Introduction
Battery-powered PIR sensors enable wireless installations in locations without mains power. Achieving multi-year battery life requires careful power management.
PIR Sensor Power Consumption Basics
| Sensor Type |
Standby Current |
Active Current |
HC-SR501 (module) |
50-65 µA
~3 mA
AM312 (mini module) |
35 µA
~3 mA
Panasonic EKMB |
1-6 µA
~100 µA
Excelitas PYD 2597 |
2 µA
~10 µA
表
Power Management Techniques
Duty Cycling (Polling)
Periodically power the sensor, sample, then power down. Trade-off: power savings vs. missed events.
Wake-on-Motion (Interrupt-Driven)
Use a sensor with interrupt output (like PYD 2597) that can wake the microcontroller only when motion occurs.
Sensor Selection
Choose the lowest-power sensor that meets your performance requirements.
Battery Life Calculation Example
PYD 2597 (2 µA) + microcontroller in sleep (5 µA) + wake every hour to transmit (10 mA for 100 ms)
Average current = 2 µA + 5 µA + (10 mA × 0.1/3600) ≈ 7.0003 µA
With a 2000 mAh battery: 2000 mAh / 0.007 mA ≈ 285,000 hours ≈ 32.5 years (theoretical)
Conclusion
With modern ultra-low power PIR sensors and careful system design, multi-year battery life is achievable.
