SmartElex LHI778 PIR Motion Sensor Module

🔹 Overview
The SmartElex LHI778 PIR Motion Sensor Module is a compact passive infrared (PIR) motion detection module designed for detecting human movement based on infrared radiation changes.
Uses LHI778 pyroelectric sensor element
Provides digital output (HIGH/LOW)
Designed for low-power motion detection systems
👉 Commonly used as a core PIR sensing module in automation and security systems
🔹 Working Principle
Detects infrared radiation (7–14 µm wavelength) emitted by human bodies
Internal process:
IR change → pyroelectric signal
Amplification + filtering
Threshold detection → digital output
👉 Motion causes change in IR → output goes HIGH
🔹 Measurement & Detection Characteristics
Detection Range: 0.1 m to 6 m (typical ~3 m)
Detection Angle: ~120° field of view
Infrared Band: 7 – 14 µm
👉 Performance depends on:
Fresnel lens
Ambient temperature
Motion direction
🔹 Electrical Characteristics
Operating Voltage: 3V – 5V
Current Consumption: ~100 – 150 µA
👉 Low power → suitable for battery-powered systems
🔹 Output Characteristics
Type: Digital output
Logic:
HIGH → Motion detected
LOW → No motion
👉 Direct interface with microcontrollers
🔹 Timing Characteristics
Delay Time: 0.3 seconds to 25 seconds (adjustable)
👉 Determines how long output stays HIGH after detection
🔹 Internal Architecture
Pyroelectric sensor (LHI778 element)
Signal amplifier
Band-pass filter
Comparator / threshold detector
Control circuit
👉 Fully integrated motion detection system
🔹 Functional Features
Adjustable:
Detection range
Output delay
High sensitivity to human motion
Built-in noise filtering
Stable digital output
🔹 Performance Characteristics
High sensitivity and reliability
Low power consumption
Good noise immunity
Fast response to motion
🔹 Functional Behavior
Detects dynamic IR changes only
Best sensitivity when motion is:
Across the sensor field
Output:
HIGH during detection + delay period
Returns LOW after timeout
🔹 Key Technical Features
PIR-based motion detection
Wide detection angle (120°)
Adjustable delay (0.3–25 s)
Low power consumption (µA range)
Digital output
Compact design
Works on 3V–5V
🔹 Advantages
Simple and easy to use
Low power consumption
Adjustable parameters
Reliable motion detection
Compatible with most microcontrollers
🔹 Limitations
Cannot detect stationary objects
Sensitive to:
Temperature variations
Heat sources
Requires proper lens alignment
Limited range compared to advanced PIR modules
🔹 Technical Summary
The LHI778 PIR module is a basic yet reliable motion detection solution that:
Uses pyroelectric IR sensing
Provides digital motion output
Offers adjustable delay and range
👉 It is best suited for:
Simple motion detection systems
Low-power embedded and IoT applications