Arduino Weather Data Logger with SD Card
Arduino Weather Data Logger with SD Card
In the last Arduino project I’ve built a temperature data logger using SD card and DS18B20 digital temperature sensor.
This post shows how to make an Arduino weather data logger (& station) that logs temperature (in °C), humidity (in %RH) and pressure (in hectopascal) using SD card, BME280 barometric pressure & humidity & temperature sensor.
The logged data is saved to a text file stored on the SD card. DS3231 real time clock board is used to get time and date information.
Time, date, temperature, humidity and pressure values are displayed on 20×4 LCD screen and sent to PC serial monitor.
To see how to interface Arduino with SD card, visit the following post:
Arduino and SD card example – Read and write files
To see how to interface Arduino with BME280 sensor (I2C mode) for the first time, take a look at this post:
Arduino with BME280 pressure, temperature and humidity sensor
And the link below shows how to build Arduino temperature data logger:
Arduino Temperature Data Logger with SD Card
Hardware Required:
This is a list of all components required to build this project.
- Arduino UNO board —> Board details —> Atmega328P datasheet
- micro SD card with FAT16 or FAT32 file system
- micro SD card module
- 20×4 LCD screen
- BME280 sensor module (with built-in 3.3V regulator and level shifter) —-> BME280 datasheet
- DS3231 module —-> DS3231 datasheet
- 330 ohm resistor
- 2 x push button
- 10k ohm variable resistor or potentiometer
- 3V coin cell battery
- Breadboard
- Jumper wires
Arduino Weather Data Logger with SD Card Circuit:
The image below shows project circuit diagram.
In this project I used micro SD card module, this module is supplied from circuit 5V source that comes from the Arduino UNO board. This module contains AMS1117-3V3 voltage regulator which is used to supply the SD card with 3.3V. Also this module contains an IC which is 74LVC125A and it’s used as level translator (from 5V to 3.3V).
Hint:
The BME280 chip works with maximum voltage of 3.6V (supply voltage range is from 1.71 to 3.6V) which means we’ve to use a 3V3 voltage regulator to supply it from a 5V source.
Also, if we’re working with a 5V system (development board, microcontroller …) like the Arduino UNO board (ATmega328P microcontroller), we’ve to use a voltage level shifter (level converter) which converts the 3.3V (comes from the BME280 chip) into 5V (goes to the ATmega328P) and vice versa. This level shifter is for the I2C bus lines (clock and data).
The BME280 module shown in project circuit diagram has a built-in 3.3V regulator and level shifter.
The microSD card module is connected to the Arduino as follows (from left to right):
The first pin of the micro SD card module (GND) is connected to Arduino GND.
The second pin of the micro SD card module (VCC) is connected to Arduino 5V.
The third pin of the micro SD card module (MISO) is connected to Arduino digital pin 12.
The fourth pin of the micro SD card module (MOSI) is connected to Arduino digital pin 11.
The fifth pin of the micro SD card module (SCK) is connected to Arduino digital pin 13.
The last pin of the micro SD card module (CS) is connected to Arduino digital pin 10.
The digital pins 10, 11, 12 and 13 are hardware SPI module pins of ATmega328P microcontroller (Arduino UNO microcontroller).
The DS3231 RTC module SDA (serial data) and SCL (serial clock) pins are respectively connected to Arduino A4 and A5 pins (ATmega328P hardware I2C module pins).
VCC is connected to Arduino 5V and GND is connected to Arduino GND.
The BME280 sensor module has at least 4 pins because it can work in SPI mode or I2C mode. For the I2C mode we need 4 pins: GND, VCC, SDA and SCL where:
GND (ground) is connected to Arduino GND pin,
VCC is the supply pin which is connected to Arduino 5V pin,
SDA is I2C bus serial data line, connected to Arduino analog pin 4 (A4),
SCL is I2C bus serial clock line, connected to Arduino analog pin 5 (A5).
The DS3231 RTC and the BME280 sensor are connected to the same I2C bus (slave devices), the I2C slave address of the DS3231 chip differs from the one of the BME280 sensor, that allows the master device (Arduino) to talk to one of them (only one at a time).
The 20×4 LCD screen (4 rows and 20 columns) is used to display time, date, pressure, humidity and temperature values where:
RS —> Arduino digital pin 2
E —> Arduino digital pin 3
D4 —> Arduino digital pin 4
D5 —> Arduino digital pin 5
D6 —> Arduino digital pin 6
D7 —> Arduino digital pin 7
VSS, RW, D0, D1, D2, D3 and K are connected to Arduino GND,
VEE to the 10k ohm variable resistor (or potentiometer) output,
VDD to Arduino 5V and A to Arduino 5V through 330 ohm resistor.
