I've created a THC with LCD using a Teensy 3.1 that works with a Mesa THCAD card to send up/down outputs out to a control. It works by reading the undivided frequency from the THCAD, mapping the range to the specifications provided on the THCAD card and then working the with target/hysteresis to set outputs. I have spent a significant amount of time testing different ways to print to the LCD to keep code impact minimal and I believe the run time is acceptable now. The board is just something I knocked out quickly in KICAD so I didn't have to keep using shields and such to connect the LCD, I have a limited understanding of electrical/Arduino coding so any input is appreciated.



Code Features/Issues

Features
- 7-12 microsecond loop time
- Adjustable hysteresis
- Values can be saved to eeprom with encoder button and are automatically loaded on boot
- EEPROM values can be recalled with encoder button
- Can run on an Arduino UNO with a simple pin swap between button and frequency input, have not tested the effect of lower clock speed. Teensy is running at 96 MHz vs 16 MHz on Uno.

Issues
- Currently I lock the output to off if the voltage it outside 100-150 volts (I map the undivided frequency from the THCAD to the specifications provided on the card and do the math to get back to tip volts) but this has a problem if the torch starts and falls below 100 while moving it will never recover. I was thinking to either move the floor down to around 50 volts or have a moving floor/ceiling that is target +- 50volts?

Source
https://github.com/limited660/Teensy-Plasma-THC-Master



PCB Features/Issues

Features
- IDC sockets for Reprap Smart Controller LCD (SD card, buzzer, and reset button not wired, ideas for use?)
- Female headers for plugging in the Teensy
- Male headers for all of the pins going to the female headers
- Headers for VIN and GND
- Screw terminals for THCAD and Outputs

Issues
- No power input (I also didn't want to cut the USB jumper on the Teensy but power could be added as long as you don't use power and USB)
- Output/THCAD/Teensy grounds not all shared, maybe add jumper to connect output ground to the others that can be cut?
- IDC connector for EXP2 hangs off board
- Use plugs instead of screw terminals for THCAD/Outputs?
- Limited mounting options
- Some pins have odd traces (+ jumper all connected on top but only 3 connected on bottom layer, minor but annoying)
- Requires Mesa THCAD

Source
- To be added later



A short video of it in action with UCCNC and a UC100

https://www.youtube.com/watch?v=GcG85IwxP2Y