Presence or motion sensors? Start with the room.

The first question is how you use the room

A welcoming light is easy to imagine: you walk in and it comes on. The more useful question is what happens next. Do you keep moving, sit down for an hour, or leave someone else in the room?

For a smart lighting plan, think about arrival, time spent in the room and departure separately. A sensor provides a signal. The lighting rules decide what that signal means.

Motion and presence measure different clues

Many motion sensors use passive infrared, or PIR, to detect changes in infrared energy as a person moves through their field of view. Someone sitting quietly may produce too little change for the sensor to keep reporting movement.

A millimetre-wave, or mmWave, presence sensor uses radar to detect smaller movements. Some models can also report occupancy in configured zones. Aqara’s FP2 is one example; its zone features and power requirements are specific to that product. This is an explanation of the technology, not a selected UKEI sensor package.

Neither label tells you how a sensor will behave in your room. Placement, settings and testing still matter. A useful design leaves room for an ordinary manual control.

Further reading: Aqara: how presence and PIR motion sensing differ · Aqara: Presence Sensor FP2 features and requirements

Four rooms, four different starting points

These are planning examples to discuss, rather than routines that every installation can provide.

• Hallway: consider motion sensing for a journey through the space. Aim to detect you before you reach a dark section, allow enough time to reach your destination, and check both directions of travel. Include the person who pauses to put on shoes.
• Living room: staying still matters as much as arriving. Consider presence sensing around the actual seating positions, then test reading and watching television. Decide whether an active movie scene should prevent the arrival routine from turning the main lights back up.
• Open-plan kitchen and dining: someone making tea should not necessarily change the light over someone else’s dinner. If the selected sensor supports suitable zones, plan them around the activities and the separately controllable lights. Check what happens when two people use different areas.
• Bedroom and night-time path: decide whether you want light for getting up, entering the room or both. Plan a sleep setting so turning over in bed does not trigger the main lights. A gentler pathway needs a suitable light source or compatible dimming equipment.

Give “off” as much thought as “on”

A sensor’s detection interval and an automation’s switch-off delay are different settings. Aqara’s P1, for example, has a configurable detection timeout. That does not decide how long your room should stay lit; the automation needs its own agreed behaviour.

Before buying equipment, write down these decisions:

Further reading: Aqara: Motion Sensor P1 detection settings

• When is the room dark enough to need the lights?
• What should happen while someone is seated or just out of the sensor’s view?
• How long should the room wait after the last occupancy signal before changing the lights?
• When someone uses a switch, how long should that choice take priority, and what brings automatic control back?
• How will the setup be checked with doors open and closed, pets nearby, a fan running and normal furniture in place?

Start with one useful room

Choose a room where lighting currently needs too much prompting. Describe the small improvement you want, then assess the sensor, lighting and controls together. Keep an easy way to turn the light on while the routine is being refined.

UKEI starts with lighting and the way you live. Sensor choice, coverage, timing and manual controls are scoped for your home. The agreed proposal confirms the equipment and behaviour included.