The MacBook has a sensor that knows the exact angle of the screen hinge

Original Article ↗ Hacker News Discussion ↗

Lid / Hinge Detection and Sleep Behavior

  • Many comments contrast Apple’s lid behavior with Windows/Linux laptops.
    • Several users report non‑Apple laptops waking in bags or failing to sleep, blaming Windows “Modern Standby” and misbehaving apps more than the physical sensor.
    • Others report MacBooks (especially older Intel models) also overheating in bags, sometimes due to corporate “security” agents or wake-on-LAN.
  • Consensus: lid sensors are ubiquitous; the difference is reliability of the whole sleep stack (OS, drivers, wake sources), not just the presence of a magnet or switch.

How the Mac Hinge Sensor Likely Works

  • Discussion concludes it’s a Hall-effect angle sensor in the hinge, reading a magnet continuously, not just a binary reed switch.
  • Angle information is “almost free” once you use such a sensor:
    • One part can handle both “lid closed” detection and continuous angle.
    • Modern angle-sensing ICs are cheap and often no more expensive than simple switches.
  • Uses speculated in the thread: faster wake as soon as lid starts moving, better control of when the display sleeps, thermal tuning (vents near hinge), Desk View keystone correction, and hardware mic cut‑off when closed.

Not Unique to Apple

  • Other devices with hinge/angle sensors are mentioned: ThinkPad Yogas, Surface Book, Android foldables (with a public API), some Intel reference designs, Nintendo Switch 2 rumors, and Framework tablets.
  • Distinction drawn: Apple hides this behind private APIs; Android and Linux expose hinge angle more directly.

Whimsical and Experimental Uses

  • The project mapping hinge angle to sound triggers a long riff on “hinge instruments”: theremin, accordion, trombone, dungeon door, joke volume controls, even games where you “jerk the hinge” to move.
  • Nostalgia for older macOS that allowed arbitrary UI sound effects.

Bugs, Failures, and Repair

  • Several anecdotes of failed lid angle sensors causing black screens, crashes on sleep/wake, or constant wake with the lid closed; replacing the sensor fixed issues.
  • The lid angle sensor is serialized and requires Apple calibration; third‑party or recycled parts are effectively blocked unless you buy Apple‑blessed components.
  • Big subthread argues whether this is:
    • Vendor lock‑in and an attack on right‑to‑repair, or
    • A security/supply‑chain measure (preventing tampered parts, ensuring mic cut‑off, deterring theft and parts fraud).
  • Many remain skeptical that security justifies the degree of lock‑in.