What Are Car Alarm Sensors and How Do They Work?

Car-alarm Transmitters

The keychain transmitter from the Sidewinder security system: The transmitter lets you lock the doors, arm and disarm the alarm and set off the siren from outside the car.
PHOTO COURTESY DIRECTED ELECTRONICS
­M­ost car alarm systems come with some sort of portable keychain transmitter. With this device, you can send instructions to the brain to control the alarm system remotely. This works in basically the same way as radio-controlled toys. It uses radio-wave pulse modulation to send specific messages (to see how this works, check out How Radio Controlled Toys Work).
The primary purpose of the keychain transmitter is to give you a way to turn your alarm system on and off. After you've stepped out of your car and closed the door, you can arm the system with the touch of a button; when you return to the car, you can disarm it just as easily. In most systems, the brain will flash the lights and tap the horn when you arm and disarm your car. This lets you, and anyone in the area, know the alarm system is working.
This innovation has made car alarms a lot easier to use. Before remote transmitters, alarm systems acted on a delay mechanism. As with a home security system, you activated the alarm when you parked your car, and you had 30 seconds or so to get out and lock the doors. When you unlocked your car, you had the same amount of time to shut off the alarm once you got in. This system was highly problematic, as it gave thieves an opportunity to break into the car and disable the alarm before any siren sounded.
Remote transmitters also let you open your power door locks, turn on your lights and set off the alarm before you get into your car. Some systems give you even more control over the system's brain. These devices have a central computer and a built-in pager system. When an intruder disturbs your car, the central computer calls up your keychain pager and tells you which sensors were triggered. In the most advanced systems, you can communicate with the brain, signaling it to shut down the engine.
Since the transmitter controls your alarm system, the pattern of pulse modulation must act like a key. For a particular line of transmitter devices, there might be millions of different pulse codes. This makes the communication language for your alarm system unique, so other people can't gain access to your car using another transmitter.
This system is fairly effective, but not foolproof. If a determined criminal really wants to break into your car, he or she can use a code-grabber to make a copy of your "key." A code grabber is a radio receiver that is sensitive to your transmitter's signal. It receives the code and records it. If the thief intercepts your "disarm code," he or she can program another transmitter to exactly mimic your unique signal. With this copied key, the thief can completely bypass the alarm system the next time you leave your car unattended.
To address this problem, advanced alarm systems establish a new series of codes every time you activate the alarm. Using rolling code algorithms, the receiver encrypts the new disarm code and sends it to your transmitter. Since the transmitter only uses that disarm code once, any information intercepted by a code snatcher is worthless.
Since the early 1990s, car alarm systems have evolved a great deal, and they've become a lot more common. In the next 10 years, we are sure to see a new crop of technological advances in car alarms. Onboard GPS receivers have opened up a wide range of security possibilities. If the receiver were connected to the alarm-system brain, it could tell you and the police where your car is at all times. This way, even if somebody does bypass your alarm system, he or she won't have the car for long.
For more information on car alarms and related topics, check out the links below.
Originally Published: Aug 2, 2001
Avtomobil signallari qanday ishlaydi
Muallif: Tom Xarris | Yangilangan: 2021-yil 9-fevral

Sidewinder avtomobil signalizatsiya tizimi bir qator sensorlar va signal signallarini o'z ichiga oladi.

Sidewinder avtomobil signalizatsiya tizimi bir qator sensorlar va signal signallarini o'z ichiga oladi.
FOTO BO'LGAN ELEKTRONIKA
Avtoulovni o'g'irlashning birinchi hujjatlashtirilgan holati 1896 yilda, gazda ishlaydigan mashinalar paydo bo'lganidan atigi o'n yil o'tgach sodir bo'lgan. O'sha dastlabki davrdan bugungi kungacha avtomobillar o'g'rilar uchun tabiiy nishon bo'lib kelgan: ular qimmatli, qayta sotish juda oson va ular o'rnatilgan qochish tizimiga ega. Ba'zi tadqiqotlarga ko'ra, faqat AQShda avtomobil har 20 soniyada buziladi.

Ushbu hayratlanarli statistikani hisobga olgan holda, millionlab amerikaliklar qimmat signalizatsiya tizimlariga sarmoya kiritganlari ajablanarli emas. Bugungi kunda har bir boshqa avtomobil murakkab elektron sensorlar, jiringlash sirenalari va masofadan faollashtirish tizimlari bilan jihozlanganga o'xshaydi. Bu mashinalar g'ildiraklardagi yuqori himoyalangan qal'alardir!

Ushbu maqolada biz zamonaviy avtomobil signallarini ko'rib chiqamiz, ular nima qilishlari va buni qanday qilishlarini bilib olamiz. Zamonaviy avtomashina signalizatsiyasi naqadar ishlab chiqilganligi hayratlanarli, lekin avtomobil o‘g‘rilari hali ham ulardan o‘tib ketish yo‘lini topayotgani yanada diqqatga sazovordir.

