This article will provide a walkthrough of how you can build a Particulate Matter Air Quality meter that integrates with your Home Assistant for under 20$, without any soldering or coding skills needed.
The sensor will provide multiple air-quality measurements directly visible in Home Assistant.
After seeing all kinds of air purifiers in the market, like the one from Xiaomi and Philips. I got interested in the topic air quality. First, I needed to learn more about how and what to measure, followed by actually measuring the air quality in my home. I don’t want to buy a air purifier if the quality of the air in my home is not bad. But how do you measure air quality?
What is a Particulate Matter sensor?
My search started with looking for a particulate matter sensor. A particulate matter sensor measures tiny particles or droplets in the air that have a specific size in microns or micrometers (µm). Like inches, meters and miles, a micron is a unit of measurement for distance. There are about 25,000 microns in an inch.
Particulate matter is the sum of all solid and liquid particles suspended in air many of which are hazardous. This complex mixture includes both organic and inorganic particles, such as dust, pollen, soot, smoke, and liquid droplets. These particles vary greatly in size, composition, and origin.
Particulate matter (PM) is generally classified into two main size categories: PM10 and PM2.5. As an example, the particulate classified as PM2.5 is the size of 2.5 µm and would be thirty times smaller than that of a human hair.
Note: The PIN name is translated from the physical D number printed on the ESP to the addressable name used in configurations and programming. E.g. pin D7 is referred to as GPIO13, all mappings can be found in the image in the ESP Intro section.
UPDATE (thanks Petr): “Fortunately ESPHome knows the mapping from the on-board pin numbers to the internal pin numbering, but you need to prefix the pin numbers with D as in the image below in order for this automatic mapping to occur. In general, it is best to just use the D0, D1, … pin numbering to avoid confusion”
We are adding three switches of the platform type GPIO, this means that the switch will 1:1 control the GPIO pins. For every switch we define the GPIO pin that is controlled, and we provide a name and ID.
Flash the firmware Over The Air (OTA)
That’s it, now flash the firmware of the ESP with the updated firmware based on our new configuration. We do not need to use the flasher tool anymore, we can use the Over-The-Air flash feature to flash the chip with the new firmware over the WiFi Connection. It is as easy as clicking the UPLOAD button.
ESPHome will compile the new firmware, send it over to the ESP that will than flash itself. After flashing the ESP will come back online with the new firmware. It does not get much easier!
Control the relay from Home Assistant
Wait till the ESP has been flashed successful and is connected to the WiFi.
Find your device in Home Assistant, noticed that the device now has 3 entities. Click on the device and you’ll see that it has three switches, called IN1, IN2 and IN3.
Press the switches and enjoy the sound of clicking relays. Every switch should control the matching relay.
Create timing to control the fireplace
To control the fireplace I need to match following sequences with the switches:
Ignition, close contacts 1 and 3 simultaneously for 2 seconds
Fire off, clos contact 1,2, and 3 simultaneously for 1 second
We need to control the relays in these sequences with the ESP board. We can do this by extending the ESP configuration. We’ll add an Ignition switch that will execute sequences above when turned on and off.
Open ESP home and click edit on the node to go to the configuration editor.
Add a new Switch (right under IN3) with following configuration.