[SOLVED] Wemos D1 mini - 5v and 3.3v pins

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1

Hallo Arduino people,
Forgive my ignorance, I'm a software developer and don't know much about electronics (yet). I hope you can help me, I've search the internet long enough already without finding answers.

The Wemos D1 mini has both 5v and 3.3v pins.

I know I can power it via the 5v pin, which is practically the same as powering it via USB.
Question 1: Is this pin INput only?

I've also noticed a 3.3v pin, in some diagrams also used to connect logic level shifter.
Question 2: What's this pin for? Is it input and/or output?
Question 3: Why would the logic shifter need to have both 5v and 3.3v connected? To close the circuit?

The upload image is from this page https://www.instructables.com/id/A-Quick-Guide-on-Logic-Level-Shifting/

Thanks.

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1 Like
2

Question 1: Is this pin INput only?
I've also noticed a 3.3v pin, in some diagrams also used to connect logic level shifter.
Question 2: What's this pin for? Is it input and/or output?
Question 3: Why would the logic shifter need to have both 5v and 3.3v connected? To close the circuit?

  1. No, it can be used as an output if you’re powering through USB.
  2. The 3.3v pin is an output only.
  3. The level shifter needs both voltages as inputs so it can provide both voltages as outputs. You should study the schematics of the level converters to better understand why both voltages are required.
3

Thanks you so much. 8)

Voltage pins are clear now. 5v in/out, 3.3v out. Tried to look at schematic of the Wemos, but could get to this conclusion.

I'll search for the schematic on the logic level shifter and try to read it knowing what you just tought me.

4

You should be able to use the 3.3V pin as an input also. This is useful if you want to power the board directly from a 3.3 V power source.

5

I think you about 3.3V also being input. Have not tested it yet though.

6

On Arduino boards where the microcontroller runs at 5 V (e.g. Uno), the 3.3V pin could be considered output only because it is being supplied directly from a 3.3 V voltage regulator (or a 3.3 V output pin on the USB chip in some cases). However, the ESP8266 microcontroller on the D1 Mini is running at 3.3 V so you can also supply it with 3.3 V via the 3.3V pin.