Build a Homemade GSM Car Security System

This super simple circuit design of a gsm car security system really works. Don’t believe it? Find out and learn the simple method of constructing it.


How would you feel if you had the power of controlling your vehicle through your own cell phone, from any part of the world? Learn more how to build a homemade gsm car security system.

I always wondered how to become rich by inventing or developing an idea that may be simple in design yet breakthrough in its features. Cell phones have always intrigued me for the simple reason that, these gadgets are so compact and sleek in appearance and yet are able to do the monstrous task of sending signals wirelessly across the globe within seconds. One day it struck me – can there be a simple way of exploiting this outstanding feature so that it may be used as a “cell phone remote control” to operate any equipment by just a flick of a button from any part of the planet? Since all the commercial gsm based remote controls use a modem for the purpose so why can’t a mobile phone be used as a modem? Such a “modem” will be easy to acquire, user friendly, low cost and easy to install. Besides, the conventional types of gsm modems are costly, difficult to wire and require special SIM cards and prior intimation to the network providers for it to become functional.
Inspired by the brilliant idea and after a relentless hard work it was a true sitting moment of success when I finally was able to complete a reasonably good, very economical gsm car security system that could not only immobilize a vehicle and do central locking but also send a revert back call to the owner’s mobile phone in case of an intrusion. The system is armed and disarmed through subsequent miss calls from the owner’s cell phone and no call costs are incurred during the process.
Exuberant with the successful venture, I decided to contact relevant companies for the promotion of the unit.
But the news was really shocking. These companies rejected my product saying that the design wasn’t “industrial” and the use of an attached cell phone as a modem was not acceptable.
Very dejected I tried to promote and sell the unit through my friends and relatives, but, the task was uphill since the operation demanded lot of initial investment and after-sales service, so finally, I had to drop the decision.
But folks, there’s a good news, I am ready to share the success story with you all and unleash complete details of this truly  amazing circuit. The circuit is very simple, foolproof, fail proof and mind you it’s already working perfectly in four of the vehicles and in one of the jewelers shops (as a security door lock) since last six months or so.


The Salient Features of the Circuit

Locking and unlocking of the vehicle is done through subsequent miss calls, thus no call costs incurred.
The above operation may be done from any part of the world.
The engine of the vehicle may be stopped even when it’s in motion, from any part of the world.
Vehicle Locked confirmation is done by rejecting the miss call while a continuous ring in the owner’s cell phone indicates that the vehicle has been unlocked.
Any quantity of phone numbers may be assigned into the system’s cell phone so that it responds and can be operated only through these numbers.
A break-in or an intrusion is effectively converted into a revert back call to the owner’s cell phone as a warning.
The device includes a built-in automatic locking system, in case the owner forgets to lock the vehicle.
Prerequisite: A prepaid SIM card to be fitted inside the modem (attached cell phone module)
An entire unit will cost you not more than $80 USD.
Warning: The unit will not work if installed in conjunction with some other form of security system already present in the vehicle.
Let’s move on to know exactly how to build this gsm car security system.

The Trigger Circuit

  As shown in the circuit diagram, the small two transistor circuit forms the basic “beep once” tone amplifier coming out of the headphone socket of the cell phone.
As this ring tone is accompanied with a variety of unwanted glitches or strong RF disturbances, it became very important to stop these from entering the main control circuit. These disturbances could easily rattle the entire circuit and produce bizarre results.
Resistor R18, capacitor C16 and inductor L1 are all included just for the above rectification.
The amplified signal moves into a relay to energize it momentarily as long the tone persists.
The unit’s supply voltage is wired across the relay’s N/O contacts so that when it operates, a logic high signal is transmitted to the main flip/flop control circuit.
The employment of a relay ensures that it is operated only by a genuine ringtone pulse and not by any other obscure stray disturbance emanating from the cell phone (if at all they are able to break into the defenses of R18, C16 and L1).

Related Circuits:

PARTS LIST 

All Resistors are ¼ watt 5% CFR, unless otherwise stated.

R18- 100 ohms,
R19- 22K,
R20- 4K7,
R21- 220 Ohms,
R22- 1K,
R23- 10K
C14- 2.2μF PPC (PolyPropelene Capacitor),
C15- 47μF/25V,
C16 = 0.1/100V PPC
L1 = 40mH, BUZZER COIL, OR THINNEST POSSIBLE COPPER WIRE WOUND OVER ANY FERRITE MATERIAL WITH 1000 TO 2000TURNS.
Relay- 12V/400 Ohms
Diode- 1N4007
T4/T5 -BC547,
T6- BC557

Alternatively, L1 may be retrieved from any standard piezo buzzer…..the example image below provides a clear view of the buzzer inductor:

The Main Control Circuit

  This circuit is basically a Flip/Flop circuit that toggles to alternately produce a stable logic Hi or a logic Lo in response to the input signal received from the above circuit. I won’t go into a detailed  circuit description as the particular circuit has already been discussed in one of my previous articles.
The out put of this circuit is used to activate/deactivate the ignition system and the central locking of the vehicle.

PARTS LIST

All Resistors are ¼ watt 5% CFR, unless otherwise stated.
R1/R7-1M,
R2-10K,
R3-39K,
R4/R5-2M2,
R6-10K,
R8-22E(2W)
C1-100uF/25V,
C2-10uF/25V,
C3/C4/C5-0.22PPC,
C6/C7/C8-33uF/25V, C9-0.1PPC
All Diodes are 1N4148, T1-BC547,
Zener-4.7V/400mW
IC1, IC2 = 4093

The Auto Lock Facility

 The auto lock facility of this gsm car security system may be understood as follows:
Referring to the figure, as long as the output of N2 is high (system in locked position), the auto lock comprising of N4 and N5 is disabled and cannot operate. The moment the output of N2 toggles low, N4 starts counting and after the set period of time (depending on the values of R1 and C1), the output of N5 goes high producing a trigger pulse at the input of N1, toggling it back to the locked position and once again disabling the auto lock. Thus the system can never be kept in an unlocked position for more than the set period. Within this set period of time the owner of the vehicle needs to insert the vehicles ignition key into its slot to stop the auto lock from initiating. Once the vehicle is locked, the ignition key will not work unless and until the system is unlocked through the owner’s cell phone.

The Ignition Control Circuit and the Central Locking Circuit

 As shown in the figure, it is basically a simple relay driver circuit comprising of R24, T7 and T8. T7 and T8 alternately makes and breaks the ignition relay contacts in response to the pulse received from the above circuit. The central locking relay group is also rigged to T1 for a simultaneous operation with the ignition system. Central locking operation is responsible for locking and unlocking the doors of the vehicle (the car).
The central locking machine generally incorporated in car doors is actually made up of a DC motor operated through subsequent positive and negative momentary voltage pulses to alternately lock (push) and unlock (pull) the lever of the door respectively. Keeping this particular feature in mind the present groups of relays and the capacitors have been arranged to result in the above operation.

