Smart alarm system with Senvolon presence sensor KL MZ & Home Assistant

Here's how to build your own alarm system in one afternoon, one that can do more than many commercial solutions, without any monthly costs.

Why an Alarm System?

Be honest: have you ever thought about what happens when you are not at home? In Germany, around 83,000 home burglaries were recently registered per year (PKS 2025), the fourth year in a row with a rising trend. That is more than 220 burglaries a day. The good news: around 45 percent of burglaries fail at the attempt stage, often because security technology deters the burglars or raises the alarm early.

An alarm system gives you a better sense of security while also acting as a deterrent. Visible security technology is one of the most important deterrence factors. Some insurers even reward its use with lower premiums.

However, commercial alarm systems are often expensive, tied to cloud services, and require monthly fees. There is another way.

Why Radar Presence Sensors Are Ideal

Classic motion detectors (PIR sensors) have two decisive weaknesses:

1. They only detect movement. If someone stands still, whether listening or hiding, they go undetected.
2. They do not know zones. The entire detection area is a single, undifferentiated space. Targeted monitoring of a door, window, or specific room zones is not possible.

The Senvolon presence sensor KL MZ solves both problems at once:

• 60 GHz radar detects even completely motionless people. Breathing alone is enough of a signal.
• Up to 4 freely configurable detection zones per device: you decide which area counts as "door," "window," or "room," and monitor these areas separately and specifically.
• Double the use from a single sensor: when the alarm system is disarmed, the same zones can be used for other purposes. For example, to automatically turn the light on or off when you enter or leave the room.
• Built-in siren, a real difference from other sensors: no external device needed, every room with a presence sensor also has a siren built right in. If an alarm is detected, all sirens activate.
• 100% local: no cloud required, no dependency on third-party providers.
• MQTT integration: direct integration into Home Assistant, including automatic recognition via MQTT Discovery.
• Climate sensors included: temperature, humidity, air pressure, and brightness as a basis for further automations.

Combined with Home Assistant, this becomes a full-featured, smart alarm system. Flexible, expandable, and with no ongoing costs at all.

Cost Comparison: Off-the-Shelf System vs. DIY

System	Purchase Cost	Monthly Cost	Cloud Required
Comparable off-the-shelf alarm system	€500–1,000	€10–30/month	usually
DIY with Senvolon + Home Assistant	€300–450	€0	No

DIY cost example:

• 3× Senvolon presence sensor KL MZ: 3 × €99 = €297
• Home Assistant on an existing Raspberry Pi or mini PC: €0–150
• Total: approx. €300–450, no ongoing costs

After 2 years with a cloud-based off-the-shelf solution (at €15/month), you would already have spent €360 on the subscription alone, and would still be limited to PIR detection without zones.

What Do You Need?

Component	Details	Cost
2–3× Senvolon presence sensor KL MZ	Order in the shop	€99 each
Home Assistant	On a Raspberry Pi 4/5, mini PC, or NUC	€0–150
Wi-Fi router	Probably already on hand	€0
USB-C power adapters	5V/2A per sensor (USB-C cable included)	€0–10
Smartphone	For notifications (HA Companion App)	already on hand

No separate control panel, no gateway, no additional siren needed.

Step by Step: Setting Up Your Alarm System

Step 1: Positioning and Mounting the Sensors

Think about which rooms you want to monitor. A typical setup for an apartment:

Room	Position	Monitors
Hallway	Wall opposite the front door, 1.8 m high	Entrance area
Living Room	Wall facing the balcony door, 1.8 m high	Balcony door & center of room
Bedroom	Wall facing the window, 1.8 m high	Window area

Mounting tips:

• Mounting height: 1.50–2.00 m (wall) or on the ceiling
• Clear line of sight to the monitored area, no furniture in the way
• Avoid reflections: do not mount directly opposite mirrors or large glass surfaces
• 120° detection angle: the sensor covers a cone-shaped area of the room in front of it
• For ceiling mounting: the higher the ceiling, the larger the detection area

The power supply is provided via USB-C (cable included). Route the cable neatly along the wall, or use the internal 5V connector for hidden wiring.