Asoslar
Agar siz eng oddiy shaklda avtomobil signali haqida o'ylashni istasangiz, u qandaydir sirenaga ulangan bir yoki bir nechta sensorlardan boshqa narsa emas. Eng oddiy signal haydovchining eshigidagi kalitga ega bo'lar edi va u simli bo'lib, agar kimdir eshikni ochsa, sirena yig'lay boshlaydi. Siz ushbu avtomobil signalini kalit, bir nechta sim va sirena yordamida amalga oshirishingiz mumkin.

Aksariyat zamonaviy avtomobil signalizatsiya tizimlari bundan ancha murakkab. Ular quyidagilardan iborat:

Kalitlarni, bosim sensorlarini va harakat detektorlarini o'z ichiga olishi mumkin bo'lgan sensorlar majmuasi

Avtomobilingiz uchun aniq ovozni tanlashingiz uchun ko'pincha turli xil tovushlarni yaratishga qodir sirena
Asosiy fobdan simsiz boshqarish imkonini beruvchi radio qabul qiluvchi
Yordamchi batareya, asosiy batareya uzilib qolganda ham signal ishlay oladi
Hamma narsani kuzatib turadigan va signal beradigan kompyuter boshqaruv bloki -- tizimning "miyasi"
Eng ilg'or tizimlardagi miya aslida kichik kompyuterdir. Miyaning vazifasi signalizatsiya moslamalarini faollashtiradigan kalitlarni - shox, faralar yoki o'rnatilgan sirenani - quvvat sensori qurilmalari ochilgan yoki yopilganda ba'zi kalitlarni yopishdir. Xavfsizlik tizimlari asosan qaysi sensorlar ishlatilishi va turli qurilmalar miyaga qanday ulanganligi bilan farqlanadi.

Miya va signal funksiyalari avtomobilning asosiy akkumulyatoriga ulangan bo'lishi mumkin, lekin ular odatda zaxira quvvat manbaiga ega. Bu yashirin batareya kimdir asosiy quvvat manbasini uzib qo'yganda (masalan, batareya kabellarini kesish orqali) ishga tushadi. Quvvatni uzib qo'yish buzg'unchining mumkin bo'lgan belgisi bo'lganligi sababli, u miyani signal berish uchun ishga tushiradi.

Keyingi bo'limlarda biz turli xil sensorlarni ko'rib chiqamiz, ular qanday ishlaydi va ular signal tizimining miyasiga qanday bog'lanadi.

Tarkib
Avtomobil signalizatsiyasi uchun eshik sensorlari

Avtomobil signallari zarba datchiklari
Avtomobil signalizatsiya oynasi va bosim datchiklari
Avtomobil signalining harakat va egilish sensorlari
Avtomobil signallari
Avtomobil signal uzatgichlari
Avtomobil signalizatsiyasi uchun eshik sensorlari
Valet switch - bu signal tizimini vaqtincha o'chirib qo'yadigan qo'lda o'chirish (shuning uchun siz, masalan, valetga mashinangizni qo'yishga ruxsat berishingiz mumkin). Valet kaliti mashinada yo'ldan tashqarida yashiringan. Bu erda tasvirlangan kalit avtomobilning sug'urta kirish paneli ostida o'rnatilgan.
Valet switch - bu signal tizimini vaqtincha o'chirib qo'yadigan qo'lda o'chirish (shuning uchun siz, masalan, valetga mashinangizni qo'yishga ruxsat berishingiz mumkin). Valet kaliti mashinada yo'ldan tashqarida yashiringan. Bu erda tasvirlangan kalit avtomobilning sug'urta kirish paneli ostida o'rnatilgan.
FOTO BO'LGAN ELEKTRONIKA
Avtomobil signalizatsiya tizimining eng asosiy elementi eshik signalidir. To'liq himoyalangan mashinada old kapot, magistral yoki biron bir eshikni ochsangiz, miya signal tizimini ishga tushiradi.

Ko'pgina avtomobil signalizatsiya tizimlari allaqachon eshiklarga o'rnatilgan almashtirish mexanizmidan foydalanadi. Zamonaviy avtoulovlarda eshik yoki magistralni ochish ichki chiroqlarni yoqadi. Bu ishni bajaradigan kalit sovutgichingizdagi yorug'likni boshqaradigan mexanizmga o'xshaydi. Eshik yopilganda, u kichik, bahorda faollashtirilgan tugmani yoki tutqichni bosadi, bu kontaktlarning zanglashiga olib keladi. Eshik ochilganda, bahor tugmachani bosadi, kontaktni yopadi va ichki chiroqlarga elektr energiyasini yuboradi.

Eshik datchiklarini o'rnatish uchun qilishingiz kerak bo'lgan yagona narsa bu oldindan simli sxemaga yangi element qo'shishdir. Yangi simlar o'rnatilganda, eshikni ochish (kalitni yopish) ichki yorug'likdan tashqari, miyaga elektr tokini yuboradi. Bu oqim oqib o'tganda, u miyaning signal berishiga olib keladi.

Umumiy himoya chorasi sifatida zamonaviy signalizatsiya tizimlari odatda avtomobilning butun elektr pallasida kuchlanishni nazorat qiladi. Agar ushbu sxemada kuchlanishning pasayishi bo'lsa, miya kimdir elektr tizimiga aralashganligini biladi. Chiroqni yoqish (eshikni ochish), kaput ostidagi elektr simlari bilan aralashish