 Assembled, tested kit available, contact hitman200@live.in 

PARTS LIST

All Resistors are ¼ watt 5% CFR, unless otherwise stated.
R24-15K,
R25-4K7
C18/C17-470uF/25V
T7-BC547,
T8-D1351
D14-1N4007
RL1-12V/100 Ohms/10Amps.
RL2-12V/100 Ohms/10Amps. DPDT


The Call Back Feature

Looking at the circuit diagram we see that the IC 4060 is wired in its basic oscillator mode.
The coil of relay (extreme left) is connected externally to the door switch of the vehicle. In the locked position if the door is opened, the system takes it as an “intrusion”, momentarily activating the relay and triggering a monostable comprising of N6 and N7. As a result the output of N7 instantly goes low resetting pin # 12 IC 4060 and it starts counting. Pin # 2 of the IC goes high after a few seconds and latches itself, but during this particular period of time its pin # 15 produces exactly 4 pulses and is used to operate a relay whose contacts are wired with the call button of the attached cell phone (modem) internally. Therefore the cell phone starts making a call and the owner is immediately informed of a possible theft or a break in.
Now monostable N6 and N7 will release itself exactly after one and a half minutes, until this period of time the entire circuit will be “sealed” and will not respond even to the miss calls from the owner’s cell phone. This feature has been purposely incorporated to ensure that the circuit is not disturbed when the attached cell phone (Modem) is trying to make a call to the owner.

Assembled, tested kit available, contact hitman200@live.in 

PARTS LIST

All Resistors are ¼ watt 5% CFR, unless otherwise stated.
R9-10K,
R10-2M2,
R11-330K,
R12-4K7,
R13-39K,
R14-1M,
R15-1K,
R16-330E,
R17-1K
C10/C12-100uF/25V,
C11-0.001uFDISC,
C13-47uF/25V.
D9/D10-1N4148,
D8/D11/D12-1N4007
T2, T3 = BC547
IC2 (N6,N7,N8)-4093
IC3-4069
Relays-12V/400 Ohms

The Call Rejection Feature

Another relay driver circuit as shown in the above figure takes care of the “call rejection” facility. When the system is locked through the owner’s miss call, a pulse is sent to the base of the driver transistor which operates a relay momentarily. Now since the contacts of the relay are wired across the “cancel” button of the attached cell phone (Modem), the received call from the owner’s cell phone is immediately rejected and a “network busy” is indicated in the owner’s cell phone confirming that the vehicle is securely locked.

How to do the Internal Wiring to the Modem Cell Phone

The internal wiring of the modem of this gsm car security system may be understood as follows:
You will have to do this part of the wiring very carefully and if you are not crafty enough, things can get pretty messy and spoil the whole “game”. It would be better if you took the help of some mobile phone technician to complete the following operations:

It goes without saying that the outer cover of the cell phone is to be removed and also the inner metal mesh which is used to shield the keypads.
Carefully and very slowly peel off the keypad sticker and keep it in some secured place for later use.
You will find the embedded keypads exposed. But the sad thing is that the pads aren’t solderable, therefore the external wires from the relevant relay contacts cannot be attached to them through soldering. So the only possible way is to fix the relevant wires by sticking there stripped ends to these keypads and let the keypad sticker and the metal mesh frame do the rest by firmly pressing these wires against the keypads to make a reliable contact.
The wires used may be the thin insulated ones, typically used to wire piezo transducers or simply a 36 SWG super enameled wire will do the job quite nicely. Do not forget to “tin” the stripped ends of the wires so that they make good contact with the keypads.
Also remember to remove the small disc shaped metallic contacts in the sticker from the points which correspond to the cancel button and the call button. After this you may replace the sticker carefully back in its position so that it secures the connected wires further in there places. Go on to fix the metallic wire mesh and screw it firmly to complete the “modem” assembly. The outer most plastic cover is not required, so do not try to replace it.
This modem assembly is now ready and can be connected to the main circuit after the whole circuit assembly is over.

The Charger Section

The charger section of this gsm car security system utilizes a regulator IC 7805 and a current limiting resistor. It is connected to the cell phone modem permanently and is used to trickle charge its battery. There’s no danger of overcharging the battery as every Nokia phone has a built-in self regulating automatic cut-off circuit.

Setting up the Attached Cell Phone Modem

Once the entire circuit assembly and all the connections are completed, the above cell phone modem may be set up through the following simple steps:
Insert a pre-paid SIM card into the cell phone (Modem),
Switch it ON the by short circuiting its “cancel button” wires externally using a piece of conductor. Since the keypads no longer exist, this is the only way to switch it ON.
Save the mobile phone numbers through which the unit would be operated.
Go to the name section of all the above saved numbers – press options – Assign Tone – Select No Tone.
Next, go to settings – Tone settings – Select empty (default ringtone switched OFF). Similarly set the tone for the messages in the OFF position. Also switch OFF the keypad tones, warning tones and the start-up tone by selecting the relevant commands.
Finally, make a call through this modem cell phone into your cell phone by shorting its call button thrice externally using a piece of conductor, so that now the Modem “knows” exactly where to call back once a theft is sensed and will always call you back on this particular number every time the door of the car is opened (only when the system is in locked position).
The Modem is now set perfectly and ready to use.

How to Test the Unit?

After concluding the whole assembly procedure as explained in the whole article, you may test this outstanding gsm car security system through the following simple methods:
Connect a good quality 12 volt regulated power supply to the circuit,
The cell phone modem should immediately read “Charging”, indicating that the charging process has initiated and is working perfectly.
Connect small 12 volt motor to the “central lock” outputs of the circuit.
Start dialing the SIM card number, the moment your call hits the cell phone Modem, you will find the relays operating accordingly and the connected motor reverses its direction of rotation alternately on every subsequent calls made. This confirms that the central lock section is operating perfectly and also the entire circuit.
Check the continuity of the ignition section using a DMM. It should make and break on every subsequent calls made.
Similarly you may connect a horn (siren type) at the alarm output to check the relevant section. The alarm should sound for a moment and stop at each and every received call by the modem.
In the locked position (ignition relays in deactivated position), ground C10/R9’s common point as might happen if the door of the car is opened (intrusion). The modem should immediately start calling the stored number and you will receive a call in your cell phone – the call back facility is working.
The above steps should be enough to confirm the correct operation of the system and you are all set to fix it in your car and actually witness the amazing feats.

267 Replies to “Build a Homemade GSM Car Security System”

  1. Anonymous

    Let me first commend you on having your own site. Ithink its great. However Ihave attempted making this sircuit on several occasions and on these occasins the tone amplifier circuit would just latch and not turn off. The only difference is that I cannot use the BC 557 Transistor you suggested because it is not available on the soft ware program Iam using Iam only able to use a NPN TRANSISTOR iWOULD CERTAINLY appriciate your sugestion to correct this situatiion

    Reply
  2. Swagatam Post author

    Hi,
    Thanks!

    The circuit has to be built exactly the way its shown, otherwise it may not work.
    In place of BC557 you can use any other PNP transistor like 8550, 187 etc.

    Reply
    1. Anonymous

      1. Your sugestion worked perfectly using my software program.However the difficulty now is that when it comes to building the circuit. Thus far Ihave opened up three radio shack buzzers the last one was a 6vDC Mini Buzzer and from what I am seeing they are definitely unsuitable. Could you be a bit more specific and give the manufacturer and any other specs. on the buzzer. Also if an inductor coil can be used please indicate a supplier and specs on the inductor in order for me to source one.
      2. Iam an amature in electronics. But can an IC CMOS 4017B decade counter being driven by a 555 monostabl timing circuit be used. All I need is three relays to operate sequentially in order to lock the car doors and shut the car down.
      3. Would using a decade counter not simplify matters and have several operations take place in a sequence whenever the circuit is triggered. From my perspective just looking at that control circuit with the IC 4093 it certainly looks complicated and challenging for an amatuer

      Reply
    2. Swagatam Post author

      Yes, that's possible but then you will have to provide three separate calls (commands) one after the other for implementing the three actions sequentially.

