Knowledge base: What is LED? LED (led, led, light emitting diode)

LEDs are becoming more and more popular solutions in various fields. They can be used as decorative items or to illuminate premises, as well as various areas outside buildings. LEDs are supplied to the market in a wide range of modifications. At the same time, the developers of the corresponding products periodically offer innovative solutions, which in the future are capable of creating new market niches. What are the most common types of LEDs today? For what purposes can they be used?

What are LEDs?

Before looking at the common types of LEDs, let's look at the general information about the respective devices. An LED is a semiconductor that is capable of converting electrical current into light. In this case, the semiconductor crystal, which is its main component, consists of several layers, characterized by 2 types of conductivity. Namely - hole and electronic.

Conductivity of the first type involves the transition of an electron from one atom to another, on which there is a free space. In turn, another electron comes to the first atom, another one to the previous one, etc. This mechanism operates due to covalent bonds between atoms. In this case, their movement does not occur. In fact, a positive charge moves, which physicists conventionally call a hole. In this case, when the electron passes into holes, light is released.

In its structure, an LED is generally similar to a rectifier diode. That is, it has 2 outputs - the anode and the cathode. This feature predetermines the need to observe polarity when connecting the LED to an electric current source.

The corresponding products are calculated in the general case for a direct current of 20 milliamperes. In principle, this value can be reduced, however, in this case, the color may change and the brightness of the LED may decrease. In turn, it is undesirable to increase the corresponding parameter. If the current exceeds the optimal value, then in order to reduce it to the required level, a limiting resistor is used.

There are quite a few things to keep in mind when installing LEDs. This is predetermined by their internal structure, form of performance. In some cases, it may be necessary to use a stabilizer for LEDs and other electronic components to ensure the functioning of the device into which the product in question is installed.

Depending on the composition of the semiconductors in the LED, it can be red, yellow, green or blue. For example, if the structure of the corresponding electronic component contains gallium nitride, then the LED will glow blue. Actually, one of the criteria based on which certain types of LEDs are distinguished may be their color.

Application

The first LEDs on the market were manufactured in metal housings. Gradually, plastic began to replace it. In this case, by color, it is, as a rule, selected taking into account the color of the LED glow. However, transparent plastic cases are also quite common.

The considered electronic devices are widely used in various fields. This is due to the fact that almost all are characterized by:

Energy efficiency;

Long service life;

The ability to determine the color of the glow, as well as adjust its power;

Security;

Environmentally friendly.

If we talk about energy efficiency, LEDs with the same luminous efficacy can have a significantly lower wattage than conventional lamps. The lower power output of the LED reduces the overall load on the building's power system. The service life of devices can be several tens of times longer than that of conventional lamps. At the same time, from the point of view of functions, LEDs may not be inferior to them at all.

With the formation of mass demand for such products, as well as their reduction in price, LEDs are increasingly used for the same purposes as conventional lamps. There are no difficulties in installing the corresponding solutions in comparison with traditional lighting devices. It is only important to make sure that a particular LED is suitable for installation in the electrical network of the room. This may require in advance - before purchasing LEDs - to identify its main parameters.

What other benefits might the solutions under consideration have?

So, it can be noted that the color temperature of the LED can be almost any - including the combination of the above colors. In addition, the devices can be supplemented with various light filters, which can significantly expand the scope of LEDs in terms of selecting the required color temperature.

The ability to control the power of the glow is another advantage of the devices under consideration. This option is perfectly combined with their high energy efficiency. The power of the LED can be adjusted automatically, based on the actual conditions of use of lighting devices. And this practically does not affect their service life.

LEDs are environmentally friendly, since they do not emit types of radiation harmful to humans. This characteristic, again, expands the possibilities of using the considered devices.

Classification: indicator and lighting solutions

Experts distinguish 2 main categories of LEDs - indicator and lighting. The first ones are intended mainly for creating a decorative light effect and are used as an element of decorating a building, room, or vehicle. Or as a tool for styling text - for example, on an advertising banner.

In turn, there are lighting LEDs. They are designed to increase the brightness of lighting in a room or in a certain area of \u200b\u200bthe territory - for example, if we consider LEDs for a car. The corresponding type of solution is an alternative to the use of conventional lamps and in many cases is more beneficial in terms of energy efficiency and environmental friendliness.

Execution types

But back to the classification of LEDs. You can define the widest range of reasons for their assignment to one or another category. The approach that is widespread among experts involves identifying the following main types of LEDs:

Fiber;

Let's consider them in more detail.

What is the specificity of DIP LEDs?

If we study in more detail how these types of LEDs appeared on the market, then DIP class devices can be attributed to the first that began to be sold in large quantities. These solutions are crystals that are housed in packages with optical components, in particular, a lens that creates a light beam.

DIP LEDs belong to the indicator category. They have another name - DIL. They are installed on the board, on which you first need to make holes. It can be noted that within the framework of the category under consideration, various types of LEDs can be distinguished, which differ in bulb diameter, color, and material of manufacture. In this case, the corresponding parameters can be presented in the widest range. The solutions under consideration are cylindrical in shape. The corresponding LEDs include both monochrome and multicolor devices.

Spider LED

This type of LED is generally very similar to previous devices. But they have twice as many pins - 4. While DIP LEDs have 2. The fact that the presented type of solutions has more outputs optimizes the heat dissipation and increases the reliability of the corresponding components. In practice, they are used in various fields, in particular as LEDs for cars.

SMD LEDs

These solutions are manufactured using the surface mount concept. That is, they are LEDs installed on a surface, while other solutions can be installed through push-through mounting.

The dimensions of LEDs of this type can be significantly smaller than those of alternative solutions, as well as the structures on which they are installed. Again, in this case, it is legitimate to talk about a more optimal heat sink. Using SMD LEDs in many cases allows you to expand the variability of the design of lighting structures.

