Twilight switch. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

 Comments on the article

The device is an automatic switch on / off of a powerful load (up to 6 A, from a 220 V network) depending on the illumination of the photosensitive element. The device has an on/off threshold adjustment. Small size and weight, high reliability, ease of manufacture makes the twilight switch extremely effective in order to automate the control of your electrical equipment and save energy. In addition, the device does not interfere with the mains.

You can assemble such a device from the MASTER KIT NK005.

On the street, in a country house or in a city apartment, it often becomes necessary to control electrical appliances depending on the time of day (in other words, on the light illumination of the object). How convenient it is when, with the advent of twilight, the light bulb for lighting the street, the front or dark staircase of the entrance will automatically turn on, and turn off in the morning; in the country, the heating element in your shower will turn on or the pump will start, storing water for morning watering. In addition to the automation of switching processes, it is necessary to recall the possibility of significant energy savings with such a time division of the operation of electrical appliances. All these functions can be assigned to a light-sensitive load on / off switch, which is called a twilight switch.

Technical specifications

• Supply voltage, V .............................. 220
• Connected load power, W.......1300
• PCB dimensions, mm.......................61x36

Such devices are quite widespread. There are more than a dozen different circuit solutions, both the simplest and very complex microprocessor-controlled systems. Therefore, the developers of MASTER KIT were tasked with making the most simple, modern (relative to the element base), cheap, small-sized, but at the same time, device with the most attractive consumer properties and reliability.

Description of the module

Schematic diagram of the twilight switch is shown in Fig.1.

(click to enlarge)

The twilight switch consists of a VD1 photodetector (a photodiode in reverse connection is an analogue of a photoresistance), a Schmitt trigger, a transistor switch, an electromagnetic relay and a power source. The Schmitt trigger is made on the operational amplifier DA1, covered by positive feedback through the resistor R6. The non-inverting input DA1 is connected through the resistor R5 to the engine of the variable resistor R2, which serves to adjust the switching threshold. The output voltage of the Schmitt trigger through the resistor R7 controls the operation of the electronic key, made on the transistor VT1. In the collector circuit VT1, through the resistor R9 and capacitor C2 connected in parallel, the winding of the electromagnetic relay K1 is connected, the contact group K1.1 of which closes / opens (depending on the load connection points, namely points 5-6 for short circuit, 5-7 for opening of the relay, respectively) the power supply circuit of the load connected through the XS2 connector. When the electronic key VT1 is closed, the capacitor C2, charging through the winding of the relay K1, creates a current pulse sufficient to attract the armature of this relay.

After the capacitor is charged, the armature of the relay is held by less current flowing through the resistor R9, which makes the device more economical in terms of current consumption. Diode VD1 protects the transistor VT2 from impulse breakdown at the time of starting the relay K1. The twilight switch power supply consists of a resistor R10, a zener diode VD2 with a stabilization voltage of 24 V, a capacitor C3 and a diode bridge VD3. The diode bridge through the quenching resistor R11 and the capacitor C4, connected in parallel, receives a mains voltage of 220 V (connector XS2). When power is disconnected from the device, capacitor C4 is discharged through resistor R11, which reduces the risk of electric shock.

If it is necessary to switch a load with a consumption current of more than 6 A, relay K1 can be replaced with a more high-current one (with similar parameters for closing the primary winding) or relay K1 can be used to turn on another, more powerful relay.

Many will ask: "Why was an electromagnetic relay chosen as a switching element? After all, it would be possible to use a thyristor with a clear conscience?" The answer to this question is extremely obvious.

Firstly, the relay makes it possible to provide absolute electrical isolation of the light machine and the switched equipment.

Secondly, since the thyristor is a multilayer semiconductor structure, in the open state the voltage drop across it is about 2 V, which at a current of 6 A will be 12 W of dissipated power.

And now you can compare the dimensions of the electromagnetic relay and the thyristor with a radiator. It is possible to greatly reduce the dissipated power by using modern field-effect transistors with low drain-source resistance in the open state instead of a thyristor. In this case, we have the minimum power dissipation, but we do not have the galvanic isolation of the twilight switch and the switched devices.