      Reply
    3. Anonymous

      Hi
      What is the inductance of the buzzer coil that buzzer coil is difficult to obtain.
      I may have to end up just buying an inductor coil. What other device uses a similar coil.

      Reply
    4. Swagatam Post author

      Hi,
      I don't know the value actually…..I had used a ready made one and it worked very well. In India the relevant buzzer coil is available plentifully at a very cheap rate.
      The referred buzzer coil is specifically made for buzzers, and used only in buzzer circuits.

      Reply
    5. IB-Mukhtar

      Hello brother, This work of yours really looks grate and I want to give it a trial. What I really do not understand is the call back and call reject circuit. I want to know if it requires codes to work. Thanks a lot.

      Reply
    6. Swagatam Post author

      Hello Mukhtar,

      No it does not require any code, it simply responds to the "missed calls" and automatically triggers the respective actions.

      Reply
  3. Anonymous

    hi, I'm from Indonesia and very interested with your project. its the great project.I try to make a call reject circuit like your diagram. and I try to conect the input (c13) to + (12 volt) trough 1k resistor. I think it should be make a momentary contact in relay even the input still connect to + . but why in my circuit the relay is contacted permanently as long as the input connected to + ?
    thanks for your answer

    Reply
    1. Swagatam Post author

      Hi,

      Thanks!
      C13 positive should be connected to the collector of T8, check your capacitor, it might be faulty, because adding a capacitor at the base of a transistor will activate it momentarily and cannot keep it triggered permanently….

      Regards.

      Reply
  4. Anonymous

    ok Mr. Swagatam,thanks for your answer. I'm checking my circuit just now. and I change the capasitor with the same value. it works…thanks. I don't know why…because I check the old capasitor, it's ok…

    I do the experiment inspired by your project. I want to try to make a remote gsm. but I want to make a modification in auto reject circuit section. I want the reject action when turn on much longer than the rejection action when turn it of. so it can be a "code" for user whether the unit remotely is on or off.

    so, I want to add the delayed circuit to make this.
    what is your opinion ? can be made like that ?

    Tank you very much..n sorry my english is bad

    Reply
    1. Swagatam Post author

      Hi,

      You can choose the relay contacts as the inputs for triggering C3, for example N/O for OFF and N/C for ON.

      C3 should not be connected to the base of the transistor, rather two individual capacitors should be connected to the above relay contacts.

      The positives of the capacitors goes to the relay contacts and the negatives are made common and connected to the junction of R16/R17.

      One of the capacitor should be of higher value and the other one of lower value.

      This should make the reject relay produce different delay periods for switch ON and OFF of the T8 relay.

      Regards.

      Reply
    2. Anonymous

      Hi bro,
      can u plz explay, a)what relay should I put in order to get this code, another one or the same used to cancel button(?, b)where are the wires of the "cancel" button going to be connected to? also, c)u said that c3 should not be connected to t3 so I have to remove it?. d)the negatives of the relay go to ground and same time r16 and r17 how is this sir? e) what value do u recommend me to use the two capacitors?

      Thanks in advance

      Reply
  5. Anonymous

    Hi Swagatam

    congrats for your new blog,how ever it seems to be not so easy as it was with previous site.I have asked for some more circuit that can be controlled with mobile.Kindly publish more projects.
    Thanks & regards,
    MOHIT PARIKH

    Reply
    1. Anonymous

      helo sir i sunil kumar from jammu sir i want to make GSM based mini ckt using mt8870 dtmf to operate relay and i control solenoid valve for bike security system.

      Reply
  6. Anonymous

    Good Day toYou
    Mr. SWAGATAM

    Just two brief questions

    1.Ican recall reading on someone of your blogs where you mentioned that the BEEP OUNCE RING TONE can only be used on the older model Nokia Phones. What is the alternative to getting your GSM Alarm to work with a Mobile Phone.

    2. Following up on what Sunil Kumar just said how can your GSM ALARM be alternatively be made to work using a DTMF decoder / Pic Microcontroller. Iwould certainly appriciate your responce on this. Probably this might solve the problem of using a Mobile Phone with a Beep Ounce ring tone.

    Reply
    1. Swagatam Post author

      Hi Good day to you,

      The circuit was designed with the given "beep once" feature of NOKIA phone, I haven't thought of other compatible options yet.

      The DTMF based system incur call charges for the operations I guess, so the idea is not very good according to me.

      Thanks and Regards.

      Reply
    1. Anonymous

      hi swagatam
      please do u know a site or have a circuit diagram of a gsm car alarm system that uses an internal moderm and that can send sms, call the owner's cell phone and also disconnect the car engine when stolen?
      Thanks.

      Reply
  7. Mohit

    Sir, This is Mohit Nagpal from Madhu vihar Patparganj New Delhi
    I Am intrested in buying ur circuit
    kindly contact me regarding that

    Regards

    Mohit Nagpal
    Contact Number #9990592348

    Reply
  8. Engr. MUHAMMAD IQBAL SIDDIQUI

    Hi swagatam,
    its IQBAL . and i need ur help to make a simple circuit , i have no idea to make it . i have a hydraulic plate bender and its controller circuit is very complicated and got busted. and i want to make it new which should be simple in construction . i have tried with 555 but didnt succssed , so do help me .
    it has a function to bend the sheet only . and it includes sensors . it has only 3 steps .

    1 . in steady state position or at zero position by sensor 1
    2. when we push the button blades moves downward and has to stop 1 inch before banding the sheet (with the help of sensor 2) for confirm our target of bend.
    3 . by pushing button again it has to bend the sheet for certain limit which is fixed by sensor 3 and has to go back its zero position and stop by the help of sensor 1.

    you can also send me mail on my id
    siddiqui.engineer@gmail.com

    i hope u will easily made this . please send me this on my id . thanx

    Reply
    1. Swagatam Post author

      Hi Iqbal,

      This circuit can be a bit complicated, but I'll try to design it.

      The concept is not difficult however making it practically happen will need some thinking.

      If I am able to finish the design I'll surely inform you.

      Thanks and Regards.

      Reply
  9. Anonymous

    Hi
    Its me here again due to the problem Iam having to sourse a buzzer coil for the alarm circuit. Could an alternate circuit using an op amp be used. If not could you explain. However if it can be used can you provide a circuit diagram for it.

    Thanking YOU
    Bo

    Reply
  10. Anonymous

    This is to seek your valuable help for furnishing the" Homemade GSM Car Security System Circuit" which I've chosen for my Major Project to be submitted next week.

    The layout of all four circuits(Mailed) is completed but having difficulty in interconnecting the circuits as listed :

    1.I will be deploying a self made power supply for output of 12V, 5 V & grounding, but how do i extend them to all 4 circuits (requiring earthing, 12V, 5V respectively)as that amount of wiring will be messing using 2/3 pin connectors.

    2.Control Ckt. Difficulties :
    a) Four IC's (IC 4093) are used,do each require separate 12V on pin 14 and grounding on pin 7?If so then again the wire mess?
    b) Where are C8,C9 connected to IC1?
    c) Doesn't D7 connect to Call Back Ckt. rather Auto Lock as shown in your diagram?

