Introduction
Specifications
SigFox
Consumption
Theorical consumption
Measurments
Improvement
Solar panel
Bugs

Team ST connect & Co:

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Published January 17, 2019 © GPL3+

ST Connect (Dike Monitoring)

ST Connect is an autonomous connected object that collect and send data, in order to monitore dikes in the Barcellonette. #PolytechSorbonne

IntermediateFull instructions provided15 hours893

Things used in this project

Hardware components

STMicroelectronics nucleo_l432kc

Low consuming mirocontroller

Seeed Studio Grove 101990019

DHT22 Temperature Sensor

DFRobot SEN0193

Seeed Studio Grove - Barometer (High-Accuracy)

Honeywell HMC5883L

This component is actually a QMC5883L

Sigfox BRKWS01

Accu Li-Ion 3,7V 1050mA

Microchip MCP73831T

Maxim Integrated MAX1921EUT33

TE Connectivity PRASA1-16F-BB0BW

SOL1W

Software apps and online services

Sigfox

Story

Introduction

During our studies at Polytech Sorbonne in 2018, Earth Science teachers needed to monitor dikes in the Barcelonnette, a municipality of France in the south of the Alps. They asked us to find a solution to collect regularly data such as ground and air temperature and humidity, pressure and magnetic field in order to detect landslide.

We chose to design an autonomous connecting object that send data they need on a website, where it will be available to consult on. This object will be put on dikes, and it has to works without human interaction except a single visit per year.

Specifications

As Earth teachers tell us, to monitor dikes, they need to be able to consult 6 physical measures :

Air temperature
Air humidity
Ground temperature
Ground humidity
Local magnetic field
Pressure variations (to detect altitude variations)

We will use sensors to get data and a communication module to send it on a website. In order to do that, we will use a microcontroller to manage sensors and communications.

Dikes monitoring requires regular data, optimally, every minute, but in our case Earth teachers asked us to send data every 10 minutes.

Our object has to be energy self sufficient, because it will be put on the dike and has to work during a year without human interaction. Even if we can use an efficient battery, we have to charge it regularly if we want it to work during a year. Due to all these constraints, we have to design our object with:

An efficient battery
A solar panel
Sensors, communication module and a low consuming microcontroller (in sleep mode)

Moreover, if we want our object to work a whole year, it has to be solid (to resist to a rock fall) and be waterproof, in order to protect the electronic circuits inside of the box. After some researches, we decided to certify our object IP54S that correspond to a total protection to dust, a protection to water projections and a resistance to 1J shocks.

SigFox

Sigfox network allows us to send 140 messages per day, so we chose to send a message every 12 minutes (120 message per day).

A Sigfox message is composed of 12 bytes and we have to send all the data on this 12 bytes, so we chose to use this frame :

Consumption

Theorical consumption

Measurments

Improvement

First, to reduce the power consumption of the system, we turn the sensors and the microcontroller in deep sleep mode. Moreover, we used a transistor to cut off the alimentation of the ground humidity sensor which is the only one to be analogic.

After that, we have desoldered the resistor sb9 and sb14 in order to cut off the 5V regulator of the NUCLEO development board because its efficiency is lower than MAX1921EUT33’s one. It will also disable the RGB Led which was blinking when the system was running.

Then, we tried to turn the microcontroller into shutdown mode but we did not succeed because the development card do not wake up. In shutdown mode all features of the board and all peripherals are disabled except the RTC used to wake up the microcontroller.

Using shutdown mode instead of deep sleep mode could reduce the average consumption from 2, 6 mA to 1 mA.

Solar panel

To charge the battery, we use a 90x80mm solar panel that produce around 40mA under the sun. In the barcelonnette there is sunshine around 30% of the year (2600 h per year), so the solar panel can deliver on average 12mA. ST connect consume on average 2, 6mA, so the energy produce by this solar panel will be enough to make our device energy self-sufficient.

Bugs

We have fixed the decoding from the website to get more precision on the temperatures. (21/01/2019)

We have detected a bug on the negative temperature. The problem is coming from the code on the micro-controller. (NOT FIXED) (21/01/2019)

Schematics

Code

// Time during the deepsleep in ms
#define DEEPSLEEP_TIME (12*60000)

// Enabling components
#define ENABLE_BAROMETER 1
#define ENABLE_MAGNETOMETER 1
#define ENABLE_GROUND_TEMPERATURE 1
#define ENABLE_GROUND_HUMIDITY 1
#define ENABLE_DHT22 1

// Sigfox constants
#define MESSAGE_SIZE 32
#define TRAME_SIZE 25

// Enable the debug
// #define DEBUG

// Enable the sending over Sigfox
#define SEND_SIGFOX 1

// Object initializations
#ifdef DEBUG
    Serial pc(USBTX, USBRX);
    DigitalOut myled(LED1);
#endif

