Hi,
I am developing a low-cost accelerometer to measure seismic activity in an area. I have used Arduino Uno, MEMS ADXL 345, Micro SD card Module with a 16 GB SD card and I will possibly add a RTC module such as DS3231.
There is a trigger mechanism involved. If the resultant acceleration in the XY plane exceeds a certain value the accelerometer will record the data into the SD card at 100 samples per second (txt or CSV format) and if the measured data is below the threshold for a minute, the device will save data data in the name format of the DD:MM: YYYY HH:MM:SS of the start of the data storing.
The problem is the trigger mechanism is not working. I have tried thresholds like 0.05 g, 0.1 g 0.5 g, etc., but either it gives gibberish results or it gives nothing at all. what might cause the problem?
Due to that problem, I am measuring the data continuously, which gives rise to storage issues.
I am attaching the connections and the code here:
Connections:
MicroSD Card Module
VCC - Arduino Uno 5V pin.
GND - Arduino Uno GND pin.
CS - Arduino Uno pin 4.
MOSI - Arduino Uno pin 11.
MISO - Arduino Uno pin 12.
SCK - Arduino Uno pin 13.
ADXL345 Module:
VCC - 3.3V power supply of Arduino Uno.
GND - GND pin of Arduino Uno.
SDA - analog input pin A4
SCL - analog input pin A5
The Code
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>
#include <SPI.h>
#include <SD.h>
#include <TimeLib.h>
// Constants for accelerometer
#define ADXL345_ADDRESS (0x53)
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);
// Constants for SD card
const int chipSelect = 4;
File dataFile;
unsigned long lastDataTime = 0;
unsigned long noReadingStartTime = 0;
bool recordingData = false;
const unsigned long noReadingTimeout = 60000; // 1 minute
// Variables for data
float accelerationX, accelerationY, accelerationZ;
float prevMagnitude = 0.0;
const float threshold = 0.5; // 0.0981 m/s²
void setup() {
Serial.begin(115200);
// Initialize accelerometer
if (!accel.begin()) {
Serial.println("Could not find a valid ADXL345 sensor, check wiring!");
while (1);
}
// Initialize SD card
if (!SD.begin(chipSelect)) {
Serial.println("SD card initialization failed!");
while (1);
}
}
void loop() {
unsigned long currentTime = millis();
sensors_event_t event;
accel.getEvent(&event);
accelerationX = event.acceleration.x;
accelerationY = event.acceleration.y;
accelerationZ = event.acceleration.z;
float magnitude = sqrt(sq(accelerationX) + sq(accelerationY));
float deltaMagnitude = abs(magnitude - prevMagnitude);
if (deltaMagnitude > threshold) {
// Reset noReadingStartTime when threshold is exceeded
noReadingStartTime = currentTime;
if (!recordingData) {
// Start recording data
startRecording();
}
if (recordingData) {
// Store data on SD card
String dataString = String(currentTime) + "," + String(accelerationX) + "," + String(accelerationY) + "," + String(accelerationZ);
dataFile.println(dataString);
}
} else {
if (recordingData && (currentTime - noReadingStartTime >= noReadingTimeout)) {
// Stop recording and save data
stopRecording();
}
}
prevMagnitude = magnitude;
// Maintain data measurement frequency
unsigned long timeSinceLastData = currentTime - lastDataTime;
if (timeSinceLastData >= 10) { // 10 milliseconds for 100 samples per second
lastDataTime = currentTime;
}
}
void startRecording() {
String fileName = getFormattedDateTime() + ".csv";
dataFile = SD.open(fileName, FILE_WRITE);
if (dataFile) {
recordingData = true;
Serial.println("Recording data...");
}
}
void stopRecording() {
if (recordingData) {
dataFile.close();
recordingData = false;
Serial.println("Stopped recording data.");
}
}
String getFormattedDateTime() {
char buffer[20];
sprintf(buffer, "Data_%02d-%02d-%04d_%02d-%02d-%02d",
day(), month(), year(), hour(), minute(), second());
return String(buffer);
}