    3. Auto Lock Ckt .Difficulties:
    a)Three Relays are used here ,but where are NC/NO of Relay3(RL3) connected,to Central Lock or to Reley 2(RL2)?
    b) If so,where are C17,C18's positive terminals connected?
    c) Is R24 to be connected to D7 of Control Ckt as shown in diag. ?
    d) From where Call Reject ckt is to be connected to this ckt. as shown in diag?

    4.Call Back Ckt. Difficulties:
    a) Isn't IC3, 4060 rather than IC 4069 as stated in parts list?
    b) Where is C13 to be connected?
    c) Where exactly is the Mobile to be connected to Tone Amp Input?
    d) Also confused about 5V from Control Circuit to Mobile Unit

    I request you to kindly empower me with your valuable suggestions in furnishing the important project.

    Thanking you in anticipation.

    Reply
    1. Swagatam

      1) make all the +12V points common and connect it to the power supply 12V, do same with the +5V points. Make all the negative or grounnd lines common and connect with the supply negative point.

      2) Only two IC4093 are used (8gates), pin14 of both the ICs should be connected to the +5V point,and pin#8 to ground.

      3)C8/9 are connected to pin14 of the IC1
      D7 is correctly assigned in the diagram.
      RL3 is DPDT, joined contact is N/C, N/O goes to central lock.
      C17/18 connect to the poles of the relays
      See and connect the blue circle for R24
      From D14 to Call reject input.

      4) Yes IC3 is 4060
      C13 to D14
      Mobile headphone output to Tone Amp input
      Connect R8 to mobile charging input for keeping it charged all the time.

      Reply
    2. Anonymous

      Hi Sir,
      In a car, where/how could i get the 5 volts supply for the circuit wherein i well connect pin 14 of both IC's as you mentioned?
      If i where not going to use the circuit in a car, meaning i have to use two separate power source one for the 12v and another for 5v inputs. am i right Sir? sorry i was confuse with the TONE AMPLIFIER CIRCUIT DIAGRAM showing a +5v connected to N/C pin of the relay. Thanks for your guidance Sir.

      Reply
    3. Anonymous

      Greetings!!!
      Sir in "THE CONTROL CIRCUIT" it is possible to connect the supply pins of the two IC's to the 5v output of 7805 IC which is use to charge the modem phone? or can i accommodate another addt'l. 7805 IC to the circuit for this purpose?

      Reply
  11. Anonymous

    Thanks for clarifications.
    Few doubts thereby arise as follows:

    1. Ignition control ckt:

    a) As both RL2 and RL3 are DPDTs, so kindly specify the complete connections of poles, N/Os, N/cs of each relay.

    2. Control Ckt:

    a) As I've used 4 ICs 4093 instead of 2, due to wiring issues, so which pins to connect to the ground and supply.

    Thank you

    Reply
    1. Swagatam

      1)
      a)The two white circles are N/C and N/O points, the central black pole is the movable contact.

      2)
      a)pin#14 will go to the positive +5V, pin#7 will go to negative or ground. Make sure all the unused gate inputs are shorted to ground.

      Reply
  12. Anonymous

    Sir the question is a bit misunderstood so I frame them again clearly:

    * In the Ignition Control Circuit and the Central Locking Circuit three Relays(RL1,RL2,RL3) are used:

    1) Are RL2 & RL3 each DPDT?

    2) If so the ckt. shows 6 white dots and 4 black dots surrounding Relays RL2 & RL3.Please specify connectivity of these 10 dots each clearly.

    * As I would not be physically connecting this project to a car so:

    3) In Call Back & Call Reject Ckt instead of Car Door Switch where do i connect R9 as shown in ckt.?Should ground them?

    4)In Control Ckt.:
    a)Where does R2 Connect?
    b)Where does D6 Connect to rather than Car Battery?

    Thanks a lot for clarifying all the issues.
    It has helped a lot.

    Reply
    1. Swagatam

      RL2 and RL3 are both DPDT.

      There are total 8 white circles, two can be seen connected with the central lock wires.

      RL2 black dots are joind with RL3 black dots, these junctions are also connected with RL3 coil.

      eplace door switch with a push button, presing it manually would activate the corresponding relay. one end of the push button should be connected to ground.

      When R2 is connected to (+) the IC 4093 gets disabled and will not respond to any calls.

      D6 to positive of your power supply

      Reply
  13. sharan.

    SIR,
    IN YOUR GSM BASED CELL PHONE CONTROL REMOTE SWITCHING CKT CAPACITOR C1,C4,C5 IS 0.22UF DISC TYPE MY QUESTION IS 1) IS CERAMIC CAPACITOR OR POLYPROPLANE 2) NEAR CURRENT IC 7805 OUT PUT RESISTANCE VALUE NOT MENTIONED

    Reply
  14. Anonymous

    DEAR SWAGATAM
    Thanks FOR YOUR CONTINUES SUPPORT TO ELECTRONIC ENTHUSIASTIC AND HOBBYIST.PLEASE PUBLISH GSM MOBILE PHONE BASED CONTROLLING CIRCUIT FOR ON AND OF APPLIANCES WITH SMS OR CALL MAKING
    REGARDS,
    MOHIT PARIKH

    Reply
  15. Bruce B

    Hi Swagatam,

    Great article.

    Would it be possible to attach a DC motor in the mix to be powered by the phone when needed? My project requires the motor to turn when a call is received or SMS is received. You think your kit can help me?

    Thanks

    Reply
  16. sharan.

    Mr swagtam
    I WANT TO FIT THIS CKT TO SHOP SHUTTER PLEASE GIVE ME IDEA HOW CAN I FIT THIS CKT & I DON'T WANT TO MAKE RELAY DRIVER CKT CAN WORKING THIS CKT ON CAR DOOR SWITCH I WANT TO FIT CAR DOOR SWITCH TO SHUTTER. PLEASE TELL ME

    Reply
  17. Anonymous

    Hi Swagatam

    This is a reminder to you for my comment on 23rd Nov 12 for GSM based mains device control circuits !
    Regards,

    Mohit Parikh

    Reply
  18. Anonymous

    hello I like ur proyect. can u please tell me what transistor can use instead of t8 (d1351) 'cause where I live, there's no that kind of transitor… they told me that i might use nt152 transitor but they dont have it either. so I'm kind of stuck.

    regards

    Reply
  19. sharan.

    Mr.SWAGTAM
    IN THIS CIRCUIT IC 4060 PINS 1,3,4,5,6,7,8,13,14,16 NOT VISIBLE PLEASE TELL ME WHAT POSITION OF THIS PINS & WHERE TO SUPPLY CURRENT TO THIS IC THANKS

    Reply
    1. Swagatam

      Mr.Sharan,

      except 16 and 8 all other pins are not used in this circuit therefore not shown. Nothing should be connected on these pins except 16 and 8.

      16 is the positive, will go to the +5V, and 8 is the ground.

      Reply
  20. Anonymous

    hello mr. swagtam.
    I have a problem. I dont know how to connect the headphone to the amp ckt imput, cause the headphone has 2 wires. One would be connected to the amp imput and the other one where would be connected?

    another thing, in the control circuit, where would R2 be actually connected to? it says 12v suppy after ignition, so has to receive 12v exactly when ignition has started?
    thnks for your help!

    Reply
    1. Anonymous

      thnks very much mr. Im trying to make it work but still nothing moves at all, I connected everything the way it is, I dont know if its the power supply that doesnt support all the circuit and I have to put 2 power supplys, one of 5v and the other one 12… its pretty weird I have tested some good 12v power supplys and the phone dont even get charged, I used a DMM to check the 7805 output and no reading. also have tested the 7805 alone and now works, just when it is with the circuit doesnt work. I really appreciate ur help.

