---
layout: page
title: "Flash lights when intruder detected"
description: "Detect intruders by checking if the light is turning on while no one is home."
date: 2016-02-14 0:40 -0800
sidebar: true
comments: false
sharing: true
footer: true
ha_category: Automation in Python Examples
---

This example component will detect intruders. It does so by checking if lights are being turned on while there is no one at home. When this happens it will turn the lights red, flash them for 30 seconds and send a message via [the notifiy component](/components/notify/). It will also flash a specific light when a known person comes home.

This component depends on the components [device_tracker](/components/device_tracker/) and [light](/components/light/) being setup.

To set it up, add the following lines to your `configuration.yaml` file:

```yaml
# Example configuration.yaml entry
simple_alarm:
  known_light: light.Bowl
  unknown_light: group.living_room
```

Configuration variables:

- **known_light** (*Optional*): Which light/light group has to flash when a known device comes home.
- **unknown_light** (*Optional*): Which light/light group has to flash red when light turns on while no one home.

Create the file `<config dir>/custom_components/simple_alarm.py` and copy paste the content below:

```python
"""Simple alarm component."""
import logging

import homeassistant.loader as loader
from homeassistant.components import device_tracker, light, notify
from homeassistant.helpers.event import track_state_change
from homeassistant.const import STATE_ON, STATE_OFF, STATE_HOME, STATE_NOT_HOME

DOMAIN = "simple_alarm"

DEPENDENCIES = ['group', 'device_tracker', 'light']

# Attribute to tell which light has to flash whem a known person comes home
# If omitted will flash all.
CONF_KNOWN_LIGHT = "known_light"

# Attribute to tell which light has to flash whem an unknown person comes home
# If omitted will flash all.
CONF_UNKNOWN_LIGHT = "unknown_light"

# Services to test the alarms
SERVICE_TEST_KNOWN_ALARM = "test_known"
SERVICE_TEST_UNKNOWN_ALARM = "test_unknown"


def setup(hass, config):
    """ Sets up the simple alarms. """
    logger = logging.getLogger(__name__)

    light_ids = []

    for conf_key in (CONF_KNOWN_LIGHT, CONF_UNKNOWN_LIGHT):
        light_id = config[DOMAIN].get(conf_key, light.ENTITY_ID_ALL_LIGHTS)

        if hass.states.get(light_id) is None:
            logger.error(
                'Light id %s could not be found in state machine', light_id)

            return False

        light_ids.append(light_id)

    # pylint: disable=unbalanced-tuple-unpacking
    known_light_id, unknown_light_id = light_ids

    if hass.states.get(device_tracker.ENTITY_ID_ALL_DEVICES) is None:
        logger.error('No devices are being tracked, cannot setup alarm')

        return False

    def known_alarm():
        """ Fire an alarm if a known person arrives home. """
        light.turn_on(hass, known_light_id, flash=light.FLASH_SHORT)

    def unknown_alarm():
        """ Fire an alarm if the light turns on while no one is home. """
        light.turn_on(
            hass, unknown_light_id,
            flash=light.FLASH_LONG, rgb_color=[255, 0, 0])

        # Send a message to the user
        notify.send_message(
            hass, "The lights just got turned on while no one was home.")

    # Setup services to test the effect
    hass.services.register(
        DOMAIN, SERVICE_TEST_KNOWN_ALARM, lambda call: known_alarm())
    hass.services.register(
        DOMAIN, SERVICE_TEST_UNKNOWN_ALARM, lambda call: unknown_alarm())

    def unknown_alarm_if_lights_on(entity_id, old_state, new_state):
        """ Called when a light has been turned on. """
        if not device_tracker.is_on(hass):
            unknown_alarm()

    track_state_change(
        hass, light.ENTITY_ID_ALL_LIGHTS,
        unknown_alarm_if_lights_on, STATE_OFF, STATE_ON)

    def ring_known_alarm(entity_id, old_state, new_state):
        """ Called when a known person comes home. """
        if light.is_on(hass, known_light_id):
            known_alarm()

    # Track home coming of each device
    track_state_change(
        hass, hass.states.entity_ids(device_tracker.DOMAIN),
        ring_known_alarm, STATE_NOT_HOME, STATE_HOME)

    return True
```
