Circuit Documentation

Summary

This circuit is designed to monitor for impacts using an accelerometer and to provide location data using a GPS module. It features an Arduino Nano as the central microcontroller, interfaced with a SIM800L GSM module for communication, a GPS NEO 6M module for location tracking, an ADXL335 accelerometer for impact detection, a buzzer for audio alerts, a pushbutton for user interaction, and an LM2596 voltage regulator to step down the voltage from a 12V battery to a suitable level for the other components.

Component List

Arduino Nano

• Microcontroller board based on the ATmega328P
• Provides digital and analog I/O pins
• Capable of serial communication

SIM800L

• GSM/GPRS module
• Allows for SMS and voice communication
• Interfaces with the Arduino via serial connection

ADXL335

• 3-axis accelerometer
• Measures acceleration in x, y, and z directions
• Used for impact detection

GPS NEO 6M

• GPS module
• Provides location data
• Communicates with the Arduino via serial connection

LM2596

• Voltage regulator
• Steps down the input voltage to a lower level
• Powers the SIM800L module

Pushbutton

• Momentary switch
• Used for user input to control the circuit

Buzzer

• Audio signaling device
• Provides audible alerts

12V Battery (Small Size)

• Power source for the circuit
• Provides 12V which is regulated down for other components

Wiring Details

Arduino Nano

• GND connected to the common ground net
• 5V connected to the 5V net from the LM2596
• D2 connected to SIM800L RXD
• D3 connected to SIM800L TXD
• D5 connected to Buzzer PIN
• D6 connected to Pushbutton Pin 1 (in)
• D8 connected to GPS NEO 6M TX
• D9 connected to GPS NEO 6M RX
• VIN connected to 12V Battery VCC
• A0 connected to ADXL335 X-OUT
• A1 connected to ADXL335 Y-OUT
• A2 connected to ADXL335 Z-OUT

SIM800L

• RXD connected to Arduino Nano D2
• TXD connected to Arduino Nano D3
• VCC connected to LM2596 OUT
• GND connected to the common ground net

ADXL335

• VCC connected to the 5V net from the LM2596
• GND connected to the common ground net
• X-OUT connected to Arduino Nano A0
• Y-OUT connected to Arduino Nano A1
• Z-OUT connected to Arduino Nano A2

GPS NEO 6M

• VCC connected to the 5V net from the LM2596
• GND connected to the common ground net
• RX connected to Arduino Nano D9
• TX connected to Arduino Nano D8

LM2596

• IN connected to 12V Battery VCC and the common ground net
• OUT connected to SIM800L VCC and GND, and provides the 5V net

Pushbutton

• Pin 3 (out) connected to the common ground net
• Pin 1 (in) connected to Arduino Nano D6

Buzzer

• PIN connected to Arduino Nano D5
• GND connected to the common ground net

12V Battery (Small Size)

• VCC connected to Arduino Nano VIN and LM2596 IN
• GND connected to the common ground net

Documented Code

The code is written for the Arduino Nano and is responsible for the following functions:

• Initializing the SIM800L module and GPS module
• Reading the ADXL335 accelerometer values and detecting impacts
• Sending an SMS with GPS location data when an impact is detected
• Allowing the user to cancel the alert with the pushbutton
• Handling incoming SMS commands to retrieve GPS location data

#include <AltSoftSerial.h>
#include <TinyGPS++.h>
#include <Wire.h>
#include <math.h>
#include <SoftwareSerial.h>

const String EMERGENCY_PHONE = "+918939843825";
#define rxPin 2
#define txPin 3

SoftwareSerial sim800(rxPin, txPin);
AltSoftSerial neogps;
TinyGPSPlus gps;
//RX Pin To D9
//TX Pin To D8

String sms_status, sender_number, received_date, msg;
String latitude, longitude;
#define BUZZER 5
#define BUTTON 6
#define xPin A0
#define yPin A1
#define zPin A2

byte updateflag;

int xaxis = 0, yaxis = 0, zaxis = 0;
int deltx = 0, delty = 0, deltz = 0;
int vibration = 2;
int devibrate = 75;
int magnitude = 0;
int sensitivity = 20;

double angle;
boolean impact_detected = false;
unsigned long time1;
unsigned long impact_time;
unsigned long alert_delay = 30000;

void setup()
{
  Serial.begin(9600);
  sim800.begin(9600);
  neogps.begin(9600);
  pinMode(BUZZER, OUTPUT);
  pinMode(BUTTON, INPUT_PULLUP);

  sms_status = "";
  sender_number = "";
  received_date = "";
  msg = "";
  sim800.println("AT");
  delay(1000);
  sim800.println("ATE1");
  delay(1000);
  sim800.println("AT+CPIN?");
  delay(1000);
  sim800.println("AT+CMGF=1");
  delay(1000);
  sim800.println("AT+CNMI=1,1,0,0,0");
  delay(1000);
  time1 = micros();
  xaxis = analogRead(xPin);
  yaxis = analogRead(yPin);
  zaxis = analogRead(zPin);
}

void loop()
{
  if (micros() - time1 > 4999) Impact();
  if (updateflag > 0)
  {
    updateflag = 0;
    Serial.println("Impact detected!!");
    Serial.print("Magnitude:");
    Serial.println(magnitude);

    getGps();
    digitalWrite(BUZZER, HIGH);
    impact_detected = true;
    impact_time = millis();
  }
  if (impact_detected == true)
  {
    if (millis() - impact_time >= alert_delay) {
      digitalWrite(BUZZER, LOW);
      makeCall();
      delay(1000);
      sendAlert();
      impact_detected = false;
      impact_time = 0;
    }
  }

  if (digitalRead(BUTTON) == LOW) {
    delay(200);
    digitalWrite(BUZZER, LOW);
    impact_detected = false;
    impact_time = 0;
  }
  while (sim800.available()) {
    parseData(sim800.readString());
  }
  while (Serial.available())  {
    sim800.println(Serial.readString());
  }
}

void Impact()
{
  time1 = micros();
  int oldx = xaxis;
  int oldy = yaxis;
  int oldz = zaxis;

  xaxis = analogRead(xPin);
  yaxis = analogRead(yPin);
  zaxis = analogRead(zPin);

  vibration--;
  Serial.print("Vibration = ");
  Serial.println(vibration);
  if (vibration < 0) vibration = 0;
  if (vibration > 0) return;
  deltx = xaxis - oldx;
  delty = yaxis - oldy;
  deltz = zaxis - oldz;

  magnitude = sqrt(sq(deltx) + sq(delty) + sq(deltz));
  if (magnitude >= sensitivity) //impact detected
  {
    updateflag = 1;
    vibration = devibrate;
  }
  else
  {
    magnitude = 0;
  }
}

void parseData(String buff) {
  Serial.println(buff);

  unsigned int len, index;
  index = buff.indexOf("\r");
  buff.remove(0, index + 2);
  buff.trim();
  if (buff != "OK") {
    index = buff.indexOf(":");
    String cmd = buff.substring(0, index);
    cmd.trim();

    buff.remove(0, index + 2);
    if (cmd == "+CMTI") {
      index = buff.indexOf(",");
      String temp = buff.substring(index + 1, buff.length());
      temp = "AT+CMGR=" + temp + "\r";
      sim800.println(temp);
    }
    else if (cmd == "+CMGR") {
      if (buff.indexOf(EMERGENCY_PHONE) > 1) {
        buff.toLowerCase();
        if (buff.indexOf("get gps") > 1) {
          getGps();
          String sms_data;
          sms_data = "GPS Location Data\r";
          sms_data += "http://maps.google.com/maps?q=loc:";
          sms