Projects / Industrial automation and embedded control
Hardware-in-the-loop bench for HVAC PLC validation: STM32 signal emulator, physical NTC channels, Modbus diagnostics, PyQt6 interface, scenarios and logs.
The task was to check HVAC PLC algorithms without a real ventilation unit. On the real object it is slow and inconvenient to reproduce faults, boundary modes, temperature transients and event sequences. The bench had to emulate external signals and record the controller response.
A debug system was built around an STM32F407 hardware emulator and a Python/PyQt6 desktop application. The bench controls digital and analog signals, physically changes NTC-channel temperature, injects Open/Short faults, works with Modbus RTU, runs CSV scenarios and records test logs.
Project materials
Engineering context
An HVAC controller is connected to many sensors, valves, fans, alarm inputs and Modbus registers.
Algorithm errors are better found on a repeatable bench than on a real installation.
Temperature inputs need to be checked not only numerically, but physically through real NTC channels.
Regression checks require profiles, logs and reproducible scenarios.
Work done
Bench architecture: PLC, field emulator and desktop studio.
STM32F407 firmware with JSON-over-USB-CDC protocol.
Digital inputs and outputs.
Measurement of PLC analog outputs in the 0-10 V range.
Physical temperature channels with PI regulation.
Open and short fault diagnostics for temperature lines.
Modbus RTU master functions and port diagnostics.
PyQt6 application with manual control, graphs, CSV profiles and logs.
Details
The PC controls test scenarios, while the STM32 emulator acts on the real PLC and collects telemetry. This format allows the controller to be checked as part of the equipment without starting the full ventilation unit every time.
The bench can safely reproduce states that are inconvenient to test on site: open and shorted sensors, temperature faults, reactions to discrete alarm signals and changes in Modbus states.
The desktop application is used by an engineer or tester: manual control, live monitoring, graphs, scenarios, logs and diagnostic tabs shorten debugging time. The bench also emulates parts of ventilation-unit and environment behavior.
Contact
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