esp_billy

DIY Motion and Temperature sensor using an Attiny85 and ESP8366 (Esp12-e).

Key Features

• Reads PIR sensor output to detect motion
• Reads ambient room temperature
• Periodically publishes status over MQTT for easy integration with Home Assistant
• Low power (battery operated) with cutoff to avoid hurting batteries

Key Details

• For Arduino IDE and uses standard Attinycore, WiFi manager, MQTT Pubsub libraries
• Low power tricks include Attiny sleep and PCI/WDT wake up, mosfet switching off ESP8266, and Fastconnect for reduced WiFi boot time (eg static IP)
• Can last 4-6 weeks between battery changes using 4 x AAA Nimh

BOM

• 1 x Attiny85
• 1 x ESP8266: I used an ESP12-E with those adapters
• 1 x MCP1825s: 500mA LDO to regulate 3.3V-sensitive ESP
• 1 x IRLZ44N: N channel logic-level Mosfet
• Multiple ceramic capacitors: 4.7 uF, 1 uF for LDO output; 0.1 uF for decoupling cap on Attiny85
• 1 x 10 uF electrolytic capacitor for ESP-12E
• 3 x 10k resistors
• 1 x PIR sensor (I ended up tapping into the one attached to this light

Home Assistant Configuration

To parse the MQTT messages in Home Assistant, I created several MQTT sensors for the Presence, Voltage and Temperature readings:

mqtt:
  sensor:
    - name: "Billy1 Motion Sensor Presence"
      state_topic: "billies/billy1/recent_presence"
      value_template: >-
        {% if "detectedMotion" in value %}
        {% set detected = value.split(',')[0].split(':') %}
        {{ detected[1]}}
        {% endif %}
    - name: "Billy1 Motion Sensor Voltage"
      state_topic: "billies/billy1/recent_presence"
      device_class: voltage
      value_template: >-
        {% if "detectedMotion" in value %}
        {% set voltage = value.split(',')[1].split(':') %}
        {{ voltage[1]}}
        {% endif %}
    - name: "Billy1 Motion Sensor Temperature"
      state_topic: "billies/billy1/recent_presence"
      device_class: temperature
      unit_of_measurement: '°C'
      value_template: >-
        {% if "detectedMotion" in value %}
        {% set temperature = value.split(',')[2].split(':') %}
        {{ temperature[1]}}
        {% endif %}

Read more on the Project Write-up here.