SMD LEDs belong to the lighting category. They are characterized by a rather complex structure. So, the LED itself consists of a metal substrate. A crystal is fixed on it, which is soldered directly to the contacts of the substrate body. A lens is placed over the crystal. In this case, 1-3 LEDs can be installed on one substrate. SMD includes common types of ultra-bright LEDs such as 3528. These solutions are in high demand.

COB LEDs

The next popular type of LED is COB. It is made using a technology that involves installing a crystal directly on the board. This solution has many advantages:

Protection of the compound from oxidation;

Small design dimensions;

Heat dissipation efficiency;

Reducing the cost of LED installation - in comparison, in particular, with devices such as SMD.

If we consider the above types of LEDs, then it can be noted that the COB brand solutions can be attributed to the most innovative. This technology was first implemented by Japanese engineers in the late 2000s. Now these types of LEDs continue to gain popularity.

According to experts, the solutions under consideration may even become the most demanded on the market, especially if we talk about the commercial segment, about the field of household lighting. It is worth noting that there are areas in which the use of COB LEDs can be difficult. Among them is the production of professional lighting equipment. The fact is that the LEDs under consideration are not very optimal from the point of view of adapting to the organization of lighting with a set luminous intensity curve. In such cases, SMD devices may be more suitable.

The described diodes are lighting diodes. According to experts, they can be attributed to the best, based on the characteristics of the luminous flux. Available in a variety of colors, such as red, green, blue and white. The luminous flux of these models has a dispersion angle of 40-120 degrees.

More than 9 COB LEDs can be mounted on one substrate. They are covered with a phosphor, as a result of which they acquire a high brightness. It can be noted that the luminous flux of these solutions is higher than that of SMD devices. Thus, if we consider which type of LEDs is better, then according to the specified criterion, a COB class solution may have an advantage.

COB LEDs are also used in the automotive industry. They can be used as a component of headlights, rear lights, turn signals. The main thing is to correctly install the purchased devices. For this, it makes sense to contact experienced professionals.

Fiber LEDs

Fiber LEDs can be considered innovative. They appeared on the market recently, in 2015. The solutions in question were developed by engineers from South Korea.

These types of LEDs can be used in the manufacture of clothing. That is, it is quite possible to sew a shirt or T-shirt out of them that can glow. The production of clothing based on fiber LEDs also involves the use of various polymers, as well as aluminum compounds.

Filament LEDs

Another example of innovative LEDs is Filament solutions. Their main advantage is high energy efficiency. With the same wattage, for example with LEDs such as COB, solutions like Filament can provide higher light levels.

The one in question is most often used in manufacturing. Among the notable characteristics of the production of the corresponding LEDs is the implementation of mounting directly on a substrate made of glass. This approach makes it possible to spread the light emitted by the LED 360 degrees.

How to choose the best option?

How to determine the type of LED that is optimal for a particular design? There are a large number of criteria that can be guided in this issue. In principle, it is quite legitimate to determine the scope of the LED based on its classification according to the features that we discussed above. Let's study the specifics of choosing the appropriate electronic components, taking into account the characteristics of the devices:

LED selection: features of DIP solutions

As we noted above, DIP LEDs are among the earliest products to hit the market. Thus, they involve rather old, but still in demand technologies. Their main advantages are ease of installation, convenience of shape, low power consumption, low heating, as well as a fairly high degree of protection from external influences.

Most often, the LEDs in question are available in diameters of 3 and 5 mm. If we compare LEDs by type, then we can come to the conclusion that the solutions under consideration are the most optimal for use:

As elements of car tuning;

As decorative components;

As part of low-power - as an option for homemade - lanterns.

The LEDs under consideration have a relatively low cost and availability in the market. It can be noted that among the most common modifications are 12 volt LEDs. They can be found in a variety of online catalogs as well as a wide range of specialized stores. Actually, any 12 volt LEDs are characterized by a fairly high demand in the market.

Choice of LEDs: features of SMD solutions

The appearance of the corresponding type of solution is fundamentally different from others in that they have a flat shape. These electronic components are mounted without the use of feet. The current for LEDs of the SMD type is supplied to the terminals, which are located on their back side.

Thus, the installation of these devices is carried out without the use of holes. The placement of the LEDs can be done very compactly. As a result, the structure on which the corresponding devices are located may also be reduced.

The main ways of using the devices under consideration are the same auto-tuning, various types of interior lighting. Among the most significant advantages of these options are high brightness and light output. Combined with their small size, these solutions offer significant advantages over alternative product models.

Among the most common on the market today is the type of LED 3528. These products are widely used in the production of LED strips. The design of the corresponding products allows the production of three-color LEDs - with red, blue and green glow colors. Many other electronic components are manufactured based on the 3528 solutions, for example the SMD 5050 LED.

The products under consideration are also characterized by affordability. They are usually presented on the market in a wide range.

Choice of LEDs: Features of COB Solutions

First of all, it should be noted that a significant part of LEDs of the corresponding type are very powerful designs. Their characteristic feature is rapid light scattering, thanks to the placement of crystals on the surface, which provides dynamic heat dissipation.

The LEDs in question are very bright. This makes them in demand just for use in the construction of car headlights. It should be noted that these products should be installed taking into account a number of significant nuances - only experienced specialists can know them. Therefore, we recommend that you contact a competent service department to install the appropriate solutions.

Oleg Losev

Back in 1907, a faint glow was first noted emitted by silicon carbide crystals due to then unknown electronic transformations. In 1923, our compatriot, an employee of the Nizhny Novgorod radio laboratory, Oleg Losev, noted this phenomenon during his radio engineering studies with semiconductor detectors, but the intensity of the observed radiation was so insignificant that the Russian scientific community was not seriously interested in this phenomenon at that time.

