This isn't installing a professional monitored alarm system. You're building extra logic inside Home Assistant that calls script.intrusion_alarm from Lesson 3: with escalation, repeats, and a local siren. A certified alarm system still protects the house independently of HA.

Plan on about 90 to 105 minutes. Start with one perimeter zone and a 60-second disarm window. Then add an interior zone with PIR.

An HA restart during the entry delay interrupts the countdown: the system may fail to trigger the alarm, or get stuck in an in-between state. A timer, or storing the end time, is more resilient. Reset timed helpers after HA starts up.

A real-life problem: you come home, open the door: and the alarm fires instantly

In Lesson 8, the entering_home_in_progress entry delay only protects you if the phone detects your return before you open the door. GPS can lag. Away mode might stick around a bit longer than it should. In that case, the Lesson 6 automation fires the alarm the instant the door opens: with no second to disarm.

Professional alarms solve this with an entry delay: once the door opens, you have, say, 60 seconds to punch in a code or disarm the alarm. In this lesson, you'll build similar logic in HA: simple, but honestly described for what it is.

A supporting alarm versus a monitored system

A supporting alarm in HA makes sense as an extra layer: fast household notifications, a Zigbee siren, lights, SMS escalation. It doesn't replace a contract with a security company or a certified panel.

Zones: perimeter and interior

Professional alarm systems have zones. In HA, we'll simplify this to two groups:

The alarm_sensors group combines both zones for the dashboard and for "did anything trigger" conditions. Separate perimeter_zone and interior_zone groups let you tell the response apart.

What's actually the risk

Which entities we're watching

You're using entities from earlier lessons. Example names below: swap in your own.

Alarm helpers

Add these to your configuration.yaml or helpers file:

input_boolean:
  home_alarm_armed:
    name: "Home alarm armed"
    icon: mdi:shield-home

  disarming_in_progress:
    name: "Disarming in progress"
    icon: mdi:shield-key

  automatic_arming:
    name: "Automatic arming with Away mode"
    icon: mdi:shield-sync

  home_alarm_test:
    name: "Home alarm test"
    icon: mdi:shield-alert

input_number:
  alarm_entry_delay_seconds:
    name: "Alarm entry delay"
    min: 30
    max: 120
    step: 15
    initial: 60
    unit_of_measurement: "s"
    icon: mdi:timer-sand

home_alarm_armed is the main switch: when it's on, the system watches the zones. disarming_in_progress means an active entry delay: you have time to turn off the alarm after opening the door. automatic_arming lets the alarm arm together with Away mode from Lesson 8, but you can turn it off by hand when you have guests.

The alarm_entry_delay_seconds number lives on the dashboard for tuning. In the automations below we use a hard-coded 60 seconds in delay:: the same approach as the Away delay in Lesson 8. You can swap it for a template referencing the helper later.

Zone groups

group:
  perimeter_zone:
    name: "Perimeter zone"
    entities:
      - binary_sensor.front_door
      - binary_sensor.living_room_window
      - binary_sensor.garage_gate
      - binary_sensor.garden_gate

  interior_zone:
    name: "Interior zone"
    entities:
      - binary_sensor.hallway_motion
      - binary_sensor.garage_motion

  alarm_sensors:
    name: "Alarm sensors"
    entities:
      - group.perimeter_zone
      - group.interior_zone

The entities in these groups come from Lesson 6. If you don't have PIR yet: leave interior_zone empty and start with just the perimeter. You'll add the interior alarm once you install motion sensors.

Automation 1: arming with Away mode

When home mode switches to Away and you have automatic arming enabled: the alarm arms. In Guests mode, the alarm doesn't arm.

automation:
  - alias: "Alarm: arming with Away mode"
    description: "Turns on home_alarm_armed when the house is empty"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_select.home_mode
        to: "Away"
    conditions:
      - condition: state
        entity_id: input_boolean.automatic_arming
        state: "on"
      - condition: not
        conditions:
          - condition: state
            entity_id: input_select.home_mode
            state: "Guests"
    actions:
      - action: input_boolean.turn_on
        target:
          entity_id: input_boolean.home_alarm_armed
      - action: script.notify_household
        data:
          title: "Alarm armed"
          message: "Away mode: supporting alarm turned on."

