Omega Controller (Python)

Lightweight Python driver for Omega CN-series temperature controllers using Modbus over serial (via minimalmodbus).

Features

• PV/SV: get present value and set temperature setpoint
• On/Off: get and set the controller on/off
• Modes: PID, ON/OFF, MANUAL, and PID Program (Ramp/Soak)
• PID tuning: get/set P, I, D
• Program params: read/write 64-register blocks for Ramp/Soak (A/B)
• Error handling: maps Omega error/status codes and raises helpful exceptions

Install dependencies:

pip install minimalmodbus

Install this driver from via pypi:

pip install omega-controller

Quickstart

from omega_controller import OmegaController, OmegaControllerError

# Adjust port/slave as needed for your setup
ctrl = OmegaController(port="COM3", slave_address=1, baudrate=9600, parity="even", bytesize=7, stopbits=1, mode="ascii")

try:
    # Optional: raise if the controller is reporting an error
    ctrl.check_errors()

    # Read process value (°C)
    pv = ctrl.get_pv()
    print("PV:", pv)

    # Set temperature setpoint (°C)
    ctrl.set_sv(150.0)

    # Switch to PID Program (Ramp/Soak) mode
    ctrl.set_control_method("program")

    # Tune PID
    ctrl.set_p(12.3)
    ctrl.set_i(600)
    ctrl.set_d(120)

except OmegaControllerError as e:
    print("Controller error:", e)
finally:
    ctrl.close()

API Overview

• PV/SV
  • get_pv(raise_on_error=False) -> Optional[float]
  • get_sv() -> Optional[float]
  • set_sv(temp_c: float) -> None
• Control method
  • get_control_method() -> Optional[int] (0=PID, 1=ON/OFF, 2=MANUAL, 3=PROGRAM)
  • set_control_method(method: int|str) -> None
• PID
  • get_p()/set_p() – proportional band (0.1 resolution)
  • get_i()/set_i() – integral time (seconds)
  • get_d()/set_d() – derivative time (seconds)
• Ramp/Soak program parameters
  • Blocks: A = 0x2000–0x203F, B = 0x2080–0x20BF (64 regs each)
  • read_program_block(block) / write_program_block(block, values)
  • read_program_param(block, offset) / write_program_param(block, offset, value)
• Errors
  • check_errors(raise_on_error=True) – checks status and PV error codes
  • Raises OmegaControllerError with descriptive message

Serial Settings

• Some models use alternate status/PV addresses; this driver handles common variants

Compatibility

• Tested on: Omega CN7800
• Expected to work with many CN-series models using the same Modbus map

Roadmap - Contributions Welcome

• Test on additional Omega models
• Add remaining serial commands from the manual (alarms, limits, etc.)