Here is the proper schematic diagram:
The PCB design:
I ordered it from SeeedStudio, so the professionally made board is also in my hands:
The built electronics:
Actually the design is not as good as it can be. I rather like my things in enclosed boxes. Here it wasn't an option as I need to access to the current limiting potentiometer.
And finally in working:
Just additional video (it is made with the prototype on the breadboard), what this small circuit is usable for:
I've a better device in my mind, I may build it sometimes.