      BTW I bought a special relay for cars DPTD(supports high current) (just one) because I thought I would have had to connect the circuit to a battery car, which have a lot of current. Is ok If I use it in the circuit?

      regards

      Reply
    2. Anonymous

      good day mr swagtam
      I dont know how to set up my nokia phone ir order to get the ring tone on the headphones ir order to do this project, cause I connected it and the ringtone sounds by the speaker of the phone. my model is nokia 1616 its a good phone and allows me to assign tone. but only thats the problem. could u help me out

      greetings

      Reply
    3. Swagatam

      It will be difficult for me to diagnose the problems without seeing it.
      One thing I can say, that you should check the stages separately with the help of the given explanations, and join them together only once they all work as expected from them.

      Regards.

      Reply
    4. Swagatam

      After assigning the tone to a selected number you should put the default tone to empty.

      It doesn't matter if the ringtone sounds from the speaker, the tone will be also produced from the headphone socket and will activate the relay.

      Reply
  21. Anonymous

    ok thanks for ur, it worked almost perfectly, only the call back feature. I have to check y the other features dont work. thks for ur help ._.!

    Reply
  22. Nour Ahmed

    pleas i need a circuit that have a led matrix (Multidisplay)
    so can you help me pleas ???
    pleas leave me tell me if you intend to help
    if not its okay cuz u have a treasure of circuits her ^_^

    Reply
  23. Anonymous

    This is to seek your valuable help in the following mentioned problems:

    Autolock ckt problem:
    1. As I will not be employing this ckt to a car, so what do I attach instead of ignition to the pole and n/o of relay 1

    Control circuit problem:
    2. From R2, what do I connect instead of '12 volt supply after ignition'

    Reply
    1. Swagatam

      You may remove RL1/D14 entirely.

      A positive supply at R2 keeps the auto lock operation inactive, if no supply is present here, the circuit will go in autolock mode after the set time has elapsed, whenever the lock is in open position.

      If you don't want this facility remove all that's on the left of D1 and also remove D1.

      Reply
  24. Anonymous

    Thanx 4 the clarification.

    Mobile connecting issue:
    1. I took the mobile to the technician for the connections to the mobile. He soldered the rings and the phone got disabled. Now I m using another phone. What adhesive should be used to make the connections.I have tried fevicols, electric tapes etc, but none works. Can fevi quick be used?

    Tone amplifier ckt issue:
    2.All connections to tone amplifier are complete, but when the call is made to the cell phone which is connected to the head phone, the relay's pole does not switch its connection from n/c to n/o? Hence the 5 volts appears at n/c. How to sort it out?

    3. I have used 12v/100 ohms relay. Can it be used, coz 12v/400ohms relays arent available.

    Autolock ckt issue:
    4.If relay 1 is used, and not removed, what can be connected instead of "to ignition"?

    Reply
    1. Swagatam

      The wire ends should be nicely tinned and placed over the relevant keypad points, then very gently and skillfully the white sticker should be firmly replaced over the connection.
      The wire portion which just comes out from the sticker edge should be immediately glued with cynoacralite kind of bond, making sure the glue does not enter under the sticker. When it dries the portion may be further stuck with any two-element epoxy.

      The tone amplifier will work only with a 1208 NOKiA cellphone.

      12/400 Ohm relay is only recommended, others may not respond.

      Go stage wise….first make the tone amplifier work then proceed to other stages.

      Reply
  25. Anonymous

    Good evening Sir.

    Thaxs for a great design. I designed my circuit with DTMF and it is expensive. I am in the process of studying your design and i noted that you Talk about "R18,C16 and L1" I could only found "R18",can you please explane C16 and L1. I allso noted that L1 caused some questions. Looking forward to your repliy.

    Regards

    Reply
  26. yaseen

    dear sir

    i have made PCB and assemble this circuit, i Found that if intrusion made then call back, Suppose during call back network is busy then this circuit does attempt to second,third time.

    Reply
    1. Swagatam Post author

      Dear Yaseen,

      Yes it will only call-back once, if the network is busy then the owner will not get the alert.

      We can upgrade the circuit by adding another timer section such that the circuit activates and calls many times at intervals of a minute or so.

      Reply
  27. yaseen

    Dear Sir.

    Good morning.thank you very much for suggestion.please guide me how can i add NE555 timer in this circuit for calling every 1 minute and how to make acknowledge for stopping the call back function.further guide me how can i replace intrusion contact(door lock switch) to a touch system.if any body touch the nickle parts then call back system became active.all body of the vehicle is grounded so please guide me .

    Reply
    1. Swagatam Post author

      Dear Yaseen,

      I am sorry, presently it won't be feasible for me.

      All these will be quite an elaborate design which will be difficult for me to explain and draw immediately here.

      I may consider it in the near future and might update the article accordingly.

      Regards.

      Reply
  28. Franz Asoka

    Dear Mr.Swagatam Majumdar
    I saw your circuit diagram "How to Build a Cell Phone Remote Control Circuit.wmv" in following site "http://www.youtube.com/watch?v=6yVv8GJ-3gk"
    according to that video I log to the following page "Avenuesound.com/viper-vss4000.html" there I saw your complete circuit diagram, I found link there named "Parts list has been enclosed HERE" but I couldn't be able to get that part list!!!
    Mr.Swagatam Majumdar can you help me to get that part list?
    my mail address is lokuwelasoka@gmail.com

    Reply
  29. Anonymous

    Hello Mr Swagatman
    thanks for your Ideas and Circuits

    Plz i want to know Ic1 & Ic2 & IC3 Also Can I use TIP31 instead of D1351

    thankx

    Reply
    1. Anonymous

      Thankx man
      i finish the circuit but it is not completely work when open the door all is ok the modem call me but when i call the modem nothing happend i look many times for the tone circuit and Rejection circuit but i did not find error only the Diode D9 in the tone circuit have a direction bot like in the call back circuit i try the 2 dircation of the Diode but nothing happend
      plz told how i can test the tone an rejection circuit

      Reply
    2. Swagatam Post author

      when the modem calls to the owner, the circuit gets latched for 2 minutes, so you cannot call the system immediately within these 2 minutes..wait for 2 minutes to lapse and then you can call the system for unlocking.

      Reply
    3. Anonymous

      sorry man , but plz told me the direction of Diode D9
      and also C14 i found only 2.2 uf/400 Volt and the circuit did not feel by the call tone
      thanx

      Reply
    4. Swagatam Post author

      The direction which is given in "tone amplifier" is correct, the other direction at the output of N8 is wrong, it's a mistake (double D9 symbols).

      As mentioned in the article, only NOKiA1208 will work here, no other models will work….which model you have used??

      Reply
    5. Anonymous

      hello man,, my nokia is 1209 and i chose tone is beep one

      Also i use Ic1 & IC2 CD4093 IC3 is 4060
      also if u can told me the steps of order action
      i have no 10 days for try to find the wrong
      thanxs

      Reply
    1. Anonymous

      Thks 4 ur answer Ok but u have it in order to print it? In the computer format? Could send it to me Id appreciatte it so much.cause 4 me its kind of difficult to desing the lines & everything un order to put it on a board. I dont want to mess up the components. I have the circuit still on a breadboard.
      Regards

      Reply
    2. Swagatam Post author

      I have ready PCBs with me, the computer design is deleted long ago…even if I had the design it would be entirely impossible to trace out the parts positions over the PCB for others, because the component side is not printed.

