Shelly’s Presence Gen4 uses millimetre-wave radar instead of a camera to sense people in a room. The Verge reports that it can follow up to ten people at once. This guide explains how the technology works and what to check before you buy one.
What has Shelly announced?
The Verge reports that Shelly has announced a new smart home accessory called the Shelly Presence Gen4. It is a presence sensor that uses mmWave radar rather than a camera. The publication says it can keep track of several people as they move through rooms or larger spaces, without recording them, and the headline puts the limit at ten people at once. The launch comes about a month after Shelly released a security camera that The Verge describes as costing $50 and needing no subscription. The source material does not include the sensor’s price, release date, regional availability or full technical specifications. Those details should be checked against Shelly’s own product information before you decide to buy.
What is a presence sensor, and how does it differ from a motion sensor?
Most low-cost smart home motion sensors use passive infrared, usually shortened to PIR. A PIR sensor reacts to changes in heat as a warm body crosses its field of view. That works well for spotting someone walking into a room. It works poorly once the person sits still to read, work at a desk or watch television. The sensor then reports the room as empty, and automations such as lights may switch off while someone is still there. A presence sensor is designed to answer a different question: is anyone in the space at all, even if they are barely moving? Radar-based presence sensors aim to pick up very small movements, so they can tell that a room is occupied without needing obvious motion.
How does mmWave radar detect people without a camera?
Millimetre-wave radar sends out radio signals at very short wavelengths and measures the reflections that come back. When something in the room moves, the reflected signal changes. The sensor can use those changes to estimate how far away the object is and, depending on the design, which direction it lies in and how fast it is moving. Because the wavelengths are so short, the technique can be sensitive enough to notice small movements, which is why such sensors are often marketed as able to tell when a still person is present. The sensor builds up a picture of reflections and positions, not a photograph. It has no lens and captures no recognisable image of a face or body.
Why does tracking several people at once matter?
A basic occupancy sensor gives a simple yes-or-no answer: someone is present or nobody is. The Verge reports that the Presence Gen4 can follow multiple people as they move around, with the headline figure being up to ten. In principle, tracking individual targets lets a system do more than switch on when a room is occupied. It could count how many people are in a space, follow movement between zones within a large room, or tell when the last person has left. How Shelly exposes this information to users and to automation platforms is not described in the source material. Whether you can set separate zones, read a live headcount or trigger rules on specific positions remains to be confirmed.
Does a radar sensor record images of the people it detects?
According to The Verge, the Presence Gen4 tracks people without recording them, and it uses radar rather than a camera. Radar returns are not visual images, so the device cannot produce a photograph or video of who is in the room. That makes this kind of sensor attractive for bedrooms, bathrooms and other places where many people would not accept a camera. It does not mean the device collects no data. A sensor that tracks positions and movement still produces information about when people are present and how they move around a home. How that data is processed, whether it stays on the local network and whether a cloud account is needed are not covered in the source material.
What could you automate with a multi-person presence sensor?
Common uses for presence sensing in a smart home include:
- keeping lights on while someone sits still
- turning heating or cooling down when a room empties
- switching off media devices when everyone has left
Tracking several people could support more detailed rules. For example, a living room could stay lit while anyone remains, and turn off only when the count reaches zero. In a larger open-plan space, different lighting areas could respond to where people actually are. Shared offices, meeting rooms or workshops could use occupancy information to manage energy use. Which of these are possible with the Presence Gen4 depends on how it connects to the rest of a smart home. That includes Shelly’s own app and any third-party platforms it supports. The source material does not set out those integrations, so check them before you plan a setup.
What details about the Presence Gen4 are still unknown?
The source material leaves several practical questions open:
- Detection: the sensor’s range, field of view and accuracy are not given.
- Power: it is not stated whether the sensor plugs into mains power or runs on batteries.
- Connectivity: the wireless protocols it uses are not listed.
- Compatibility: support for common smart home standards and platforms is not described.
- Data handling: it is not clear whether processing happens on the device or in the cloud.
- Price and availability: the cost and the markets where it will be sold are not included.
Anyone considering the sensor should look for this information in Shelly’s official documentation. Independent reviews will also help show how well it performs in real homes once they appear.
Where should a radar presence sensor be placed?
Placement advice depends on each manufacturer’s guidance, but some general principles apply to radar sensors. They need a reasonably clear view of the area they are meant to cover. Many are designed to be mounted on a wall or ceiling at a set height and angle. Radio waves can pass through some thin materials, so a sensor may pick up movement beyond the room you intended, such as through a partition wall. Moving objects can produce false readings. Examples include fans, swaying curtains, plants near a heater and pets. Mounting the sensor away from these sources and adjusting its detection area, where the software allows, usually reduces errors. Shelly’s installation guidance for the Presence Gen4 has not been described in the source material.
What are the limitations of mmWave presence sensing?
Radar presence sensors are generally more reliable than PIR sensors at detecting people who are sitting still. They still have trade-offs:
- Sensitivity: they can be sensitive enough to react to things other than people, such as the movements described above, so they may need tuning.
- Coverage: walls and furniture affect how radio signals reflect, so results can vary from one room to another.
- Identification: a radar sensor can show that someone is present but cannot tell who that person is. Automations that depend on a specific resident would need another source of information.
- Large groups: tracking many people at once is harder than detecting a single occupant. How the Presence Gen4 performs with a full room is something only testing can show.
How should you decide whether you need one?
Start with the problem you want to solve. If your lights already behave well with a standard motion sensor, a radar device may add little. A presence sensor makes more sense where people spend long periods sitting still, such as a home office, lounge or bedroom. It is also worth considering if you want occupancy-based control without putting a camera in a private room. Multi-person tracking is most useful in shared or larger spaces where counting or zoning would improve automations. Before buying, confirm that the sensor works with the platform you already use, check its power and mounting needs, and read how it handles data. Since price and specifications for the Presence Gen4 were not in the source material, compare those details once they are published.
Sources and further reading
- The Verge: its report on the announcement of the Shelly Presence Gen4 sensor
- Shelly: official product pages and documentation for specifications and setup
- Smart home standards bodies: material on interoperability between devices and platforms
- Independent technology reviewers: hands-on testing of mmWave presence sensors in homes
Surfaced from the rss:verge signal “smart home sensor launch”. AI-assisted draft, editorially reviewed.
