bsiever/pxt-sen66 0.2.1 GitHub

sen66=github:bsiever/pxt-sen66

SEN66 Air Quality Sensor

This extension supports the Sensirion SEN66 Environmental Sensor Node, which includes sensors for:

• Airborne Particulate Matter (Particle sizes of up to 1.0, 2.5, 4.0, and 10.0 µm)
• Volatile Organic Compounds (VOCs)
• Nitrogen Oxides (NOx)
• CO₂ (Carbon Dioxide)
• Relative Humidity
• Temperature

Sensor details and data sheets can be found at: https://sensirion.com/products/catalog/SEN66/

Parts & Wiring

Parts

Almost all the parts necessary for this project can be purchased from DigiKey:

1. Sensirion SEN66: https://www.digikey.com/en/products/detail/sensirion-ag/SEN66-SIN-T/25700945
2. A MicroBit Breakout Board: https://www.digikey.com/en/products/detail/sparkfun-electronics/BOB-16446/14557733

There are also a few parts that are available in a variety of kits and from other sources. Below are variations that are available via Amazon:

1. A breadboard (only one needed)
2. Jumper wires
3. A 3.3V power supply (or use the 3.3V pin from the micro:bit breakout).

Wiring

The SEN66 pin layout (looking at the connector):

Pin	Color (typical)	Signal	Notes
1	Red	VDD	3.3V supply
2	Black	GND	Ground
3	Green	SDA	I2C data (TTL 5V compatible)
4	Yellow	SCL	I2C clock (TTL 5V compatible)
5	—	NC	Do not connect (internally tied to GND)
6	—	NC	Do not connect (internally tied to VDD)

The I2C address of the SEN66 is 0x6B.

Connect:

1. SEN66 Pin 1 (VDD) to the 3.3V rail.
2. SEN66 Pin 2 (GND) to ground.
3. SEN66 Pin 3 (SDA) to the micro:bit SDA (Pin 20).
4. SEN66 Pin 4 (SCL) to the micro:bit SCL (Pin 19).
5. Leave Pins 5 and 6 unconnected.

Start Measurements

sen66.startMeasurements() : void

Start making measurements. Measurements must be started before data can be read. The sensor requires a warm-up period before measurements are accurate.

Mass of particles by particle size

sen66.particleMass(size?: Sen66ParticleMasses) : number

Get the mass of particles of size 0.3µm up to the given size per volume (µg/m³). Returns NaN on error.

Measurements must be started via sen66.startMeasurements() prior to use.

Count of particles by particle size

sen66.particleCount(size?: Sen66ParticleCounts) : number

Get the count of particles of size 0.3µm up to the given size per volume (#/cm³).

Measurements must be started via sen66.startMeasurements() prior to use. Returns NaN on error.

CO2 Concentration

sen66.CO2(): number

Get the CO₂ concentration in ppm [0-40000]. Returns NaN on error. Note: CO₂ is not available for the first 5-6 seconds after power-on or reset.

VOC Index

sen66.VOCIndex(): number

Get the VOC index [1-500]. See https://sensirion.com/media/documents/02232963/6294E043/Info_Note_VOC_Index.pdf . Returns NaN on error.

NOx Index

sen66.NOxIndex(): number

Get the NOx index [1-500]. See https://sensirion.com/media/documents/9F289B95/6294DFFC/Info_Note_NOx_Index.pdf . Returns NaN on error.

Temperature

sen66.temperature(): number

Get the temperature in Celsius. The temperature value will be compensated based on Sensirion’s STAR algorithm.

Humidity

sen66.humidity(): number

Get the relative humidity (0-100%). The humidity value will be compensated based on Sensirion’s STAR algorithm. Returns NaN on error.

Stop Measurements

sen66.stopMeasurements() : void

Stop making measurements and return to low-power idle mode.

On Error

sen66.onError(errCallback: (reason: string) => void) : void

Respond to any errors. reason will be a description of the error.

Device Status

sen66.deviceStatus(): number

Get the device status. Returns a number with bit masks given in sen66.StatusMasks. Returns -1 on error.

Raw VOC

sen66.rawVOC(): number

Get the raw VOC ticks (not an index). The raw value is proportional to the logarithm of the corresponding sensor resistance. Returns NaN on error.

Raw NOx

sen66.rawNOx(): number

Get the raw NOx ticks (not an index). The raw value is proportional to the logarithm of the corresponding sensor resistance. Returns NaN on error.

Raw CO2

sen66.rawCO2(): number

Get the raw (un-interpolated) CO₂ concentration in ppm, updated every 5 seconds. Returns NaN on error.

Raw Temperature

sen66.rawTemperature(): number

Get the raw temperature value °C (not compensated). Returns NaN on error.

Raw Humidity

sen66.rawHumidity(): number

Get the raw relative humidity (not compensated). Returns NaN on error.

Product Name

sen66.productName(): string

Get the product name. Returns an empty string on error.

Serial Number

sen66.serialNumber(): string

Get the Serial number. Returns an empty string on error.

Firmware Version

sen66.firmwareVersion(): number

Get the firmware version. Returns -1 on error.

Reset

sen66.reset(): void

Reset the sensor (back to startup conditions; Not performing measurements).

Clear Device Status

sen66.clearDeviceStatus(): void

Clear the device status.

Start Fan Cleaning

sen66.startFanCleaning(): void

Start cleaning the fan. Takes ~10s and all values are invalid while cleaning.

Fan will automatically be cleaned if the device is continuously running without reset/restart for 1 week (168 hours).

Example

The following program will get air quality measures every second and relay them to the serial console / logger.

basic.showIcon(IconNames.Heart)
sen66.startMeasurements()

sen66.onError(function (reason) {
    serial.writeLine(reason)
})

loops.everyInterval(1000, function () {
    serial.writeValue("pm10", sen66.particleMass(Sen66ParticleMasses.PM100))
    serial.writeValue("co2", sen66.CO2())
    serial.writeValue("voc", sen66.VOCIndex())
    serial.writeValue("NOx", sen66.NOxIndex())
    serial.writeValue("temp", sen66.temperature())
    serial.writeValue("rh", sen66.humidity())
})

Acknowledgements

Icon based on Font Awesome icon 0xf0c2 SVG.

Miscellaneous

I develop micro:bit extensions in my spare time to support activities I’m enthusiastic about, like summer camps and science curricula. You are welcome to become a sponsor of my micro:bit work (one time or recurring payments), which helps offset equipment costs: https://github.com/sponsors/bsiever. Any support at all is greatly appreciated!

Supported targets

for PXT/microbit

makeCodeRender(“{{ site.makecode.home_url }}”, “{{ site.github.owner_name }}/{{ site.github.repository_name }}”);

sen66=github:bsiever/pxt-sen66#v0.2.1