Step 2: Setting Up MQTT in Home Assistant

MQTT is the communication protocol between your sensors and Home Assistant. You need an MQTT broker. The easiest option is the Mosquitto add-on in HA.

Installing Mosquitto:

1. Go to Settings → Add-ons → Add-on Store in Home Assistant
2. Search for "Mosquitto broker" and install it
3. Start the add-on and enable "Start on boot"

Creating an MQTT user:

1. Go to Settings → People → Users
2. Create a new user, e.g.:
   • Username: mqtt_user
   • Password: sicheres_passwort

Adding the MQTT integration:

1. Go to Settings → Devices & Services → Add Integration
2. Search for "MQTT" and set up the integration
3. Broker: localhost (or core-mosquitto), port: 1883

You can also find a compact overview of all the MQTT steps in our quick start guide Integrating the presence sensor into Home Assistant.

Step 3: Connecting the Sensor to Wi-Fi and MQTT

Each presence sensor has its own web interface for configuration.

1. Initial setup: on first start, the sensor sets up its own Wi-Fi network. Connect to it and open the configuration page in your browser.
2. Set up Wi-Fi: enter the details of your home Wi-Fi (2.4 GHz).
3. Configure MQTT under "Connections":
   • Broker address: the IP address of your Home Assistant (e.g., 192.168.1.100)
   • Port: 1883
   • Username: mqtt_user
   • Password: sicheres_passwort
   • Topic: the sensor's name, e.g., Flur, Wohnzimmer, or Schlafzimmer. This name is used as the base for all MQTT messages from this device.
4. Set up zones: under "Zones," define the detection areas and give them meaningful names without umlauts (Home Assistant takes over the name directly):
   • Zone 1: the door or window area, e.g., Tuer or Balkon, for early detection during a break-in
   • Zone 2: the center of the room, e.g., Raum, detects movement throughout the whole room. When the alarm system is disarmed, this zone also works great for lighting control: the light turns on automatically when someone enters the room.
   • Optional: define interference zones to avoid false alarms caused by fans, moving curtains, or similar.
5. Siren: the built-in siren can be controlled via MQTT at any time. This works independently of any further configuration. Home Assistant handles the control entirely through the automations in step 6.

Repeat these steps for each sensor.

Step 4: Automatically Adding the Sensors to Home Assistant

The presence sensor supports MQTT Auto-Discovery: as soon as MQTT is set up, the sensor registers itself with Home Assistant automatically. You do not need to write any YAML configuration.

At least the following entities are created automatically:

Entity	Description	Type
Presence	Presence in the room (yes/no)	binary_sensor
Detection	Number of people detected	sensor
[Zonenname]	Presence in the respective zone	binary_sensor
Siren	Siren on/off	switch
Temperature	Room temperature	sensor
Humidity	Humidity	sensor
Air Pressure	Air pressure	sensor
Brightness	Brightness	sensor

The zones appear in Home Assistant with exactly the name you configured in the presence sensor. Give your zones meaningful names (without umlauts), and you get clear, easy-to-use entities in HA right away.

Tip: name your devices in the presence sensor after the room they are mounted in (e.g., Flur, Wohnzimmer, Schlafzimmer). Then all entities in Home Assistant are sorted by room right away, and the entity IDs in these instructions match without renaming. The entity IDs are in fact derived from the topic you set: a sensor with the topic Flur creates binary_sensor.flur_presence, while a sensor with the topic multi_zone_presence_sensor creates binary_sensor.multi_zone_presence_sensor_presence. You can see the exact IDs for your system at any time under Developer Tools → States.

Step 5: Setting Up the Alarm Control Panel

The alarm control panel is the central hub of your alarm system in Home Assistant.

Standard Installation (Home Assistant OS / Supervised)

Set it up via the user interface:

Settings → Devices & Services → Add Integration → "Manual Alarm Control Panel"

Configure the following:

• Name: Alarmanlage
• Arming delay (arming time): 30 seconds, time to leave the home
• Trigger delay (delay time): 30 seconds, time to disarm after returning
• Trigger duration (trigger time): 300 seconds, this is how long the alarm state stays active, matching the automatic siren shutoff after 5 minutes in step 6
• Code: your personal PIN

Docker Installation (e.g., via Portainer)

Note for Docker users: unlike the standard installation, this integration currently cannot be set up via the user interface in the Docker/Portainer version. It must be entered manually into configuration.yaml.

