{"id":59896,"date":"2024-12-10T08:34:26","date_gmt":"2024-12-10T13:34:26","guid":{"rendered":"https:\/\/www.engineersgarage.com\/microcontroller-projects-tf\/arduino-home-security-with-gsm-pir-and-reed-switch\/"},"modified":"2025-01-09T07:47:35","modified_gmt":"2025-01-09T12:47:35","slug":"arduino-home-security-with-gsm-pir-and-reed-switch","status":"publish","type":"post","link":"https:\/\/www.engineersgarage.com\/arduino-home-security-with-gsm-pir-and-reed-switch\/","title":{"rendered":"Arduino home security system using Sim900 Gsm module, Pir motion detector and magnetic door contact switch"},"content":{"rendered":"
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\u200bIn this tutorial i am going to make an arduino home security system. One can install this diy arduino security\u00a0system project on his home main door. The diy arduino security system checks two things. First it checks if some one approached the door? Second it checks if door is opened by the person? When the former two conditions meet an sms\/text message will be send to the owner of the house. The presence\/motion\u00a0of the person in front of the door is detected by the pir motion detector and door opening\u00a0is checked by door contact switch OR reed switch. Both the sensors(pir motion and reed switch) are connected to arduino uno and any intrusion detected by the sensors is conveyed\u00a0instantly to arduino uno. Arduino as an intrusion alert sends a sms\/text message to the owner mobile number using gsm module.<\/span><\/div>\n
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\"Arduino <\/a><\/p>\n

Arduino Gsm Pir and door sensor security system<\/div>\n<\/div>\n<\/div>\n
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PIR motion detection sensor<\/h3>\n<\/div>\n<\/div>\n
I used popular hcsr501 passive infrared motion detection sensor in the diy project. It can detect motion at a max distance of 7 meters. Sensitivity range of hcsr501 pir motion detector can be set by rotating the variable resistor\/potentiometer mounted on the circuit board of hcsr501 pir motion sensor. It also has a second variable resistor\/potentiometer which is used to set the <\/span>delay time <\/span><\/strong>i will talk about it later(With Out pin of Hcsr501). Hcsr501 pir sensor has 3 pin. Two are power pins. Vcc is connected to +ve lead of power supply and Gnd is connected to -ve of power supply. The third pin is out pin. <\/strong>It normally remains low.\u00a0When pir sensor detects\u00a0presence\u00a0of infrared emitting\u00a0body in its range it sets the out pin<\/strong> high. Now the question is For how long does pir out pin<\/strong> remains high once the presence of person is detected? For this purpose\u00a0the second variable resistor\/potentiometer is present on hcsr501 pcb board you can set the delay time<\/strong> or out pin high time<\/strong> using the second variable\u00a0resistor.
\nSo where the pir sensor is to be mounted in order to detect the presence\u00a0of person. It must be mounted on the upper portion of inlet of door. Below diagram best illustrates\u00a0the mounting of pir above the door.\u00a0<\/span><\/div>\n
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Pir sensor installation above door and area covering angle.<\/div>\n<\/div>\n<\/div>\n
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Sim900 Gsm module(Arduino Gsm)<\/h3>\n<\/div>\n<\/div>\n
I am using SainSmart Sim900 GPRS\/Gsm Module<\/a> in the project. Its easy to use and its documentation is pretty straight forward. I worked with many other gsm modules build on SIMCom<\/a>\u00a0sim900 chip. I found SaintSmart to be best of all. The Chinese\u00a0cheap sim900 gsm modules are really hard to use and due to bad circuit designs their power requirements\u00a0differ from each other. SaintSmart gsm module works on 5 volts. It has five pins. In five three are power pins. Two ground pins and one +ve power pin. We supply power 5 volts to +ve pin and ground the Gnd pins. The remaining two pins are Uart pins.
\nAll sim900 gsm modules communicates with external controllers\/microcontrollers on Uart protocol. Uart protocol has two pins. One is TxD(Transmit) and other is RxD(Receive). In order to send and receive data to sim900 gsm module the external microcontroller must also have a Uart port. In simple words Uart communication takes place between two Uart ports. Gsm sim900 module has Uart port so our external microcontroller must also have one to communicate with gsm module. In Uart communication we connect TxD pin of first device to RxD of second one. Similarly Rxd of first one is connected with TxD of second one. After connection we set the baud rate of communication in software. Baud rate is simply the speed of communication\u00a0between two devices communicating on Uart port. In circuit diagram of the project it will be cleared to you about uart connections.
\nSim900 gsm module works on AT<\/strong> command set. Their are lot of AT<\/strong> commands if you go through the data sheet of sim900 chip set. We will use in our project only ones which a necessary to send an sms text message. I have an another tutorial on how to send an Sms with sim900 gsm module. You can visit it by clicking the below button.\u00a0\u00a0<\/span><\/div>\n
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Gsm Arduino: Send an sms with Sim900 <\/span> <\/a><\/p>\n