Five years later, Losev specially engaged in studies of this effect and continued them almost until the end of his life (OV Losev died in besieged Leningrad in January 1942, before he was 39). Opening "Losev Licht", as the effect was called in Germany, where Losev was published in scientific journals, became a world sensation. And after the invention of the transistor (in 1948) and the creation of the theory of the p-n-junction (the basis of all semiconductors), the nature of the glow became clear.

In 1962, the American Nick Holonyak demonstrated the operation of the first LED, and soon afterwards announced the beginning of the semi-industrial production of LEDs.

LED (light emission diode - LED) is a semiconductor device, its active part, called a "crystal" or "chip", like conventional diodes, consists of two types of semiconductors - with electronic (n-type) and hole (p-type) conductivity. In contrast to a conventional diode, a light-emitting diode has a certain energy barrier at the interface between semiconductors of different types, which prevents the recombination of electron-hole pairs. An electric field applied to the crystal allows one to overcome this barrier and recombination (annihilation) of a pair occurs with the emission of a quantum of light. The wavelength of the emitted light is determined by the magnitude of the energy barrier, which, in turn, depends on the material and structure of the semiconductor, as well as the presence of impurities.

This means, first of all, a p-n junction is needed, that is, a contact between two semiconductors with different types of conductivity. For this, the contact layers of the semiconductor crystal are doped with different impurities: acceptor on one side, donor on the other.

But not every pn junction emits light. Why? First, the bandgap in the active region of the LED should be close to the energy of visible light quanta. Second, the probability of radiation during recombination of electron-hole pairs should be high, for which the semiconductor crystal should contain few defects, due to which recombination occurs without radiation. These conditions contradict each other to one degree or another.

In reality, in order to comply with both conditions, one p-n-junction in the crystal is not enough, and it is necessary to produce multilayer semiconductor structures, the so-called heterostructures, for the study of which the Russian physicist Academician Zhores Alferov received the Nobel Prize in 2000.

How the LED works

The main modern materials used in LED crystals:

• InGaN - high brightness blue, green and ultraviolet LEDs;
• AlGaInP - high brightness yellow, orange and red LEDs;
• AlGaAs - red and infrared LEDs;
• GaP - yellow and green LEDs.

In addition to lamp-type LEDs (3, 5, 10 mm, their shape really resembles a miniature light bulb with two leads), recently SMD - LEDs are becoming more common. They are of a completely different design that meets the requirements of the technology of automatic surface mounting on a printed circuit board ( surface mounted devices - SMD).

And super-bright LEDs of this type are called emitters (emitters).

SMD LEDs are more compact in size, allow automatic placement and soldering to the board surface without manual assembly. Some LED manufacturers produce special SMD diodes containing three crystals in one package, emitting light in three primary colors - red, blue and green. This makes it possible to obtain, by mixing their radiation, the entire color gamut, including white, in an ultra-compact size.

LED brightness characterized by luminous flux (Lumens) and axial luminous intensity (Candela), as well as the directional pattern. Existing LEDs of various designs emitting in a solid angle from 4 to 140 degrees.

Colour, as usual, is determined by the coordinates of chromaticity, the color temperature of white light (Kelvin), and the wavelength of the radiation (nanometers).

To compare the efficiency of LEDs with each other and with other light sources, the luminous efficiency is used: the value of the luminous flux per watt of electrical power (characteristic "Lumen / Watt").

Also an interesting characteristic is price of one lumen ($ / Lumen).

So, any LED consists of one or more crystals placed in a case with contact leads and an optical system (lens) that forms a luminous flux. The crystal radiation wavelength (color) depends on the semiconductor material and on dopants. Binovka (wavelength bin) crystals by the wavelength of radiation occurs during their manufacture. Crystals close in radiation spectrum are selected in a delivery batch at a modern production facility.

A wide range of optical characteristics, miniature size and flexible discrete control capabilities have provided the use of LEDs for creating a wide variety of lighting devices and products. The LED emits in a narrow part of the spectrum, at a certain wavelength its color is clear, which is especially appreciated by designers.

LED lifetime

The main characteristic of the reliability of LEDs is their service life. During operation, two situations are possible: the luminous flux of the emitter either partially decreased, or stopped altogether. The service life reflects these facts: they distinguish between the useful life (until the luminous flux falls below a certain limit) and full (until the device fails).

The lifespan directly depends on the type of LED, the current applied to it, the cooling of the LED chip, the composition and quality of the chip, the layout and assembly in general.

LEDs are believed to be extremely durable. But it is not so. The more current is passed through the LED during its service, the higher its temperature and the faster aging occurs. Therefore, the service life of high-power LEDs is shorter than that of low-power signal LEDs. Aging is expressed primarily in a decrease in brightness. When the brightness is reduced by 30% or half, the LED must be changed.

It is obvious, for example, that in LEDs with a power of 1 W (operating current 0.350 A) and more powerful, the heat release is much more abundant than in LEDs of the "5 mm" type, designed for a current of 0.02 A. In terms of light output, 1 LED with a power of 1 W replaces about 50 LEDs of the "5 mm" type, but also heats up more. Therefore, LED assemblies with high power LEDs require passive cooling (mounting on an MCPCB board (metal based PCB) and a heat sink).

Average service life

5mm -LED and SMD-LED:

White up to 50,000 hours with a luminous flux drop of up to 35% during the first 15,000 hours.
blue, green up to 70,000 hours with a drop in luminous flux up to 15% during the first 25,000 hours.
red, yellow up to 90,000 hours with a slight drop in luminous flux.

HI-POWER LED from 1W and above:

White up to 80,000 hours with a luminous flux drop of up to 15% during the first 10,000 hours.
blue, green up to 80,000 h.
red, yellow up to 80,000 h.

Why do white LEDs have the shortest lifespan?