1. Accessing the Configuration File via SSH

Since Home Assistant runs in a Docker container, the configuration files are located in a protected system directory.

Open your terminal (PowerShell, CMD, or macOS Terminal) and connect:

ssh admin@192.168.1.100

Open the configuration file with administrator rights in the Nano editor:

sudo nano /var/lib/docker/volumes/HASS_Config/_data/configuration.yaml

2. Inserting the YAML Configuration

Scroll all the way to the bottom of the file and insert the following block. Make sure alarm_control_panel: starts at the very left margin (no spaces before it):

# Manual alarm control panel
alarm_control_panel:
  - platform: manual
    name: Alarmanlage
    code: "0815"                # Your personal PIN
    delay_time: 30              # Time to disarm after returning (entry delay)
    arming_time: 30             # Time to leave the home (exit delay)
    trigger_time: 300           # Duration of the alarm state (300 sec = 5 min, matches step 6)

Save & exit: Ctrl + O → Enter → Ctrl + X

3. Checking the Configuration and Restarting

1. Open Home Assistant in your browser
2. Go to Developer Tools → YAML tab
3. Click Check Configuration
4. If the green text "Configuration will not prevent homeassistant from starting…" appears, click Restart and confirm

4. Adding the Panel to the Dashboard

After the restart, the alarm system is registered in the system and still needs to be made visible in the interface:

1. Go to your Overview (Dashboard)
2. Click the three dots at the top right → Edit Dashboard
3. Click Add Card and search for Alarm Panel
4. Select the entity alarm_control_panel.alarmanlage and click Save

Step 6: Creating the Alarm Automations

Now comes the heart of the system: the automations that turn your sensors into a real alarm system.

Where do you edit automations? The easiest way is directly in the HA interface under Settings → Automations → Create Automation → Start with an Empty Automation. There, paste the YAML code for each of the following automations, one at a time, and save.

A note on the code: the automations use the note: field, which lets you comment directly on triggers, conditions, and actions. These notes also appear in the visual editor at the relevant step and mark, among other things, the places where you need to enter your own entity IDs. If your Home Assistant version does not yet know this field, simply delete the note: lines; the function of the automations will not change as a result.

Automation 1: Trigger the Alarm on Presence

alias: "Alarm: Presence Detected"
description: >
  Triggers the alarm when presence is detected while the system is armed.

triggers:
  - trigger: state
    entity_id:
      - binary_sensor.flur_presence
      - binary_sensor.wohnzimmer_presence
      - binary_sensor.schlafzimmer_presence
    to: "on"
    note: >-
      Enter the presence entities of all your sensors here. If you only
      want to arm individual zones, enter the zone entities instead,
      such as binary_sensor.flur_tuer.

conditions:
  - condition: state
    entity_id: alarm_control_panel.alarmanlage
    state: "armed_away"
    note: "The alarm only triggers when the system is armed."

actions:
  - action: alarm_control_panel.alarm_trigger
    target:
      entity_id: alarm_control_panel.alarmanlage

mode: single

Automation 2: Activate the Sirens on Alarm

alias: "Alarm: Turn On Sirens"
description: >
  Activates all sirens when the alarm is triggered.

triggers:
  - trigger: state
    entity_id: alarm_control_panel.alarmanlage
    to: "triggered"

actions:
  - action: switch.turn_on
    target:
      entity_id:
        - switch.flur_siren
        - switch.wohnzimmer_siren
        - switch.schlafzimmer_siren
    note: "Enter the siren entities of all your sensors here."

mode: single

Automation 3: Turn Off the Sirens on Disarm or After 5 Minutes

alias: "Alarm: Turn Off Sirens"
description: >
  Deactivates all sirens when disarming or after 5 minutes.

