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Recommendations for installing car alarms

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Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms

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What can be done to prevent car theft? Of course, install an alarm system.

Currently, the market is saturated with various signaling devices. Many firms and installation stations can offer the car owner a number of ways to protect the car from theft.

A good alarm is not a guarantee of complete security. You also need a competent, and sometimes non-standard installation of an alarm. A qualified installer knows the most common methods used by hijackers and uses this knowledge when installing. This, of course, also does not give a complete guarantee against theft, but it fulfills the main task: when trying to steal, to complicate the work of the thief as much as possible and gain time.

Common ways to break into a car

A variety of methods are used to penetrate the car - from breaking a window with a brick to reprogramming the remote control.

After figuring out the location of an LED or examining window stickers, many car thieves begin to consider whether it's worth the effort to have a car with an alarm, or if it's better to bypass it.

There is an opinion that if someone decides to steal a car, then he will do it, and there is no way to stop him by any means. The statistics of thefts do not doubt this, but still you should not neglect measures to protect the car. The task of installers and firms selling anti-theft devices is to complicate the work of the hijacker as much as possible.

So what can a car thief do to get into a car? First of all, open the door.

Despite the fact that car manufacturers have begun to place various mechanisms in the doors that complicate the work of the hijacker, they still continue to use crowbars, as this allows you to open the car quickly and quietly and, most importantly, without damaging the interior of the car.

A thief can also break the glass with his hand or some tool. In the USA, for example, a center punch is sometimes used for this purpose. The thief puts the spring-loaded tip of the tool to the corner of the window and when the glass breaks, a popping sound is heard. After that, you can safely push the glass inside the car.

In our country, more crude methods are usually used. Burglars begin to act with a crowbar or other blunt object. Often two are involved, one stands on the lookout, and the other hits the glass with a brick, climbs inside and pulls the hood opening handle. Then the second hijacker reaches into the engine bay and disconnects the siren wire or another wire that was apparently added to the battery. This is not space technology, it does not take much time.

Increasingly, thieves are taking a different approach: destroying the car's battery and leaving the alarm system without power. As more and more security systems are installed on cars, the pores are starting to get more creative in dealing with them. They know that if you hit the front of the car with a screwdriver and hit the battery, then in an hour all the electrolyte will leak out and there will be no voltage.

Electronic attacks on the car can also be undertaken. Some car thieves try to copy the code transmitted by the remote control to another transmitter, or use a scanner to determine the vehicle's code.

If you think about it, there are not many manufacturers of security systems. So every time the owner hands over the car keys to someone, there is a danger that the future car thief will program an additional transmitter to disable the security system. This can easily be done by someone the car owner trusts. Security systems currently available on the market cannot determine if an optional remote control has been programmed.

Although code scanning is no longer a threat, the debate continues about how real the threat of code interception is.

There are no permanent solutions to the issue of scanning and intercepting codes. Everything that can be encoded will sooner or later be decoded.

Regardless of the different views expressed on the issue of interception of codes, no individual or organization has been able to provide concrete evidence that such a device was used for car theft.

Installation methods hinder hijacking attempts

Once the thief has entered the vehicle, the next step is to disable the security system, if he has not already done so. The typical hijacker will try to do this by attacking the five security components that are considered the most vulnerable: the siren, the system control module, the starter disable relay, the auxiliary switch, and the ignition and starter wires.

What can installers do to make it harder for a hijacker to work? The quality of a security system cannot be better than the quality of its installation.

In practice, the installer can often complete the job in two hours. He attaches the shock sensor to the steering column, installs the auxiliary switch, and tucks the control module under the dashboard. It solders very well and makes all connections reliably. It all looks great, and you can even get some kind of bonus for such a setup, but it is not reliable.

There are several reliable options for installing the system. In vehicles with plastic inner fender covers, you can unscrew the screws securing the cover and fix the siren inside the fender. Under the battery mounting plate there is often a place where the siren can be fixed. After the installer replaces the battery, the siren will be very difficult to find, and it will sound very loud, maybe even louder than when installed near the radiator grill.

If the siren is installed in plain sight, then, at a minimum, its wires should be out of the reach of hijackers. Wires should not just come out of the back of the siren. It is recommended to use as much tape and cable holders as possible to secure the siren and its wires. The more time it takes for the hijacker to unravel all of this, the more likely it is that he will give up his intention.

But wherever the installer chooses to mount the siren (or other system components), it must not be placed near moving parts, manifolds or exposed to moisture to be effective. If all this is done, then you can protect the car from theft and ensure the normal operation of the security system. The central control module of the alarm system must also be placed wisely. For some reason, some installers believe that the only places to put the control module are in the steering column and the dash or side panel on the driver's side. In many vehicles, the control module can just as easily be installed behind the glove box, where it will be much more secure. As a rule, below the glove box is the equipment of the heater or air conditioner, so getting there is not so easy. Especially after the hijacker lifted the dashboard and found nothing there.

At a minimum, the installer should place the control module as high as possible behind the dash, perhaps on or behind the air duct.

Most installers mount the starter relay exactly where the thieves are looking for it: at the bottom of the steering column or near the ignition coil. If it is not there, then the hijacker will not know which wire to cut. It is advisable to install this relay on the other side of the car.

Similar advice can be given for the placement of an auxiliary or system switch. But it is not always possible to use exotic locations to install the switch and, at a minimum, the switch must be located below the dashboard on the passenger side.

Any parts of the alarm wiring are also vulnerable, especially the starter and ignition wires. Connect to the ignition and starter wires as far as possible from the ignition switch. After making the connection, do not leave large single-ended connectors hanging, but tape the wires to the factory cable harness so that the connection points are not visible. If everything is wrapped with tape, and the hijacker does not have a razor with him, then it will take him more time.

