Monitor and assess the levels of pollutants with MQ-135 and PIC18F97J94
Your trusted ally in the pursuit of purer air
Published Feb 12, 2024
Click board™
Air quality Click
Dev. board
CLICKER 4 for PIC18F
Compiler
NECTO Studio
MCU
PIC18F97J94
By providing real-time monitoring and analysis of air pollutants, this air quality solution aims to protect human health and well-being, reducing the risk of respiratory issues, allergies, and other adverse health effects associated with poor air quality
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Hardware Overview
How does it work?
Air Quality Click is based on the MQ-135, an air quality sensor module for poisonous gases from Zhengzhou Winsen Electronics Technology. The MQ-135 can detect the presence and concentration of toxic gases in the air, such as ammonia gas, sulfide, and benzene steam. It consists of a tin dioxide sensitive layer (SnO2) inside an aluminum oxide AL2O3 ceramic tube (measuring electrodes) alongside a heating element inside its tubular casing. The heater is fixed into a plastic and stainless steel net crust, providing necessary work
conditions for sensitive components. Besides its high sensitivity, the MQ-135 is also characterized by a detection range from 10 to 1000ppm for ammonia gas, toluene, hydrogen, and smoke. The MQ-3 provides an analog representation of polluted concentration in the air sent directly to an analog pin of the mikroBUS™ socket labeled OUT. The analog output voltage the sensor provides varies in proportion to the toxic gas concentration; the higher the toxic gas concentration in the air, the higher the output voltage. Also, this Click board™ has a
built-in potentiometer that allows users to adjust the load resistance of the MQ-135 circuit for optimum performance. This Click board™ can be operated only with a 5V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.
Features overview
Development board
Clicker 4 for PIC18F is a compact development board designed as a complete solution to build your own gadgets with unique functionalities quickly. It features a PIC18F97J94MCU, four mikroBUS™ sockets for Click boards™ connectivity, power management, and more, and it is a perfect solution for the rapid development of many different types of applications. At its core is an 8-bit PIC18F97J94 MCU, a powerful microcontroller produced by Microchip, based on the high-performance CPU with two external clock modes, up to 64MHz. It
provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the development board much simpler and, thus, faster. The usability of Clicker 4 doesn’t end with its ability
to accelerate the prototyping and application development stages: it is designed as a complete solution that can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws. For most applications, a nice, stylish casing is all that is needed to turn the Clicker 4 development board into a fully functional, custom design.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC
MCU Memory (KB)
128
Silicon Vendor
Microchip
Pin count
100
RAM (Bytes)
3862
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the CLICKER 4 for PIC18F as your development board.
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.
2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.
3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.
Software Support
Library Description
This library contains API for Air Quality Click driver.
Key functions:
airquality_read_an_pin_value- This function reads results of AD conversion of the AN pinairquality_read_an_pin_voltage- This function reads results of AD conversion of the AN pin and converts them to proportional voltage level
Open Source
Code example
The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.
/*!
* @file main.c
* @brief Air quality Click Example.
*
* # Description
* The demo application shows the reading of the adc
* values given by the sensors.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Configuring clicks and log objects.
*
* ## Application Task
* Reads the adc value and prints in two forms (DEC and HEX).
*
* @author Jelena Milosavljevic
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "airquality.h"
// ------------------------------------------------------------------ VARIABLES
static airquality_t airquality; /**< Air quality Click driver object. */
static log_t logger; /**< Logger object. */
void application_init ( void ) {
log_cfg_t log_cfg; /**< Logger config object. */
airquality_cfg_t airquality_cfg; /**< Click config object. */
/**
* Logger initialization.
* Default baud rate: 115200
* Default log level: LOG_LEVEL_DEBUG
* @note If USB_UART_RX and USB_UART_TX
* are defined as HAL_PIN_NC, you will
* need to define them manually for log to work.
* See @b LOG_MAP_USB_UART macro definition for detailed explanation.
*/
LOG_MAP_USB_UART( log_cfg );
log_init( &logger, &log_cfg );
log_info( &logger, " Application Init " );
// Click initialization.
airquality_cfg_setup( &airquality_cfg );
AIRQUALITY_MAP_MIKROBUS( airquality_cfg, MIKROBUS_1 );
if ( airquality_init( &airquality, &airquality_cfg ) == ADC_ERROR ) {
log_error( &logger, " Application Init Error. " );
log_info( &logger, " Please, run program again... " );
for ( ; ; );
}
log_info( &logger, " Application Task " );
}
void application_task ( void ) {
uint16_t airquality_an_value = 0;
if ( airquality_read_an_pin_value ( &airquality, &airquality_an_value ) != ADC_ERROR ) {
log_printf( &logger, " ADC Value : %u\r\n", airquality_an_value );
}
float airquality_an_voltage = 0;
if ( airquality_read_an_pin_voltage ( &airquality, &airquality_an_voltage ) != ADC_ERROR ) {
log_printf( &logger, " AN Voltage : %.3f[V]\r\n\n", airquality_an_voltage );
}
Delay_ms( 1000 );
}
void main ( void ) {
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
