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Microwave vs. Photocell vs. PIR Sensors: Which Should You Use?

As autumn creeps up on us, you might be considering purchasing outdoor lights so that you can still enjoy your garden space in the early evening after the sun has gone down or to be guided by lights on your arrival home in the evening. Many outdoor lights are now sensor-operated to increase their effectiveness and convenience; saving on energy bills, alerting you of unexpected guests, and turning on automatically.

The three main types of sensors are microwave, PIR (passive infrared), and photocell. In this article, we will compare the three different types. That way, you can make the most of your outdoor space this winter and feel safe and secure.


Microwave sensors are motion detectors that work by emitting microwave signals. These signals are reflected toward a sensor with the time taken for this to known as the echo time. If a person or an object passes the sensor, it will take the microwaves longer to reach it, lengthening the echo time and triggering the lights to turn on.



On the other hand, PIR sensors work by using infrared beams and detect heat to sense movement. They can measure the temperature of a room or an outdoor space, yet when something moves across the beams they will detect a different temperature, triggering the lights. Once all the infrared beams sense a uniform temperature, they turn off again.

As PIR sensors rely on ambient temperatures to form a comparison, they are often overly sensitive in lower outdoor temperatures. This can be overcome by combining a thermometer to help the PIR sensors alter their sensitivity depending on the outdoor temperature.


Comparatively, photocells do not detect physical movement but instead respond to changes in light levels. This is done through semiconductors which under normal conditions do not allow electricity to flow, however, when light levels increase, current passes through the circuit. This way, photocells are often used as “dusk to dawn” sensors, turning on at sunset and off at dawn to create ambient outdoor lighting.

Which sensors you choose to operate your lights depends on their purpose. Often, a combination is an ideal solution; this allows lights to only be triggered after the sun has gone down, and when somebody walks past the detector. Commonly, homeowners opt for photocell ambient lighting, with more illuminating light triggered by motions detector sensors to create a unique and welcoming atmosphere.

Created by Gary Baker on 5th January, 2021


Gary Baker

Gary Baker

BLT Direct