Air Quality Bricklet¶

Features¶

• Measures IAQ (indoor air quality) index, air pressure, humidity and temperature
• IAQ index and humidity values are temperature compensated
• Configurable temperature compensation for use cases in enclosures

Description¶

The Air Quality Bricklet can measure

• IAQ (indoor air quality) index,
• Air pressure in hPa,
• Humidity in %RH and
• Temperature in °C.

The IAQ index is a measurement for the quality of air. To calculate the IAQ index the Bricklet detects ethane, isoprene (2-methylbuta-1,3-diene), ethanol, acetone and carbon monoxide (often called VOC, volatile organic components) by adsorption. These gas measurements are combined with the measurements of air pressure, humidity and temperature to calculate the final IAQ index.

The IAQ index has a range of 0-500:

Typical applications for this Bricklet are the monitoring of air quality, environmental statistics, home automation and similar.

Technical Specifications¶

* This is the temperature at the exact position of the sensor. If the Bricklet is used inside of an enclosure, the air around the Bricklet may heat up more than the ambient air. The Bricklet does have API to calibrate this kind of offset.

Calibration of the temperature value is recommended, since the temperature value is used to compensate the IAQ index and humidity values.

Resources¶

• BME680 datasheet (Download)
• Schematic (Download)
• Outline and drilling plan (Download)
• Source code and design files (Download)
• 3D model (View online | Download: STEP, FreeCAD)

IAQ Accuracy and Automatic Calibration¶

The Bricklet is building a database of measurements and uses this data to do an automatic background calibration and calculate an accurate IAQ index over time. It will take a few days until the IAQ index has a high reliability.

The IAQ accuracy is reflects the current state of the background calibration process.

• Accuracy 0: The Bricklet was just started and the sensor is stabilizing.
• Accuracy 1: The background history is uncertain. This typically means the gas sensor data was too stable for the calibration algorithm to clearly define its references.
• Accuracy 2: The Bricklet found new calibration data and is currently calibrating.
• Accuracy 3: The Bricklets is calibrated successfully.

The effective duration of the calibration process depends on the stimuli observed by the sensor. An IAQ accuracy going back and fourth between 2 and 3 is expected, the Bricklet is recalibrating itself.

The Bricklet saves the current database of values and calculated coefficients every 12 hours in its internal flash memory. If the Bricklet loses power it will not take as long to receive reliable data again.

Starting with firmware version 2.0.3 the automatic background calibration considers 28 days of data. We recommend that you run the Bricklet for 28 full days before you consider the data as completely reliable. It is possible to reduce the calibration window to 4 days with the API.

Test your Air Quality Bricklet¶

To test a Air Quality Bricklet you need to have Brick Daemon and Brick Viewer installed. Brick Daemon acts as a proxy between the USB interface of the Bricks and the API bindings. Brick Viewer connects to Brick Daemon. It helps to figure out basic information about the connected Bricks and Bricklets and allows to test them.

Connect the Air Quality Bricklet to a Brick with a Bricklet Cable.

If you connect the Brick to the PC over USB, you should see a new tab named "Air Quality Bricklet" in the Brick Viewer after a moment. Select this tab. If everything went as expected you can now see the values for IAQ index, air pressure, humidity and temperature.

After this test you can go on with writing your own application. See the Programming Interface section for the API of the Air Quality Bricklet and examples in different programming languages.

Case¶

A laser-cut case for the Air Quality Bricklet is available.

The assembly is easiest if you follow the following steps:

• Screw spacers to the Bricklet,
• screw bottom plate to bottom spacers,
• build up side plates,
• plug side plates into bottom plate and
• screw top plate to top spacers.

Below you can see an exploded assembly drawing of the Air Quality Bricklet case:

Hint: There is a protective film on both sides of the plates, you have to remove it before assembly.

Programming Interface¶

See Programming Interface for a detailed description.