I’m working on a project in which I use a simple flash that normally uses 2 AA batteries (=3 volt). My power source is a 3.7v LiPo battery. Can I directly connect the flash (3v) to the battery (3.7v) or would that destroy the flash or the battery?
Or could I use the Arduino Nano 3.3v pin? Unfortunately, I don’t know the power consumption of the flash. Maybe the picture attached helps.
If I can’t do that, what would be the recommended way to get 3v out of 3.7v, I’ve seen a lot of tutorials doing that with resistors, is that the way I should go?
Odds are you'll be OK with 3.7V.
I wouldn't try the Arduino's 3.3V output because it has very-limited current capability.
Put a diode such as 1N4001 in series with the battery and it’ll drop around 0.4 to 0.7 volts - and provide reverse connection protection to boot.
As jackrae says, put a single standard diode in series and you will be fine.
Although i would use a more beefier one than 1N4001 (only rated for 1 Amp)
When the flash is charging it draws 5-10A+ from the battery, so there is no way that you can power this from an Arduino-pin.
Don't forget that the charged voltage of a 3.7V battery is 4.2V.
When you buy the battery you'll want to look for one that has a battery protection circuit built in. With a cylindrical cell it's easy to identify as there will be a dimple on the negative (flat) end.