Arduino data logging to SD card - Emerging Technologies

When it comes to collecting data for various applications, the Arduino platform is one of the most versatile options available. By adding an SD card to your Arduino project, you can store data such as sensor readings, timestamps, or measurements for future use. This guide walks you through the process of data logging using Arduino and an SD card.

What is Arduino Data Logging?

Arduino data logging involves recording sensor data or other variables, and saving them for later analysis. An Arduino, equipped with sensors and an SD card module, can capture information and write it directly to the SD card. The data saved on the card can then be retrieved for processing or visualization, making it an invaluable tool for projects like environmental monitoring, home automation, and scientific experiments.

How to Set Up Arduino for Data Logging

Required Components

To begin your Arduino data logging project, you will need the following components:

Arduino board (Uno, Mega, or any compatible model)
SD card module
MicroSD card (formatted with FAT16 or FAT32)
Jumper wires
Breadboard (optional)
Sensors (e.g., temperature, humidity, or light sensors)
Arduino IDE for coding

Connecting the SD Card to Arduino

SD Card Module Pins: The SD card module typically has the following pins:
- VCC: Connect to 5V or 3.3V on Arduino (depending on module specifications)
- GND: Connect to GND on Arduino
- MOSI (Master Out Slave In): Connect to pin 11 (on Arduino Uno)
- MISO (Master In Slave Out): Connect to pin 12 (on Arduino Uno)
- SCK (Serial Clock): Connect to pin 13 (on Arduino Uno)
- CS (Chip Select): Connect to pin 10 (on Arduino Uno)
Sensor Connection: Depending on your sensors, make sure they are connected to appropriate pins on the Arduino.

Arduino IDE

Importing Required Libraries

To interface with the SD card and handle data storage, the Arduino IDE provides a library called SD.h. This library helps the Arduino interact with the SD card module, allowing data to be written or read from the card.

Basic Arduino Code for Data Logging

cpp

#include <SD.h> #include <SPI.h> File dataFile; void setup() { Serial.begin(9600); if (!SD.begin(10)) { Serial.println(“Initialization failed!”); return; } Serial.println(“Initialization successful.”); dataFile = SD.open(“datalog.txt”, FILE_WRITE); if (dataFile) { dataFile.println(“Sensor Data Log:”); dataFile.close(); } else { Serial.println(“Error opening datalog.txt”); } } void loop() { int sensorValue = analogRead(A0); // Read from a sensor float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage dataFile = SD.open(“datalog.txt”, FILE_WRITE); if (dataFile) { dataFile.print(“Voltage: “); dataFile.println(voltage); dataFile.close(); } else { Serial.println(“Error opening datalog.txt”); } delay(1000); // Wait for a second }

Explanation of the Code

The SD.begin(10) initializes the SD card on pin 10 of the Arduino. If initialization fails, an error message is displayed.
The dataFile = SD.open(“datalog.txt”, FILE_WRITE) line opens the datalog.txt file in write mode. If the file doesn’t exist, it creates a new one.
The sensor value is read from analog pin A0, converted to voltage, and then written to the SD card.
The loop continuously logs the data every second.

Reading and Analyzing Data from the SD Card

Retrieving Stored Data

Once data is logged to the SD card, you can remove the card from the module and read it on your computer. Simply insert the SD card into a card reader, and access the text file (e.g., datalog.txt). The data is saved in plain text, making it easy to analyze using software like Excel or Python.

Example of Data Saved on the SD Card

This text file can then be imported into data analysis software for further processing, like graphing the data or calculating averages.

Expanding Your Data Logging Project

Using Multiple Sensors

Arduino’s versatility allows for the use of multiple sensors in a single project. For example, you can log temperature, humidity, and light levels in the same file or create separate files for each sensor. The logic remains the same: connect your sensors to the Arduino, read the data, and write it to the SD card.

Timestamping Your Data

For more detailed logs, you might want to include timestamps. You can add real-time data using the RTC (Real-Time Clock) module or rely on Arduino’s millis() function to approximate timestamps. By adding the current time to your data logs, you can better track when measurements were taken.

Troubleshooting Common Issues

SD Card Not Initializing

If the SD card does not initialize, ensure:

The card is properly inserted and formatted with FAT16 or FAT32.
The wiring is correct and secure.
The CS pin (Chip Select) is connected to the right Arduino pin.

Data Not Being Saved

If your Arduino fails to save data:

Verify that the SD card module is working properly.
Check if there is enough available space on the SD card.
Ensure your code correctly opens the file in write mode.

Conclusion

Arduino data logging to an SD card is a powerful technique for capturing sensor data and storing it for later analysis. With just a few components and some basic coding, you can log various types of data from sensors, store it on an SD card, and later retrieve it for analysis. Whether you’re working on environmental projects, home automation systems, or scientific experiments, Arduino’s data logging capabilities can help you efficiently record and track your data.