I like engineering and Electronics and always looking to use my spare parts for something. I have accrued plenty of Arduino parts and wanted to put them to good use. A friend had a pair of helicopter APU's in the yard (as you do) and never got around to playing with them.

Time to start a new Project. With nothing but the engines I set about looking into how they operated and controlled. A strip down and re-build of one of the engines looked promising, time to dig out the Arduino's.

I could have used a more power full processor or ran off a pc but I like a challenge and what follows is the result of a year long project.

There are three parts to this project,

Firstly, the engine, this is just a bunch of servos and relays, its all down to timing each to a precise time. If you have a Jet Engine aka APU in the shed, this could be a project for you.

Secondly, connecting it together. This is the boring part but necessary, Connection pins, Layout, Heavy duty relays and a huge home made resistor but this is all dependant on the engine type and how you want to build your control unit.

Lastly, an Arduino or similar. This is where you can get creative, buttons, relays, box or container and a display. This is the bit that took the longest and I found it easier to build another box that emulates the engine, that also has an Arduino in it too.

More about the build and other stuff

USSR AI-9 (АИ-9) APU Gas Turbine (finishthoseprojects.blogspot.com)

Gas Turbine APU Control Center & Diagnostic using Arduino Uno's

Extreme Engineering: Jet Engine ECU

The Gas Turbine ECU Control System is arguably the most dangerous and critical application of microcontroller logic. Whether simulating the process or controlling an actual RC jet engine, this project demands absolute precision and failsafe state-machine programming.

The Startup Sequence (State Machine)

A jet engine will melt itself into a ball of slag if started incorrectly. The Arduino must control the exact sequence via relays and PWM speed controllers.

1. State 1 (Spool up): The Arduino engages the electric starter motor. It monitors a digital Hall-Effect RPM sensor. It waits until the turbine hits 3,000 RPM.
2. State 2 (Ignition/Gas): At 3K RPM, the Arduino pulses a spark plug and opens a propane gas valve. It monitors a K-Type Thermocouple reading the exhaust gas temperature (EGT). If it sees the temperature spike (proving ignition), it moves to State 3.
3. State 3 (Kerosene Ramp): The Arduino slowly ramps the PWM signal to the liquid fuel pump while decreasing the propane.
4. State 4 (Run/Failsafe): The engine is running. If RPM drops violently or EGT exceeds 700°C, the code immediately snaps all fuel relays shut (Emergency Stop).

Critical Hardware Used

• Arduino Mega: Multiple high-speed interrupts required.
• MAX6675 / MAX31855 Amp + K-Type Thermocouple: The only sensor capable of reading 1000°C exhaust gas.
• Hall Effect Sensor / Optical Tachometer: For extreme high-speed RPM reading (up to 120,000 RPM).
• MOSFETs and Relays: To control the massive current of the starter motor and the valves.

Warning: This requires rigorous safety protocols. A software glitch can cause catastrophic hardware failure and fire.