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					                  Build a Homemade GSM Car Security System

Is that a car security system super easy GSM project really works. Do you not think? Do
know and learn, and create a simple method. How would you feel if you had the right to
check the vehicle with a cell phone anywhere in the world? In this way, you can build a
system of security GSM home car. I have always wondered how you rich quickly, came
the idea to stand up, that it may simply but a breakthrough has. Mobile phones have
always fascinated me, for the simple reason that these devices are compact and look
stylish instead of a monstrous task wireless everywhere must send signals in the world in
a few seconds. Sometimes it hits me, there may be an easy way, the excellent feature
click "Mobile remote control", but the film with a pen on a part of the world use, so that
it can be used such as the? When using the commercial exploitation of GSM modem
remote controls end so why not your cell phone as a modem? "Modem" is a simple, user
friendly, cheap, and easy-to-install user. In addition to the normal GSM modems are
required expensive, difficult, wire, a special SIM card and network providers to make it
work. Inspired by the hard work, the sleeve up and it a resounding success for the time
when I finally was, the option of having a car relatively well, make very cheap GSM
alarm had, that was able to stop the vehicle and to do not only with the remote, but can
also send messages to a mobile phone in case of an invasion to the owner after the
session restore. The system is armed and disarmed to miss from his mobile phone and the
call is not made, the cost, then. Exuberant and successful society has decided to promote
and focus on returns. But the message was really shocking. You rejected that my product,
that the project was not "industrial" and the cell phone as a modem is not acceptable.
Very depressed, I tried to promote and sell the destination for friends and family, but it
was uphill, because the work requires significant initial investment and maintenance, so
that in the end, I will not. But people, this is good news, all I am ready for a success story
to tell and publish all details of this truly amazing neighborhood. The circuit is very
simple and foolproof evidence in the eye, you are already in the last six months or so
working in vehicles and the jeweller shops (for example, that the safety door interlock).
To lock and unlock of the vehicle will be ready for the next call, to miss any
payments.This can be done anywhere in the world.The engine of the vehicle can be
interrupted, even if it is in the world.To reject an incoming call makes a reception by
vehicle type, Miss on mobile phone indicating that the vehicle is unlocked at the same
time is.Phone number of digits can has been implemented so that it corresponds to, and is
accessible only by these numbers be specified mobile. Theft with burglary or assault
effectively converts back to the owner's cell phone warning. The device is integrated into
the automatic locking system, if the owner forgets to lock the vehicle. Prerequisite: into
the modem (GSM module attached) prepaid SIM card be installed. The entire unit to pay
more than $80. Warning: when installing to the vehicle security system with different
already exists. Go to the next, such as a GSM build car alarm system. As shown in the
diagram "a" beep "tone in the mobile headphone amplifier that comes. provides two
transistor circuit of based on small

Is which reach to prevent the internal sound engaged in a variety of unwanted errors or
strong RF interference, was very important for this reason. These errors can easily rattle
district and strange results. The resistance of the capacitor and the inductor L1, R18 C16,
is all included in the price, but the healing process. Amplified signal moved him the timer
use to promote, so long the sound does not disappear. The device is connected to contacts
that routes about N/O voltage, so that, if it works, a high signal on the main/flop, the
logical chain flap will be sent.

The relay operation ensures that it only hiking from a cell phone works with a pulse of
your true ring and no other vague disorder (if you have the ability to penetrate defense
R18, C16 and L1).

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

R18- 10K,
R19- 22K,
R20- 4K7,
R21- 220 Ohms,
R22- 1K,
R23- 10K
C14- 2.2µF PPC (Polypropylene Capacitor),
C15- 47µF/25V,
Relay- 12V/400 Ohms
Diode- 1N4007
T4/T5 -BC547,
T6- BC557

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.

Assembled, tested kit available, contact


All Resistors are ¼ watt 5% CFR, unless otherwise stated.
C6/C7/C8-33uF/25V, C9-0.1PPC
All Diodes are 1N4148, T1-BC547,

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 make and break 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


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


All Resistors are ¼ watt 5% CFR, unless otherwise stated.
IC2 (N6,N7,N8)-4093
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
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.

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