Air quality 5 click
PID: MIKROE‐3056
Weight: 24 g
Air quality 5 click is a triple MOS sensor on a single Click board™, which can detect gas
pollution for a number of different gases. The onboard sensor is specially designed to
detect the pollution from automobile exhausts, as well as the gas pollution from the
industrial or agricultural industry. This Click board™ uses the MiCS-6814, a compact
MOS sensor with three fully independent sensing elements in one package: RED sensor,
OX sensor, and NH3 sensor. Each of these sensors reacts with the specific type of gases,
providing gas readings that including carbon monoxide (CO), nitrogen dioxide (NO2),
ethanol (C2H5OH), hydrogen (H2), ammonia (NH3), methane (CH4), propane (C3H8),
and isobutane (C4H10). Measurement conversion is handled by the onboard 12bit ADC
converter and it is available via the I2C interface.
Featuring the MiCS-6814 MOS sensor with increased robustness for harsh environments,
low noise 12bit onboard ADC converter, short preheat time requirement and reasonably
high sensitivity, this Click board™ can be used for development of various
environmental pollution measurement and detection applications, or various types of
gas alarms in automotive industry or production/manufacturing chambers with a high
risk of gas poisoning.
How does it work?
The Click board™ contains the MiCS‐6814, a compact triple MOS sensor from SGX
Sensortech, with three fully independent sensors. The Click board™ also contains
the ADS1015, a low-power 12bit ADC with Internal reference, and programmable
comparator, from Texas Instruments. The MiCS-6814 sensor consists of three
independent metal oxide sensors, heated by three separate heater structures. Chemicals
which are absorbed by the metal oxide surface, change the resistive properties of the
sensor. The typical baseline resistance may vary a lot from a sensor to a sensor and it
can be affected by the measurement conditions, sensor aging, and several other factors.
Therefore, it is recommended to periodically monitor the relative change of the sensing
resistance against the baseline resistance. It allows development of applications which
detect relative gas concentration changes, rather than measuring the absolute gas
concentration values.
As mentioned, there are three sensors on the same die. Each of them reacts with a
different type of gas. There is a RED sensor which reacts with the reducing gas agents,
an OX sensor which reacts with the oxidizing gas agents, and lastly, a sensor which
reacts with NH3. These sensors provide readings (in ppm) for eight different gasses,
which are of interest to be monitored in the automotive, industry or agriculture polluted
atmosphere.
Every heating structure is powered from the mikroBUS™ 5V power rail via the resistor,
recommended by the manufacturer. This ensures the maximum life cycle of the device
to be achieved since current ratings above the recommended would damage the
sensors and heaters. It is recommended to pre-heat the sensors for at least 30 seconds
before valid readings can be made. The longer the pre-heat period is, the more accurate
the measurement becomes.
The changes of the sensor resistance are measured and sampled by the onboard ADC.
The ADS1015 ADC has four multiplexed inputs, of which three are connected to each of
the sensors. The ADC has an internal reference, it is very simple to operate, it offers
inputs that can handle voltages across the sensors, and require a low number of external
components. These attributes make it perfectly suitable for this Click board™. In
addition, it is possible to change the slave I2C address of the device. This is done by
using the SMD jumper, labeled as ADD SEL. This jumper allows selection of the I2C LSB
bit state (0 or 1), allowing more than one Click board™ on the same I2C bus.
The ADS1015 IC also has a READY pin, which is used to signal or alert the host MCU that
the conversion is ready for reading. This pin is routed to the mikroBUS™ INT pin and it is
labeled as RDY. More information on how to configure and use this pin can be found in
the ADS1015 datasheet.
Both 5V and 3.3V rails from the mikroBUS™ are used. The ADC is powered by 3.3V rail,
but the sensor requires 5V rail to be used as well. Therefore, the Click board™ requires
both 3.3V and 5V pins to be supplied with the power.
Specifications
Type
Gas
Various environmental pollution measurement and detection applications,
Applications
or various types of gas alarms in the automotive industry or
production/manufacturing chambers with a high risk of gas poisoning.
On-board
modules
MiCS-6814, a compact triple MOS sensor from SGX Sensortech; ADS1015, a
low-power 12bit ADC with Internal reference and programmable
comparator, from Texas Instruments.
Increased robustness for harsh environments, low noise 12bit onboard ADC
Key Features
converter, reasonably high accuracy, three separate sensors on the same die
for sensing of the number of different types of gases.
Interface
I2C
Input Voltage
3.3V,5V
Click board
size
M (42.9 x 25.4 mm)
Pinout diagram
This table shows how the pinout on Air quality 5 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
NC
2
RST
INT
15
RDY
NC
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
3.3V
7
3.3V
5V
10
5V
Ready
Power supply
Power supply
Ground
8
GND
GND
GND
9
GND
Ground
Onboard settings and indicators
Label
Name
Default
PWR
PWR
-
ADD SEL
Left
ADD
SEL
Description
Power LED indicator
I2C address bit selection: left position 0, right
position 1
Software support
We provide a demo application for Air quality 5 click on our Libstock page, as well as a
demo application (example), developed using MikroElektronika compilers. The demo
can run on all the main MikroElektronika development boards.
Library Description
The library initializes and defines the I2C bus driver and drivers that offer a choice for
writing data in registers and reading data from registers. The library includes functions
for full initialization of the chip, reading 3 sensors (CO, NH3 and NO2 data). The user can
check the state of the RDY pin indicating if that data is ready for reading.
Key functions:
void airq5_setConfiguration(uint16_t config) - The functions for configuration.
uint16_t airq5_readSensorData(uint16_t channel_data) - The functions for reading the
sensor data.
Example description
The application is composed of three sections:
System Initialization - Initializes I2C module and sets INT pin as INPUT.
Application Initialization - Initializes driver init and configuration chip.
Application Task - (code snippet) - Reads the values of CO, NH3 and NO2 sensor and logs data
on USBUART every 500ms.
void applicationTask()
{
NO2_sensorData = airq5_readSensorData(_AIRQ5_DATA_CHANNEL_NO2);
NH3_sensorData = airq5_readSensorData(_AIRQ5_DATA_CHANNEL_NH3);
CO_sensorData = airq5_readSensorData(_AIRQ5_DATA_CHANNEL_CO);
IntToStr(NO2_sensorData, dataText);
mikrobus_logWrite(" NO2 data: ", _LOG_TEXT);
mikrobus_logWrite(dataText, _LOG_LINE);
IntToStr(NH3_sensorData, dataText);
mikrobus_logWrite(" NH3 data: ", _LOG_TEXT);
mikrobus_logWrite(dataText, _LOG_LINE);
IntToStr(CO_sensorData, dataText);
mikrobus_logWrite(" CO data: ", _LOG_TEXT);
mikrobus_logWrite(dataText, _LOG_LINE);
mikrobus_logWrite(" ‐‐‐‐‐‐‐‐ ", _LOG_LINE);
Delay_ms( 500 );
}
The full application code, and ready to use projects can be found on our Libstock page.
Other MikroElektronika libraries used in the example:
Conversions
I2C
UART
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.
https://www.mikroe.com/air‐quality‐5‐click?search_query=MIKROE‐3056&results=1 7‐11‐18