Device for delaying turning off the light in the room. Scheme, description

Free technical library

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

Device for delaying turning off the light in the room. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Lighting

Comments on the article

Sometimes it is required that the light in the room was on for some time after turning it off with a switch. During this time, you can safely leave the room, after which the light goes out. In amateur radio literature, such devices were described, for example, in [1], but they contain an additional button (to the already existing switch), which creates some inconvenience when using. In addition, the device from [1] has an electromechanical relay, the winding resistance of which must correspond to the power of lighting lamps.

In the proposed device, no additional switching elements, except for the already existing switch, are used. The device is connected in parallel to the contacts of the SA1 switch using terminals XT1 and XT2.

Light switch-off delay device in the room

With open contacts SA1, the mains voltage is supplied to the circuit through the lighting lamp EL1, rectified by a bridge rectifier VD3 and fed to the electrodes (anode and cathode) of the thyristor VS1. as well as on the parametric voltage regulator R4-VD1. Capacitor C2 through resistor R2 is charged almost to the voltage at the zener diode VD1. which corresponds to the level of the logical "1". which is fed to the inputs of the Schmitt trigger DD1. In this case, the output (pin 3) of the Schmitt trigger is logical "0", and the transistor VT1 is closed. Thyristor VS1 is also closed. Current flows through the lamp EL1. determined mainly by the resistance of the resistor R4 (approximately 5 mA).

This current does not cause the lamp to glow. In this state, the device can be indefinitely long.

When the contacts of the SA1 switch are closed, the lighting turns on, and the voltage between the anode and cathode of the thyristor drops to zero. Capacitor C1 is discharged through resistor R1. and the capacitor C2 - through the diode VD2 and the resistor R1. The time constant of the discharge target is approximately 5 s. The device can also be in this state for a long time.

When the SA1 contacts are opened, the capacitor C1 quickly (within tenths of a second) charges up to the stabilization voltage VD1, and C2 charges through the resistor R2 much more slowly, due to which "G" is set at the output DD1, which leads to the opening of the transistor VT1 and the thyristor VS1. lamp EL1 continues to glow.

The opening of the thyristor occurs not at the very beginning of the next half-cycle of the mains voltage, but 1 ... 2 ms later, when the control electrode current exceeds the threshold value. In this case, the voltage on the lamp is slightly lower than the mains voltage (170 ... 180 V), and the voltage between the anode and cathode of the thyristor has a stern of pulses formed by a part of the sinusoid. This voltage is sufficient to provide power to the DD1 chip and the open state of the transistor VT1. It should be noted that the opening of the thyristor VS1 with a delay relative to the beginning of the half-cycle is a necessary condition for the operation of the device.

After some time, determined by the time constant of the C2-R2 circuit, the voltage across C2 reaches the switching threshold DD1, the transistor VT1 and the thyristor VS1 close. For the ratings R2 and C2 indicated on the diagram, this happens after 70., .80 s.

The device uses commonly available parts. As a thyristor VS1, you can take U201K (L), KU202K (L, M, N), as well as T112, T122, T132, T142. Transistor VT1 - KT940. KT604. KT605. KT8108...KT8110. KT8120. KT8121 with any letters. The bridge rectifier can be with the BR index and numbers greater than those indicated on the diagram (the first number indicates the allowable current in amperes, and the second indicates the voltage in hundreds of volts). You can also use domestic rectifier bridges of the KTs405 or KTs409 types (with the letters A ... G). The thyristor and rectifier, in principle, must be rated for current. higher rated current of the lighting lamp EL1 (with a lamp power of 200 W, the permissible current of the thyristor and bridge is at least 1 A). When mounting the device, the rectifier bridge and the thyristor are installed on the radiator if the lamp power exceeds 300 W.

To change the turn-off delay time, C2 and R2 are selected. If you increase the capacitance of the capacitor C1 to 50 ... 100 uF. then you can achieve the effect of flashing the EL1 lamp before turning it off. This will be a kind of warning about the imminent turning off of the light. The number of flashes and their frequency depend on the capacity of C2.

Literature

I. Nechaev. Lighting off delay machine. - Radio. 1999, No. 6, p.53.

Author: A. Evseev, Tula

See other articles Section Lighting.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

Three human brains tied into a net 05.10.2018

In recent years, scientists have developed tools that provide the ability to "read thoughts" and transmit them to the brain. To a very limited extent, but sufficient to demonstrate the most fundamental possibility of such an exchange of information.

In 2015, using electroencephalography (EEG) to record the electrical activity of the brain and transcranial magnetic stimulation (TMS) to relay information to the brain, researchers at the University of Washington were able to connect the brains of one participant in an experiment to those of another. During the experiment, participants played a question game.

The obvious next step was to create a network of three people. This time, the participants sent thoughts to each other while playing a Tetris-style game.

The participants were isolated from each other. Two were wearing EEG instruments. These participants saw the entire screen and could pass "commands" to rotate the figures to a third participant who only saw the top of the screen where the figures appear, but could not know whether to rotate them or not. He had to receive commands using TMS.

In order to transmit the turn command, the corresponding participant had to look at the LED on the edge of the screen flashing at a frequency of 15 Hz. A second LED flashing at a frequency of 17 Hz served to transmit the command to refuse to turn. The fact is that when perceiving flashes of light, the brain generates impulses with the same frequency, fixed by the EEG. And if certain areas of the brain are stimulated at this frequency with the help of TMS, a person experiences a sensation of flashes. Having received signals from two partners, the "receiver" carried out the command required by them.

To complicate the experiment, the scientists tried to arbitrarily change the commands received by the "receiver". So they introduced an element of error that is present in real communication. As it turned out, a person is able to distinguish correct information from false, having only the "protocol" of interaction with partners described above.

According to the researchers, the technology is easily scalable - both in terms of the number of network participants and the distances separating them.

Other interesting news:

▪ SpaceX floating spaceports

▪ Monochrome Epson Printing Factory

▪ Killer satellites

▪ Single-layer graphene demonstrates giant magnetoresistance

▪ saffron against cancer

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Power supply. Article selection

▪ article The more interesting a century is for a historian, the sadder it is for a contemporary. Popular expression

▪ article What is a sound barrier? Detailed answer

▪ article Zopnik tuberous. Legends, cultivation, methods of application