Security system with digital indication. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Security system with digital indication

Free technical library

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

Comments on the article

The system described in the proposed article is designed to protect remote objects that are inaccessible to a watchman or sentry.

The object of protection can be a garage, a car, etc. In addition to monitoring the status of sensors, the system provides:

automatic shutdown of the sound signal when the sensor is triggered for more than one minute, which saves battery power;
digital display of the number of operations, which is convenient for their registration when changing duty, as well as for monitoring the object;
automatic setting of the standby mode when the closed state of the sensor contacts is restored.

The diagram of the device is shown in the figure.

(click to enlarge)

A control unit is assembled on the DD1 chip, a digital indication unit is assembled on the DD3 and HL1, and a siren is assembled on the DD2 chip and the VT2 transistor. The siren was assembled according to the scheme described in the article by M. Shustov "Sirens of Personal Security" in the journal "Radio Amateur", No. 8, 1995.

To arm the system, you need to turn on the power with the SA1 secret toggle switch, leave the room and close the door, while the contacts of the SF1 door sensor will close (several sensors connected in series can be used). The charging current of the capacitor C1, flowing through the resistor R1, creates a high-level voltage at the input of the element DD1.1. At its output - a low level, and at the output of DD1.2 - high. Therefore, the output of element DD1.4 will also be high and the siren will not work. The high level from the resistor R1 is fed to the input R of the counter-decoder DD3 and sets it to zero. The HL1 indicator shows the number "0". The charging time of the capacitor C1 is about 20 s. At this time, you can open and close the contacts of the door sensor - the siren will not work and the indicator will remain in the "zero" state.

After charging the capacitor C1, the system goes into standby mode. At the input of DD1.1, a low level is set, which is fed to pin 5 of DD3, allowing the counter to work. At the output of DD1.1 - a high level, and if the contacts of the sensor SF1 are closed, the output of DD1.2 will be the same level: the siren does not work.

After opening the door (opening the contacts SF1), it is necessary to turn off the system with the toggle switch SA1. If this is not done, then after about 5 s (capacitor C2 charging time), a low level will appear at the output of element DD1.2, and a high level will appear at the output of DD1.3. From the output of the element DD1.2, a low level is fed to the input C of the counter DD3, and "1" is displayed on the HL1 indicator. At pin 13 DD1.4, a high level is present only during the charging of the capacitor C3, which is approximately equal to one minute. During this time, the output of the DD1.4 element is low, which allows the siren to work. After one minute, C3 will be charged and a low level will appear at pin 13 of element DD1.4. A high level at the output of DD1.4 will disable the siren. The system will also work if, when it was armed, the SF1 sensor was not closed, which allows you to control the state of the sensor.

When contacts SF1 are closed, capacitors C2 and C3 are discharged and the system enters standby mode. The counter DD3 is triggered only during the opening of the contacts SF1, the indicator HL1 displays the number of openings.

By including additional sensors between terminal b of DD1.2 and the connection point of SF1 and C2, it is possible to ensure that the system will operate instantly when they are opened and with a delay when SF1 is opened.

The device uses MLT resistors, K53-1 capacitors. Since the system was developed to control an object guarded by a sentry, the display device was placed in a separate case and installed inside the object with the possibility of visual control from the outside to take indicator readings during the transfer of a shift. The connecting cable from the alarm system to the display device was carefully disguised.

In standby mode, the main part of the consumed energy is spent on the operation of the indicator. When the system is powered by a rechargeable battery, it is advisable to turn on the indicator only for the time of monitoring. To do this, you need to install a button that would close the connection point of pins 3 and 8 of the HL1 indicator with a common wire. In this way, the current consumption in standby mode can be reduced to a minimum. In alarm mode, the current increases to 0,7...0,8 A.

In the proposed device, the high stability of the time intervals specified by RC circuits does not matter. Only the reliability of the system in various temperature conditions depends on the quality of the capacitors used.

Author: O. Soldatov, Balakovo, Saratov region; Publication: radioradar.net

See other articles Section Security devices and object signaling.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

The main problem of the colonization of Mars 08.06.2020

The founder and head of SpaceX, Elon Musk, said that he was being prevented from creating the first Martian colony.

In order for the dream to become a reality, it is necessary to achieve a reduction in economic costs when launching a payload into low Earth orbit. After that, humanity will be able to create a full-fledged colony on Mars.

The start was made back in December 2015, when SpaceX returned the first stage of the Falcon 9 launch vehicle to Earth. Technically, this event played a major role in the transition to fully reusable rockets.

However, in order to create a self-sufficient Martian city, it is necessary to optimize the cost of transporting each ton of payload to a stationary orbit. To do this, it is necessary to reduce costs by more than 1000% compared to the performance of Falcon missiles.

Elon Musk also believes that the current situation in the development of space technology does not give contemporaries reason to count on the active colonization of Mars.

Other interesting news:

▪ Football with electronics

▪ The age of a person is determined by blood

▪ laziness full

▪ The world's largest Cherenkov telescope launched

▪ Processor based on superconductors

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Normative documentation on labor protection. Article selection

▪ article Boltzmann Ludwig. Biography of a scientist

▪ article Why did the British spread the belief that carrots directly improve eyesight? Detailed answer

▪ article Rules on labor protection (POT). Directory

▪ article A simple electronic fishing rod. Encyclopedia of radio electronics and electrical engineering

▪ article Pashtun proverbs and sayings. Large selection

Leave your comment on this article:

All languages of this page

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