Thermostat for 3D Printer extruder head

This will detail the final installation on to the CNC, though the full conversion to 3D printing will likely be its own project... :-)

This part will detail controlling the 12vdc power source to the heating element. I don't expect it to be all that complicated (relays are cheap and easy but a mosfet might be a better idea if I want to rapidly control voltage, e.g. PWM). This part is TBD.

This is the part that is currently underway -- Since I don't know what thermistor was used I don't have a data sheet that tells me its resistance at a known temperature (25C) or its beta value. If you use an extruder head with a known part number for the thermistor you will not have to do this part...

This is done, but as Part 4 will explain having the pre-installed thermistor isn't as convenient as I thought it would be...

This part will detail hooking up the Nokia LCD and displaying characters on it (this is done, I just have to add content here...

I have a Zen Toolworks CNC mill that has sat in a closet mostly unused (CAM software is too darn expensive, and free CAM software is not really sufficient for anything I'd want to really do). Because of this (and the request of my son who wants to make things) we decided to convert the mill to a 3D printer. Zen Toolworks also sells a pre-made 3D printer conversion kit, though I just bought their mounting plate with stepper-based feeder and JHead mount.

I've never done more with embedded programming beyond turning I/O pins on and off (camera intervalometer, larson scanner) so I knew this was going to be a step in my evolution as an embedded systems tinkerer. :-) Since I had the Tiva C launchpad and Nokia LCD screen, I decided to go with those. I could probably scale this down to an MSP430 (depending on its ADC capabilities) but I wanted to start with the Tiva C since it has more pins and a 12-bit ADC.

I bought the J-Head hot end from E-Bay. Though it was rather convenient to have a pre-assembled hot end, no part numbers were provided so I have really no idea what kind of thermistor was used. That means that instead of reading a data sheet for specifications (namely the resistance at 25C and the Beta value), I will have to calibrate the head before I can get really accurate temperatures.

Based on the previous experiences I've had with Launchpad tinkering, I decided to use Energia. It takes away the annoyance of building tool-chains and you really can't beat the price (free). Some of the examples are handy, too. Mostly, I like it because it knows how to support all of the launchpad versions that I own (MSP430 value line, F-RAM, Tiva C) so if I decide to upgrade a project I can just switch the board type on my project and keep going.

(To be continued: Setting up Energia and finding examples)