Arduino Based GSM Home Security System

By Joy Mujherji


As shown in Fig. 1, Arduino Board 1 and GSM module get ground connection through transistor TIP142 (T1). Also, very little drive current (<5mA) is required from Board 1. A 12V, 2A regulated power supply is recommended. It should be able to deliver 2A of current for the GSM module. An optional battery backup system can be added for additional security in case the burglar decides to turn off the electricity.

House the circuit in a plastic box and place it in a locked wooden cabinet. Make sure the GSM module has good signal strength. The alarm system can also be used to protect warehouses, shops, banks and office buildings.


Software is written in Arduino programming languange. Arduino Uno Board 1 and Board 2 are programmed using Arduino IDE software. Atmega328P on Arduino Uno comes with a pre-programmed bootloader that allows you to upload a new code to it without using an external hardware programmer.

Connect both Arduino boards one by one to the PC and select the correct COM port in Arduino IDE. Compile the program (sketch). Then, select the correct board from Tools→Board menu in Arduino IDE and upload the sketch.

Fig. 4: Author’s prototype showing transistor T3 connected to power key terminal of the GSM module

Arduino1.ino sketch is at the heart of the alarm system and carries out all major functions of the circuit. Arduino2.ino sketch is used to reset Board 1 and GSM module by switching off the power for a few seconds via T1. Please refer to source codes for details.
The author’s prototype is shown in Fig. 4.

Download source code

Joy Mukherji is an electronics hobbyist and a small business owner in New York, USA, and Lucknow, India. His interests include designing radio-frequency circuits


  1. sir i am using SIM900A GSM Module instead of SIM900 GSM Module is this module compatible with this circuit or i have to use SIM900 GSM module.

  2. Dear sir … I see that there is a difference between the scheme and the print layout with the components on it, which is correct. I would like to make an answer because it is an interesting projeckt.
    Yours sincerely

  3. Hi Joy

    Thanks for the great project! I have searched the net for a while and finally stumbled upon your design and it is the closest to what I would want to build. I have a few questions:

    1: I am not going to use the reed switches, how do I omit that part of the circuit without affecting the rest of the circuit and do I need to change the code?
    2: I have two 12V alarm PIR sensors with NO contacts, can I use them as is or do I need to alter the wiring and or code?
    PS: Is there any way of contacting you directly as I would have a lot of question during my build?
    Thanks in advance!

    • You can just short the wiring for the reed switches on the pcb. No need to change anything else. For PIR sensor, if it is normally Open contact , then connect one pin to positive 5V and the other to the PIR inputs on the alarm system . This way when the PIR sensor is triggered it will output a +5V and it should trigger the circuit. Just increase value of R14 to 1.5 K

  4. sir in schemetic arduino board 1 pin no 5 is connected with R8,R9 and R10 but pcb layout is not present.
    and what is the value of r13 in schem is 2.2k and component list u give 220 ohm value please clear this
    advance thanks for your reply

  5. My Questions are:
    1. How can i get the Arduino IC , because i know its a program based PIC.
    2. I am currently using CCSC compiler, and arduino has its own compiler… therefore how can i achieve this.

    Thank you

    • Arduino clone are easily available online. Look up Arduino nano board on eBay and sites like amazon. To complile and upload the code you will need to download the free arduino IDE program and install it on your computer. It’s available at

    • Yes you can use a long wire having a resistance of up to 15K or so. No problem! A 1Km or 1000m long copper wire with 0.5mm diameter has a resistance of 100ohm or so.

      The 100uH RFC and 100n capacitors keep RF out so long wire is not a problem. Use any length you like.

  6. I have done this project but now i’m facing an issue that the registered numbers are called one by one. I have regiestered six numbers in it. After calling those six numbers by the device only I can be able to send the message command to the device. But I need to send the turn OFF command in the middle of the phone call. Is there any corrections to fix it.? Please help me.! Thank you.!


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