Hello,
I have a class project to do: I would like to power a microbit IOT card with solar panels that provide a voltage of 5 V by USB cable (panels from my hiking backpack) but the card only accepts 3 V
I read that I could add a voltage regulator but I didn’t find which component to choose, can you please advise me?
thanks
Note: I sorta wrote my response backwards. Please note that the most important information goes from bottom to top 
The micro:bit does accept 5v through USB, or if you know how to strip the cable and get to the direct wires, you can solder a 5v connection right to the back of the board:
Of course, you should also keep milliamps in mind. There’s some very useful info here:
https://tech.microbit.org/hardware/powersupply
Now, if you knew for sure that the solar panel would always be sending 5v, you’d probably be fine going through the USB, but since solar panels are notoriously variable, you might want to consider either adding a variable-in step-down like this one:
However, if it were me, and if you’re not trying to operate the micro:bit only when there’s light, I’d hook the solar panel up to a rechargeable battery pack and (depending on the one you get) it should handle that conversion for you and store the extra energy instead of dispersing it.
Please keep in mind, I’m not a professional electrician and I don’t work for micro:bit…I’m just a maker.