Hi there!
I’m working on some easy stuff but it’s not working. Under some conditions I want a led flash. No problems. At the same time I want a pin 2 to go high and wire that pin to a dfplayer vcc-in. My arduino gives about 4,9 v on pin 2 and the mp3 player won’t start.
When I connect the player direct to the arduino nanos 5v it starts.
Any ideas?
Digital output pins cannot be used to power devices like an MP3 player.
You can safely draw 20 mA from a Arduino Classic Nano pin, not much more. With other MCUs, usually far less than 20 mA.
2 questions:
When you have determined the answer to those 2 questions, you will have answered your topic question.
Current you say? What's that? 
Despite whatever resistance some may put up, I believe that most have the capacity to learn and that the prospect of being inducted into the halls of learning is an extremely motivating force (or EMF for short).
At least, I currently believe that. 
Hi there. I solved the problem. The player needed 5 v and just had 4,5 v. Two restistors and another 5v from the arduino added the missing 0,5. Thanks.
Bad idea, even if you use two pins to power the DFPlayer.
That module can draw up to 1Amp, depending on speaker impedance and volume.
You will have running problems and eventually burn out the pin(s).
Leave VCC of the DFPlayer connected to 5volt, and use the module's software to turn the module on/off.
Not the problem. A DFPlayer runs fine from 3.5volt.
Leo..
I see watt you did there.
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
Another Arduino?
Tom... 
Glad you have it working.
Have a nice day!
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