      Regards.

      Reply
  30. Anonymous

    Hi
    Pls Mr Swagatam
    I want to use this your wonderful project to present my final year project can u realy assist me in time of defficulties and can this project be assembled only in a car because its going to be a school project,and I can't give the school car.
    And also is there any write up for this project. Thank you so much I realy appricaite your hand work, its people like you we need in this world.
    Please I await for your response,its ulgent thank u.

    Reply
    1. Swagatam Post author

      Hi,

      Thanks you very much!

      I have provided everything I could in this article,,beyond this it is difficult to contribute further.

      This project is quite difficult, not for the newbies, so please be cautioned if you are intending to build it.

      I can assist you, but only to an extent.

      Regards.

      Reply
  31. Anonymous

    Hello Mr Swagatam,,

    this the second time i make the circuit but not completely work , if u have a layout you tasted it before plz send it to me, or plz say to me the sequence of the circuit work

    my email : Future0124915305@yahoo.com
    thanks very much

    Reply
    1. Swagatam Post author

      Hello Mr.Future,

      Build the explained stages on separate boards, test them separately, and then integrate them together.

      Everything is correct in the diagrams, and all's been tested thoroughly, so it has to work.

      Regards.

      Reply
    2. Anonymous

      thanx man i will do this only with tone circuit i will make every circuit in a board i hope i have some luck

      also may be i did not understand exactly the steps of calling and when it reject the call i try again thanks for ur help

      Reply
    3. Anonymous

      Hello man i make ur old tone circuit it is work without Coil and i make many coils ,, if i use any coil the tone circuit not work
      i did not understand why, the circuit now need only some for exactly work so Plz told me the steps after i connect it with the door switsh and Power when i open the dower it is call me but the Igination relay some times work some times not and also all times after this when i call the car told me busy reject the call .
      thanks for ur help

      Reply
    4. Swagatam Post author

      hello, the coil is very important, without it the circuit will tend to get activated without any reasons, anytime.

      I cannot diagnose the problems because my circuit worked perfectly…it will be difficul to assess without checking practically.

      Reply
    5. Anonymous

      same happens with me, the circuit will not work unless I take the coil off. so weird. everythinh is exactly as in diagram… I had to make my own coil cause here there's nobody who sells that kind of things… they have everythin exept coil. I made mine with a piece of copper with a hollow, and give it approx 120 turns of thin wire enameled.

      I cant also make the control circuit work once the signal of 5v comes from the amp tone ctk. I wonder if the direction of D4 is right. I checked it with the multimeter and it says that 5v doesn get to pin 1 and 2, it gets stuck before C5 and doesnt allow the ckt to make the binary thing of the gates. so when I call it just activates the amp ckt relay but nothing else, nither the door locks. what it works perfectly is only the call back feature. could u please help me? everything is exactly how its on the diagram,, I checked it alot of times.

      Reply
  32. Anonymous

    Hi Mr. Can u pliz explain me what has to do c15 in the amplifier circuit. Another thing. Doesn't the relay of such circuit be always activated because of the capacitors and buzzer that are connected directly to 12v. Cause a positive supply would be applied always at the base of T6 & would not turn the relay on exactly when the crkt receives our call.
    Btw I don't get how the buzzer and c16 will work.
    Id appreciate ur help

    Reply
    1. Swagatam Post author

      L1 is not a buzzer, it's an inductor (coil) which are commonly used in piezo buzzers.

      everything's right in the circuit, you can make it and check it.

      Reply
  33. Anonymous

    hello, mr.
    Im havin problems with the control ckt, in the ic1 says that 12 and 13 are connected each other, and then another line comes from above, that is conected to the output of 7805. what pin is this?????? the same happens with ic2, another line comes from below going directly to ground.

    Reply
  34. Anonymous

    Hi. Im trying to make the amp ckt work but the relay doesnt do anything when I call the modem. What I do is turning on the power supply & then I hear the relay of the door locks turning on. After that I call the number and doesn turn the respecting relay. everything is connected exactly the way u said. I wonder about the polarity of c15. The buzzer coil I made it the way u said it. 120 turns of very thin copper wire over a ferrite material (a screw).

    Reply
    1. Swagatam Post author

      Hi,

      You will need to check and complete the circuit stages-wise.
      Disconnect everything from the tone amp output and first concentrate on this sage.

      You can try making R18 = 100 Ohms, this might help, please do it and check.

      C15 polarity is correct in the diagram.

      Reply
    2. Anonymous

      Hello ,, sorry for man questions what r u mean by 12 Volt after Ignintion

      idid not undestand this and what r you need this

      Reply
    3. Swagatam Post author

      when you self start car ignition, your car interior gets a voltage for activating stereo, AC, roof lights etc…..that voltage is referred as the "12V after ignition" in the article.

      Reply
    4. Anonymous

      Ok I got what u said about the amp ckt. I hope it works. i hope also that the problem is nothing related with the transistors . U think they couldav got messed up because of not having the coil & the c16? It worked at first but suddenly didnt do anything.
      Thks in advance

      Reply
    5. Swagatam Post author

      the coil and C16 are for filtering the occasional unwanted RF disturbances, even without them the circuit should work….check the cell phones output signal, it should be at least 100mV for making the circuit work.

      Reply
  35. Anonymous

    Hello Man the circuit i working now but i habe a problem i can't have pure tone and i use many coil and make by by hand many also so if u can told me the write way for make the coil or the Resistance of ur coil
    thanks

    Reply
    1. Anonymous

      Hi man wasup.
      I could finally make the amp crkt work but I used the other crkt u specially made for activating a load via gsm that was in another article. The thing is that I put everything as it was said there except a resistance of 100 kohms, I put just 10kohms. I don't know if that makes the crkt function different but I had to take the coil off in order to make it function I just left the capacitor u mention in this article that'd be of .1uf so that it doesn't have problems with RF disturbance. I don't know why but the relay doesn't get activated unless I take the coil off. What would the best in order to function as it should. I'd appreciate ur help very much.

      Reply
  36. Anonymous

    Hi
    Could I put a led on the emisor of t8 so that when the system is in locked position the led goes on and can tell the status of system. do I need to put a resistence or something before the led?? Another thing, ignition would be connected to the nc contacts of the relay RL1 or to the NO contacts??? I need help in these to things. thks

    Reply
  37. Anonymous

    Hi
    One important question,
    What can I use instead of inductor L1 cause where I live theres no that value of coil. I got a 100uH instead of 100mH as you mentioned. would that one work????????
    Also my software tells me that in order to make a coil with inductance of 100mH I have to give 4000 turns, not 100 to 200. That would be a 100uH coil.
    Plz help me. Ill appreciate

    Reply
    1. Anonymous

      finally I worked, but I had to collect several coils to sum 100 ohms, it work perfect.. tks. Im just havin' problems with the control crkt… I had checked it a lot of times and the same, even I make it in computer with livewire to see it work but no success :L

      regards

      Reply
  38. Anonymous

    hi mr.
    thks for ur help,
    I wonder if u could help me in this, in the relay assembly t8 is always on because is connected to 12v through a resistence (R25), and is turning on the relay 1 always, without the pulse of control circuit. so when the pulse comes it does not do anything… what can be done here??? if u give 5v always to base of a transistor the transistor will be always on, passing current from C to E. Tks 4 being willing to help

    regards

    Reply
  39. Anonymous

    hi mr
    finally the circuit worked, but the problem when I call, on every tone the phone will turn on and off, and it was supposed to stay on a mode and then the circuit should reject the call. but the circuit turns on and off like 4 times in a just a simple call. it should stay in the same mode right for every call right???