VEE pin is used to control the contrast of the LCD. A (anode) and K (cathode) are the back light LED pins.
In the circuit there are two push buttons: B1 and B2, they are respectively connected to Arduino analog pins 1 (A1) and 2 (A2), these buttons are used to set time and date of the real time clock.
Arduino Weather Data Logger with SD Card Code:
The following Arduino code requires 3 libraries from Adafruit Industries:
The first library is for the DS3231 RTC, download link is below:
Adafruit RTC library —-> direct link
The 2nd one is for the BME280 sensor:
Adafruit BME280 Library —-> direct link
You may need to install the Adafruit Unified Sensor library if it’s not already installed:
Adafruit Unified Sensor library —-> direct link
After the download, go to Arduino IDE —> Sketch —> Include Library —> Add .ZIP Library … and browse for the .zip file (previously downloaded).
The same thing for the other library files.
Programming hints:
There are 4 libraries included in the Arduino code as shown below.
The first library is for the SD card,
the 2nd one is for the LCD display,
the 3rd is for the DS3231 RTC,
and the last library is for the BME280 sensor.
|
1
2
3
4
|
#include <SD.h> // include Arduino SD library
#include <LiquidCrystal.h> // include Arduino LCD library
#include <RTClib.h> // include Adafruit RTC library
#include <Adafruit_BME280.h> // include Adafruit BME280 sensor library
|
The default I2C address of the BME280 library is defined as 0x77 and my device I2C address is 0x76.
In the code, the definition of BME280 sensor I2C slave address and the initialization of its library are as shown below:
|
1
2
3
4
|
// define BME280 sensor I2C address: 0x76 or 0x77 (0x77 is library default address)
#define BME280_I2C_ADDRESS 0x76
// initialize Adafruit BME280 library
Adafruit_BME280 bme280;
|
The Arduino reads pressure, temperature & humidity values from the BME280 sensor and saves them (with time and date) to the SD card every 1 second, for that I used the following if condition:
|
1
|
if( mytime->seconds != p_second )
|
where the variable p_second is used to save only one value every 1 second.
Functions used in the code:
SD Card functions:
SD.begin(): this function initializes the SD card as well as the file system (FAT16 or FAT32), it returns 1 (true) if OK and 0 (false) if error.
SD.exists(“Log.txt”): tests whether the file “Log.txt” exists on the SD card, returns 1 if the file already exists and 0 if not.
SD.open(“Log.txt”, FILE_WRITE): opens the file “Log.txt” and moves the cursor to the end of the file. This function will create the file if it doesn’t already exist. Returns 0 if error.
dataLog.close(): closes the file associated with dataLog.
DS3231 Functions:
bool debounce (): this function is for button B1 debounce, returns 1 if button is debounced.
void RTC_display(): displays day of the week, date and time on the display.
byte edit(byte parameter): this function is for setting the real time clock, returns the edited parameter.
BME280 Functions:
bme280.begin(BME280_I2C_ADDRESS): this function initializes the BME280 sensor, returns 1 if OK and 0 if error.
Reading the values of temperature, humidity and pressure is done as shown below:
|
1
2
3
4
|
// read temperature, humidity and pressure from the BME280 sensor
float temp = bme280.readTemperature(); // get temperature in degree Celsius
float humi = bme280.readHumidity(); // get humidity in rH%
float pres = bme280.readPressure(); // get pressure in Pa
|
Temperature, humidity and pressure values (with time and date) are displayed on the 20×4 LCD screen.
If there is a problem with the BME280 sensor (for example wrong device address) the LCD will display BME Sensor Error! on the 4th row.
Also and instead of the 3 quantities (temperature, humidity and pressure), the Arduino will print Error in the text file “Log.txt”.
1 bar = 10000 Pa = 100 hPa. ( 1 hPa = 100 Pa = 1 millibar)
Pa: Pascal
hPa: hectoPascal
Full Arduino code:
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
|
/* Temperature, humidity & pressure data logger using Arduino UNO,
SD card, BME280 sensor and DS3231 RTC.
* Time, date, temperature, humidity and pressure values are displayed on 20×4 LCD.
* This is a free software with NO WARRANTY.
