Hi guys,
I'm making a 3D printer for my school final project. I bought an extruder from ebay. It has a 12Vdc heater and a k-type thermocouple for the temperature. I connected the thermocouple to a multimeter and connected 12Vdc to the heater, and obviously the temperature kept going up more than I needed to. Somehow I need to control the temperature. I'm using the arduino mega as the project MCU. From the research I did I found that max31855 can be used. What do you think of it ? Also do you know other methods of how I can control the temperature?
Your help is highly appreciated 
yes you use a thermistor ,, conected to the arduino 8)
then look for 100k one or 1k ,, and then ,, if (thermistor == 180c) relay off ;,, or use N-type mosfet to switch
i use a relay for my heatbed , and switched true mosfet ,,12v from pc power thingy ,
and it get 5 v and it switches the negative side then ,
look at the Ramps 1,4 schematic , < the mosfet switching part >
this wil help you if you understand schematics , :o