Hi Sokol1,

That's correct it is a 5v voltage regulator as simply put I decided to go with an older design of mega_mozg_13 work, the one shown by him on a picture.

There is also a spare red cable going from vcc promicro and a jumper pin in order to not to use external power and isolate the voltage regulator. Just in case if I will not have the external power for some reason.