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Build a Simple Low Cost Car Security System

written by: Swagatam • edited by: Lamar Stonecypher • updated: 12/6/2010

With car thieves getting smarter day by day, installing a car security system becomes a must for every car owner today. However these systems are very expensive and sometimes unpredictable with functions. Unbelievably, a small electronic circuit costing less than a dollar may prove very useful.

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    Introduction

    A car is a great means of transport and can carry you to any desired location within minutes. Moreover it is also accompanied with most of the luxuries that may be comparable to those present in our house. But compared to a home, a car and its many electronic accessories can be more vulnerable to thefts simply because many of us don’t own personal garages or secured parking areas and are forced to leave theirs vehicles in desolate remote areas. Also, car thieves nowadays are getting smarter and know ways to lock-pick your ignition.

    Car security systems lately have become very popular and indispensable exactly due to the above safety concerns. In the market they come with a variety of features and specs but are never cheap. Moreover the complicated technicalities involved can make the buyer (layman) totally perplexed regarding the choice of such security systems.

    So what features do we exactly need with a security gadget to make a car totally foolproof to most thefts? Conventional sophisticated security systems are definitely very smart, but the features are mostly exaggerated and are there just to attract customers. For example why would you require a motion sensor inside your car when already a vibration detector is installed? And why would you require your car ignition to be controlled through your cell phone when much simpler, easier, foolproof and cheaper options are available. Moreover sophisticated devices are quite prone to malfunctions and sometimes may cause huge unnecessary harassments.

    You will be surprised to learn that even a simple electronic circuit, rather an ordinary capacitor/switch wiring, costing not more than a dollar can be enough to secure your vehicle comprehensively and make it impossible for any burglar to run away with your vehicle.

    Here we will discuss one such simple car security system.

    Let’s see how the circuit functions.

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    Circuit Description

    Simple Vehicle Immobilizer Circuit Wiring, Image   As the name suggests the ignition system of a car or any vehicle needs its fuel mixture to be ignited inside the ignition chamber to initiate piston movement. The procedure is sparked-off and sustained using high voltage arcing received from the ignition coil, which in turn receives the triggers from the alternator. It simply means that if some how we stop the sparking from taking place, we can keep the car immobilized and safe from intruders.

    Referring to the figure alongside we see how the ignition coil is basically wired to generate the required arching.

    Now, as discussed above we just need to sink the trigger voltage from the alternator to the coil to stop the arching from taking place, this is very easily done by introducing a high voltage electrolytic capacitor C1 across the primary input of the coil and ground.

    The capacitor may be activated and grounded through a hidden toggle switch, whose location is specifically known only to the owner of the vehicle. Once installed, it will successfully ground the trigger voltages and stop it from reaching the coil primary winding, completely immobilizing the vehicle.

    Now it’s just a matter of toggling the hidden switch ON and OFF to alternately mobilize and immobilize the ignition system of the vehicle at will… and how much does it cost to make this simple car security system? Precisely, not more than a dollar.



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