Menu English Ukrainian russian Home

Free technical library for hobbyists and professionals Free technical library

Free library / Schemes of radio-electronic and electrical devices

Car guard with a small number of parts. Encyclopedia of radio electronics and electrical engineering

Free technical library

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

Comments on the article Comments on the article

This simple autoguard is made on a single chip. Its characteristic feature is the minimum of parts used.

The main technical characteristics of the device:

  • Time to switch to armed mode, min.......1
  • Alarm delay time, s.......5
  • Alarm duration, s.......20
  • Frequency of alarm interruptions, Hz.......1
  • Current consumption in security mode, not more than, uA.......50
  • The size of the board of a simple guard, mm.......25x40

Schematic diagram of the autoguard is shown in Fig.1. Standard door switches are used as contact sensors. Similar switches can be installed for the hood and trunk lid by connecting them in parallel with the door switches.

Car caretaker with a small number of parts

To transfer the guard to the armed mode, you must turn on the SA1 toggle switch, located in a secret place in the car's saloon. The time interval between the moments when the power is turned on and when the auto-guard switches off the armed mode is about one minute. During this time, it is necessary to close all doors, the hood and the trunk lid (if contact sensors SBn are installed there).

When opening any door, hood, trunk lid, the contacts of the push-button switches SB1-SBn are closed and the circuit goes into alarm mode. If the owner of the car does not have time to turn off the alarm in 5 seconds using the secret toggle switch SA1, an audible alarm sounds. In alarm mode, an intermittent sound signal is heard for 20 seconds. After 20 seconds, the watchman automatically switches to armed mode.

The autoguard works as follows. When the watchdog is turned on, capacitor C1 is charged through the resistor R5 for about 4 min. At the same time, there is zero potential at pin 11 of the OD1,5 element, and the multivibrator on the elements DD1.5 and DD1.6 is blocked. After 1 minute, the circuit switches to the protection mode.

When any contact sensor SB1 - SBn is closed, zero potential is supplied to pin 1 of the DD1.1 element through the diode VD1. As a result, a zero potential appears at pin 4 of the DD1.2 element, which leads to the appearance of a positive potential at pin 6 of the DD1.3 element, which, through the delay circuit R4, C3, enters the cathode of the VD3 diode. The diode closes, which allows the operation of the multivibrator (DD1.5 and DD1.6). Circuit R4, C3 generates a 5 s alarm delay. The multivibrator generates rectangular pulses with a repetition rate of 1 Hz, which, through the resistor R9, are fed to the key on transistors VT1 and VT2, in the collector circuit of which the winding of the car horn relay K1 is turned on. The sounding time of the signal is determined by the time constant of the circuit R3, C2. After charging the capacitor C2 (after about 20 s), a zero potential is set at the output 11 of the multivibrator (element DD1.5) and it is blocked. The circuit goes into protection mode. If any contact sensor SB1-SBn is closed, the alarm sounds continuously.

When using door switches as sensors, a situation may arise when voltage is supplied to the inputs of the microcircuit (pin 1 DD1) of the CMOS structure on which the device is made, while it will be absent in the power circuit (the guard is turned off). This can lead to the failure of the microcircuit. To protect the microcircuit, a circuit is used, consisting of a diode VD1 and resistors R1, R2, R7.

In the device, instead of the K561LN2 chip, you can use the K564LN2 (in this case, you will have to change the pattern of the printed circuit board). The KT315 transistor can be replaced with KT342, KT3102, and KT815 with KT817 or KT819. Capacitances of all capacitors may differ by ± 50% from the ratings shown in the diagram, however this will change the selected time intervals. They can be adjusted by selecting the appropriate resistors. It is desirable to use electrolytic capacitors with an operating voltage of 16 V and a small leakage current, this is especially important for capacitors C2 and C4, which, with a significant capacity, are paired with high-resistance resistors. Otherwise, a large leakage current may render the circuit unusable.

The device is mounted on a printed circuit board made of one-sided foil textolite (Fig. 2). With a properly assembled circuit and serviceable elements, the device does not need to be adjusted. The setting consists in setting the desired delay time intervals by selecting the resistances of the resistors R3, R4 and R5.

Car caretaker with a small number of parts

The guard is mounted in a miniature plastic case, for example, from children's counting sticks, and filled with epoxy to prevent moisture. It can be installed in an inconspicuous place under the dashboard, and the SA1 toggle switch can be installed in a convenient hidden place in the car interior. The watchman can work with other mechanical swing sensors. At the same time, it is important that when triggered, their output is at zero potential. The connection of the autoguard to the elements of the car is carried out by the contacts indicated in the diagram X1.1 -X1.4.