    Reply
  40. Anonymous

    Hello sir
    It works good but what is not doin well is the call rejection, the relay with the cancel button turns the phone off. the relay doesnt discharge quickly so it turns it off. Id say it never discharge. I changed capacitor and the same. Plz helpd me sir, id líke to make it work

    Reply
  41. Anonymous

    Good day sir!
    I wanted to know if u could help in this issue. The relay of the call rejection ckt doesnt get desactivated and turns the phone, because the same button of "hang" is the same for turning off. when I call to the ckt t8 gets activated and the this relay is always on… even if I call again it wont turn it off…

    Reply
  42. Anonymous

    hello man
    what position should the system be in at the instant when I connect the main power supply??? b)if i put a led on t8, would the state of on mean that the car is locked? c) n how long would the crkt stay unlocked for, so that it turns locked?

    Best Regards

    Reply
  43. Anonymous

    hi mr swagatam
    sorry for my question, but, could I take off n8 and connect pin 2 of 4060 (c3)to d9?? waht do u think? I said this because I analized everythin and I see that that gate is making the low output of n2 be high to 5v and blockin the amp ckt… I noticed from the beginning pin 2 is low, so it wont allow the ckt amp to get activated.
    pls consider my concern abot this issue
    Regards

    Reply
    1. Anonymous

      please could you help me out in the thing of changing the call reject ckt in order to make a code to know whether the system is on or off when we call??? I dont understand
      Best regards Mr Swagatam

      Reply
    2. Anonymous

      but u mentioned we could make it by adding two capacitors and a few things ir order to make the reject relay produce different delay periods for switch ON and OFF of the T8 relay…it was somebody who ask on April 1, 2012 at 1:27 AM.. I just dont understand well what u told them. Id appeciate if u could explain

      Reply
    1. Anonymous

      is it necessary to put the relays of 10amps on the relay driver. can two of them be standard, and just one of them 10 amp… what about the rest of the ckt, will it work well with the current of the battery????

      Reply
  44. Anonymous

    Hello Sir,
    In the tone amplifier circuit, where should i connect the 5volts supply that is connected to NORMALLY CLOSED pin of the relay? Thanks…

    Reply
  45. Anonymous

    Hi Sir Swagatam,
    How could i test separately the "CONTROL CIRCUIT" and "THE CALL BACK AND THE CALL REJECT CIRCUIT" wherein the pin # 1,2,3 of IC2 was in the first mentioned circuit and the rest of the pins was incorporated in the later one? should i test it together? Thank you very much Sir….JLC

    Reply
  46. Anonymous

    Hi Sir Swagatam,
    How could i test separately the "CONTROL CIRCUIT" and "THE CALL BACK AND THE CALL REJECT CIRCUIT" wherein the pin # 1,2,3 of IC2 was in the first mentioned circuit and the rest of the pins was incorporated in the later one? should i test it together? Thank you very much Sir

    Reply
    1. Swagatam Post author

      Make the circuits on separate boards, and then test them for the required results as explained in the above article.

      Once tested, you can interlink them all slowly…

      Reply
    2. Anonymous

      Hello Sir, The question is a bit misunderstood Sir, my query is about the IC2, one gate was in the "CONTROL CIRCUIT" ( pin 1,2,3 ) the rest three gates was in "THE CALL BACK AND THE CALL REJECT CIRCUIT. Thanks…

      Reply
  47. Anonymous

    Hi bro
    Just a brief question. How could I connect the according relay to ignition so that it prevents the motor to run?

    Reply
    1. Swagatam Post author

      You can connect one of the motor wires in series with the shown relay contacts, such that the current passes through the relay contacts before reaching the motor.

      Reply
    2. Anonymous

      but is the relay contacts able to support that kind of voltage and current??? is it not approx. 1000V or 40AMPs that the motor uses??

      Reply
  48. Anonymous

    Hi sir
    Which value of resistance should r1 and capacitor c1 have in order to activate the autolock system in 1min instead of 1:30?

    Reply
  49. Anonymous

    Hi man
    I made ur ckt and I noticed that when the car is unlocked , if u open the door the system will activate and start making a call to the owner. Pin 3of ic1 is going from being high to low when someone opens the door. You said u had it functioning on some cars,, I do here to prevent this??

    Reply
  50. Khai

    hi..
    can i ask you about .. transistor D1351?
    what another components that can be used same function with component D1351?
    at my place dont have this compenent..

    Reply
  51. Anonymous

    Hi sir ..
    i tested the circuit in my car every things work lock and unlock door it is working .Only in the igni tion section there was nothing happen i connected all wires in correct way .

    Reply
  52. Sayad Hadia

    Your Projects are always valuable Mr Swagatam Majumdar.

    Can you Please show me ho to use a circuit for controlling one Device by the cell phone without the charger

    thanks

    regards

    Reply
  53. Anonymous

    Good Day Sir Swagatam,

    In "THE CALL BACK AND THE CALL REJECT CIRCUITS" what determines the exactly 4 pulses from PIN # 15 of IC 4060 Sir? a capacitor or a resistor? how to increase or decrease pulses Sir?

    This is an irrelevant question Sir, im just wondering how pulses happens with this IC's.

    Thank you Sir.

    Reply
    1. Swagatam Post author

      It's the pin number, other pinouts will produce other number of pulses, you can either double it of half it….meaning produce 8 pulses or 2 pulses but not 3 or 5 etc.

      Reply
    2. Anonymous

      Thank you very Sir, but i just need 3 pulses only from these IC for my circuit Sir, do you have any suggestion?

      Reply
  54. Anonymous

    Buenos Dias Sir Swagatam,

    Just want to seek some info. about these IC 4093,

    what should be done with unused inputs gates and output gates Sir?

    Should both unused inputs and outputs be connected to 0v / ground?

    Does the same be done with unused pins of IC 4060?

    Thank you very much Sir.

    Reply
    1. Swagatam Post author

      unused cmos gates (nand, NOT etc) inputs should be always connected to some logic level, either ground or positive.

      the inputs of 4060 are 9,10,11,12, rest all are outputs, unused outputs of all cmos gates can be kept open, no issues.

      Reply
  55. Dudley Meyer

    Hi,

    I want to build a simple system to when dailed it activates and phoned again deactivates the main ignition system for a vehicle with no central locking and when broken into signal my phone if you could help

    Reply
    1. Swagatam Post author

      Hi,

      The above circuit is exactly what you are referring to.

      just eliminate the central lock relays, and it becomes precisely as per your application.

      Reply
  56. salman khan

    Hi sir…
    i assembled the circuit for many time but it doesnt work.. sir can you send me PCB design so i can print it and place every component correctly. i shall be very thanksfull to you…
    or any one in posts with have the correct and working PCB design plz send me in pcb format.. thank you all..

