Air quality 3 click
PID: MIKROE-2953
Weight: 24 g
Air quality 3 click is the air quality measurement device, which is able to output both
equivalent CO2 levels and total volatile organic compounds (TVOC) concentration in the
indoor environment. The Click board™ is equipped with the state-of-the-art air quality
sensor IC, which has an integrated MCU and a specially designed metal oxide (MOX) gas
sensor microplate, allowing for high reliability, fast cycle times and a significant reduction
in the power consumption, compared to other MOX sensor-based devices. The Click board™
is also equipped with a temperature compensating element, which allows for increased
measurement accuracy.
This Click board™ outputs processed values for the equivalent CO2 levels (parts per million
- ppm) and TVOC (parts per billion - ppb), based on raw gas readings, processed by the
internal MCU. The values can be directly accessed via the I2C bus, which saves the software
development time, allowing faster time to market. These features make Air quality 3 click a
perfect solution for a wide range of both portable and stationary applications for
measuring and monitoring the air quality in offices, storage areas, for home and building
air conditioning automation and similar applications that require a reliable, low power
eCO2 and TVOC level measurements.
How does it work?
Air quality 3 click is equipped with the CCS811, an advanced ultra-low power digital gas
sensor for monitoring the indoor air quality (IAQ), from ams. This IC consists of an analog
section consisting of a MOX gas sensor, based on ams unique micro-hotplate technology
which allows high reliability, fast cycle times and very low power consumption; and the
digital section, which consists of an embedded microcontroller (MCU) and an analog to
digital converter (ADC). The CCS811 sensor IC employs advanced algorithms to calculate
the raw sensor data and output the equivalent CO2 and TVOC values. It utilizes the internal
MCU for this purpose, reducing the payload on the host MCU.
Because of the nature of the MOX sensors, the CCS811 sensitivity will change over the time,
especially in early life use. The internal sensor resistance will change the most for the first 48 hours
of operation. So, to achieve a proper operation of this sensor, it has to be calibrated during several
different phases of its lifecycle. Since this step is important for achieving accurate IAQ results, it is
strongly advised to be carefully studied from the CCS811 datasheet.
There are five operating modes available for the Air quality 3 click:
1. Mode 0 (idle mode), which uses the least power of all modes. The sensor stays dormant and no
readings are made in this mode
2. Mode 1 (constant power mode) the IAQ measurement is performed every second
3. Mode 2 (pulse heating mode) the IAQ measurement is performed every 10 seconds
4. Mode 3 (low power pulse heating mode) the IAQ measurement is performed every 60 seconds
5. Mode 4 (constant power mode) the IAQ measurement is performed every 250ms
These modes affect the power consumption of the Air Quality 3 click, as well as the
frequency of the data sampling. Depending on the given conditions, the device can be set to
be operated in any of these modes. However, it should be noted that the device should be
set to idle mode for at least 10 minutes, before switching from higher frequency
measurement mode, to a lower frequency measurement mode. The TVOC and eCO2 values
are calculated for modes 1, 2 and 3, while Mode 4 is intended to be used when external data
processing is required, giving only raw value readings.
The Click board™ communicates with the host MCU via the I2C bus. SCL and SDA pins of the
CCS811 IC are routed to the corresponding mikroBUS™ pins, allowing easy and secure
connection with the development system. There is yet another pin used with the I2C
communication, that is not the part of the standard I2C bus: the #WAKE pin has to be set to
a LOW logic level before the communication is attempted. This pin is routed to the CS pin of
the mikroBUS™. The I2C bus lines are equipped with the pull-up resistors, so a
communication can be established as soon as the click board is installed on the mikroBUS™.
The least significant bit of the I2C address is routed to the external pin of the CCS811 IC and
it can be set to either HIGH or a LOW logic level. This can be done by an onboard SMD
jumper, labeled as ADDR. It is useful when more than one device is used on the same I2C
bus.
The #RESET pin is used to reset the device and it has to be pulled to a LOW logic level for at
least 20μs. It is pulled to a HIGH logic level by the onboard resistor and filtered by a
capacitor, to prevent random reset of the device. The #RESET of the CCS811 sensor IC is
routed to the mikroBUS RST pin.
