Could I connect such a PID temperature controller to an existing Makerbot hot-end?
Would that work with the existing thermistor or are there vast differences and I need to find a way to drill an hole+thread into it to insert the temperature probe that comes with the PID controller?
http://www.jonshobbies.com/convert-a-cnc-router-to-a-3d-printer.html
He says in the post that it’s a thermocouple. Thermocouples act on a different physical characteristic than thermistors, so it’s unlikely give useful results.
I think this most common type of thermocouple gives an output of 41uV/C (ref http://en.wikipedia.org/wiki/Thermocouple#K) and thermistors have a varying resistance, and you have to provide an electrical network and external voltage in order for there to be any output (ref http://en.wikipedia.org/wiki/Thermistor#B_or_.CE.B2_parameter_equation).
You’ll have to thermally couple the thermocouple to the hotend of you want it to work with a PID controller that takes thermocouple inputs. You can probably just use kapton to tape it to the hotend and insulate around it (with what, I’m not sure) and get an accurate enough reading.
Maxim makes a few thermocouple adc and amplifiers. They need cold junction compensation to get useful values.