The BL412 is a compact passive infrared (PIR) motion sensor designed for detecting movement from people and animals at distances of approximately 3–8 m. Much smaller than standard PIR modules, it is well suited for unobtrusive projects and fits easily on breadboards or perfboard.

The sensor runs on 3.3 V and requires only power, ground, and an optional resistor divider to set the output hold time — from 2 seconds (pin 2 tied to ground) up to one hour (pin 2 at 3.3 V). The digital signal output is 3.3 V high/low. The snap-on lens provides a 120° detection spread focused at approximately 5 m.

Key Features

• Compact Size – Smaller than standard PIR modules for discreet installations
• 3.3 V Operation – Low-voltage, breadboard-friendly
• Adjustable Hold Time – 2 seconds to 1 hour via resistor divider on pin 2
• 120° Detection Angle – Wide field of view with snap-on lens
• Simple Wiring – Only 4 pins: GND, on-time, VCC, signal

Wiring

• Pin 1 – Ground
• Pin 2 – On-time control (ground for 2 s; resistor divider for longer delays)
• Pin 3 – 3.3 V power
• Pin 4 – Digital signal output (3.3 V high when motion detected)

Specifications

• Model – BL412
• Supply Voltage – 3.3 V
• Detection Range – Approximately 3–8 m (optimised at 5 m)
• Detection Angle – 120°
• Output – Digital, 3.3 V high/low
• Hold Time – 2 s to 1 hour (adjustable)
• Sensor Window – 5 × 3.8 mm

Ideal For

• Motion-activated lighting and alarms
• Occupancy detection projects
• Low-power battery-operated sensors
• Arduino and Raspberry Pi motion sensing

Package Contents

• 1× BL412 Mini PIR sensor with snap-on lens

Resources

• PIR Sensor Tutorial (Adafruit)