What is a hidden sensor? Concealed lighting sensors
A hidden sensor is a lighting sensor fully concealed inside the luminaire cover — invisible from outside. It is really a 5.8GHz microwave doppler sensor whose radio waves pass through plastic and glass. Here is how it works and how to choose one, from a manufacturer that designs the modules.
A hidden sensor = a doppler sensor behind the cover
‘Hidden sensor’ is not a part name — it describes a configuration where the sensor is fully embedded behind the luminaire cover (diffuser) with no visible lens hole or sensor window, for a clean fixture look.
This works because 5.8GHz microwave radio waves pass through non-metallic covers like plastic and glass. The sensor emits from behind the cover and reads the frequency shift (doppler effect) of waves reflected by moving people or vehicles.
A PIR (passive infrared) sensor, by contrast, must expose its Fresnel lens to collect body-heat infrared — so a true hidden sensor is only possible with the doppler (microwave) approach.
Why hidden-sensor luminaires
Clean appearance
No visible sensor window or lens hole — a seamless fixture. Ideal for interior and premium residential lighting.
Fully enclosed
Behind the cover, the sensor is protected from dust, moisture, impact and debris — durable in outdoor and parking environments.
Wide coverage
Radio-based detection gives 0.3–7 m radius / 15 m linear / 120° coverage with few blind spots.
No temperature effect
It senses reflected waves, not body heat, so sensitivity holds up in summer when PIR gets sluggish.
Detection vs cover material
For a hidden sensor, what matters is how well the cover passes radio waves. Most non-metals pass; metal and metallised coatings block.
| Cover material | RF penetration | Hidden-sensor use |
|---|---|---|
| Plastic (PC / PMMA / PP) | Excellent | Recommended — most diffusers |
| Glass | Good | OK — tune sensitivity by thickness |
| Opal / diffuser cover | Good | OK if non-metallic |
| Metal frame / metallic paint | Blocked | Not possible — RF cannot pass |
| Metallised (half-mirror) cover | Blocked | Not possible — needs a sensor window |
Where it is used
Ceiling-mount & downlights
Embed a compact doppler module (e.g. 18×18 mm BIO58K1-1818) behind the cover for a fixture with no visible sensor.
Parking & factory lights
Hide the sensor behind the cover to resist dust and fumes while covering a wide area — combined with AI group control.
Residential common areas
Corridors, stairs and entrances get clean looks plus occupancy detection, with low standby power.
BIO-24AD-IRF — Smart PIR Sensor Controller
2–8 m detection · 10–90 s hold · 0–30% standby PWM · soft dimming · optional 40-group RF. Compare it hands-on with our 5.8GHz doppler lineup (JA58K1(G)-3123, BIO58K1-1818) via a sample.
FAQ
Q. Is a hidden sensor the same as a microwave sensor?
Effectively yes. ‘Hidden sensor’ emphasises the concealed configuration; the device itself is a 5.8GHz microwave (doppler) sensor. It can be hidden because RF passes through the cover.
Q. Can a PIR sensor also be hidden?
No. PIR needs its infrared lens exposed, so it won't work fully concealed. A true hidden sensor is only possible with the doppler (microwave) approach.
Q. Does a thick cover block detection?
Non-metallic covers mostly pass RF, but a very thick cover can reduce sensitivity. BIO sensors let you tune detection range and sensitivity on site via IR remote or app to match the cover.
Q. Can we source just the hidden-sensor module?
Yes. BIO Electronics supplies 5.8GHz doppler modules standalone and offers luminaire OEM/ODM (firmware and antenna tuning). Samples available.
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