Unfortunately, no one has yet invented structures that emit white light. The white diode is based on the InGaN structure, emitting at a wavelength of 470 nm (blue) and a phosphor (special composition) applied on top of it, emitting in a wide range of the visible spectrum and having a maximum in its yellow part. The human eye perceives a combination of this kind as white. The phosphor degrades the thermal performance of the LED, thus shortening the lifespan. Now world manufacturers are inventing new and new options for the effective application of the phosphor.

Most ultra-bright LEDs last between 50,000 and 80,000 hours. Is it a lot or a little?

50,000 hours is:

24 hours a day 5.7 years
18 hours a day 7.4 years
12 hours a day 11.4 years
8 hours a day 17.1 years

LEDs are warming up

Many people believe that LEDs practically do not heat up. So why do LEDs need a heat sink and what happens if there is no heat sink?

LEDs produce heat in a semiconductor junction. And the more powerful the LED, the more heat. Of course, indicator LEDs, for example, car alarm sensors, do not get very hot. But they have little in common with super-bright LEDs. If powerful LEDs are combined into a kind of assembly, and even installed in a sealed case, then the heating becomes significant.

And if there is no heat removal, the semiconductor junction overheats, which changes the characteristics of the crystal, and after a while the LED may fail. So it is very important to strictly control the amount of heat and ensure efficient heat dissipation.

How does the LED react to heating

Speaking about the temperature of the LED, it is necessary to distinguish between the temperature on the surface of the crystal and in the region of the pn junction. The service life depends on the first, the light output depends on the second. In general, with an increase in the pn junction temperature, the brightness of the LED decreases, because the internal quantum yield decreases due to the influence of crystal lattice vibrations. This is why good heat dissipation is so important.

The drop in brightness with increasing temperature is not the same for LEDs of different colors. It is higher for red and yellow LEDs, and less for green, blue and white.

Source: website of NGO RoSAT

Overall material rating: 5

SIMILAR MATERIALS (BY LABELS):

Father of the video Alexander Ponyatov and AMPEX

LED Graphic designation

Free translation of the "LED" article from Wikipedia.

A light emitting diode (LED) is a semiconductor light source. LEDs are used as indicators in many devices and are increasingly used for lighting purposes. It was developed as an electronic component suitable for practical use in 1962. The first samples emitted low intensity red light, but modern versions emit very high brightness in the entire visible, ultraviolet and infrared regions of the spectrum.

The LED is designed on the basis of a semiconductor diode. When an operating voltage is applied to the diode, the electrons with the holes swap places, releasing energy in the form of photons. This effect is called electroluminescence and the color of light (corresponds to the photon energy) is determined by the energy of the semiconductor's band gap. LED crystals, as a rule, are small in area (less than 1 mm2), the light distribution pattern and the reflection index are formed by an additional optical system included in the LED design. LEDs have many advantages over incandescent bulbs and other light sources, including lower power consumption, longer lifespan, increased reliability, smaller size, faster turn-on and longer durability. However, they are quite expensive and have higher power and heat dissipation requirements compared to traditional light sources. Current LED general lighting products are more expensive than comparable fluorescent sources.

LEDs are increasingly being used in automotive electronics as direction indicators, side lights and brake lights. LED traffic lights are already a common way to regulate traffic. The compact size of LEDs enables the development of new types of displays and screens, and their high switching speed is beneficial in advanced communication technologies.

Invention and first samples

The electroluminescence of a silicon carbide crystal (green) was discovered in 1907 by the English scientist Round in the Marconi laboratory. This phenomenon was then ignored. In 1923, the Soviet scientist O.V. Losev, working at the NRL (Nizhny Novgorod Radio Laboratory), carried out in-depth studies of such a phenomenon as radiative recombination, and also observed the emission of light emanating from crystals of silicon carbide SiC (carborundum). Long-term studies have made it possible to formulate the main principle of electroluminescence of semiconductor structures - injection recombination. In 1927 Losev patented the principle of semiconductor luminescence. The invention was published in Russian, German and English scientific journals, but did not receive practical application. In 1955, R. Braunstein of the Radio Corporation of America announced the presence of infrared radiation from gallium arsenide (GaAs) in combination with other semiconductor alloys. Braunstein observed infrared radiation generated by a simple diode structure based on gallium antimonide (GaSb), gallium arsenide, indium phosphide (InP), and silicon-germanium alloy (SiGe) at room temperature.

In 1961, developers R. Bard and G. Pitman, working at Texas Instruments, discovered that an alloy of gallium arsenide produces infrared radiation when an electric current is passed through it and received a patent for an IR LED.

The first LED emitting light in the visible spectrum was invented in 1962 by N. Holonyak, who works for General Electric. Since then, many have called him the "father" of modern LEDs. To understand that this is not so, it is enough to study the historical information about the research of O. V. Losev and other eminent scientists of 20-50. twentieth century. However, history is not fair, and we have what we have, and in the 60s Russia lost its priority in the invention of semiconductor light sources.

In 1972, former Holonyak student G. Graford invented the yellow LED and increased the brightness of red and red-orange LEDs tenfold. In 1976, T. Pearsell created the first super-bright LED for optical fiber telecommunications, inventing new semiconductor alloys specially adapted for transmitting light through optical fibers.

Until 1968, visible and infrared LEDs had a huge cost, about 200 USD apiece, which created difficulties for practical use. But in 1968, Monsanto pioneered the mass production of gallium arsenide phosphide (GaAsP) -based visible light LEDs, suitable for use as indicators. Hewlett Paccard, which introduced LEDs in 1968, used Monsanto LEDs to make digital displays and calculators.

Practical use of the first LEDs

The first commercial use of LEDs was associated with their use as a replacement for indicators previously based on the use of incandescent lamps. Seven-segment indicators were made from LEDs, built into expensive laboratory instruments, used in test equipment, but later LEDs began to be used in the manufacture of televisions, radios, telephones, calculators and even watches. Red LEDs used for these purposes had a brightness sufficient for use only as indicators. LEDs of other colors were even less bright. All types of led were produced in standard sizes 3 or 5 mm.