Attention! This device has a transformerless power supply, so touching open current-carrying parts of the board is life-threatening.

Design

The appearance of the twilight switch is shown in the photo, the printed circuit board in fig. 2 (on a scale of 2:1), the arrangement of elements in fig. 3.

Structurally, the twilight switch is made on a printed circuit board made of foil fiberglass. To fix the board, mounting holes for 2,5 mm screws are reserved.

The design of the device allows you to mount the device in the BOX-G025 case under the clamping of the edges of the board with screws.

For the convenience of connecting the supply voltage, load and photodiode, the board has reserved seats for terminal screw clamps (paired - points X1 and X2, X3 and X4; triple - points X5, X6, X7).

Attention! Since the device is not galvanically isolated from the AC mains, the twilight switch must be carefully insulated from moisture and from possible contact with current-carrying conductors.

Due to the lack of galvanic isolation from the AC voltage network, it is recommended to install a photodiode inside the body of the light machine, which will make the device as electrically safe as possible.

A correctly assembled twilight switch does not require adjustment. However, before using it for the first time, check that the installation is correct. Attention! Especially carefully check the correct installation of the transistor, microcircuit, diode, zener diode, diode bridge and electrolytic capacitors.

Conclusion

MASTER KIT is preparing to release a new version of the NK005 kit, which consists of a printed circuit board, a BOX-G025 case, all necessary components, an assembly and configuration manual. Additional information can be obtained on the site masterkit.ru

Author: G.Ganichev, Moscow.

See other articles Section Lighting.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

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 ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive Sony mirrorless camera and NEX-5T 02.09.2013 The Japanese manufacturer introduced the Sony camera NEX-5T. The novelty belongs to the category of mirrorless cameras with interchangeable lenses. Its features include a high-speed autofocus system, as well as support for NFC technology, thanks to which you can connect via Wi-Fi by simply touching the camera with an Android device. Communication with non-NFC-enabled devices uses the standard procedure and the Sony PlayMemories Mobile app, available for iOS and Android. The camera uses an APS-C format CMOS-type Exmor image sensor with a resolution of 16,1 MP. The camera will be sold with the SELP1650 zoom lens, which protrudes from the camera body by only three centimeters when fully extended. This lens is equipped with optical SteadyShot and motorized zoom. The advantages of the camera include the Smart Remote Control function. It allows you to use the screen of a mobile device connected to the camera via Wi-Fi as an external monitor. As for the aforementioned high-speed autofocus system, it is hybrid, as reflected in the name Fast Hybrid AF. It is called hybrid because it combines phase and contrast methods. Phase focusing relies on information about the distance to objects obtained from 99 points built into the image sensor and used for the first stage of focusing. At the second stage, the contrast method providing higher accuracy is used. In Speed ​​Priority mode, the camera uses a phase method for tracking focus and can take up to 10 shots per second. The NEX-5T features a fully programmable control wheel and Fn button, which the manufacturer says will appeal to photographers accustomed to the flexible and direct control of SLR cameras. The touch screen of the camera is fixed movably. The NEX-5T will be available in silver, black and white. The price of a kit with a SELP1650 lens is about $700, and the cameras alone are $550. Optional LCS-EBA case, LCS-EMJ bag and BC-QM1 charger will be available for $25, $40 and $60 respectively. Sales start in September.

Other interesting news:

▪ Microcontrollers STM32 Value Line

▪ Mont Blanc has risen again

▪ Brown-eyed people are trusted more

▪ 10 GW solar panels in China

▪ Mobile router with electronic ink screen

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site History of technology, technology, objects around us. Article selection

▪ article And instead of a lamp, a plasma motor. video art

▪ article What do the Statue of Liberty and the Eiffel Tower have in common? Detailed answer

▪ article American buckthorn. Legends, cultivation, methods of application

▪ article Power regulator on three parts. Encyclopedia of radio electronics and electrical engineering

▪ article Two transformerless power supplies, 220/1,4 volts 1 milliamp. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

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

www.diagram.com.ua
2000-2024