If the installer takes the time, he can combine the anti-theft system wiring with the vehicle's main wiring, allowing for greater stealth. In this case, the hijacker will not know if this wire goes to the siren, or to the windshield wiper.

Unexpected for the hijacker may be the presence of a mechanical device for blocking the hood Hood Lock. The inability to quickly open the hood and turn off the siren significantly reduces the chances of a hijacker.

A combination of unconventional vehicle protection methods can be effective. For example, covering the side windows (at least the front ones) with a reinforcing film and installing blockers in both front doors (door-pillar latch) with electric drives. The inability to open the front doors leaves the hijacker in a dilemma: either give up their intentions, or, making their way through the back seat, be trapped.

In conclusion, it must be added that the complication of the security system should not be excessive. Otherwise, it can make life more difficult for the owner than for the hijacker.

Wires in the door? No problem!

Everyone who has ever encountered the installation of door locks knows that the most unreliable and weak point is the wiring harness from the rack to the car door. Several wiring methods are currently in use. Consider them in ascending order of reliability.

At small installation points and individual installers, the "loose loop" method is used. With this method, the wiring harness is either enclosed in a PVC tube, or simply wrapped with electrical tape and passed from under the interior upholstery under the door upholstery, leaving a free loop. This method is also used by more reputable companies if the client does not want additional holes to be drilled in his car. The method is quite simple, but the hanging loop, firstly, looks, to put it mildly, unaesthetic, and secondly, there is always a risk that it will either be accidentally torn or the wires will break at the entry point under the upholstery, since the wires are constantly working bending with a small radius.

The S-loop method is used quite often. With this method, misaligned holes are drilled in the pillar and in the car door. The wires are passed in such a way that an S-shaped loop is formed. Variations on this topic are quite diverse and depend on the level of solidity of the company and the professionalism of the installers. In the simplest case, bare wires are passed through the holes. It is good if rubber bushings are inserted into the holes, and the wires are enclosed in a PVC tube or wrapped with electrical tape. In more reputable companies, wires are passed in corrugated rubber tubes, which are sometimes completed with Taiwanese-made wires. The disadvantages of this method include the fact that the wires work simultaneously for bending and twisting. If this method is used on imported machines, where the gap between the rack and the door is large enough, this is not a problem, since the bending radius of the wires in this case has acceptable values, and the twisting angle can be generally neglected. It is better not to use this method on domestic-made machines, since the gap between the rack and the door has a minimum size, and when the door is closed, the wires bend almost at a right angle. It is not difficult to imagine what will happen to the wires after several hundred door closings. In addition, Taiwan-made corrugated rubber tubes do not stand up to criticism in terms of rubber quality. It is clearly designed for the mild Taiwanese climate and does not stand the test of our frosts. It’s better not to talk about oil and petrol resistance at all.

On domestic-made machines, the method used on VAZ-2107 cars is most suitable, where rubber bushings are used for these purposes, which are fixed at one end in the rack, and the other end freely passes through the hole in the door. Firstly, the wires are reliably protected from external influences by sufficiently thick walls of the bushing (therefore sometimes called a protective cover), and secondly, the bending radius of the wires passing between the rack and the door has a value of no more than 100 mm, which is much larger than with any other wiring method. The section of wires inside the car door bends only under the action of its own gravity and, when opening and closing the door, has only a small longitudinal movement.

Various types of bushings are currently in use. Italian-made bushings are widely used. Unfortunately, they have one big drawback. Made of plastic, they have good oil and petrol resistance, but at temperatures below -25 degrees they become brittle. In our conditions, apparently, it is better to use domestic-made bushings made of frost-resistant rubber.

His Majesty the trailer

In most cases, when installing car alarm systems, standard limit switches are used as door opening sensors. This option can be used when everything is in order with the standard wiring, and there is no complete or partial short circuit to the vehicle ground. When a wire is shorted to ground in the interior lighting, the car doors are, as it were, always open. This will trigger an alarm.

In the event of a partial short to ground, a “stray effect” may occur, leading to unpredictable alarm behavior. Often this happens in winter due to the increased likelihood of corrosion of wiring and connections laid along the bottom of the car. Leakage resistance can vary from tens to hundreds of ohms, and it will depend on many factors: temperature and humidity in the cabin, wet rugs, etc.

In this case, we can recommend three options:

1. Normal - fix the wiring and use the standard limit switches. However, this option can take a long time, and on some foreign cars, due to the complexity of the wiring, it is simply unacceptable.

2. Independent - insert additional limit switches into the doors specifically for connecting the alarm.

3. Improved - use standard limit switches by connecting the alarm according to the diagram above

Recommendations for installing car alarms

1 - regular limit switches;

2 - diodes with an average current sufficient to operate the interior lighting lamp;

3 - unknown full or partial short to ground:

4 - interior lighting lamp;

5 - additional wires for connection to the alarm.

Also, in addition to eliminating the search for damage in the car's electrical circuit, the use of diodes in the circuit of regular limit switches allows you to use limit switches to connect an alarm, where there is a time delay in turning on the interior lighting. It should be remembered that in this case it is necessary to carry a wire from each limit switch to the alarm unit.

If it is easy to find the place of the wire indicated on the diagram by number 6, it is enough to use only one diode instead of four, which is included in the wire break at point 6 by the cathode to the limit switches.

For machines in which door limit switches are used independently, for example, each limit switch controls its own interior or door lighting bulb, it is necessary to turn on additional diodes for each wire extending from the limit switch to the alarm (diodes are included in wire breaks, which are indicated by the # sign in the diagram), cathode to the terminal. In this way, it is possible to completely untie the limit switches from each other and use them to operate the alarm system.


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