NOT all stl-files have to be printed for a single lamp!
The circuit diagram and the firmware (ATtiny85) for the dimmer can be found at http://dede67.bplaced.net/Arduino/LED-Dimmer/LED-Dimmer.html.
Screws (DIN 933) needed: M4x25, M4x30, (M5x40 for ZwingeBuegel only)
EDIT 2018-04-11: uploaded a new (better!) version.
Instead of ZwingeBuegel I now use FoldbackAdapterV2ab for mounting the lamp.
I now have three of these lamps productive - two of them are dimmable.
A customizable version of FoldbackAdapterV2ab can be found at https://cults3d.com/en/3d-model/tool/foldback-clip-adapter.
Printed in PLA.