Magnetometer — tdlidar_magnetometer

Read the raw magnetic field around the phone — wave a magnet, sense a motor, or detect a metal object passing by.

Category: Motion · Tier: Free · Needs: any iPhone (no LiDAR required)

What it does

Streams the raw magnetic field measured at the phone, as three components (X, Y, Z) in microtesla. It picks up the Earth’s field plus anything magnetic nearby — speakers, motors, a handheld magnet, large steel structures. It is not a finished compass heading; it’s the unprocessed field, which makes it great for reacting to magnetic changes in a space rather than for “point me north”.

OSC in

| address | type | range | rate | |—|—|—|—| | /tdlidar/motion/magnetic/x | float | µT (raw field, not heading) | ≤50 Hz | | /tdlidar/motion/magnetic/y | float | µT (raw field, not heading) | ≤50 Hz | | /tdlidar/motion/magnetic/z | float | µT (raw field, not heading) | ≤50 Hz |

Outputs

out1 (CHOP) — three channels magx, magy, magz (µT). The node tile previews out1.

Parameters

| par | default | what it does | |—|—|—| | OSC Port | 9000 | UDP port to listen on (match the app) |

Quick start (beginner)

  1. Enable Magnetometer in the app’s Motion sensors.
  2. Drop the Magnetometer op — three lines hovering at the local field strength (often tens of µT).
  3. Move a fridge magnet near the phone and watch a channel swing hard.
  4. Wire a Math CHOP Length of the three axes into a parameter so total field strength drives a visual — proximity-to-metal as a controller.

Advanced patterns

  • Field-change trigger: Subtract a slow Lag CHOP copy of a channel from the live channel (a Math CHOP Subtract) to get only the change; feed that into a Trigger CHOP so a magnet swipe fires an event while the steady background field is ignored.
  • DIY compass-ish: A Math CHOP atan2 of magx/magy gives a rough planar heading, but expect drift and tilt error — for real orientation use the QuaternionEuler op instead.
  • Calibrate-by-subtract: Sample the resting field once into a Constant CHOP and subtract it so your installation responds to added magnetism, not the room’s baseline.
  • Multi-sensor scene: Combine with Proximity or Acceleration so “object near + metallic” gates a specific cue.

Gotchas

  • Not a heading. These are raw µT components — there is no north channel here. Don’t treat any one channel as a compass bearing.
  • The reading drifts with the phone’s own electronics and is easily swamped by nearby ferrous metal — calibrate against the resting baseline if absolute level matters.
  • Magnetic stays raw — it is not zeroed by the app’s Calibrate button (unlike pitch/roll/yaw and rotation).