Testing a Motorized Throttle Lever for my Flight Simulator. When the auto-throttle is engaged, aircraft's systems are supposed to control the engine throttles automatically, which includes moving the actual levers.

I've used a 12V 28BYJ48 Stepper Motor (modified for bipolar format for more torque) and a A4988 Bipolar Stepper Driver, together with a potentiometer to sense the Throttle position.

Right now I'm still testing it standalone, with a Raspberry Pi generating pulses every 30 milliseconds, and direction manually controlled by a switch. Position is displayed as 0-12V on a multimeter.

The mod'ed 28BYJ48 appears to have enough torque to move the levers, which is good as they are small enough to fit neatly inside the Throttle Quadrant body. When the coils are energized, it is still possible to move the lever by hand (to override the system) with a little bit more effort than usual.

The stepper gets slightly warm when it is energized for some time (even if it is not moving and just "holding" the lever in place). This should not be a problem as I don't plan to have the steppers continuously energized; instead it will only be powered whenever the throttle position differs from the expected position, at which the Pi will move the lever in the appropriate direction. Once the lever is in the correct place, the coils will be switched off. This will require 3 GPIO signals to the A4988: (a) to trigger a STEP (b) to indicate DIRrection and (c) to ENABLE/disable power to the coils.

This should be interesting once the software is hooked up to the flight simulator!


Wiring A4988 to 28BYJ48:
  • 2B - Blue
  • 2A - Pink
  • 1A - Yellow
  • 1B - Orange
  • N/A - Red