Hacks to the RepRap Extruder Controller v2.2
This allows you to use a K-type thermocouple for temperature sensing as opposed to the standard thermistor. It uses the MAX6675 chip, and is easily put together on a small piece of stripboard that plugs into the I2C connector on the extruder controller board.
The first thing you'll need to do is to remove the 10uF capacitor C8 from the board at B in the picture. You can also remove the thermistor connector (at A) and replace it with a pin. Alternatively, just screw the connection from the new board into the thermistor connector. Getting the capacitor off can be a bit tricky: I levered too hard as I melted the solder and so removed the pad underneath. That's why there is the short white wire connected to the top of R6 is in the picture. If you are more careful, you won't need this...
The I2C connector that you will plug the device into is the 4-pin connector just below R6 in the picture.
Here is the schematic. This is in [the RepRap subversion repository here].