Recessed ceiling PIR motion sensor
An example of a ceiling PIR detector separate from the light fitting.
Check the cut-out, mounting height, detection diagram and the model's compatible LED load.
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PIR or dusk-to-dawn sensor: choosing and combining them
Choose a PIR sensor if you want the light to respond to movement; a dusk-to-dawn sensor if you want it to respond to ambient light; or a combination if it should switch on when someone passes and the light level is low. Before comparing detection ranges or power ratings, write that condition in your own words. This will help you avoid choosing a device that works correctly but does something different from what you need.
Then check where the sensor will go, which light fitting it will control and which adjustments the specific model offers.
What each system detects
PIR motion sensor
PIR stands for passive infrared. It detects changes in infrared radiation associated with movement within its field. STEINEL explains this principle in the IS 360-3 detector documentation. It is useful for switching a light on as someone passes, provided their route stays within the area it can actually monitor.
Dusk-to-dawn sensor
A dusk-to-dawn sensor measures the surrounding light level and responds to a threshold. A control such as the STEINEL NightMatic 2000 lets you choose the level at which it responds. It does not need someone to pass by, so it can be useful when you want lighting while it is dark, even without movement.
Combining movement and darkness
Many devices combine both functions. In the usual combined mode, the light sensor permits switching on and the PIR triggers it when movement is detected. The exact behaviour depends on the available programmes: continuous or reduced-light modes may change this logic.
| Situation | Motion only | Dusk-to-dawn only | Motion plus dusk-to-dawn |
|---|---|---|---|
| Movement with sufficient light | May switch on | Not triggered by darkness | Does not switch on |
| Movement with low light | Switches on | Switches on because it is dark | Switches on |
| No movement with low light | Does not trigger a new switch-on | May keep the light on | Does not trigger a new switch-on |
The table describes the basic logic without additional programmes. A light that is already on may stay on until its timer runs out.
Position determines what it can detect
Sketch the usual route and mark doors, shelving or walls that could hide it. With a PIR, the direction of travel matters: in its L 605 S documentation STEINEL recommends positioning the sensor so that movement crosses its detection zone, with no obstacles in between. This is a positioning principle; its range must not be assumed to apply to other models.
An advertised 360° coverage describes detection around the sensor; it does not guarantee visibility into every corner of a room. Check the diagram for the intended installation height. If the sensor is built into a bulb, also check that the shade leaves its sensing area exposed as required by the instructions.
For a dusk-to-dawn sensor, do not choose the position solely for convenient wiring. Check how it receives daylight and whether a nearby light fitting affects its reading. A sensor hidden in a dark area may respond differently from what you expect for the rest of the space.
Three settings to test separately
- Light-level threshold: determines the ambient light level at which a response is allowed. Adjust and check it at dusk in the actual location.
- Time setting: sets how long the light stays on according to the device's operating logic. Test the full route and a typical pause.
- Detection zone: check the range, orientation and any masking options supported by the model. Not every device has electronic sensitivity adjustment.
Change one setting at a time and note the result. Distinguish between a light switching on late and switching off too soon: these usually call for different checks. Keep a record of the final settings so you can restore them after maintenance or a change of position.
LED compatibility: check the specific load
A separate detector must be compatible with the connected light fittings. Check the voltage, load type, total power and number of devices allowed by the manufacturer. The data sheet for the IS 360-3 mentioned above gives different limits for different types of LED, showing why an incandescent load rating should not be treated as a universal limit.
Give the installer the model details of the sensor and the drivers or bulbs. If the manufacturer requires you to consider start-up behaviour or a maximum number of units, follow both requirements. Fixed wiring and electrical checks must be carried out by qualified professionals.
Practical example: a hallway with a window
You want the hallway to light up when you enter at night, while making use of the window during the day. Your buying requirement is ‘movement and low light’. During a test, walk along the hallway from both doors and stop where you usually look for your keys. Then repeat when the window provides enough daylight.
If it switches on during the day, check the threshold and the sensor's position. If it stops detecting movement after a corner, check the coverage. If it switches off while you are still, consider the time setting and whether that activity needs a different type of control.
Two catalogue formats to consider
The recessed ceiling PIR sensor is a separate control option: mounting and load compatibility need to be checked. The 10 W bulb with PIR and dusk-to-dawn sensors combines lighting and detection. Confirm its cap, dimensions, conditions of use and position before choosing it.
10 W bulb with PIR motion and dusk-to-dawn sensors
An example of a bulb combining PIR detection with a dusk-to-dawn condition.
Check the cap, dimensions and whether the shade allows detection as required by the instructions.
View details and optionsChecklist before buying
- Switch-on condition written down and available modes checked.
- Route, obstacles and installation height identified.
- Threshold, timing and the adjustments actually available checked.
- Electrical compatibility and LED load checked.
- Access to the sensor for adjustment, cleaning and maintenance.
Frequently asked questions
Can I connect any LED to a separate sensor?
Check the load table and the instructions. Adding up the wattages alone may not be enough.
Will a sensor bulb work inside any shade?
Check that it fits and that the shade does not obstruct detection or breach the conditions of use.
If you are also replacing the ceiling light, see the differences between recessed and surface-mounted downlights. To install the detector, follow the instructions for its specific model. If you are comparing where to integrate these functions, see integrated LEDs and replaceable bulbs. Keep exploring the lighting guides index.