Making an outdoor motion sensor smart using a Shelly 1

shelly_pir.yaml

/** 
* I figured out you can fit a Shelly 1 inside the case of many outdoor motion sensors. 
* Coupled with that fact that recently, Shelly added a feature to de-couple the switch from the relay 
* so they act independently, makes this a great combo! Simply wire the output of the PIR motion sensor 
* (the wire that normally goes to your outdoor light) to the switch input of the Shelly and wire 
* the lightbulb to the L output of the Shelly. Then, in the Shelly app or directly via the devices webpage, 
* select the button type as 'Detached Switch' and use the code below to make it work normally. 
* Don't forget to adjust the daylight sensitivity to full daylight if you want the motion detection to work 24/7.
*/

#### AUTOMATIONS ####
automation:

  - alias: Shelly PIR Auto
    # initial_state: true
    # hide_entity: true
    trigger:
     - platform: state
       entity_id: sensor.pir_motion_sensor_status
    condition:
      condition: or
      conditions:
      - condition: sun
        before: sunrise
      - condition: sun
        after: sunset
    action:
     - service_template: "{% if is_state('sensor.pir_motion_sensor_status' , '1')
        %} light.turn_on {% else %}
        light.turn_off {% endif %}"
       entity_id: light.pir_motion_sensor

light:
  - platform: mqtt
    name: "PIR Motion Sensor"
    state_topic: "shellies/shelly1-0x0x0x/relay/0"
    command_topic: "shellies/shelly1-0x0x0x/relay/0/command"
    availability_topic: shellies/shelly1-0x0x0x/online
    payload_available: "true"
    payload_not_available: "false"
    qos: 2
    payload_on: "on"
    payload_off: "off"
    retain: false
    optimistic: false

## SENSORS ##
sensor:
#### Status of Shelly switch input for PIR ###
  - platform: mqtt
    name: "PIR Motion Sensor Status"
    state_topic: "shellies/shelly1-0x0x0x/input/0"

UPDATE 6/2025

Thought I'd do some testing with the newer Gen3 Shelly mini with this cheap PIR motion sensor from Mitre10. Seems to work flawlessly with the switch input on the Shelly dropping to 0.1vac when the motion sensor is off. Added bonus is the the Shelly mini devices are half the size of the Gen1 Shelly I was using so much easier to fit inside the base of the motion sensor.

Note that the original MQTT code above is no longer required if you use the HA native Shelly integration (recommended)