Home myTHC-RU01 USB/RS485 Torch height controller (THC)

(updated 2011-01-13) Available for testing.



Torch height controller for plasma cutting applications - myCNC-THC-RU01. The board is based on 32 bit
100MHz ARM Cortex M3 CPU.
THC controller works with myCNC-UP3, myCNC-ET1 or myCNC-ET2 CNC controllers and myCNC software.

Main features:

  • Advanced algorithm for torch height control:
    • Automatic controls torch-to-work distance during plasma cutting proccess;
    • Automatic detection cutting-over-edge to prevent the torch fall;
    • Automatic sets the piercing height (if used with initial height sensing IHS);
    • Automatic low cutting speed detection and temporarily turn-off tracing to prevent falling torch;
    • Separate setting for PI-controller while motion up and down for height control system fine tuning;
  • Two-channel Arc Voltage measure (Power Source voltage and Arc Voltage) for improved trace algorithm;
  • Connection to Host myCNC-UP3/ET1/ET2 controller via RS485 interface and Modbus-like protocol;
  • Input/output for Initial Height Sensors (IHS);
  • Additional Open Collector keys/PWM outputs and opto-isolated inputs with control interface
    from HOST PC software;
  • Complete integration into myCNC control software. All THC configuration parameters and information data
    are available from softwrare dialogs:
    • Arc voltage reference value;
    • Arc volatge measured value in real-time mode;
    • THC motion speed;
    • THC low speed indicator;
    • THC turn-on delay (THC control will be turned-on after given delay after ignition);
    • THC enable/disable switcher;
    • Motion speed value for "Low Speed mode" (percentage of cutting speed);
    • PI control configuration parameters;


THC configuration in myCNC software


A picture below shows working "THC Low Speed mode".



THC control board drives:

  • DC brush motors (up to 48V @ 5A DC) through integrated CMOS H-Bridge DC brushedmotor driver
  • Stepper motor driver with integrated STEP/DIR outputs
  • Sends back to CNC controller commands to control torch-to-work distance trough third axis (Z-axis);



At the moment we are testing new revision of myTHC-RU01 board. New THC boad has compact design and contains

more powerful processor on-board. On a picture there are both revisions of myTHC boards.

 myTHC control boards



Electrical characteristics

Power supply (THC contoller)

 24V DC @ 0.5A
Power supply (Brushed DC driver) 24...48V DC @ 1...5A
THC board specification

Host PC/Controller connection


STEP/DIR output

 5V, RS422 compatible

Arc Voltage measure range 0 -300V

Number of open-collector general purpose/PWM outputs(24V @ 50mA)


Number of opto-isolated inputs (slow-speed - 20us)

Arc Voltage measure ADC inputs (0-300V)  2
RS485 port
USB port

THC controller board CPU

 32-bit ARM 70MHz/

32-bit ARM Cortex-M3 100MHz





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