    Email Khaaan_1@yahoo.com

    Reply
  57. Anonymous

    about the gsm car security alarm , may u pliz give me the specs of TRANSISTORS T2 AND T3 of the call back call reject circuit. its not given in the parts list.
    regards pk

    Reply
  58. Anonymous

    hi,
    1.may pliz give me the specs of the transistors T2 and T3 of the call back , call reject circuit.
    2.shall i also get the specs for ic1?

    regards

    Reply
  59. Anonymous

    Hi sir thank you for the good work you done for the electronic hobbies im quiet appreciate about it thank you once again sir in this 4 circuit you put it here i want to try and build it but im very confused becos from call back and the call reject circuit,sir please and again i know you will not ignore my request and i well be very happy to if you can do that for me becos we living in the opening house i main there's no fence wall so when my brother pack his car bad person come to stole thing from the car like tape so i been searching this kind of circuit,so please can you send me the PCB of the circuit through this email address(dandu5050@yahoo.com) or all the circuit arrange together? thank you hope to hear from you soon.

    Reply
  60. Anonymous

    Hi sir very nice presentation. can ask some favor sir do have circuit for security alarm using laser with mobile phone with call back and call reject circuit. i need your help sir if you have one you can send it to my email t.rowel@yahoo.com thank you and more power sir.

    Reply
  61. aladin

    hi mr Swagatam
    i would like to replace the headphone with a signal from de phone speaker, with full volume i can get around 1.2 volt (with a digital multimeter), i can also get a 2.5 volt dc from de vibrator output (but it will trigger for all calls), what minimum amplification stage do i need, is the coil necessary in this case.
    i realy need your help…
    thanks

    Reply
    1. Swagatam Post author

      Hi Aladin, the input should be referenced with ground, only then it will work, or perhaps you can try using an optocoupler in between the speaker output and the control circuit input for the triggering.

      Reply
  62. aladin

    thanks for replying Mr Swagatam
    but i want some details…
    here his what i am going to do;
    i will trow away the phone speaker and get the two wires from its driver into the tone amplifier input (i used the one in "GSM Based Cell Phone Controlled Remote Switching Circuit");
    i thought i may not need T1 and T2, what do you think ?
    the impedance of the speaker was 8 ohms; knowing that the input impedance of the amplifier is bigger, will it cause damage to the speaker driver in th phone (i don't want the driver to know that i replaced the speaker with an amplifier !).
    thank you very much.

    Reply
    1. Swagatam Post author

      Aladin, as far as i know the speaker of cell phones are not configured with reference to ground, therefore it could produce erratic results when connected with the above circuit, in fact it could even damage your cell phone in the process, that's why I recommended the use of an optocoupler.

      Reply
  63. ala eddine ELMOUETS

    hi sir
    i thought may be the tone frequency is too high for the relay to respond; the relay will be driven by an ac signal during the beep, will that damage the relay and how could it respond in the first place ? the simulation shows thr relay closing and opening at the frequency of the beep (by the way, what is the range of that frequency? because the simulation shows a band pass filter for 2 kHz – 2 MHz )
    i really want to understand …
    thanks.

    Reply
    1. Swagatam Post author

      Hi Ala,
      the circuit has been tested by me thoroughly so there's no doubt about anything….the tone gets converted into 12v DC across the coil, yet you may connect a 100uF cap across the coil for better response.

      Reply
  64. aladin

    hi sir
    i am a 2nd year student in electronics and i am amazed by your design and i want to build one (with some changes) for a school project but there are things i want to understand:

    1) i build the tone amplifier replacing the coil with a 270 ohms resistor (does not work with the coil) and i had to add a 100uF in parallel with the relay for the circuit to respond, so what's the use of the coil, is it for filtering low frequency signals ?(ex:fluctuation in the power supply).

    2) i think the 30 mV signal from the phone is not enough amplified, so can i use a different amplification stage : BC547 transistor followed by uA741 amplifier (or LM325) followed by a filter( C16 + L1) followed by T6 and the relay ?

    3) what is the use of R18 ?

    4) for the control circuit i used a jk flip flop (4027) and it worked, can i replace it by 5vdc latching relay ?

    5) can i replace some of the electromechanical relays withe solid state relays and which ones could i use ?

    thank you very much sir, i would be very grateful for your support.

    Reply
    1. Swagatam Post author

      Hi Aladin,

      L1/C16 are important. You will understand the importance of L1 when you'll see the circuit activating by itself without any phone triggering. It's for filtering high frequency RF disturbances.
      adding a 100uF cap with the relay coil is fine.
      R18 is for safeguarding the transistor from sudden inrush currents.

      For greater amplification you can add another transistor sage as shown here:

      http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-build-gsm-based-cell-phone.html

      you can use solid state relay here.

      Reply
    2. aladin

      thank you very much Mr Swagatam
      a have an other question please:
      how did you choose the value of R8 ? i used a 10 ohm 1 watt for a nokia 1280, is it fine ?

      Reply
  65. Aditha

    Hey Mr.Swagatam, have you tried with any telecommunications service provider? so they can offer this instrument as a service alongside their SIM cards. Isn't it? you should try it. and I think that mounting with a cell phone doesn't matter that telecom: service providers can arrange a one similar to a cell phone that can deal with your circuit's inputs and outputs.Isn't it? So it'll be a new service alongside the sim card service 🙂

    Reply
    1. Swagatam Post author

      Hi Aditha, thanks for the suggestion!
      However, the concept is already in use in the form of GSM modules, controlled and managed by the SIM providers.
      The GSM module is what they have approved since it features text messaging during a threat to the vehicle from an intruder.

      Reply
  66. Aditha

    really ? a quite developed one! have you any concepts with voip adapters, I mean a simple one, like to convert analog signals to digital from phone line… Is it a hard one for beginners like me?. or Can you give me some links for simple circuits that can be worked with the land phone that have RJ11 cabel as the input? simply it's a request 🙂 thanks in advance Mr.Swagatam.

    Reply
    1. Swagatam Post author

      Aditha, voIP concept could be difficult even for me since it would require some serious programming of the ICs, ready made programmed ICs aren't available for this.
      But surely I would investigate the concept and post it in my blog if possible or provide you with the links.

      Thanks!

      Reply
  67. sharan.

    hello sir
    my question is in call back and call reject circuit
    1) ic 4060 pins connection are confusion please
    tell me all pins where connect 2) in ic 2 4093
    pin 11 12 13 14 where to connect please tell me

    Reply
    1. Swagatam Post author

      hello sharan, connect only those pins which are shown, the remaining pins of the 4060 IC can be left unused.

      the pin14 of 4093 will go to +12V, rest are indicated in the diagram.

      Reply
  68. sharan.

    hello mr.swagatam
    I am confused in relay driver RL2 relay two black dot i think this is NC contact connect to RL3 NC contact means RL3 relay two black dots these black dots pin connect to center lock instrument then other pins of relay RL3 where to connect so tell me i am confused in relay RL3

    Reply
    1. Swagatam Post author

      the black dots are the poles of the relay, the white circles are the N/C and N/O contacts fro the relevant relays, the blue squares indicate the coils of the relays.

      Reply
  69. sharan.

    sirji
    There are two ICS 4093 so tell me how many current require for both Ics in your control circuit IC 1 shows +5v from IC 7805 and 2nd IC2 4093 not shows how many current is required

    Reply
  70. Bryan Villanueva

    Dear Sir,
    Good day, we would like to inquire about the assembled kit of your homemade gsm car security system. How much does it cost and could you teach us how to install it if ever we avail it.

    Hoping for your immediate response because the deadline of submission is fast approaching which is two weeks from now.

    Thank you and have a great day.

    Reply

Leave a Reply

Your email address will not be published. Required fields are marked *