* https://simple-circuit.com/
*/
#include <SD.h> // include Arduino SD library
#include <LiquidCrystal.h> // include Arduino LCD library
#include <RTClib.h> // include Adafruit RTC library
#include <Adafruit_BME280.h> // include Adafruit BME280 sensor library
// LCD module connections (RS, E, D4, D5, D6, D7)
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);
// initialize RTC library
RTC_DS3231 rtc;
DateTime now;
// buttons definition
#define button1 A1 // button B1 is connected to Arduino pin A1
#define button2 A2 // button B2 is connected to Arduino pin A2
// define BME280 sensor I2C address: 0x76 or 0x77 (0x77 is library default address)
#define BME280_I2C_ADDRESS 0x76
// initialize Adafruit BME280 library
Adafruit_BME280 bme280;
boolean sd_ok = 0, sensor_ok = 0;
void setup()
{
pinMode(button1, INPUT_PULLUP);
pinMode(button2, INPUT_PULLUP);
rtc.begin(); // initialize RTC chip
lcd.begin(20, 4); // initialize LCD module
lcd.setCursor(0, 0); lcd.print(“TIME:”);
lcd.setCursor(0, 1); lcd.print(“DATE:”);
// open serial communications and wait for port to open:
Serial.begin(9600);
Serial.print(“Initializing SD card…”);
// initialize the SD card
if ( !SD.begin() )
Serial.println(“failed!”); // initialization error
else { // initialization OK
sd_ok = true;
Serial.println(“OK.”);
if( SD.exists(“Log.txt”) == 0 ) // test if file with name ‘Log.txt’ already exists
{ // create a text file named ‘Log.txt’
Serial.print(“\r\nCreate ‘Log.txt’ file…”);
File dataLog;
dataLog = SD.open(“Log.txt”, FILE_WRITE); // create (&open) file Log.txt
if(dataLog) { // if the file opened okay, write to it:
Serial.println(“OK”);
// write some texts to ‘Log.txt’ file
dataLog.println(” DATE | TIME | TEMPERATURE | HUMIDITY | PRESSURE”);
dataLog.close(); // close the file
}
else
Serial.println(“failed!”);
}
}
// initialize the BME280 sensor
Serial.print(“\r\nInitializing BME280 sensor…”);
if( bme280.begin(BME280_I2C_ADDRESS) )
{
Serial.println(“done.”);
lcd.setCursor(0, 2); lcd.print(“T:”);
lcd.setCursor(10, 2); lcd.print(“|H:”);
lcd.setCursor(0, 3); lcd.print(“P:”);
lcd.setCursor(8, 2);
lcd.write(223); // print degree symbol (°)
lcd.write(‘C’);
sensor_ok = true;
}
else
{ // connection error or device address wrong!
Serial.println(“failed!”);
lcd.setCursor(0, 3);
lcd.print(“BME280 Sensor Error!”);
}
Serial.println(“\r\n DATE | TIME | TEMPERATURE | HUMIDITY | PRESSURE”);
}
// main loop
void loop()
{
now = rtc.now(); // read current time and date from the RTC chip
RTC_display(); // diaplay time & calendar
if( !digitalRead(button1) ) // if B1 is pressed
if( debounce() ) // call debounce function (make sure B1 is pressed)
{
while( debounce() ); // call debounce function (wait for B1 to be released)
byte hour = edit( now.hour() ); // edit hours
byte minute = edit( now.minute() ); // edit minutes
byte day = edit( now.day() ); // edit date
byte month = edit( now.month() ); // edit month
byte year = edit( now.year() – 2000 ); // edit year
// write time & date data to the RTC chip
rtc.adjust(DateTime(2000 + year, month, day, hour, minute, 0));
while(debounce()); // call debounce function (wait for button B1 to be released)
}
static byte p_second;
if( p_second != now.second() )
{ // read & print sensor data every 1 second
char temp_a[7], humi_a[7], pres_a[12];
char buffer1[22];
p_second = now.second();
if( sensor_ok )
{
// read temperature, humidity and pressure from the BME280 sensor
float temp = bme280.readTemperature(); // get temperature in °C
float humi = bme280.readHumidity(); // get humidity in rH%
float pres = bme280.readPressure(); // get pressure in Pa
// save all data to arrays
// 1: temperature
if(temp < 0) // if temperature is negative
sprintf( temp_a, “-%02u.%02u”, (int)abs(temp), (int)(abs(temp) * 100) % 100 );