Automation 2: disarming with Home or Guests mode

When the house is in normal use: someone's back, or you have guests: the alarm should disarm. Guests mode from Lesson 8 is manual, but once you set it, the alarm shouldn't stay armed.

automation:
  - alias: "Alarm: disarming with Home or Guests mode"
    description: "Turns off the alarm when the house is in normal use"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_select.home_mode
        to: "Home"
      - trigger: state
        entity_id: input_select.home_mode
        to: "Guests"
    actions:
      - action: input_boolean.turn_off
        target:
          entity_id:
            - input_boolean.home_alarm_armed
            - input_boolean.disarming_in_progress

This works when Lesson 8 manages to switch the mode to Home before the door opens. When GPS lags: you need Automation 3 with its entry delay.

Automation 3: entry delay after a perimeter opening

This is the heart of the lesson. The alarm is armed. Someone opens the door: the system doesn't immediately call the escalation. It turns on disarming_in_progress, sends a countdown message, and waits 60 seconds. If you disarm the alarm in that window: silence. If not: it triggers script.intrusion_alarm.

automation:
  - alias: "Alarm: entry delay after a perimeter opening"
    description: "60 seconds to disarm after entering through the perimeter zone"
    mode: restart
    triggers:
      - trigger: state
        entity_id:
          - binary_sensor.front_door
          - binary_sensor.living_room_window
          - binary_sensor.garage_gate
          - binary_sensor.garden_gate
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.home_alarm_armed
        state: "on"
      - condition: state
        entity_id: input_boolean.disarming_in_progress
        state: "off"
      - condition: state
        entity_id: input_boolean.leaving_home_in_progress
        state: "off"
    actions:
      - action: input_boolean.turn_on
        target:
          entity_id: input_boolean.disarming_in_progress
      - action: script.notify_household
        data:
          title: "Disarm: 60 seconds"
          message: >
            {{ state_attr(trigger.entity_id, 'friendly_name') or trigger.entity_id }}.
            You have 60 seconds to disarm the alarm on the dashboard.
      - delay:
          seconds: 60
      - choose:
          - conditions:
              - condition: state
                entity_id: input_boolean.home_alarm_armed
                state: "off"
            sequence:
              - action: input_boolean.turn_off
                target:
                  entity_id: input_boolean.disarming_in_progress
        default:
          - action: script.turn_on
            target:
              entity_id: script.intrusion_alarm
            data:
              variables:
                title: "ALARM: intrusion: perimeter zone"
                message: >
                  {{ state_attr(trigger.entity_id, 'friendly_name') or trigger.entity_id }}.
                  The alarm was not disarmed within the entry window.
          - action: input_boolean.turn_off
            target:
              entity_id: input_boolean.disarming_in_progress

mode: restart means: another opening during the countdown resets the timer. That protects against a series of false triggers from a contact sensor. The leaving_home_in_progress = off condition prevents an alarm when you're just leaving and closing the door behind you with the alarm already armed.

Automation 4: motion in the interior zone

Interior motion while the alarm is armed with no active disarming window is treated as an intruder already inside the house. There's no 60 seconds here: the alarm fires right away.

automation:
  - alias: "Alarm: motion in the interior zone"
    description: "An instant alarm for interior PIR while the house is armed"
    mode: single
    triggers:
      - trigger: state
        entity_id:
          - binary_sensor.hallway_motion
          - binary_sensor.garage_motion
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.home_alarm_armed
        state: "on"
      - condition: state
        entity_id: input_boolean.disarming_in_progress
        state: "off"
      - condition: state
        entity_id: input_select.home_mode
        state: "Away"
    actions:
      - action: script.turn_on
        target:
          entity_id: script.intrusion_alarm
        data:
          variables:
            title: "ALARM: motion in the interior zone"
            message: >
              {{ state_attr(trigger.entity_id, 'friendly_name') or trigger.entity_id }}.
              Motion detected while the alarm is armed.

While disarming_in_progress is on: PIR doesn't trigger the alarm. That lets you come in, walk through the hallway, and get to the dashboard in time to disarm.

