Home Assistant Presence Sensor Setup Guide: Turn Lights On When You Enter and Off When You Leave

Many Home Assistant users start with the same idea: turn the lights on when someone enters a room and turn them off after everyone leaves. The first version often uses a motion sensor. That can work well for a quick pass-through space, but it may not describe what is happening after a person sits down, reads, works, or watches television.

A presence sensor adds a different signal to the automation. Instead of asking only whether movement was recently detected, Home Assistant can use a presence state to represent whether the room is still occupied. This guide explains the difference, then uses LinknLink eMotion Air as a practical example for building a room-lighting workflow.

Motion Sensor vs Presence Sensor

A traditional motion sensor is usually strongest at detecting movement across its field of view. That makes it useful for a hallway light, an entry light, or an automation that should start when someone walks past. Once movement stops, however, the sensor may no longer be the best signal for deciding whether the room is still in use.

A presence sensor is designed to help represent occupancy over time. In a Home Assistant lighting automation, that distinction matters: a person can be present while sitting nearly still at a desk, lying in bed, or watching a screen. The sensor and its integration still have an operating range and environmental limits, so placement and a suitable vacancy delay remain important.

The practical rule is simple: use motion as a signal that activity occurred, and use presence when the automation needs to understand that a room may still be occupied. They can also be used together when the room and the desired behavior call for both signals.

Why mmWave Can Improve Home Assistant Lighting Automation

mmWave sensing is useful for presence-oriented automations because it is intended to detect more than a single obvious movement event. In the right installation, it can help Home Assistant keep a room’s occupied state while someone remains relatively still. That can make a lighting routine feel less like a timer and more like a response to how the room is being used.

This does not mean that every mmWave installation behaves identically. Furniture, reflective surfaces, nearby movement, mounting direction, room boundaries, and the configured vacancy delay all influence the result. A good automation treats the sensor state as one input and gives the system enough time to confirm that a room has become vacant.

Example Automation: Turn Lights On When You Enter and Off When You Leave

The core example has three states: enter, stay, and leave. The goal is not to switch a light on for every movement event. It is to use the room’s presence state to start lighting, maintain lighting while the room is occupied, and switch lighting off only after a defined vacancy period.

1. Enter the room and start the lighting scene

Use the presence entity for the room as the trigger. When the entity changes to an occupied or present state, Home Assistant can turn on the selected light or lighting scene. You may also add a condition such as a time window or low-light requirement if the light should not turn on during the day.

Keep the first version small: one room, one presence entity, and one light group. This makes it easier to confirm that the trigger represents the room you intended and that the light action is connected to the correct entity.

2. Stay in the room and keep the light available

While the presence state remains occupied, the automation should not start a short inactivity timer after every small pause. This is the main difference from a motion-only approach. Someone working quietly or watching TV can remain in the room without needing to wave or stand up to keep the lighting routine active.

If the room has more than one light, consider using a scene or light group rather than repeating individual actions. The exact entities and services depend on your Home Assistant configuration; the important design choice is that the occupied state is allowed to remain active.

3. Leave the room and wait before switching off

When the presence entity changes to vacant or clear, start a vacancy delay instead of switching the light off immediately. A short delay can help accommodate a sensor state transition or a person briefly moving outside the main sensing area. A longer delay may be more comfortable in a bedroom or home office.

After the delay, check that the room is still vacant before turning the light off. This second check prevents the off action from running if someone has returned during the waiting period. The right delay is room-specific: begin with a conservative value, observe the routine, and adjust it based on normal use.

4. Separate the sensor state from the light state

The sensor reports the room condition; Home Assistant decides what the light should do. Keeping those roles separate makes the automation easier to extend. For example, you can later add a manual override, a night-time brightness level, or a condition for another connected device without changing how the presence signal is interpreted.

Why eMotion Air Is a Practical Example

eMotion Air is a battery-powered mmWave presence multi-sensor designed for room-level smart-home use. It is a useful example for this lighting pattern because a battery-powered device can be placed where the room’s presence signal makes sense without starting with a wired installation project.

Depending on the confirmed device and integration workflow, eMotion Air can provide presence-related data alongside temperature, humidity, light, and button inputs. These additional inputs can help you decide how a room routine should behave, but they do not replace the need to validate the supported Home Assistant connection and the actual entity names available in your setup.

For example, presence can determine whether the lighting routine should remain active, while the light reading can be considered when deciding whether to turn lights on. The best result comes from treating each signal according to what it measures rather than assuming that one sensor can infer every room condition.

