This circuit will give call back alerts in the form of blank calls on your cell phone whenever it senses a break in or intrusion inside the particular restricted area where it has been installed for the intended security monitoring.
Introduction
The cell phone call alert security system circuit which needs to be installed incorporates a cheap cell phone as the modem which is actually used for triggering the warning calls in the owners cell phone.
The above modem cell phone is first attached with its own SIM card as normally done with any cell phone.
For setting up the cell phone, the cover is removed and a couple of wires are neatly connected with the pads which represent the "green" button or the calling button of the phone.
After securing the two connected wires with the green button terminals, the phone is again sealed back to it normal condition.
The external ends of the above wires are then connected to the relay contacts of the control circuit as shown in the figure.
Before the installation, a call is made from the above modem cell phone to the owners cell phone so that it gets recorded inside the green button as the "last call" made from the cell phone.
Now every time the green button is activated thrice, a call gets connected to the owners cell phone.
Since the wires from the call button are connected to a relay, it simply means that if the relay contacts gets energized thrice, would result a call being sent from the above cell phone.
How the Control Circuit Works
- The control circuit basically consists of a hold circuit and a pulse circuit.
- The "hold circuit section is made up of two NAND gates configured as a timer cum latch circuit. N1 and N2 together with C12 and R14 form a timer circuit, while the resistor R15 keeps the output latched as long as the timer counts and its timing lapses.
- After which the output reverts to its original position.
- The input of the above latch is connected to a reed relay sensor which may be appropriately centered for initiating the magnetic contacts when a possible intrusion takes place.
- The reed relay activates a relay (left side of the diagram) only momentarily via the capacitor C10.
- When the above relay contacts close, N1, N2 latch, and generate a negative or a logic low at the output.
- This logic low instantly grounds the reset pin of another timer IC 4060.
- This immediately prompts the IC 4060 to start counting.
- The process generates a set of three pulses at the pin #15 of the IC activating the relay thrice via the relay driver stage. This activates the cell phone modem which starts sending a blank call to the assigned number or the owners cell phone.
- Pin #2 makes sure that the IC counting and the output from pin#15 gets locked after the three relay pulses, this is done by sending a high pulse from pin #2 to pin #11 of the IC.
- The IC remains in this position for so long as N1 and N2 are in the counting mode after which the output of N2 goes high and the entire circuit is reverted to its original state and back in the alert mode.
- The modem cell phone is kept in a charged state by employing a 7805 charger circuit.
This circuit was exclusively designed and invented by "Swagatam".
PARTS LIST
All Resistors are ΒΌ watt 5% CFR, unless otherwise stated.
R9-10K,
R10-2M2,
R11-330K,
R12-4K7,
R13-39K,
R14-1M,
R15-1K,
C10/C12-100uF/25V,
C11-0.001uFDISC,
D9/D10-1N4148,
D8/D11-1N4007
T2 = BC547
IC2 (N6,N7,N8)-4093
IC3-4069
Relays-12V/400 Ohms
Anonymous says
what is the blue part in the circuit
Anonymous says
Hello. I didn't understand the part when you take the wires from the cell phone. How do I know which wires and what should we do with them? Thank you for this project!
hebbert manuel says
Hello pls I am having problems with the simulation of the diagram pls can u help me out with a recomended simulation tool?
Anonymous says
hello . we are not able to connect the relay in the circuit , we have 5 pins in the relays , so which pin is related to the suitable connection , in your figure , there are 4 connections , and we have 5 pins in the relay ??? so please if you could help us to resolve this problem . thank you
Anonymous says
sorry for disturbing you , we are making a project and it's very urgent we need your help . we connected the element of your circuit , but we are facing some problems concerning the relays and the timer . the first relay is active but the second is inactive although there is 0V at pin 12 . and how can the pin 15 generate the signal in order to saturate the transistor . thanks for your response .
linton says
Mr Swagatam, i'm realy instrested in your wireless alarm for my school journal. do you have an email ?
Anonymous says
Mr Swagatam , i have a question : in the circuit below , threre are two NANDS , i didn't understand why you placed two NANDs and not one NAND. thank you
Anonymous says
Hello , is there a way to change the old cellphone you have used to an android phone with no hardware call button?
Anonymous says
Mr Swagatam , I have subsitute the relay coils to the transistors BC547B. But the circuit is always on when tested. Is it the transistor problem? Or you have any solution to it.