The #INT pin allows another powerful feature of the Air Quality 3 click to be used - a
programmable interrupt request. This pin can be driven to a LOW state when there is data
ready to be read via the I2C. It can also be programmed to be driven when the eCO2
measurement data exceeds the programmed threshold by the hysteresis value. This can be
extremely useful for making an early CO2 warning system. Interrupts, in general, are very
useful to avoid constant polling by the MCU, saving resources and energy that way. The
#INT of the CCS811 sensor IC is routed to the mikroBUS INT pin.
Provided Click board ™ library contains functions which can be used to read and configure
the Air quality 3 click in a simple and comprehensive way. The provided example
application demonstrates how to use these functions properly and can be used for a future
development.
Specifications
Type
Gas
Applications
A perfect solution for various air conditioning systems, ventilation
systems and other IoT applications where accurate, detailed and
reliable air quality readings are required.
On-board
CCS811, an advanced ultra-low power digital gas sensor for
modules
monitoring the indoor air quality (IAQ), from ams.
Key Features
Onboard MCU processing, programmable interrupts, advanced MOX
gas sensor technology, direct I2C reading of calculated values
which allow fast time to market and rapid development
Interface
I2C
Input Voltage
3.3V
Click board
size
M (42.9 x 25.4 mm)
Pinout diagram
This table shows how the pinout on Air quality 3 click corresponds to the pinout on the
mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Pin
Notes
NC
1
AN
PWM
16
NC
Reset
RST
2
RST
INT
15
INT
Wake up
WKE
3
CS
RX
14
NC
NC
4
SCK
TX
13
NC
NC
5
MISO
SCL
12
SCL
I2C Clock
NC
6
MOSI
SDA
11
SDA
I2C Data
Interrupt
Power supply
+3.3V
7
3.3V
5V
10
NC
GND
8
GND
GND
9
GND
Ground
Ground
Onboard settings and indicators
Label
Name
Default
LD1
PWR
-
JP1
ADDR
Left
Description
Power LED indicator
Jumper for CCS811 I2C address selection
Software support
We provide a library for Air quality 3 click on our LibStock page, as well as a demo
application (example), developed using MikroElektronika compilers. The demo application
can run on all the main MikroElektronika development boards.
Library Description
The library carries all necessary functions to have complete control over Air quality 3 click.
Key functions
void airq3_getCO2andTVOC( uint16_t *algData ) - Read Co2 and TVOC values.
void airq3_setMeasurementMode( uint8_t mode ) - Set measurement mode.
void airq3_init() - Default module initialization must be called before module usage.
Examples Description
The demo application is composed of three sections:
•
System Initialization - Initializes I2C module, set CS and RST pin as OUTPUT and INT pin as
INPUT.
•
Application Initialization - Initializes Driver, and module with default settings and also setup
measurement mode.
•
Application Task - (code snippet) - This function read CO2 and TVOC value in the air and LOG
information to UART.
The operation is repeated each one second.
void applicationTask()
{
airq3_getCO2andTVOC(&AIRQ3_Data[0]);
ByteToStr(AIRQ3_Data[0],text);
mikrobus_logWrite("CO2 value : ",_LOG_TEXT);
mikrobus_logWrite(text,_LOG_TEXT);
mikrobus_logWrite(" ppm",_LOG_LINE);
ByteToStr(AIRQ3_Data[1],text);
mikrobus_logWrite("TVOC value : ",_LOG_TEXT);
mikrobus_logWrite(text,_LOG_TEXT);
mikrobus_logWrite(" ppb",_LOG_LINE);
Delay_1sec();
}
The full application code, and ready to use projects can be found on our LibStock page.
mikroE Libraries used in the example:
•
UART
•
I2C
Additional notes and information
Depending on the development board you are using, you may need USB UART click, USB
UART 2 click or RS232 click to connect to your PC, for development systems with no UART
to USB interface available on the board. The terminal available in all
MikroElektronika compilers, or any other terminal application of your choice, can be used
to read the message.
mikroSDK
This click board is supported with mikroSDK - MikroElektronika Software Development
Kit. To ensure proper operation of mikroSDK compliant click board demo applications,
mikroSDK should be downloaded from the LibStock and installed for the compiler you are
using.
For more information about mikroSDK, visit the official page.
Downloads
mikroBUS™ Standard specification
LibStock: mikroSDK
Air quality 3 click schematic
Libstock: Air quality 3 library
CCS811 datasheet
Air quality 3 click: 2D and 3D files
https://www.mikroe.com/air-quality-3-click 3-27-18