else
sprintf( temp_a, ” %02u.%02u”, (int)temp, (int)(temp * 100) % 100 );
// 2: humidity
sprintf( humi_a, “%02u.%02u%%”, (int)humi, (int)(humi * 100) % 100 );
// 3: pressure
sprintf( pres_a, “%04u.%02u hPa”, (int)(pres/100), (int)((uint32_t)pres % 100) );
// print sensor data on the LCD
lcd.setCursor(2, 2); lcd.print(temp_a); // print temperature
lcd.setCursor(14, 2); lcd.print(humi_a); // print humidity
lcd.setCursor(3, 3); lcd.print(pres_a); // print pressure
}
sprintf( buffer1, “%02u-%02u-%04u | %02u:%02u:%02u”, now.day(), now.month(), now.year(),
now.hour(), now.minute(), now.second() );
Serial.print(buffer1);
Serial.print(” | “);
if(sensor_ok) {
Serial.print(temp_a);
Serial.print(“°C | “);
Serial.print(humi_a);
Serial.print(” | “);
Serial.println(pres_a);
}
else
Serial.println(” Error | Error | Error”);
// write data to SD card
if(sd_ok)
{ // if the SD card was successfully initialized
// open Log.txt file with write permission
File dataLog;
dataLog = SD.open(“Log.txt”, FILE_WRITE);
dataLog.print(buffer1);
dataLog.print(” | “);
if(sensor_ok) {
dataLog.print(temp_a);
dataLog.print(“°C | “);
dataLog.print(humi_a);
dataLog.print(” | “);
dataLog.println(pres_a);
}
else
dataLog.println(” Error | Error | Error”);
dataLog.close(); // close the file
}
}
delay(100); // wait 100ms
}
//////////////////////////////////////// RTC functions ////////////////////////////////////////
void RTC_display()
{
char _buffer[12];
char dow_matrix[7][4] = {“SUN”, “MON”, “TUE”, “WED”,
“THU”, “FRI”, “SAT”};
lcd.setCursor(6, 1);
lcd.print( dow_matrix[now.dayOfTheWeek()] );
// print time
sprintf( _buffer, “%02u:%02u:%02u”, now.hour(), now.minute(), now.second() );
lcd.setCursor(10, 0);
lcd.print(_buffer);
// print date
sprintf( _buffer, “-%02u-%02u-%04u”, now.day(), now.month(), now.year() );
lcd.setCursor(9, 1);
lcd.print(_buffer);
}
byte edit(byte parameter)
{
static byte i = 0, y_pos,
x_pos[5] = {10, 13, 10, 13, 18};
char text[3];
sprintf(text,“%02u”, parameter);
if(i < 2)
y_pos = 0;
else
y_pos = 1;
while( debounce() ); // call debounce function (wait for B1 to be released)
while(true) {
while( !digitalRead(button2) ) { // while B2 is pressed
parameter++;
if(i == 0 && parameter > 23) // if hours > 23 ==> hours = 0
parameter = 0;
if(i == 1 && parameter > 59) // if minutes > 59 ==> minutes = 0
parameter = 0;
if(i == 2 && parameter > 31) // if day > 31 ==> day = 1
parameter = 1;
if(i == 3 && parameter > 12) // If month > 12 ==> month = 1
parameter = 1;
if(i == 4 && parameter > 99) // If year > 99 ==> year = 0
parameter = 0;
sprintf(text,“%02u”, parameter);
lcd.setCursor(x_pos[i], y_pos);
lcd.print(text);
delay(200); // wait 200ms
}
lcd.setCursor(x_pos[i], y_pos);
lcd.print(” “);
unsigned long previous_m = millis();
while( (millis() – previous_m < 250) && digitalRead(button1) && digitalRead(button2) ) ;
lcd.setCursor(x_pos[i], y_pos);
lcd.print(text);
previous_m = millis();
while( (millis() – previous_m < 250) && digitalRead(button1) && digitalRead(button2) ) ;
if(!digitalRead(button1))
{ // if button B1 is pressed
i = (i + 1) % 5; // increment ‘i’ for the next parameter
return parameter; // return parameter value and exit
}
}
}
// a small function for button1 (B1) debounce
bool debounce ()
{
byte count = 0;
for(byte i = 0; i < 5; i++)
{
if ( !digitalRead(button1) )
count++;
delay(10);
}
if(count > 2) return 1;
else return 0;
}
////////////////////////////////////// end RTC functions //////////////////////////////////////
// end of code.
|
This project was tested in real hardware circuit using original Samsung microSD card with capacity of 32GB. The following image shows data logger file (Log.txt) created by the hardware circuit:
And the following one shows serial monitor output:
