Motion Detection Trade-offs in Outdoor Solar Lighting

Motion sensors are widely used to reduce energy consumption by adjusting output based on activity. Two technologies dominate: Passive Infrared (PIR) and microwave (radar) sensors.

PIR sensors: heat-based detection

PIR sensors detect changes in infrared radiation caused by moving heat sources. They are energy-efficient and relatively simple.

Strengths

          Low power consumption

          Fewer false triggers from inanimate objects

Limitations

          Reduced sensitivity in cold environments

          Limited detection range and angle

Microwave sensors: motion through frequency shift

Microwave sensors emit radio waves and detect motion via frequency changes. They offer broader coverage and higher sensitivity.

Strengths

          Longer detection range

         Consistent performance across temperatures

Limitations

          Higher power consumption

          Increased false triggers from moving objects such as foliage or rain

Choosing the right sensor

Sensor selection should balance detection reliability, environmental conditions, and energy budget. In some cases, hybrid strategies combining both technologies are used.

Engineering takeaway

PIR prioritizes efficiency.
Microwave prioritizes sensitivity.