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Sensors Shelly troubleshooting

Shelly Presence Gen4 misses people or detects an empty room

Lights go off while you sit still, or it says someone's there when nobody is. Check the thresholds, the room's boundary and blind spots, and how the sensor is mounted.

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  • Gen4

Start here

What are you seeing?

Pick the closest match and we'll point you to the fix most likely to sort it.

Go to the fix

Why it happens

The Presence Gen4 uses radar to track people across a room and decides a zone is occupied or empty after the thresholds you set. It picks up people who aren't moving only within 3 m.

So most problems are a threshold, the room's boundary, or a setting that doesn't match how the sensor is mounted.

Before you start

Everything here is done on the sensor's web page or in the Shelly app. The Presence Gen4 runs from USB-C, so there's no mains wiring to check.

Quick checks first

Run these checks before moving on to the fixes.

Checklist 0 of 3 checked
Watch the light

Shelly says the white light flashes slowly while it detects presence. Stand still in front of it, then walk around.

Look at the live map

The map in the app's main controls, or Room and zones on the web page, shows what the sensor sees. Check it shows you where you are, and nothing where nobody is.

Check the power adapter

Shelly says to use a dedicated 5 V adapter, not a multi-port charger, charging station or fast charger.

Fixes, most likely first

Work down the list and stop when it's fixed.

  1. The absence threshold is too short

    How to tell. The zone clears while someone sits still. Shelly marks a zone empty once nothing is detected for its absence threshold, and detects still people up to 3 m away.
    • Raise the absence threshold

      On its web page, open Room and zones, click the room, and raise Absence threshold. Do the same for each zone an automation uses.

    • Raise the sensitivity

      Shelly says high Detection sensitivity improves detection of people who aren't moving.

    • Bring the usual seat within 3 m

      If the chair or bed is further than 3 m from the sensor, moving the sensor closer helps it pick up someone sitting still.

  2. Something in the room moves

    How to tell. The map shows someone where nobody is, often in the same spot. Shelly's own example is curtains moved by the air conditioner.
    • Draw a blind spot

      On the web page, open Room and zones, click Edit room, then Map settings and Edit blind spots, and cover the area. In the app, it's Edit zones, then the pencil beside Blind spots.

    • Lower the sensitivity

      Shelly says low Detection sensitivity reduces false triggers.

    • Raise the presence threshold

      Presence threshold is how long something must be detected before the zone counts as occupied, so a brief flutter doesn't count.

  3. The room's boundary is too wide

    How to tell. It picks up people in the hallway or through a doorway. Shelly's radar can't see through walls, so the boundary taking in the open space is the likely reason.
    • Trim the boundary

      On the web page, open Edit room, then Map settings and Edit room, and remove tiles outside the room. In the app, it's Edit zones, then the pencil beside Boundaries.

    • Lower the transmission power

      Shelly says lower Transmission power gives a shorter detection distance.

  4. Pets or a robot vacuum are counted

    How to tell. It triggers when only the pet or the vacuum is moving. With the minimum detection height at 0, Shelly says a pet entering a zone counts.
    • Raise the minimum detection height

      In the room settings, raise Min detection height so low objects are ignored. Shelly doesn't give a figure, so raise it a little at a time.

  5. The mounting settings don't match

    How to tell. People show in the wrong place on the map, or mirrored. Shelly maps the room from the position, height and flip you set, so they have to match how it's fitted.
    • Set position, height and flip

      In the room settings, set Device mounting position (left, centre or right), Sensor mounting height in metres, and turn on Flipped mounting if it's upside down.

    • Calibrate the tilt

      Click Calibrate under Sensor tilt after fitting or moving it. Shelly recommends about 2 m high and a 15° tilt.

  6. Detection or the zone is switched off

    How to tell. The map stays empty, or a zone never triggers. With detection off, Shelly says the sensor shows no presence, and a disabled zone's actions don't run.
    • Turn detection and the zone back on

      Check Enable presence detection, and the toggle on each zone you use.

    • Look for a schedule that turns it off

      A schedule or action using Control Zone set to Off hides presence in that zone. Check the Schedules and Actions lists.

  7. The action's conditions don't match

    How to tell. The map shows the person in the zone, but the light doesn't switch. An action can be limited to an active time, wait out a repeat interval, or fire only when someone crosses the zone's edge.
    • Use zone occupation for lights

      Change the state of zone occupation turns on when the zone is occupied and off when it's empty. Enter and leave conditions only fire when someone crosses the edge.

    • Check active time and the clock

      Check the action's active time covers now. Shelly says actions may not work as expected if the device's time isn't synced.

Frequently asked questions

No. Shelly says it can't detect anything behind walls or other solid objects, or behind the sensor itself.

No. It's a radar sensor and doesn't use a camera.

No. Shelly says they're for show and have no effect on detection.

Shelly shows only the room's zone over Matter by default. You can expose up to ten from the Matter page on its web interface.

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