triggers:
  - trigger: state
    entity_id: alarm_control_panel.alarmanlage
    to: "disarmed"
    note: "Case 1: You disarm the system."
  - trigger: state
    entity_id: alarm_control_panel.alarmanlage
    to: "triggered"
    for:
      minutes: 5
    note: "Case 2: The alarm has been running for 5 minutes."

actions:
  - action: switch.turn_off
    target:
      entity_id:
        - switch.flur_siren
        - switch.wohnzimmer_siren
        - switch.schlafzimmer_siren
    note: "The same siren entities as in Automation 2."

mode: single

Good to know: the sirens turn off automatically in two cases: when you disarm the system, or after 5 minutes at the latest. The trigger duration of the alarm control panel from step 5 (trigger_time: 300) is set to match this value.

Step 7: Setting Up Notifications

Of course, you also want to know immediately when something happens, even while you are out.

Automation 4: Push Notification on Alarm

alias: "Alarm: Push Notification"
description: >
  Sends a notification when the alarm is triggered.

triggers:
  - trigger: state
    entity_id: alarm_control_panel.alarmanlage
    to: "triggered"

actions:
  - action: notify.mobile_app_ihr_handy
    data:
      title: "🚨 ALARM!"
      message: >
        Presence detected! The alarm has been triggered.
        Time: {{ now().strftime('%H:%M:%S') }}
      data:
        priority: high
        ttl: 0
        channel: alarm
    note: >-
      Use your own notification service, e.g.,
      notify.mobile_app_[device_name] or notify.signal.

mode: single

Tip: install the Home Assistant Companion App on your smartphone. The notification service automatically becomes available as notify.mobile_app_[device_name]; the exact name depends on the device name in the app and can be found under Developer Tools → Actions.

Step 8: Creating a Dashboard

A clear dashboard gives you your alarm system's status at a glance. Here is a Lovelace configuration:

title: Alarm System
views:
  - title: Overview
    path: alarm
    icon: mdi:shield-home
    cards:
      # Alarm panel
      - type: alarm-panel
        entity: alarm_control_panel.alarmanlage
        name: "Alarm system"
        states:
          - arm_away

      # Room overview
      - type: horizontal-stack
        cards:
          - type: entities
            title: "🚪 Hallway"
            entities:
              - entity: binary_sensor.flur_presence
                name: "Presence"
              - entity: sensor.flur_detection
                name: "People"
              - entity: binary_sensor.flur_tuer
                name: "Door zone"

          - type: entities
            title: "🛋️ Living Room"
            entities:
              - entity: binary_sensor.wohnzimmer_presence
                name: "Presence"
              - entity: sensor.wohnzimmer_detection
                name: "People"
              - entity: binary_sensor.wohnzimmer_balkon
                name: "Balcony zone"

          - type: entities
            title: "🛏️ Bedroom"
            entities:
              - entity: binary_sensor.schlafzimmer_presence
                name: "Presence"
              - entity: sensor.schlafzimmer_detection
                name: "People"
              - entity: binary_sensor.schlafzimmer_fenster
                name: "Window zone"

      # Sensor data
      - type: horizontal-stack
        cards:
          - type: sensor
            entity: sensor.flur_temperature
            name: "Hallway"
            graph: line
          - type: sensor
            entity: sensor.wohnzimmer_temperature
            name: "Living room"
            graph: line
          - type: sensor
            entity: sensor.schlafzimmer_temperature
            name: "Bedroom"
            graph: line

      # Recent events
      - type: logbook
        entities:
          - alarm_control_panel.alarmanlage
          - binary_sensor.flur_presence
          - binary_sensor.wohnzimmer_presence
          - binary_sensor.schlafzimmer_presence
        hours_to_show: 24
        title: "Recent Events"

Tip: you can find the exact entity IDs of your zones (e.g., binary_sensor.flur_tuer) under Developer Tools → States in Home Assistant. Adjust the entity IDs in the dashboard accordingly.