#ifdef ENABLE_BAROMETER
    HP20x_dev capt_barometer(D4, D5);
#endif

#ifdef ENABLE_MAGNETOMETER
    QMC5883L capt_magnetometer(D4, D5);
#endif

#ifdef ENABLE_GROUND_TEMPERATURE
    DS1820 capt_ground_temperature(A1);
#endif

#ifdef ENABLE_GROUND_HUMIDITY
    DigitalOut transistor_humidity(D12);
    AnalogIn capt_ground_humidity(A0);      // SEN0
#endif

#ifdef ENABLE_DHT22
    DHT22 capt_thermo_air_humidity(D3);     // DHT22
#endif

/*
 * Format the trame to send over Sigfox
 * Put the trame in *v_trame
 */
void format(float v_ground_temperature, float v_air_temperature, float v_ground_humidity, float v_air_humidity, long v_pressure, int16_t* v_magnetic_field, char* v_trame)
{
    // Converting our data to use as few bits as possible
    int16_t i_ground_temperature = (int16_t) round(v_ground_temperature * 10);
    int16_t i_air_temperature = (int16_t) round(v_air_temperature * 10);
    int16_t i_ground_humidity = (int16_t) round(v_ground_humidity);
    int16_t i_air_humidity = (int16_t) round(v_air_humidity);
    int32_t i_pressure = (int32_t) v_pressure;
    bool err[3] = {false, false, false};    // magnetic field error x,y,z
    
    // Checking if the values are in the range
    if(!(i_ground_temperature >= -512 && i_ground_temperature < 511))
        i_ground_temperature = -512;
        
    if(!(i_air_temperature >= -512 && i_air_temperature < 511))
        i_air_temperature = -512;
    
    if(!(i_ground_humidity <= 100))
        i_ground_humidity = 127;
    
    if(!(i_air_humidity <= 100))
        i_air_humidity = 127;
    
    if(!(i_pressure <= 131071))
        i_pressure = 0;
    
    unsigned int i;
    for(i = 0; i < 3; i++)
    {
        if(!(v_magnetic_field[i] > -65536 && v_magnetic_field[i] < 65535))
            err[i] = true;
    }
    
    // Putting them in the trame
    snprintf(v_trame, TRAME_SIZE, "%02x", (char)(i_ground_temperature >> 2));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((i_ground_temperature << 6) | ((i_air_temperature >> 4) & 0x3f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((i_air_temperature << 4) | ((i_ground_humidity >> 3) & 0x0f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((i_ground_humidity << 5) | ((i_air_humidity >> 2) & 0x1f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((i_air_humidity << 6) | ((i_pressure >> 11) & 0x3f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)(i_pressure >> 3));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((i_pressure << 5) | ((v_magnetic_field[0] >> 9) & 0x1f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)(v_magnetic_field[0] >> 1));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((v_magnetic_field[0] << 7) | ((v_magnetic_field[1] >> 7) & 0x7f)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((v_magnetic_field[1] << 1) | ((v_magnetic_field[2] >> 13) & 0x01)));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)(v_magnetic_field[2] >> 5));
    snprintf(v_trame, TRAME_SIZE, "%s%02x", v_trame, (char)((v_magnetic_field[2] << 3) | (err[0] << 2) | (err[1] << 1) | (err[2])));
}

int main()
{
    #ifdef DEBUG
        pc.printf("\r\n\r\n\r\nInit...\r\n");
    #endif
    
    sigfox.printf("\r\n");
    
    #ifdef ENABLE_BAROMETER
    if(capt_barometer.isAvailable())
        pressure = capt_barometer.ReadPressure();
    #endif
    
    #ifdef ENABLE_MAGNETOMETER
        capt_magnetometer.init();
    #endif
    
    wait(5);
    
    // Main loop
    while(1) {
        #ifdef DEBUG
            myled = 1;
            wait(5);
            myled = 0;
        #endif
        
        #ifdef ENABLE_GROUND_HUMIDITY
            // Plug the ground humidity
            transistor_humidity = 1;
        #endif
        
        // Wake Up sigfox
        reset_sigfox.output();
        reset_sigfox = 0;
        wait(5);
        
        // Set high impendance the sigfox reset pin
        reset_sigfox.input();
        
        #ifdef ENABLE_GROUND_TEMPERATURE
            // Ground Temperature
            capt_ground_temperature.convertTemperature(true, DS1820::all_devices);
            ground_temperature = capt_ground_temperature.temperature();
        #endif
        
        #ifdef ENABLE_GROUND_HUMIDITY
            // Ground Humidity
            ground_humidity = capt_ground_humidity.read() * 100;
            transistor_humidity = 0;
        #endif
        
        #ifdef ENABLE_DHT22
            // Air temperature and humidity
            if(capt_thermo_air_humidity.sample())
            {
                air_temperature = capt_thermo_air_humidity.getTemperature() / 10.0;
                air_humidity = capt_thermo_air_humidity.getHumidity() / 10.0;
            }
        #endif
        