Anonymous says
Sir , May I know the voltage output to activate the telephone button?
salman says
sir there is no parts list available for this circuit ?
Swagatam says
Actually I have decided to sell this circuit and therefore removed the parts list, because I think this circuit too good….:-)
Anonymous says
Good day Sir,
I know that your circuit was intended for sale,
but i hope you could still grant a little help Sir,
I was able to build your circuit since last week Sir
my question is how could you able to reduced into 3 pulses since the inputs of the IC produces
2,4,or 8 pulses only.
Thank You Sir.
Swagatam says
three pulses won't be possible with a 4060 IC, you can get either 4 or 8 or 2, meaning in multiples of 2…. you will have to design completely different circuit for it.
Anonymous says
hi sir, I have already started constructing my own version of this gsm based alarm ckt before I saw your website. but i'm still halfway there. I'm only using IC4020. Along the way, I accidentally made a monostable IC4020 ckt, after i mistakenly reversed voltage polarity and shorted certain pin outputs. i'm using this to lock-up the system (preset time is 2 minutes) while in dialling and calling mode, enough to make a successful call, maybe. My question is – can I utilize the dialing & calling mode of the mobile instead of using a preset timer ckt? I utilize the sound output of the mobile as a trigger to lock the system, so as not to receive any interruption from sensor if it has sense another intruder while the system is dialling, but the problem is if ever there's an incoming calls or txt message or auto text from mobile company, such will create a false pulse to lock the ckt.
What signal to utilize that indicates the mobile is still in dialing & calling mode?
any comment sir?
thanks you
Swagatam says
pls show me your circuit diagram, only then I'll be able to suggest my opinion correctly.
uel man says
hi sir, i found out that i can't finish my project using the speed dial because i don't know how to make an IC to produce longer signal enough to activate the speed dial feature of the cellphone. It's because if its relay will switch on the pad on a short pulse, the cellphone will not understand it as a command for speed dialing. Such will only be understood by the cellphone as encoding a single numeric character.
In summary I need the circuit to also produce
1. several short pulses (to reset the mobile to Home menu)
2. then single long pulse ( longer than 4 seconds) to activate speed dialing a number. I understand IC4017 can produce this long pulse, but i don't know how to integrate it to the system, minimizing the use of relays.
Kindly help me.
Thank you
Swagatam says
Hi Uel,
Please show me the entire schematic and specify the points at which you want the long pulses and the short pulses, I'll try to help you out.
Swagatam says
…..you have emailed me the block diagram…sorry that won't be of much help!
vivek says
i want this project for final year with if anyone open my door then i receive a call or sms or alarm on my cell from system send me cost
Swagatam says
you can try making the last circuit shown in the following article:
https://homemade-circuits.com/2011/12/build-homemade-gsm-car-security-system.html
Hafeez k. Hamza says
Swagatam will it be feasible for you to share the parts list for this mentioned project.
Swagatam says
Hafeez, I'll surely try to update it when I'm free…
Hafeez k. Hamza says
Thanks swagatam
Swagatam says
you are welcome!!
hebbert manuel says
Hello pls I am having problems with the simulation of the diagram pls can u help me out with a recomended simulation tool?
Swagatam says
sorry I don't use simulators, so I won't be able to recommend any.
John says
Hi Swagatam,
I want to use 4 x 1.5V batteries instead of a 12V source to make it portable. Problem is I don't think I can get a relay which will operate at such a low voltage. Can I substitute the speed dial relay for some kind of solid state device. I have noticed that touching the copper speed dial contacts with a finger is enough to activate the phone (high impedance/capacitance?)
Swagatam says
Hi John, it can be probably done by using bidirectional electronic switch such as in IC 4066….any other method is not recommended
Anonymous says
Hello Mr.Swagatam .Its a brilliant project.
I had a small doubt.
Where is the +ve terminal of diode D9 connected to? And also one of the terminals of the mobile phone? What actually is 'tone amp'?
Swagatam says
Hello, thank you very much,
Pin#14 of the IC is +Vcc for the IC 4093.
N2/D9 here is an optional connection which can be connected to an external load such as an momentary alarm, etc…since this diagram was extracted from one of the other articles, the tone amp is actually related to that article, you may read it here
https://homemade-circuits.com/2011/12/build-homemade-gsm-car-security-system.html
Manogna Srinath says
Thanks a lot! You were a lot of help!