Test 1
Wiring
Libraries
Code
Result
GSM tripwire Alarm Project
Wiring
Libraries
Code
Result

Published January 13, 2020 © GPL3+

SIM800L - LASER Tripwire GSM Alarm with Phone Number Dialing

Easy project on how to dial phone numbers using the SIM800L and as a project a GSM Tripwire alarm that will call you whenver someone passes.

BeginnerFull instructions provided1 hour6,722

SIM800L - LASER Tripwire GSM Alarm with Phone Number Dialing

Things used in this project

Hardware components

SIM800L EVB

Arduino UNO

LDR, 5 Mohm

Resistor 1k ohm

LASER emitter

Software apps and online services

Arduino IDE

Story

Tutorial if needed

Sponsored by: DigitSpace
Product used: SIM800L Module Replace SIM900A GSM GPRS 5V Serial with Antenna

Hello there and welcome to another tutorial sponsored by DigitSpace, and this time it’s about the SIM800L again, the previous article was about sending SMS/Text (Simple and sensor values) to your phone, but this time it’s about dialing phone numbers using the same module, and a little project which is a LASER tripwire GSM Alarm.

Make sure to check this tutorial about the module first:Send SMS/Text from Arduino using SIM800L GSM/GPRS Module [DigitSpace.com]

So to sum up we gonna dial numbers, not make a full phone call, because this module doesn’t have pins for Speaker/Mic like the other version:

SIM800L EVB

HALT!! Please make sure that your SIM Card is unlocked (not protected by a pin code) and that it has enough credit to be able to make a phone call/Send SMS depending on your mobile operator.

N.B: I’m powering the module using a 7.4V Li battery with a buck converter, it could be powered directly from the Arduino but it’s sketchy….

Battery + converter

Test 1

So in the test #1 all we have to do is wire the module and dial a phone number using the Serial monitor of the Arduino IDE.

The main command for dialing a number is “ATD+xxxxxxxxxx;” where the xx.. stand for your phone number including the country code.
The other command is “ATH” to hang up/stop the phone call, if not used the call will end after a certain delay.

Wiring

Can befound below (Wiring 1).

This is the basic wiring of the module, and the Arduino is powered via USB, it could be powered with the battery too, but I’m in need of the Serial monitor to be able to send AT commands to the module.

Libraries

No external library is required for this, Software Serial, but it’s already with the Arduino default libraries.

Code

Can be found below (Code 1).

This code is not something special, it just permits the communication between the module and the PC, you’ll be able to send commands to the module and check the feedback.

Result

Type the command as said in the serial monitor (the AT is just for check)

Arduino is calling

“ATH” command to hang up

GSM tripwire Alarm Project

So the project is about a tripwire alarm which call your phone number whenever someone passes through it.

I’ve choosed a LASER + LDR, you can use anything you prefer to detect presence for example PIR, Doppler Radar, or some classic modules like proximity sensors HC-SR04,FC 51,Sharp IR… Whatever suits you.

LDR

KY 008 LASER Emitter

Wiring

Wiring can be found below (Wiring 2).

So here as you can see the SIM module is powered with the battery, but for the rest they are powered by the arduino plugged in the PC, you can of course power the Arduino using the battery all you have to do is add a wire between the 5V of the Source with the 5V of the Arduino.

Libraries

Just like above, no external one is needed.

Code

Code can be found below (Code 2).

The code is meant to work without the Serial monitor, but I’ve add some functions and kept the wiring to use with Serial monitor and check the LDR value.

Result

Something prevent the light from reaching the LDR, also the values are shown in the serial monitor

Will trigger the call automatically to the phone number in the code

Well that's all folks :D

Code

/* This code can send data via serial to a module via UART and display on the serial monitor data sent by the module
 * It works with SIM800L and give the ability to send AT commands to test them
 * Refer to www.SurtrTech.com for more information */

#include <SoftwareSerial.h>    

SoftwareSerial sim800l(2, 3); // RX,TX for Arduino and for the module it's TXD RXD, they should be inverted


void setup()
    {
      
      sim800l.begin(9600);   //Module baude rate, this is on max, it depends on the version
      Serial.begin(9600); 
      
    }



void loop() {
  Serialcom();
}


void Serialcom()
    
    {
      delay(500);
      
      while (Serial.available()) 
      {
        sim800l.write(Serial.read());//Forward what Serial received to Software Serial Port
      }
      
      while(sim800l.available()) 
      {
        Serial.write(sim800l.read());//Forward what Software Serial received to Serial Port
      }
    }

/* This code works with SIM800L, LASER module and LDR for LASER GSM Tripwire Alarm
 * The LASER constantly lights up the LDR, and if someone passes by the value will drop 
 * and it will trigger a phone call alerting the phone owner
 * Refer to www.SurtrTech.com for more details
 */

#include <SoftwareSerial.h>

#define LDR A0           //Read the LDR value from the point where it meets the Resistor
#define LASER 7          //LASER trigger pin

int LDR_Value;

SoftwareSerial sim800l(2, 3);    // RX,TX for Arduino and for the module it's TXD RXD, they should be inverted

void setup() {
  
  pinMode(LDR, INPUT);          //Define pinModes
  pinMode(LASER, OUTPUT);
  Serial.begin(9600);           //Start the Serial communication with the PC and SIM800L
  sim800l.begin(9600);
  digitalWrite(LASER,HIGH);     //Put the LASER at high state
  delay(5000);

}

void loop() {
  
  LDR_Value=analogRead(LDR);      //Constantly read and display the LDR value
  Serial.println(LDR_Value);
  delay(30);                     //To avoid false reading
  
  if (LDR_Value < 800) {        //If someone passes through the value will drop, 800 is the threshold, you can chose whatever suits you, the serial monitor will help you
    
    sim800l.println("ATD+xxxxxxxxxxxxx;");  //The number to call don't forget to add the country code

 }


}

Credits

SurtrTech

9 projects • 207 followers

YT Channel bit.ly/35Ai76l, run by Automation and Electrical Engineer, Electronics amateur, no IT background so you may see wreckage in codes

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SIM800L - LASER Tripwire GSM Alarm with Phone Number Dialing