Further development of LED technology

The first super-bright blue LEDs based on InGaN were demonstrated by Sh. Nakamura from the Japanese company Nichia. This marked the beginning of a new era in the use of LEDs - the use as a light source for lighting. The combination of blue light and yellow phosphorus produced white light.

Thanks to this discovery, LED technology began to develop rapidly. In February 2008, employees at Bilkent University in Turkey announced they were receiving 300 lumens of visible light per watt of light output. It was a warm white using nanocrystals.

In January 2009, researchers from Cambridge, led by S. Humphrey, reported on the growth of gallium nitride on a silicon substrate. This method can reduce production costs in the production of ultrabright LEDs by 90% compared to the growth of structures on a sapphire substrate.

Physical aspects

How the LED works

Like a regular diode, an LED contains semiconductor crystals that create a pn junction. As with a conventional diode, the current easily flows in the forward direction from the anode to the cathode and does not flow in the opposite direction. When electrons meet holes, they lose energy, which is converted into photons. The wavelength at which photons are emitted depends on the material forming the pn junction.

The invention of LEDs began with the fabrication of gallium arsenide structures that emit red and infrared light. The current development of semiconductor technology allows visible light to be produced in a wide variety of colors.

Electrons and holes

Semiconductors are intermediate between conductors and insulators (dielectrics). At low temperatures, most of the outer electrons in a semiconductor "sit" in the atoms in their places. But they are bound to atoms weaker than in an insulator. Moreover, with an increase in temperature, the resistance of semiconductors decreases, that is, a semiconductor when heated does not reduce its electrical conductivity, like a metal, but, on the contrary, increases it. In other words, the number of free electrons capable of carrying electric current increases in a semiconductor.

When energy (heat or light) is supplied to the crystal lattices of semiconductors, some of the electrons "run away" from the upper atomic shells, and a positive charge is formed. The place where the electron is missing in the lattice is called a "hole".

Under the action of an electric voltage, electrons drift to one electrode (positive pole), and holes - to another (negative), and their place is immediately taken by free electrons. The laws of motion of holes are such that physicists conditionally ascribe both a charge (equal to the charge of an electron, but positive) and an "effective mass" to these "empty places".

In a pure semiconductor, the conductivity of which is due to thermal excitation, the same number of electrons and holes move in opposite directions. If you add atoms of other elements to the semiconductor, its conductivity can be significantly increased. When dopants are introduced into various parts of the crystal lattice of a semiconductor, the so-called impurity conductivity (as opposed to intrinsic conductivity) arises, which, depending on the valence of the alloying elements, is called either electronic (n-type conductivity) or hole (p-type).

In the same sample of semiconductor material, one section may have p-conductivity, and the other - n-conductivity. A boundary layer arises between such regions through which the majority carriers (electrons or holes) diffuse, seeking to equalize the concentration values \u200b\u200bon both sides of the layer. The pn junction formed in this layer can be acted upon by an external voltage, amplifying or, conversely, "blocking" the current passing through the crystal - on the basis of this principle, diodes and transistors operate. With a positive polarity of the external voltage (plus - to the p-band, minus - to the n-band), the barrier in the p-n-junction decreases, and electrons and holes "jump" (recombine) into opposite bands, resulting in the release of energy.

At first, semiconductor devices were only "homojunction" (as in the case of the first transistor) - the pn junction occurred inside the crystal of one chemical substance. But almost immediately the idea of \u200b\u200bhetero-devices appeared, in which such a transition is formed at the junction of two different semiconductors. The implementation of this idea made it possible to create smaller devices with greater efficiency and functionality (for example, the world's first "homojunction" semiconductor LEDs, and then lasers could operate only at liquid nitrogen temperature, and heterojunction ones that appeared later function at room temperature).

Most of the materials used to make LEDs are highly reflective. This is necessary so that as much of the light produced by the LED as possible escapes from its surface outside the enclosure. That is why a large number of studies around the world are devoted to this.

Efficiency and parameters of use

A conventional LED indicator is designed for a power of no more than 30-60 mW. In 1999 Philips Lumileds introduced a 1 Watt high-power LED. In this LED, a semiconductor crystal was used with a much larger area than those used in conventional indicator type LEDs. It was mounted on a metal base, which made it possible to organize efficient heat removal from the crystal.

One of the key positions in determining the efficiency of an LED is the light output per unit of power. White LED quickly achieved and surpassed the performance of conventional incandescent-based systems. In 2002, Lumileds produced a 5W LED with 18-22 lumen / Watt lumen output. In comparison, a typical 60-100W incandescent lamp produces about 15 lumens per watt. Fluorescent lamp - about 100 lm / W. The main problem in the development of high-power LEDs is the decrease in luminous flux with increasing current passing through the crystal.

In September 2003, Cree demonstrated a new type of blue LED that produces 24 mW at 20 mA. This made it possible to commercialize white LEDs with an efficiency of 65 lm / W at a current of 20 mA, which became the brightest on the market at that time and exceeded the efficiency of incandescent lamps by more than four times. In 2006, the same company presented a prototype of a white LED with a light output of 131 lm / W at 20 mA.

It should be noted that LED power of 1 W or more is quite sufficient for commercial use as a source of primary lighting. Typical current of such LEDs is 350 mA. Although the leading manufacturers produce LEDs with an efficiency higher than 100 lm / W, in actual use, much depends on the operating conditions and the design of the luminaire. The US Department of Energy, which tested commercially available LED lamps in 2008, provided data indicating that most of these lamps have an average efficiency of 31 lm / W.

Cree provided data on a laboratory prototype LED with an efficiency of 161 lm / W at room temperature and a light temperature of 4689 K on November 19, 2008.

