Published November 2, 2021 © Apache-2.0

Smart Pellet Stove: a wood pellets heating system made smart

How to innovate a pellet stove for remote monitoring, control and home automation integration with ESPHome, an ESP32, sensors and relay

IntermediateFull instructions provided4 hours5,503

Smart Pellet Stove: a wood pellets heating system made smart

Things used in this project

Hardware components

M5Stack ATOM Matrix ESP32 Development Kit

M5Stack Mini 3A Relay Unit

Adafruit Waterproof DS18B20 Digital temperature sensor

Maxim Integrated MAX6675 K Type Thermocouple

Maxim Integrated Current Transformer (CT) Clamp sensor

Software apps and online services

Home Assistant

ESPHome

Story

In my father's house there is a pellet stove in the basement.

It is a stove that burns compressed wood pellets to create a source of heat for classic water radiators. By steadily feeding fuel from a storage container into a burn pot area, it produces a constant flame that requires no physical adjustments.

That stove has some years, but it is very efficient, so we decided to innovate it and make it smart.

The idea was to integrate it in a home automation platform to:

remote control it (ON/OFF),
monitor its state with sensors (water temperature, smoke temperature, current absorbed by the engine that feeds the burn pot area with pellets),
create automations based on presence detection (i.e. to automatically turn the heating off when everyone is away).

We managed to do it with:

an ESP32 development board with MAX6675 (temp), DS18B20 (temp), CT Clamp (current) sensors, a relay and ESPHome firmware,
Home Assistant free and open-source software for home automation.

Components at very first placement: sorry for the cable mess :)

The smart module of the pellet stove is the Atom Matrix, an M5Stack product that comes with ESP32, wifi, and plenty of interfaces for the relay and sensors we needed.

To control the pellet stove we put a relay in parallel with the POWER button of the stove, that simulates a long push (8 seconds) of it.

Since the ignition process in a pellet stove is the most critical phase (more or less like the takeoff process for a plane), we needed a lot of sensors to monitor the state of the stove.

Basically, the idea is that when the engine requires current (more than 0.27A), it means that the stove is feeding the burn pot area, and if the pellets burn correctly, in a few minutes the smoke temperature goes over 200°C and the water termperature goes over 50°C.

The sensors we used are:

MAX6675 sensor (via SPI) for smoke termperature,
DS18B20 sensor for water temperature,
CT Clamp sensor (on analog pin) for current absorbed by the motor that feeds the burn pot area with pellets.

1 / 3 • Current Transformer (CT) Clamp sensor

To tailor a firmware for this module, I used ESPHome https://esphome.io

ESPHome is a system to control ESP8266/ESP32 by simple yet powerful configuration files and control them remotely through Home Automation systems. So I just wrote the attached YAML configuration files and used ESPHome to build the firmware and flash the ESP32. The attached YAML files also serve as documentation for sensors wiring, since its declarative definitions are very clear and concise.

It was also super-easy to interface with ESPHome: the M5Atom was auto-discovered by my Home Assistant instance, thanks to the native integration:

https://www.home-assistant.io/integrations/esphome/

1 / 3

And then it all started working.

Finally, in Home Assistant we set automations to turn the Smart Pellet Stove ON/OFF based on presence detection:

https://www.home-assistant.io/getting-started/presence-detection/

Happy tinkering!

Code

substitutions:
  devicename: smart-pellet-stove
  upper_devicename: Smart Pellet Stove

esphome:
  # This will allow for (future) project identification,
  # configuration and updates.
  project:
    name: apolselli.${devicename}
    version: "2.2"
    
packages:
  m5atom: !include m5atom-common.yaml

# Enable Home Assistant API
api:

web_server:

# MAX6675
spi:
  miso_pin: GPIO23
  clk_pin: GPIO22
  
# DS18B20
dallas:
  - pin: GPIO21
    update_interval: 5s

sensor:
  - platform: max6675
    name: $upper_devicename Smoke Temperature
    cs_pin: GPIO19
    update_interval: 5s

  - platform: dallas
    index: 0
    name: $upper_devicename Water Temperature

  - platform: ct_clamp
    sensor: adc_sensor
    id: current1
    name: $upper_devicename Motor Current
    update_interval: 2s
  - platform: adc
    pin: GPIO33
    id: adc_sensor

binary_sensor:
  - platform: template
    name: $upper_devicename Feeding
    id: feeding1
    lambda: |-
      return id(current1).state > 0.27;
    filters:
      - delayed_off: 15s

switch:
  - platform: gpio
    pin:
      number: GPIO26
    name: $upper_devicename Relay
    id: relay1
    on_turn_on:
      - delay: 8s
      - switch.turn_off: relay1

esphome:
  name: ${devicename}
  comment: ${upper_devicename}
  platform: ESP32
  board: m5stack-atom
  platformio_options:
    upload_speed: 115200

# Enable logging
logger:

ota:

wifi:
  networks:
  - ssid: !secret wifi_ssid
    password: !secret wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap: {}

# In combination with the `ap` this allows the user
# to provision wifi credentials to the device.
captive_portal:

# Sets up Bluetooth LE (Only on ESP32) to allow the user
# to provision wifi credentials to the device.
#esp32_improv:
#  authorizer: none

sensor:
  - platform: wifi_signal
    name: ${upper_devicename} WiFi Signal
  - platform: uptime
    name: ${upper_devicename} Uptime

button:
  - platform: restart
    name: ${upper_devicename} Restart

switch:
  - platform: safe_mode
    name: ${upper_devicename} Restart (Safe Mode)

Credits

Alessandro Polselli

3 projects • 16 followers

Smart Pellet Stove: a wood pellets heating system made smart

Things used in this project

Hardware components

Software apps and online services

Story

Schematics

M5Stack Atom Matrix / Lite pinout

ESP32 development board with sensors attached

Code

smart-pellet-stove.yaml

m5atom-common.yaml

Credits

Alessandro Polselli

Comments

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Smart Pellet Stove: a wood pellets heating system made smart

Smart Pellet Stove: a wood pellets heating system made smart

Things used in this project

Hardware components

Software apps and online services

Story

Schematics

M5Stack Atom Matrix / Lite pinout

ESP32 development board with sensors attached

Code

smart-pellet-stove.yaml

m5atom-common.yaml

Credits

Alessandro Polselli

Comments

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