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PIR vs Microwave Sensors: Which do you need?

Lighting can now incorporate sensors to make them even more effective. Motion detectors can now be used to pick up when someone approaches so the lights are triggered when they are needed. This can be used to save on energy bills by dimming or turning off the lights when no one is around, or it can be used as a security measure, with lights coming on to let you know when someone approaches.

There are two main types of motion detection sensors available, microwave and PIR (Passive Infrared) and we’re here to take a quick look at the pros and cons of each.


These sensors detect heat. They do this by measuring the ambient temperature of the room using several detection beams. When a difference in temperature is detected by one of the beams, the sensor is activated, switching on the lights. When all the beams sense the same temperature again, the lights will switch off.


These motion detectors emit microwave signals and measure the time taken for the signal to be reflected back to the sensor, this is known as the echo time. The echo time is used to calculate the distances from all the stationary objects in the detection zone, to establish a baseline to work from. A person moving into the detection zone causes a disruption in the microwave beam, changing the echo time and triggering the lights.


When choosing the best sensor for your application, there are many aspects to take into account;


Sensitivity Under sensitive in higher background temperatures.
Over sensitive in lower temperatures.
Consistent detection over all temperatures.


DetectionCan be insensitive when walking directly towards the sensor.Can sense movement through walls.

Because PIR uses the difference in heat to detect movement, ambient temperatures can greatly affect sensitivity. This limitation should be considered if you are looking at motion detection systems for outdoor lighting. The more extreme temperatures of outdoors can have a significant impact on devices’ effectiveness. On the other hand, microwave sensors may struggle more with smaller indoor spaces. Because they are able to detect movement through walls, they can be overly sensitive and be triggered by movement you might not want it to be. There are however solutions to both drawbacks of PIR and microwave sensors.


To combat microwaves sensors’ tendency to be overly sensitive, we have developed a fitting that can be adjusted to suit your personal needs. The Microwave Ceiling Bulkhead has been manufactured so that it can detect movement from any angle from a distance of up to 6m, with a sensitivity which can be adjusted easily with the flick of a switch. This fitting also incorporates a photocell which, thanks to its easily customisable settings, can be altered to react to different light levels to fit its desired purpose. It has been designed so it is only on when it needs to be, saving energy and, therefore, money for the end-user.


As mentioned above, a standard PIR operates differently at different temperatures, not triggering when it gets hotter but in the colder months triggering for every small, distant, movement.

To combat the PIRs temperature detection fault, Green Lighting developed a PIR sensor with Tri-Sensor Technology. The P-Lux LED Lantern Range, incorporates a sensor that combines a PIR with a thermometer, allowing the lantern to automatically adjust the PIRs sensitivity depending on the ambient temperature. This, combined with a photocell and the Lux-Up, Lux-Down feature of the P-Lux, makes these lanterns some of the best on the market, functioning perfectly all year round.


P-Lux Range