Faults and LED lifespan

Solid state devices such as LEDs are very susceptible to damage when operated at low temperatures and low currents. Many LEDs produced in the 70-80s are still in use today. In theory, LED performance is unlimited in time, however, increased current and high temperature can easily destroy them. The main symptom of a LED malfunction is a strong decrease in the light output at the nominal operating voltage. The development of new types of LEDs has led to higher operating currents and an increase in crystal temperature. The reaction of materials from which high-power LEDs are made to such conditions has not yet been fully studied, therefore crystal degradation is one of the main causes of failures. An LED is considered inoperative when its light output drops by 75%.

Materials

The following table shows the dependence of the LED light color on the semiconductor material

	Colour	Wavelength (nm)	Voltage (V)	Semiconductor material
	Infrared	λ\u003e 760	ΔV< 1.9	Gallium arsenide (GaAs) Aluminum gallium arsenide (AlGaAs)
	Red	610 < λ < 760	1.63 < ΔV < 2.03	Aluminum gallium arsenide (AlGaAs)
	Orange	590 < λ < 610	2.03 < ΔV < 2.10	Gallium arsenide phosphide (GaAsP) Aluminum gallium indium phosphide (AlGaInP) Gallium (III) phosphide (GaP)
	Yellow	570 < λ < 590	2.10 < ΔV < 2.18	Gallium arsenide phosphide (GaAsP) Aluminum gallium indium phosphide (AlGaInP) Gallium (III) phosphide (GaP)
	Green	500 < λ < 570	1.9 [ 32] < ΔV < 4.0	Indium gallium nitride (InGaN) / Gallium (III) nitride (GaN) Gallium (III) phosphide (GaP) Aluminum gallium indium phosphide (AlGaInP) Aluminum gallium phosphide (AlGaP)
	Blue	450 < λ < 500	2.48 < ΔV < 3.7	Zinc selenide (ZnSe) Indium gallium nitride (InGaN) Silicon carbide (SiC) as substrate Silicon (Si) as substrate - (under development)
	Violet	400 < λ < 450	2.76 < ΔV < 4.0	Indium gallium nitride (InGaN)
	Purple	different types	2.48 < ΔV < 3.7	Dual blue / red LEDs, blue with red phosphorus, white with magenta filter
	UV	λ < 400	3.1 < ΔV < 4.4	diamond (235 nm) [33] Boron nitride (215 nm) [34] [35] Aluminum nitride (AlN) (210 nm) [36] Aluminum gallium nitride (AlGaN) Aluminum gallium indium nitride (AlGaInN) - (down to 210 nm) [37]
	White	Wide range	ΔV \u003d 3.5	Blue / UV diode and yellow phosphorus

Blue LEDs

Blue LED

Blue LEDs are based on GaN and InGaN alloys. The combination with red and green LEDs produces pure white, but this principle of white formation is now rarely used.

The first blue LED was made in 1971 by Jacques Pankove (inventor of gallium nitride). But it produced too little light to be used in practice. The first bright blue diode was demonstrated in 1993 and gained widespread acceptance.

White light

There are two ways to get sufficient white light using LEDs. The first of them is the combination of crystals of three primary colors - red, blue and green - in one body. Mixing these colors produces white. Another way is to use a phosphor to convert blue or ultraviolet light into a broad spectrum white. A similar principle is used in the production of fluorescent lamps.

RGB systems

White can be obtained by mixing different colors, the most commonly used combination being red, blue and green. But due to the need to control the mixing and the degree of color dispersion, the production cost of RGB LEDs is quite high. Nevertheless, this method is interesting to many researchers and scientists, as it allows you to get different shades of color. Moreover, the efficiency of this method for producing white light is very high.

There are several types of multicolor white LEDs - di-, tri-, and tetrachromatic. There are several key features of each of these types, including color stability, color rendering, and luminous efficiency. High luminous efficiency means a low color rendering index (CRI). For example, a dichromatic white LED has the best luminous efficiency (around 120 lm / W) but the lowest CRI. Tetrachromatic - low light efficacy but excellent CRI. Trichromatic is located approximately in the middle.

Although multicolor LEDs are not the best solution for achieving white color, their use can create systems that produce millions of different shades of color. The main problem in this case is the different values \u200b\u200bof luminous efficacy for the primary colors. As the temperature rises, this causes the required color to "float away" and, as a consequence, to more stringent requirements for power and control systems.

Phosphorus LEDs

The spectrum of a white LED is determined by blue light, which is emitted by a GaN-based crystal (peak in the region of 465 Nm) and, passing through yellow phosphorus (500-700 Nm), is converted to white. The use of different types and shades of phosphorus produces different shades of white - from the warmest to the coldest. The quality of color rendition also depends on this. The application of several layers of phosphorus of different types to the blue crystal allows achieving the highest CRI.

Phosphorus-based LEDs are less efficient than conventional LEDs because some of the light is scattered in the phosphorus layer, and phosphorus itself is also subject to degradation. Nevertheless, this method remains the most popular in the commercial production of white LEDs. The most commonly used yellow phosphoric material is Ce3 +: YAG.

Also, white LEDs can be made on the basis of ultraviolet LEDs using red and blue phosphorus with the addition of zinc sulfide (ZnS: Cu, Al). This principle is similar to that used in fluorescent lamps. This method is worse than the previous one, but it allows you to achieve better color reproduction. In addition, UV diodes have a high luminous efficiency. On the other hand, UV radiation is harmful to humans.

Organic LEDs (OLED)

If the base of the emitting surface of the LED is organic in origin, such an LED is called OLED (Organic Light Emitting Diode). The emitting material can be a small molecule in the crystallization phase or a polymer. Polymer crystals can be flexible, they are called PLED or FLED, respectively.