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Door contact switch\/Reed switch<\/h3>\n<\/div>\n<\/div>\n
A reed switch is an electrical device operated using a magnet in place. It consists of two half’s. One half contains actual switch and the other half contains just a magnet in it. When the magnetic half is brought near the switch half it starts conducting electricity. So how does it all happens? Actually the switch half contains a pair of magnetic rods. Normally when their is no magnetic filed present near switch the rods are a part from each other(Open circuit – No electric path). When we bring the magnetic half near the switch half the magnetic\u00a0field\u00a0brings the rods close and when the strength of magnetic field\u00a0reaches the threshold limit the rods attach with each other(Making a physical contact – Path for electricity flow).
\nHow to install the door reed switch? We usually mount the switch half on fix\/immovable surface and the magnetic half is installed\u00a0on the moving surface.\u00a0In our case, i installed the magnetic half on door and the switch half on the wall near to door closing point. Both half’s must be in correct position and at correct distance to make a contact. Below you can see the correct placement and installation of door contact sensor.\u00a0 \u00a0<\/span><\/div>\n
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\"Door <\/a><\/p>\n

Door contact reed switch installation<\/div>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n
The block and flow diagram of the aduino home security system is given below. Pir motion detector and magnetic door switch sends their respective status to arduino. Arduino then decides what to do next with the inputs from pir and door sensor. If arduino finds both the sensors transmitted the positive status. It alerts the gsm module to activate and send a text sms on hard coded single sim number.\u00a0\u00a0<\/span><\/div>\n
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Arduino home security system block diagram<\/div>\n<\/div>\n<\/div>\n
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Arduino Home Security – Project circuit diagram<\/h3>\n<\/div>\n<\/div>\n
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Coming to the project circuit diagram. Only four I\/O pins of arduino uno are used in the project. Two pins are of Uart channel Pin#0 and 1 of arduino uno. The other two are Pin#8 and 9. Pin#8 of arduino uno is connected to pir motion sensor out pin and pin#9 of arduino uno is connected to door contact sensor. Pir motion detector and door contact sensor can be powered through the arduino +5 volt output. But i prefer to use an external power supply for powering the pir and door sensor.
\nDoor contact switch can be powered from +5v to +12v. I powered it with 5v power supply. If you input +12 volt to reed switch then you might need to insert a resistor in series with the reed switch because arduino pins are 5 volt tolerant and +12v(when contact is made) can destroy the input pin of arduino. When contact is made by reed switch the input voltage appears on the arduino digital pin. In our case on Door(Pin#9)<\/strong> pin. If the voltage is above 5 v it might destroy the input pin of arduino. So be careful before powering\u00a0the reed switch.
\nNote:<\/strong> I write +12 v due to the fact that door sensor is installed at a distance from the main microcontroller(Arduino our case) and after contact the voltage drops across wire due to length of the wire.\u00a0\u00a0<\/span><\/p>\n

Gsm module needs an extra power during sms sending time. Use an adopter which can supply continuous\u00a01 Ampere of current at 5 volts for powering sim900 gsm module. 1 ampere adopter is enough to power all the components(Arduino, Pir, Reed switch and Gsm module) used in the project circuit.<\/p>\n<\/div>\n

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Arduino home security system with pir, gsm and door contact switch<\/div>\n<\/div>\n<\/div>\n
Coming to the code portion of the security project. First i defined the arduino digital pins which are going to interface with the pir motion detector and door contact switch(Arduino Pin#8 and 9). In the setup function i declared both the pins\u00a0(Arduino Pin#8 and 9)<\/span>\u00a0as input. Since we are reading the status of the sensors so we must declare them input. After declaring the arduino sensor interfacing pins as input. I went on for the Uart module of arduino. Arduino Uart module is present on arduino pin#0 and 1. To declare and start the arduino uart module in arduino ide we use Serial.begin()<\/strong> command. To set the communication baud rate we insert the baud rate value in circular brackets after the word begin. In our case i set the communication rate at 9600 bits per second and command used to initialize it is Serial.begin(9600)<\/strong>.\u00a0 \u00a0<\/span><\/div>\n
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