Review the eMotion Air product page for the current product details, then confirm the supported connection path before planning the final automation.

Room-by-Room Lighting Use Cases

Bedroom

Use presence to keep a low-brightness light available while someone is reading or preparing for sleep. A longer vacancy delay can reduce abrupt shutoffs when a person is still in bed or moving very little. Night-time conditions can be handled in Home Assistant if your lighting setup supports them.

Living room

A living room is a natural test for presence-aware lighting because people may sit still for long periods. Use presence to maintain the room state, then combine it with a time or light-level condition so the automation does not turn on bright lights when the room already has enough daylight.

Home office

A desk-based routine should account for quiet work. Presence can keep the lighting available while someone reads or types, while a separate manual control can provide an override for calls, focused work, or a changed desk position.

Hallway or entry area

A hallway often benefits from a faster response and a shorter off delay because people are moving through it. A motion sensor may be sufficient for this room. If the space is also used as a small entry area, compare the desired behavior with the sensor’s actual coverage before selecting the longer presence-oriented workflow.

How to Set Up the Workflow in Home Assistant

Connect the sensor using the supported path

Follow the current eMotion Air instructions and the supported Home Assistant connection workflow. The exact screens and entity names can change with the app, firmware, integration, and Home Assistant release, so use the current product documentation as the source of truth.

Create a clear room presence entity

Give the sensor and its presence entity a room-based name, such as “office presence” or “living room presence.” Clear names matter when an automation has several rooms, lights, and conditions. Confirm the occupied and vacant states from the Home Assistant device page before writing the final actions.

Build the automation in two parts

The first part handles arrival: when the room becomes occupied, turn on the appropriate light or scene under the conditions you want. The second part handles departure: when the room becomes vacant, wait for the chosen delay, check the state again, and then turn the light off if the room is still vacant.

Test real room behavior

Test entering, sitting still, leaving, and returning during the vacancy delay. Test with the furniture and doors in their normal positions. If the sensor is moved later, repeat the test because a different angle or surrounding surface can change the observed presence state.

Common Tips to Improve Lighting Automation

• Start with one room: validate the presence state and light action before copying the pattern elsewhere.
• Use a room-appropriate delay: hallways may need less waiting than bedrooms or offices.
• Check the installation direction: avoid placing the sensor where furniture or a nearby doorway changes the intended sensing area.
• Separate arrival from departure: use an occupied trigger for on and a delayed vacant check for off.
• Keep a manual override: a wall switch, dashboard control, or other supported input can help when the household wants a different lighting state.
• Observe before expanding: run the automation through normal daily routines and then adjust conditions or delays.

For a broader installation and tuning workflow, read the eMotion Air Home Assistant setup guide. For a deeper comparison of sensing approaches, see the PIR vs mmWave guide.

FAQ

What is the difference between a motion sensor and a presence sensor?

A motion sensor primarily responds to movement, while a presence sensor is intended to help represent whether someone remains in a space. Motion can be a good fit for pass-through areas; presence can be useful when people may sit or remain still.

Can Home Assistant turn lights on and off automatically?

Yes. Home Assistant can use a connected sensor state as an automation trigger, turn a compatible light or scene on when a room becomes occupied, and turn it off after the room becomes vacant and a chosen delay has elapsed.

Is a mmWave presence sensor better for lighting automation?

It can be a better fit for rooms where people remain still, such as bedrooms, living rooms, and home offices. The result depends on installation, room conditions, supported integration behavior, and the vacancy delay you configure.

Can eMotion Air be used in Home Assistant?

eMotion Air is positioned for Home Assistant room-level automation use. Confirm the current supported connection workflow, firmware, and available entities before building the final automation.

How long should the light-off delay be?

There is no single setting for every room. Start with a delay that gives the presence state time to settle, then adjust it based on how people use the space. Bedrooms and offices often benefit from more time than hallways.

Can I use a motion sensor and a presence sensor together?

Yes, when the combined logic matches the room. For example, motion can provide a quick arrival signal while presence provides the longer occupied state. Test the combined triggers carefully so one sensor does not unintentionally switch the light off while the room is in use.

Conclusion

A natural “lights on when I enter, lights off when I leave” routine depends on more than detecting a single movement. In Home Assistant, a presence-oriented workflow can represent enter, stay, and leave states, giving the automation a better basis for rooms where people sit, work, relax, or sleep.

eMotion Air is one practical way to explore this pattern with a battery-powered mmWave presence multi-sensor. Start with one room, use a measured vacancy delay, test the final placement, and expand only after the automation reflects real household behavior.