This is a dimmer circuit that allows you to control the brightness level of a light bulb in 256 steps.
It currently doesn't work with dimmable LED light bulbs!
The Caretaker source code is hosted at GitHub:
https://github.com/grappendorf/caretaker-devices
Subdirectory: caretaker-device-dimmer
It contains the source code and all Eagle (V6) PCB layout files.