Arduino based 12V temperature control

This Arduino based temperature control housing was created during the development of my custom made heated printbed for the Dremel Idea Builder (http://www.thingiverse.com/thing:1608745).

The underlying PCB for the heated printbed includes already a 100k NTC thermistor as well as plugs for easy connection of temperature readout as well as power input. Unfortunately I did not find a ready made temperature controller for exactly this specific combination of 100k Ohm NTC thermistor and 500 Ohm resistor, thus decided to design my own temperature controller.

If anyone finds a better solution - feel free to post a comment / link.