Automation 5: clearing the disarm window after turning off the alarm

When the alarm gets turned off: manually, through Home mode, or after a false alarm: the disarming_in_progress helper has to go back to off. Otherwise the system could think an entry countdown is still running.

automation:
  - alias: "Alarm: clear disarm window after alarm off"
    description: "Clears disarming_in_progress when the alarm is disarmed"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_boolean.home_alarm_armed
        to: "off"
    actions:
      - action: input_boolean.turn_off
        target:
          entity_id: input_boolean.disarming_in_progress

Put a toggle for home_alarm_armed on the dashboard. That's your starter "PIN code": simple, but visible. Later you can add a numeric code via input_text and a condition in the automation.

Automation 6: a false alarm: stop the escalation

A false alarm isn't embarrassing: it's a normal part of living with automation. What matters is stopping the siren, the repeats, and the texts quickly. You'll use the script from Lesson 3.

automation:
  - alias: "Alarm: false alarm: stop"
    description: "Calls security_alarm_stop and disarms the house"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_boolean.intrusion_alarm_acknowledged
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.intrusion_alarm_active
        state: "on"
    actions:
      - action: script.turn_on
        target:
          entity_id: script.security_alarm_stop
      - action: input_boolean.turn_off
        target:
          entity_id:
            - input_boolean.home_alarm_armed
            - input_boolean.disarming_in_progress
      - action: script.notify_household
        data:
          title: "False alarm: stopped"
          message: "Escalation turned off. Check the cause and the home mode."

The intrusion_alarm_acknowledged helper from Lesson 3 works here as "I've seen it, it's a false alarm: shutting it down." After stopping it, check the log: what opened the zone, what home mode was active, whether GPS had time to catch up.

Automation 7: a home alarm test

The alarm test only runs when home_alarm_armed is on. If you click the test with the alarm disarmed, a separate automation clears the helper and shows a message, instead of leaving the test stuck on on.

automation:
  - alias: "Alarm: home alarm test"
    description: "Simulates an alarm with no door opening"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_boolean.home_alarm_test
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.home_alarm_armed
        state: "on"
    actions:
      - action: script.turn_on
        target:
          entity_id: script.intrusion_alarm
        data:
          variables:
            title: "TEST: home alarm"
            message: "This is a supporting alarm test. Check the siren, the push, and acknowledgment."
      - delay:
          seconds: 3
      - action: input_boolean.turn_off
        target:
          entity_id: input_boolean.home_alarm_test

Automation 8: reset the test when the alarm isn't armed

automation:
  - alias: "Alarm: reset test when the alarm isn't armed"
    description: "Turns off the test helper if it was triggered with the alarm disarmed"
    mode: single
    triggers:
      - trigger: state
        entity_id: input_boolean.home_alarm_test
        to: "on"
    conditions:
      - condition: state
        entity_id: input_boolean.home_alarm_armed
        state: "off"
    actions:
      - delay:
          seconds: 2
      - action: input_boolean.turn_off
        target:
          entity_id: input_boolean.home_alarm_test
      - action: script.notify_household
        data:
          title: "Alarm test canceled"
          message: "The home alarm isn't armed. Arm it if you want to run a test."

Automation 9: resetting helpers after an HA restart

automation:
  - alias: "Alarm: reset helpers after HA startup"
    description: "Clears timed helpers and acknowledgment after a restart"
    mode: single
    triggers:
      - trigger: homeassistant
        event: start
    actions:
      - action: input_boolean.turn_off
        target:
          entity_id:
            - input_boolean.disarming_in_progress
            - input_boolean.home_alarm_test
            - input_boolean.intrusion_alarm_acknowledged

We deliberately don't reset home_alarm_armed: after an HA restart, the alarm can stay armed if that's how it was saved. We clear intrusion_alarm_acknowledged, since after a restart it's unclear whether it still applies to an active alarm. If you'd rather always disarm after a restart, add home_alarm_armed to the reset list.

Dashboard: what to show

On the security card, include:

How to test: carefully, and in order

Test during the day, when the household knows the siren might sound. Start with the test helper: not by actually opening a window in the cold.

Common mistakes

What not to do

Practical assignment

Key takeaways

What's next

In Lesson 10, we'll look at what happens when the security system itself fails: no internet, no power, an offline sensor, a low battery. An alarm and its notifications are only as good as the weakest link in the chain.

After this lesson you have a coherent foundation: you detect hazards, set the home-mode context, arm zones with an entry delay, and escalate through one proven script. This is no longer a pile of separate automations: it's a response system.