PIR Sensor Output Interfaces: Digital, Analog, Open-Drain Compared

Introduction

PIR sensors and modules offer different output interfaces. Choosing the right one and interfacing correctly is essential for reliable operation.

Output Interface Types

Push-Pull Digital Output

Output is actively driven HIGH to VCC and LOW to GND. Can source and sink current.

Examples: HC-SR501, HC-SR505, AM312

Pros: Simple, no external components, clean levels

Cons: May not be 5V/3.3V compatible without level shifting

Open-Drain / Open-Collector Output

Output transistor switches to GND when active; otherwise floats (high impedance). Requires external pull-up resistor to VCC.

Examples: Panasonic EKMB series

Pros: Easy level shifting, wired-AND capability

Cons: Requires pull-up resistor, slower rise time

Analog Output

Continuous voltage proportional to IR signal. Requires ADC for reading.

Examples: Murata IRA series

Pros: Rich information, enables advanced processing

Cons: Requires ADC, more complex firmware

Interface Characteristics

LOW (0V)

HIGH (VCC)

High-Z

LOW (0V)

Yes

Mid-scale

Varies

表

Conclusion

Understanding output interface types is crucial for proper sensor integration. Open-drain outputs offer flexibility for mixed-voltage systems, push-pull is simplest for same-voltage systems, and analog provides maximum information.