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motion_sensor

Summary

The motion_sensor component detects movement from living entities near the sensor and emits computer.signal events when movement crosses a configured threshold. It is useful for alarms, security systems, trap logic, and automation that reacts to nearby players or mobs.

Detection is not global. The sensor only watches an eight-block radius around itself, only tracks living entities, ignores invisible ones, and requires line of sight to the target.

Availability

  • Repository: opencomputers
  • Component name: motion_sensor
  • Typical host: motion sensor block or compatible adapter connection

Runtime Behavior

The sensor checks for motion every 10 ticks and emits a signal named motion when:

  • a living entity enters detectable range for the first time, or
  • a tracked entity moves farther than the current sensitivity threshold.

The signal payload contains relative coordinates from the sensor center:

"motion", dx, dy, dz

On installations where username reporting is enabled in config, the event also appends the entity name:

"motion", dx, dy, dz, name

Usage

local component = require("component")
local motion = component.motion_sensor

if not motion then
  error("motion_sensor component not available")
end

Example event loop:

local event = require("event")

while true do
  local _, _, dx, dy, dz, name = event.pull("motion")
  print("Motion at:", dx, dy, dz, name or "")
end

API

getSensitivity

  • Syntax: motion.getSensitivity()
  • Returns: number
  • Purpose: Gets the current movement threshold.

Smaller values make the sensor more sensitive. Larger values require a bigger position change before another signal is emitted for an already tracked entity.

Example:

print("Sensitivity:", motion.getSensitivity())

setSensitivity

  • Syntax: motion.setSensitivity(value)
  • Returns: number
  • Purpose: Changes the movement threshold and returns the previous value.

Parameter:

  • value:number: desired sensitivity threshold.

Behavior:

  • The source clamps the value to a minimum of 0.2.
  • There is no explicit upper limit in the component itself.

Example:

local old = motion.setSensitivity(0.25)
print("Old sensitivity:", old)
print("New sensitivity:", motion.getSensitivity())

Related

  • component
  • event
  • redstone