Circuit Documentation

Summary

The circuit in question is designed to monitor for accidents using an accelerometer and a piezo sensor. Upon detecting an accident, it activates an SOS signal and sends an SMS with the location coordinates obtained from a GPS module. The system is built around an Arduino UNO microcontroller, which interfaces with an MPU-6050 accelerometer, a Neo 6M GPS module, a Sim800l GSM module for communication, and a piezo sensor for impact detection. A resistor and a diode are also included for circuit protection and signal conditioning.

Component List

Arduino UNO

• Microcontroller board based on the ATmega328P
• It has 14 digital input/output pins, 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header, and a reset button.

MPU-6050

• A 6-axis motion tracking device that combines a 3-axis gyroscope and a 3-axis accelerometer on the same silicon die.
• It has an I2C interface for communication.

Neo 6M GPS Module

• A standalone GPS receiver module that provides a solution for positioning and navigation.
• It communicates with the microcontroller via serial communication.

Sim800l

• A GSM/GPRS module that can provide SMS and voice communication capabilities to embedded systems.
• It communicates with the microcontroller via serial communication.

Piezo Sensor

• A device that can measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge.

Resistor (1 MΩ)

• A passive two-terminal electrical component that implements electrical resistance as a circuit element.

1N4007 Rectifier Diode

• A standard silicon diode used to protect sensitive electronics against voltage spikes and to rectify AC into DC.

Wiring Details

Arduino UNO

• 3.3V connected to Sim800l VCC
• 5V connected to MPU-6050 VCC and Neo 6M GPS Module VCC
• GND connected to MPU-6050 GND, Neo 6M GPS Module GND, Sim800l GND, and Piezo Sensor (-)
• A1 connected to one end of the Resistor (other end connected to Piezo Sensor (+))
• A4 (SDA) connected to MPU-6050 SDA
• A5 (SCL) connected to MPU-6050 SCL
• D2 connected to Sim800l TXD
• D3 connected to Sim800l RXD and Neo 6M GPS Module TX
• D4 connected to Neo 6M GPS Module RX

MPU-6050

• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND
• SDA connected to Arduino UNO A4
• SCL connected to Arduino UNO A5

Neo 6M GPS Module

• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND
• RX connected to Arduino UNO D4
• TX connected to Arduino UNO D3 (also connected to Sim800l RXD)

Sim800l

• VCC connected to Arduino UNO 3.3V
• GND connected to Arduino UNO GND (also connected to the Anode of the 1N4007 Diode)
• RXD connected to Arduino UNO D3 (also connected to Neo 6M GPS Module TX)
• TXD connected to Arduino UNO D2

Piezo Sensor

• + connected to one end of the Resistor (other end connected to Arduino UNO A1)
• - connected to Arduino UNO GND (also connected to the Cathode of the 1N4007 Diode)

Resistor (1 MΩ)

• One end connected to Arduino UNO A1
• Other end connected to Piezo Sensor (+)

1N4007 Rectifier Diode

• Anode connected to Sim800l GND
• Cathode connected to Piezo Sensor (+)

Documented Code

#include <Wire.h>
#include <MPU6050.h>
#include <SoftwareSerial.h>
#include <TinyGPS++.h>

MPU6050 accelgyro;
TinyGPSPlus gps;
SoftwareSerial gpsSerial(3, 4);    // RX, TX for GPS
SoftwareSerial gsmSerial(2, 3);    // RX, TX for GSM

const int piezoPin = A1;           // Piezo sensor connected to A1
const int piezoThreshold = 500;    // Threshold for piezo force detection
const int accelThreshold = 16000;  // Threshold for accelerometer

void setup() {
  Serial.begin(9600);
  gpsSerial.begin(9600);
  gsmSerial.begin(9600);

  // Initialize accelerometer
  Wire.begin();
  accelgyro.initialize();
  if (!accelgyro.testConnection()) {
    Serial.println("Accelerometer not connected!");
  }
}

void loop() {
  // Check for accident via accelerometer or piezo sensor
  if (detectAccident() || analogRead(piezoPin) > piezoThreshold) {
    activateSOS();
  }
}

bool detectAccident() {
  int16_t ax, ay, az;
  accelgyro.getAcceleration(&ax, &ay, &az);
  return (abs(ax) > accelThreshold || abs(ay) > accelThreshold || abs(az) > accelThreshold);
}

void activateSOS() {
  Serial.println("SOS Activated! Accident detected.");
  sendSMS();
}

void sendSMS() {
  if (gps.location.isValid()) {
    String message = "Accident detected! Location: ";
    message += "Lat: " + String(gps.location.lat(), 6) + ", ";
    message += "Lng: " + String(gps.location.lng(), 6);
    
    gsmSerial.println("AT+CMGF=1");             // Set SMS to text mode
    delay(100);
    gsmSerial.println("AT+CMGS=\"+1234567890\"");  // Replace with emergency contact number
    delay(100);
    gsmSerial.print(message);
    gsmSerial.write(26);                        // End message with Ctrl+Z
  } else {
    Serial.println("GPS location not valid.");
  }
}

This code is designed to run on the Arduino UNO and utilizes the MPU-6050 accelerometer to detect sudden changes in acceleration, indicative of an accident. When an accident is detected, it sends an SMS with the current GPS coordinates using the Sim800l GSM module. The piezo sensor is used as an additional means of detecting an impact. The code includes initialization and continuous monitoring in the setup and loop functions, respectively. The detectAccident function checks for high acceleration events, and the activateSOS function handles the SOS activation and SMS sending logic.