Compared to conventional LEDs, OLEDs are lighter, and polymer also makes the light source flexible. In the future, on the basis of such LEDs, it is planned to manufacture flexible inexpensive displays for portable devices, light sources, decorative systems, and luminous clothing. But so far the level of OLED development does not allow their commercial use.

Quantum Dot LEDs (Experimental Development)

A new LED technology developed by M.Bowers involves coating a blue LED with "quantum dots", which begin to emit white light when exposed to blue light from the LED. This technology produces warm yellow-white light similar to incandescent light. "Quantum dots" are semiconductor nanocrystals with unique optical characteristics. Their radiation color can be changed over a wide range - from visible to invisible - any color within the CIE diagram.

In September 2009, the Nanoco Group announced a research agreement with one of the largest Japanese companies. The topic of research is the further development of "quantum dot" technology for use in LCD television displays.

To be continued

Since the invention of electric lighting, scientists have created more and more economical sources. But a real breakthrough in this area was the invention of LEDs, which are not inferior in luminous flux to their predecessors, but consume many times less electricity. Their creation, from the first indicator element to the brightest Cree diode to date, was preceded by a huge amount of work. Today we will try to make out the various characteristics of LEDs, find out how these elements evolved and how they are classified.

Read in the article:

The principle of operation and the device of light diodes

LEDs are distinguished from conventional lighting devices by the absence of a filament in it, a fragile bulb and gas in it. This is a fundamentally different element from them. Scientifically speaking, the glow is created by the presence of p- and n-type materials in it. The former accumulate a positive charge, and the latter negative. P-type materials store electrons in themselves, while n-type materials form holes (places where electrons are absent). At the moment an electric charge appears on the contacts, they rush to the pn junction, where each electron is injected into the p-type. From the side of the opposite, negative n-type contact, as a result of such a movement, a glow appears. It is caused by the release of photons. However, not all photons emit light visible to the human eye. The force that makes the electrons move is called the LED current.

This information is useless for the average man in the street. It is enough to know that the LED has a durable housing and contacts, of which there can be from 2 to 4, and also that each LED has its own nominal voltage required for glowing.

Good to know! The connection is always made in the same order. This means that if a “+” is connected to the “-” contact on the element, then there will be no glow - p-type materials simply will not be able to charge, which means there will be no movement to the transition.

Classification of LEDs by their field of application

Such elements can be indicator and lighting. The first were invented before the second, while they have long been used in radio electronics. But with the advent of the first lighting LED, a real breakthrough in electrical engineering began. The demand for this type of lighting fixtures is growing steadily. But progress does not stand still - all new types are invented and introduced into production, which are becoming brighter, without consuming more energy. Let's take a closer look at what LEDs are.

Indicator LEDs: a little history

The first such red LED was created in the middle of the 20th century. Although it had low energy efficiency and emitted a dim glow, the direction turned out to be promising and development in this area continued. In the 70s, green and yellow elements appeared, and work on their improvement did not stop. By the 90th year, the strength of their luminous flux reaches 1 Lumen.

1993 saw the introduction of the first blue LED in Japan, which was much brighter than its predecessors. This meant that now, by combining three colors (which make up all the shades of the rainbow), you can get any. In the early 2000s, the luminous flux already reaches 100 Lumens. Nowadays, LEDs do not stop improving, increasing brightness without increasing power consumption.

The use of LEDs in domestic and industrial lighting

Now similar elements are used in all industries, whether it be machine or automobile construction, lighting production halls, streets or apartments. If we take the latest developments, we can say that even the characteristics of LEDs for flashlights are sometimes not inferior to the old 220V halogen lamps. Let's try to give one example. If we take the characteristics of a 3 W LED, then they will be comparable to the data of an incandescent lamp with a consumption of 20-25 W. It turns out that energy savings are almost 10 times, which, with daily constant use in an apartment, gives a very significant benefit.

Why are LEDs good and are there any disadvantages?

A lot can be said about the positive qualities of LEDs. The main ones are:

As for the negative sides, there are only two of them:

• They work only with constant voltage;
• It follows from the first - the high cost of lamps based on them due to the need to use (electronic stabilizing unit).

What are the main characteristics of LEDs?

When choosing such elements for a particular purpose, everyone pays attention to their technical data. The main thing to pay attention to when purchasing devices based on them:

• consumption current;
• rated voltage;
• power consumption;
• color temperature;
• luminous flux strength.

This is what we can see on the label. In fact, there are much more characteristics. Let's talk about them now.

LED current consumption - what is it

The current consumption of the LED is 0.02 A. But this applies only to elements with one crystal. There are also more powerful light diodes, which can include 2, 3 or even 4 crystals. In this case, the current consumption will increase in multiples of the number of chips. It is this parameter that dictates the need to select a resistor that is soldered to the input. In this case, the resistance of the LED prevents the high current from instantly burning out the LED element. This can happen due to high mains current.

Rated voltage

The voltage of an LED is directly related to its color. This is due to the difference in materials for their manufacture. Let's consider this dependence.

LED color	Material	Forward voltage at 20 mA
		Typical value (V)	Range (V)
IR	GaAs, GaAlAs	1,2	1,1-1,6
Red	GaAsP, GaP, AlInGaP	2,0	1,5-2,6
Orange	GaAsP, GaP, AlGaInP	2,0	1,7-2,8
Yellow	GaAsP, AlInGaP, GaP	2,0	1,7-2,5
Green	GaP, InGaN	2,2	1,7-4,0
Blue	ZnSe, InGaN	3,6	3,2-4,5
White	Blue / UV phosphor diode	3,6	2,7-4,3

Light diode resistance

By itself, the same LED can have different resistances. It changes depending on the inclusion in the circuit. In one direction - about 1 kOhm, in the other - several megohms. But there is a nuance here. LED resistance is non-linear. This means that it can change depending on the voltage applied to it. The higher the voltage, the lower the resistance will be.

