Adafruit
Mini Basic PIR Sensor - BS412
A compact passive infrared (PIR) motion sensor that detects movement from approximately 3–8 metres away. Much smaller than standard PIR modules, making it id...
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A compact passive infrared (PIR) motion sensor that detects movement from approximately 3–8 metres away. Much smaller than standard PIR modules, making it ideal for unobtrusive, space-constrained projects. Fully self-contained — just needs power, ground, and a resistor to set the delay time.
Key Features
- 3.3 V Operation – Low-voltage, low-power motion detection
- ~5 m Detection Range – Effective from approximately 3–8 m with the snap-on lens
- 120° Detection Spread – Wide field of view
- Adjustable On-Time – From 2 seconds (0 V on pin 2) up to 1 hour (3.3 V) via resistor divider
- 4 × 3 mm Sensor Window – Compact BS-series sensing element
- Breadboard Friendly – Standard pin spacing for easy prototyping
Wiring
- Pin 1 → Ground
- Pin 2 → Ground (for 2-second on-time) or resistor divider (see datasheet for values)
- Pin 3 → 3.3 V
- Pin 4 → Signal output (3.3 V high/low)
Resources
- PIR Sensor Tutorial (CircuitPython and Arduino code examples)
Jargon buster
Plain-language definitions for the technical terms used above.
- CircuitPython
- A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
- microcontroller
- A microcontroller is a small computer on a single chip that runs a stored program and controls connected inputs and outputs such as buttons, sensors, displays and communication interfaces. In a device built around one, it is the part that executes the code and coordinates the device's behaviour.
- Motion detection
- The ability to sense that something has moved, either by comparing successive camera frames or by using a dedicated sensor such as a PIR (infrared) or radar module. When a product lists motion detection, movement can be used as a trigger so a system only acts or records when there is activity rather than running continuously.
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Sensors & Input
pir passive infrared proximity motion sensor
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