely sounds like a problem with your 5V power supply. What can you tell us about that? Might be worth trying a large cap, e.g. 100uF+, to the 5V pin close to the Wemos.

Thank you all! It was the power supply. I was using a 120v to 5v phone charger type power supply and I changed to a different on and now it is working as it should.

The weird part about it is the same "block" power supply that I was using to plug the serial cable (micro usb) into was the same "block" I was using to run the 5v out of to the 5v pin.... Not exactly sure why it didn't work, but I have it going now....


Sorry, I can't understand what you are saying.

Sorry for the confusion.
Something like this is what I had the micro Usb plugged in to and it worked.
I used the same thing but ran the 5v+ wire and grnd wire coming out of it directly to the 5v and grnd pins on the wemos and it did not work. I would think the wemos should have been getting the same amount of power both ways it was connected, but obviously something wasn't right.

Let me try to guess what you are trying to say.

You used this same PSU with 2 different cables?

Cable #1 has USB-A plug at one end and micro-USB plug at the other end. You connected the micro-USB plug to the micro-USB socket on the Wemos.

Cable #2 has USB-A plug on one end and bare wires or PCB pins on the other end. You connected the PCB pins to the 5V and GND pins on the Wemos.

Is that correct?


Must have been the wrong wires. :face_with_raised_eyebrow:

Possibly. There were 4 wires, but I checked with dvm and had 5v from the two wires I used. I am not sure what the other two do….

This might help:


Thanks! This is interesting. I wonder if when I tested with dvm if I got 5v using either the data + or data - as one of the legs. And im guessing the data voltage is not constant but would be 5v at some times?


Probably. If it´s so, @Paul_B is right and you probably connected the wrong wires in your circuit.

I share your guess.

That is indeed what I am thinking.

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