SmartElex AM312 PIR Motion Sensor

Overview

The module is based on the AM312 PIR motion sensor IC, a miniature passive infrared (PIR) sensor designed to detect human motion.

• Detects:

  • Motion of warm objects (humans/animals)

   

• Output:

  • Digital HIGH/LOW signal

   

• Designed for:

  • Low-power motion detection systems

   

It is a compact and energy-efficient motion sensing solution.

Working Principle

Passive Infrared Detection

The sensor detects infrared radiation emitted by warm bodies:

1. IR Radiation Detection

• Human body emits IR radiation (~814 m wavelength)

• PIR sensor detects changes in IR levels

pyroelectric element

Generates a small voltage when IR radiation changes

3. Differential Detection

• Sensor has dual sensing elements

• Detects difference between two regions

Movement across field changing IR pattern triggers detection

4. Signal Processing

• Internal amplifier + comparator

• Produces digital output signal

Detection Characteristics

• Detection range: ~3 to 5 meters

• Detection angle: ~100

• Sensitive to:

  • Human movement

  • Warm object motion

   

Electrical Characteristics

• Supply voltage: 2.7V to 12V

• < 50 A (typical)

Ideal for battery-powered devices.

Output Interface

Digital Output

• HIGH (motion detected)

• LOW (no motion)

Output Behavior

• Motion detected output HIGH for fixed duration

• Automatically resets after delay

Internal Features

Automatic Signal Processing

• Built-in:

  • Amplifier

  • Comparator

  • Timing control

   

Fixed Delay Time

• Output remains HIGH for a short fixed period after detection

Repeatable Trigger Mode

• Can retrigger if motion continues

Low Noise Design

• Reduces false triggering

Operating Behavior

, not constant presence

Trigger Conditions

• Movement required:

  • Static object no detection

   

Environmental Sensitivity

• Affected by:

  • Temperature changes

  • Airflow

  • IR interference

   

Environmental Characteristics

• Works best at:

  • Room temperature environments

   

• Reduced sensitivity when:

  • Ambient temperature body temperature

   

Limitations

• Cannot detect:

  • Stationary humans

   

• Sensitive to:

  • Sudden temperature changes

   

• Performance affected by:

  • Obstructions (glass, walls)

   

• Fixed delay (limited customizatio

  • VCC Power supply

  • GND Ground

  • OUT Digital output

   

  Functional Role

  The module acts as a:

  • Motion detector

  • Presence sensing device

  • Trigger sensor for automation systems

   

  Summary

  The SmartElex AM312 PIR Sensor is a compact, low-power motion detection module that:

  • Uses passive infrared (PIR) sensing

  • Detects human movement via IR changes

  • Provides digital output signal

  • Offers wide detection angle and moderate range

  • Is optimized for low-power motion sensing ap