Homie based AIR Quality sensor.

Features:

• PM1.0, PM2.5, PM10 monitoring
• Temperature, himidity and pressure monitoring
• Continous measurement with average calculation for given period
• Data reporting via MQTT
• Fully configurable via MQTT (heater temperature, measure freqnecy)
• All Homie features (OTA upgrades, JSON configuration)
• Heating of intake air - avoid errors from high air humidity
• Non blocking (no delay) code with serial support

Used libraries:

• Homie ESP8266
• Homie Node Collection
• PID
• Cactus IO BME280

BOM:

• ESP8266 module (for example Wemos D1 mini)
• Air quality sensor PMS3003
• SI7021 temperature and humidity sensor
• BME280 pressure sensor
• DS18B20 1-wire bus temperature sensor
• N-MOSFET
• 4k7Ω resistor
• PTC Heater element

Schematic:

BME280 and SI7021 have to be connected to I2C 1W connector (PIN1 - Vcc, PIN2 - GND, PIN3 - SCL, PIN4 - SDA). DS18B20 sensor have to be connected to 1W connector (PIN1 - Vcc, PIN2 - data, PIN3 - GND). Connector "Heat Voltage" is voltage control of PTC Heater element (PIN1 to PIN2 - main power voltage, PIN2 to PIN3 - 5V ).

DS18B20 is used for reading temperature of air and as a source of temperature for heater driver - if multiple DS1820 are connected the highest temperature is used as reference.

Installation:

Requirements

• Visual Studio Code
• PlatformIO IDE extenstion
• GIT

1. Clone the Repository into VS Code

In VS Code press F1 enter ''git: clone'' + Enter and insert link to my repository (https://github.com/piotrC4/air-monitor)

2. Modify platformio.ini (optional)

Edit platformio.ini and setup upload_port variable acording to system settings if PlatofmIO can'd identify proper COM port

3. Build binary file

In PlatformIO menu choose PROJECT TASKS -> Build

4. Upload firmware to ESP8266

Connect ESP to PC via serial adapter. In PlatformIO menu choose option PROJECT TASKS -> Upload.

5. Installig Homie UI

Copy UI bundle to data/homie folder (See https://github.com/homieiot/homie-esp8266/tree/develop/data/homie )

6. Upload SPIFFS image to ESP8266

In Platformio menu choose option PROJECT TASKS ->Upload File System image

Initial configuration

Software is build on top of Homie framework - configuration will be done in Homie-way. Connect to MyIOT-xxxxx AP and go to configration UI. Also there is Andorid configuration app - see https://homieiot.github.io/homie-esp8266/docs/develop-v3/configuration/http-json-api/

Usage

Data reading

All reads are published in MQTT topics in Homie-way. For example - if homie prefix is homie/ and device ID: airq we have readings like:

• homie/airq/pmsensor/measureWindowSize - period of single mesurement cycle [seconds]
• homie/airq/pmsensor/heaterTargetTemp - target teperature for heater
• homie/airq/pmsensor/PM10/avg - PM10 average for given period
• homie/airq/pmsensor/PM10/min - PM10 min reading for given period
• homie/airq/pmsensor/PM10/max - PM10 max reading for given period
• homie/airq/pmsensor/PM25/avg - PM2.5 average for given period
• homie/airq/pmsensor/PM25/min - PM2.5 min reading for given period
• homie/airq/pmsensor/PM25/max - PM2.5 max reading for given period
• homie/airq/pmsensor/PM1/avg - PM1 average for given period
• homie/airq/pmsensor/PM1/min - PM1 min reading for given period
• homie/airq/pmsensor/PM1/max - PM1 max reading for given period
• homie/airq/enviro/humidity/si7021 - Humidity reading from SI7021
• homie/airq/enviro/temperature/si7021 - Temperature reading from SI7021
• homie/airq/enviro/humidity/BME280 - Humidity reading from BME280
• homie/airq/enviro/temperature/BME280 - Temperature reading from BME280
• homie/airq/enviro/pressure - Pressure reading from BME280
• homie/airq/enviro/temperature/xxxxxxxxxxxxx - Temperature reading from DS18B20 (xxxx represents device address)
• homie/airq/Log/# - log information - for example number of DS18B20 sensor, presence of SI7021 and BME280, errors

Configuration

By publishing message to specific topics configuration is possbile:

• homie/airq/pmsensor/measureWindowSize/set - set measurement period in seconds
• homie/airq/pmsensor/heaterTargetTemp/set - heater targer temperature
• homie/airq/pmsensor/debug/set - ON/OFF message - turn on off debug messages
• homie/airq/keepalive/value/set - keepalive timeout - if tick message not arrive in given time, device will reboot, 0 - disable keepalive
• homie/airq/keepalive/tic/set - any message to reset keepalive counter

Credits

Inspiration for this project:

• SMOG sensor
• SMOGLY project