        #ifdef ENABLE_BAROMETER
            // Pressure
            if(capt_barometer.isAvailable())
                pressure = capt_barometer.ReadPressure();
        #endif
        
        #ifdef ENABLE_MAGNETOMETER
            // Magnetometer
            capt_magnetometer.init();
            magnetic_field[0] = capt_magnetometer.getMagXvalue();
            magnetic_field[1] = capt_magnetometer.getMagYvalue();
            magnetic_field[2] = capt_magnetometer.getMagZvalue();
            capt_magnetometer.standby();
        #endif
        
        #ifdef DEBUG
            // Display to check your values
            pc.printf("\r\n");
            pc.printf("Pressure: %f hPa\r\n", pressure/100.0);
            pc.printf("Ground Temperature: %f\t|\t", ground_temperature);
            pc.printf("Ground Humidity: %.1f\r\n", ground_humidity);
            pc.printf("Air Temperature: %.1f\t|\tAir Humidity: %.1f\r\n", air_temperature, air_humidity);
            pc.printf("Magnetic field: x: %hd, y: %hd, z: %hd\r\n", magnetic_field[0], magnetic_field[1], magnetic_field[2]);
        #endif
        
        // Creating your sigfox trame
        format(ground_temperature, air_temperature, ground_humidity, air_humidity, pressure, magnetic_field, &(message[6]));
        message[MESSAGE_SIZE-2] = '\r';
        message[MESSAGE_SIZE-1] = '\n';
        #ifdef DEBUG
            pc.printf("msg=%s", message);
        #endif
        
        // Sending over sigfox
        #ifdef SEND_SIGFOX
            sigfox.printf("%s", message);
            wait(8);    // Time during the sigfox module is sending, do not stop the sigfox before !
        #endif
        
        // Sleep Sigfox
        sigfox.printf("AT$P=1\r\n");
        
        #ifdef DEBUG
            // Detect that the system is going in sleep mode
            pc.printf("Sleep");
            myled = 1;
            wait(0.3);
            myled = 0;
            wait(0.3);
            myled = 1;
            wait(0.3);
            myled = 0;
            wait(0.3);
            myled = 1;
            wait(0.3);
            myled = 0;
        #endif
                
        // Deepsleep
        if(disable_deep == 0)
        {
            WakeUp::set_ms(DEEPSLEEP_TIME);
            WakeUp::attach(&mycallback);
            deepsleep();
        }
    }
}

#include "mbed.h"
#include "WakeUp.h"
#include "DHT22.h"
#include "HP20x_dev.h"
#include "DS1820.h"
#include "QMC5883L.h"

// Pin to disable deepsleep
DigitalIn disable_deep(D6);

Serial sigfox(D1, D0);

// Pin to control the transistor
DigitalInOut reset_sigfox(D9);


char message[MESSAGE_SIZE] = "AT$SF=";

// Default values at the init
long pressure = 10000;
float air_temperature = 20.0;
float air_humidity = 50.0;
float ground_temperature = 20.0;
float ground_humidity = 0.5;
int16_t magnetic_field[3] = {}; // x, y, z

/*
 * Empty callback of the deepsleep because in this version of mbed, the wakeup
 * does not work without it. 
 * But the code inside it is not executed !
 */
void mycallback()
{
}

/*
 * Round the float f
 */
int16_t round(float f)
{
    int16_t res = (int16_t)f;
    if (f - res > 1/2) 
        res++;
        
    return res;
}

ST Connect (Dike Monitoring)

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Specifications

SigFox

Consumption

Theorical consumption

Measurments

Improvement

Solar panel

Bugs

Custom parts and enclosures

Gerber file of the PCB (part 1)

Gerber file of the PCB (part 2)

Prining file of the box (part 1)

Printing file of the box (part 2)

Zip file of Kikad project of the PCB

Schematics

PCB shematic

Overall fonctioning

Technical drawing

Settings for the callback on SigFox website

Code

Defines

SigFox format

Main

Libraries

Setup and Fonctions

Web interface

Credits

Julien Mongin

Remi DROUIN

Victor Dubois

Thibault Gautier

Comments

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ST Connect (Dike Monitoring)

ST Connect (Dike Monitoring)

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Specifications

SigFox

Consumption

Theorical consumption

Measurments

Improvement

Solar panel

Bugs

Custom parts and enclosures

Gerber file of the PCB (part 1)

Gerber file of the PCB (part 2)

Prining file of the box (part 1)

Printing file of the box (part 2)

Zip file of Kikad project of the PCB

Schematics

PCB shematic

Overall fonctioning

Technical drawing

Settings for the callback on SigFox website

Code

Defines

SigFox format

Main

Libraries

Setup and Fonctions

Web interface

Credits

Julien Mongin

Remi DROUIN

Victor Dubois

Thibault Gautier

Comments

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