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JEJunior Engineer LabPico W + micro:bit course
15micro:bit · MakeCode 60 minutes

Paper-flap capstone

Toggle a light paper flap slowly with button A.

Paper-flap capstone project
Illustration of the finished idea. Build from the diagram and connection table, not the photo.

Lesson goal: Button A toggles an opened state and moves the servo slowly between CLOSED_US 1400 and OPEN_US 1600 in steps of at most 10 µs every 30 ms; B requests stop.

Open MakeCode

Section 1

Understand

  • state
  • busy guard
  • stop flag
  • commanded vs actual
  • 1A toggles a light paper flap open or closed, slowly.
  • 2The display shows the commanded state, not the real position.
  • 3B stops the pulses; unplugging motor power is the real stop.

Safety first

  • Adult setup required. The servo needs an external REGULATED 5 V supply rated at least 1 A, with a suitable insulated connector. This may be an extra item not in the box.
  • External 5 V positive goes ONLY to the servo's positive lead. It connects to no micro:bit pin, not the 3V ring, and not the battery connector.
  • External supply negative connects to the servo ground AND to the micro:bit GND, so both share a reference.
  • The micro:bit stays powered by USB. Never power a servo from a pin or the 3V ring.
  • Lead colours are usually red = positive, brown/black = ground, orange/yellow = signal, but markings on your servo override colours.
  • Clamp the servo down. Test first with the horn removed. The first command can make it jump.
  • If it binds, buzzes, heats or stalls: disconnect motor power at once. Turn off both supplies before any rewiring or fitting the horn.
  • Both supplies off before mounting the flap or horn.
  • Light paper only. Parent design review needed before any future mechanism; plan a manual release.