See other articles Section Automobile. Security devices and alarms.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Improving the efficiency of PbS quantum dot solar cells 14.06.2024

The latest solar technology research represents a significant breakthrough in improving the efficiency of PbS quantum dot solar cells. This method, based on the use of pulsed light, offers promise for simplifying the production and expanding the applications of these cells. A research team from the Daegu Gyeongbuk Institute of Science and Technology has developed an innovative method that uses pulsed light to improve the electrical conductivity of PbS solar cells. This method can significantly reduce the processing time required to achieve similar results. PbS quantum dot solar cells have significant potential in solar technology due to their photovoltaic properties. However, the formation of defects on their surface can reduce their performance. The new method helps suppress defect formation and improve electrical conductivity. Using strong light to complete the process ... >>

Magnetic Power Bank 5000mAh 14.06.2024

Huawei introduces a convenient and multifunctional charger to the market - Huawei SuperCharge All-in-One Magnetic Power Bank. This magnetic battery allows you to quickly and conveniently charge your Huawei phone anywhere, anytime. With a thickness of just 11,26 mm and a weight of 141 grams, this portable power bank fits easily into a pocket or bag, making it ideal for travel and everyday use. Despite its compact size, this battery provides enough power to charge your phone on the go. The new product supports wired charging with a power of 25 W and wireless charging up to 15 W (and up to 30 W when connected to an adapter), providing fast charging for both the power bank itself and other devices. The battery is compatible with various fast charging protocols such as SCP, UFCS and PD, making it ideal for a wide range of devices. The power bank is also compatible with Huawei phones that support wireless charging. ... >>

Changes in a father's brain after the birth of a child 13.06.2024

A recent study conducted by scientists from the Hefei Institute of Physical Sciences of the Chinese Academy of Sciences found interesting changes in the brains of men after becoming fathers. These changes were associated with involvement in child care, sleep problems, and mental health symptoms. Scientists found that men who became fathers experienced a loss of brain volume after giving birth. This volume loss was associated with greater involvement in parenting, sleep problems, and mental health symptoms. Researchers have found significant changes in men's brains between the prenatal and postnatal periods. In particular, there was a loss of gray matter volume, especially in parts of the brain responsible for higher functions such as language, memory, problem solving and decision making. Men who paid more attention to their children and spent more time with them lost more gray matter in their brains. This also affected their mental health ... >>

Random news from the Archive

Power Management ICs for OMAP35xx 31.10.2008

Texas Instruments continues to expand its embedded microprocessor power chipset with three new chips that meet the power requirements of the OMAP35xx platform. The TPS65920, TPS65930 and TPS65950 are highly integrated systems that include a variety of peripheral modules in compact packages.

The TPS65950 supports up to 14 power channels. In addition to an integrated 3 MHz DC/DC converter and low noise LDO, it has dual audio codec and driver, control and monitoring system, battery charge controller, LED driver, 3-channel 10-bit ADC, keyboard and vibration driver, high-speed USB transceiver with integrated 5V power supply and PC interface.

The whole system is in a 7x7 mm BGA package. The TPS65920 and TPS65930 have some of the features of the TPS65950, support up to 8 power channels, and come in 10x10mm packages. The new devices add to the ever-growing range of single and multi-channel voltage regulators for OMAP35x processors.

In addition to the TPS659xx family, TI has already shipped millions of TPS3x single-channel 6235 MHz DC/DC converters and TPS65023 multi-channel converters. The TPS659xx, TPS65023, and TPS6235x use a dedicated I2C interface to enable proprietary SmartReflex power and performance management technology.

Other interesting news:

▪ AI algorithm beat the real pilot

▪ 6-inch 720p smartphone Lava Magnum X604

▪ Neurons with ears

▪ Mars colonies from airgel

▪ Aliens better hurry

News feed of science and technology, new electronics


Interesting materials of the Free Technical Library:

▪ site section Low frequency amplifiers. Article selection

▪ article Storm in a teacup (of water). Popular expression

▪ article What remains of the ancient temple of Jerusalem? Detailed answer

▪ article On the same track. Personal transport

▪ article Range filters. Encyclopedia of radio electronics and electrical engineering

▪ article Voltage converter for LED. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:


Email (optional):

A comment:

All languages ​​of this page

Home page | Library | Articles | Website map | Site Reviews