Advanced Tips

Using Zones Cleverly

Every presence sensor offers up to 4 detection zones. Put them to targeted use:

• Zone 1 pointed directly at a door or window → early detection right at the point of entry
• Zone 2 pointed at the center of the room → detects any movement in the room
• Zones for lighting control: when the alarm system is disarmed, the same zones can be used for smart lighting automations. Our how-to on intelligent lighting control shows how to build a brightness-dependent control with hysteresis from this.
• Interference zones can be defined to suppress false alarms from known sources (fan, curtain)

Setting Up Schedules

Arm the system automatically at night or when you leave the house:

alias: "Alarm: Arm Automatically at Night"
description: >
  Arms the system automatically every evening at a fixed time.

triggers:
  - trigger: time
    at: "23:00:00"

actions:
  - action: alarm_control_panel.alarm_arm_away
    target:
      entity_id: alarm_control_panel.alarmanlage
    data:
      code: "IHR_CODE"
    note: "Use the same code as when setting it up in step 5."

mode: single

alias: "Alarm: Disarm Automatically in the Morning"
description: >
  Disarms the system automatically every morning at a fixed time.

triggers:
  - trigger: time
    at: "06:30:00"

actions:
  - action: alarm_control_panel.alarm_disarm
    target:
      entity_id: alarm_control_panel.alarmanlage
    data:
      code: "IHR_CODE"
    note: "Use the same code as when setting it up in step 5."

mode: single

Automatic Activation When Leaving the House

Even more convenient: the system arms itself automatically as soon as the last person leaves the house, with no manual switching on at all.

Home Assistant uses the zone feature (zone.home) for this. As soon as the count of people in the home zone drops to 0, the automation is triggered.

alias: "Alarm: Arm Automatically When Leaving"
description: >
  Arms the alarm system when no one is home anymore.

triggers:
  - trigger: state
    entity_id: zone.home
    to: "0"
    note: "The state of zone.home corresponds to the number of people present."

actions:
  - action: alarm_control_panel.alarm_arm_away
    target:
      entity_id: alarm_control_panel.alarmanlage
    data:
      code: "IHR_CODE"
    note: "Use the same code as when setting it up in step 5."

mode: single

Requirement: the Home Assistant Companion App must be installed on all household members' smartphones, with location sharing enabled. Only then can HA detect when there really is no one left at home.

Open-Window Detection as a Bonus

The built-in climate sensors provide an additional clue. A sudden drop in temperature in a room can indicate an open window.

Looking Ahead: How to Expand Your System

Your alarm system is a solid foundation, and with Home Assistant, the possibilities are almost unlimited:

• Presence simulation while on vacation: the sensor's brightness sensor drives a realistic light simulation while the radar stays armed. Our how-to on vacation presence simulation shows how the two work together.
• Camera integration: add cameras and have a photo taken automatically and sent to your phone when an alarm triggers.
• Door and window sensors: add Zigbee contact sensors for an extra layer of detection, for example to react the instant a door opens, even before anyone enters the sensor's detection area.
• Light as a deterrent: have all the lights turn on automatically during an alarm. This adds an extra deterrent.
• Notifying neighbors: send a message to trusted people during an alarm, for example via a Telegram bot or Signal.
• More Senvolon presence sensors: expand your system to as many rooms as you like. Every sensor brings radar detection, zones, and its own siren. All devices are managed centrally through Home Assistant.

Conclusion

With just a few Senvolon presence sensors KL MZ and Home Assistant, you get an alarm system that surpasses classic off-the-shelf solutions in several ways:

• Built-in siren in every sensor: no separate device, no extra effort. The alarm sounds everywhere it is detected.
• Freely configurable zones: you decide which areas are monitored, and keep the door, window, and center of the room separately in view.
• Double the use: the same zones that trigger the alarm when the system is armed can otherwise control the lighting. One sensor, two jobs.
• Full flexibility: thanks to Home Assistant, you design automations, schedules, and notifications exactly to your needs, and can expand the system at any time.
• No ongoing costs, no cloud dependency, full control over your data.

Ready to get started?

👉 Order the Senvolon presence sensor KL MZ in the shop

If you have questions, the Senvolon support team is happy to help: support@senvolon.de

All models compared: Presence sensors