Light output and luminous angle

The luminous flux angle of LEDs may vary, depending on their shape and material of manufacture. It cannot exceed 120 0. For this reason, if more diffusion is required, special reflectors and lenses are used. This is the quality of "directional light" and contributes to the highest luminous flux, which can reach 300-350 lumens for a single 3W LED.

LED lamp power

The power of the LED is a purely individual value. It can vary from 0.5 to 3 watts. It can be determined by Ohm's law P \u003d I × U where I - current strength, and U - LED voltage.

Power is quite an important indicator. Especially when it is necessary to calculate which one is needed for a given number of elements.

Colour temperature

This parameter is similar to other lamps. The temperature spectrum is closest to LED fluorescent lamps. The color temperature is measured in K (Kelvin). The glow can be warm (2700-3000K), neutral (3500-4000K) or cold (5700-7000K). In fact, there are many more shades, the main ones are indicated here.

Chip size of LED element

It will not be possible to measure this parameter independently upon purchase, and now the dear reader will understand why. The most common sizes are 45x45 mil and 30x30 mil (corresponding to 1 W), 24x40 mil (0.75 W) and 24x24 mil (0.5 W). If translated into a more familiar measurement system, then 30x30 mil will be equal to 0.762x0.762mm.

There can be many chips (crystals) in one LED. If the element does not have a phosphor layer (RGB - color), then the number of crystals can be calculated.

Important! You shouldn't buy very cheap Chinese-made LEDs. They can be not only of low quality, but their characteristics are often overstated.

What are SMD LEDs: their characteristics and difference from conventional ones

A clear decoding of this abbreviation looks like Surface Mount Devices, which literally means "surface mounted". To make it clearer, you can recall that ordinary light diodes of a cylindrical shape on legs are recessed into the board and soldered on the other side. In contrast, SMD components are fixed with paws on the same side where they are. This mounting makes it possible to create double-sided printed circuit boards.

Such LEDs are much brighter and more compact than conventional ones and are elements of a new generation. Their dimensions are indicated in the marking. But do not confuse the size of the SMD LED and the crystal (chip) of which there can be many in the component. Let's take a look at several of these LEDs.

LED SMD2835 parameters: dimensions and characteristics

Many novice craftsmen confuse the SMD2835 marking with the SMD3528. On the one hand, they should be the same, because the marking indicates that these LEDs are 2.8x3.5 mm and 3.5 x 2.8 mm, which is the same. However, this is a delusion. The technical characteristics of the SMD2835 LED are much higher, while it has a thickness of only 0.7 mm versus 2 mm for the SMD3528. Consider the SMD2835 data with different wattage:

Parameter	Chinese 2835	2835 0.2W	2835 0.5W	2835 1W
Luminous flux, Lm	8	20	50	100
Power consumption, W	0,09	0,2	0,5	1
Temperature, in degrees С	+60	+80	+80	+110
Consumption current, mA	25	60	150	300
Voltage, V	3,2

As you can understand, the technical characteristics of the SMD2835 can be quite varied. It all depends on the quantity and quality of crystals.

LED 5050 Features: Larger SMD Component

Quite surprisingly, with its large dimensions, this LED has a lower luminous flux than the previous version - only 18-20 lm. The reason for this is the small number of crystals - usually there are only two of them. The most common application for such elements is found in LED strips. The density of a strip is usually 60 pcs / m, which gives a total of about 900 lm / m. Their advantage in this case is that the tape gives a uniform calm light. In this case, the angle of its illumination is maximum and is equal to 120 0.

These elements are produced with a white glow (cold or warm shade), one-color (red, blue or green), three-color (RGB), as well as four-color (RGBW).

Characteristics of SMD5730 LEDs

Compared to this component, the previous ones are already deprecated. They can already be called even super bright LEDs. 3 volts, which power both 5050 and 2835, give out here up to 50 lm at 0.5 W. The technical characteristics of the SMD5730 are an order of magnitude higher, which means they need to be considered.

Still, this is not the brightest LED of the SMD components. Comparatively recently, elements appeared on the Russian market that literally “plugged” all the others. We will talk about them now.

LEDs "Cree": characteristics and technical data

To date, there are no analogues of Cree products. The characteristics of the ultra-bright LEDs of their production are really amazing. If the previous elements could boast of a luminous flux of only 50 lm from one crystal, then, for example, the characteristics of the XHP35 LED from "Cree" speak of 1300-1500 lm from one chip as well. But their power is also greater - it is 13 watts.

If we summarize the characteristics of various modifications and models of LEDs of this brand, then you can see the following:

The luminous flux of SMD LED "Cree" is called a bin, which must be affixed to the package. Recently, a lot of fakes under this brand have appeared, mainly of Chinese origin. When buying, it is difficult to distinguish them, but after a month of use, their light dims and they cease to differ from others. At a fairly high cost, such an acquisition will be a rather unpleasant surprise.

We offer you a short video on this topic:

Checking the LED with a multimeter - how to do it

The simplest and most affordable way is to dial. Multimeters have a separate switch position specifically for diodes. Switching the device to the desired position, touch the probes to the LED legs. If the display shows the number "1", you should change the polarity. In this position, the multimeter's buzzer should beep and the LED should be on. If this did not happen, then it is out of order. If the light diode is working properly, but it does not work when soldered into the circuit, there may be two reasons for this - its incorrect location or the failure of the resistor (in modern SMD components it is already built-in, which will be clear during the "dialing" process).

LED color coding

There is no generally accepted world labeling of such products; each manufacturer designates the color as it suits him. In Russia, color coding of LEDs is used, but few people use it, because the list of elements with letter designations is quite impressive and hardly anyone wants to remember it. The most common letter designation, which many consider to be generally accepted. But such markings are more often found not on powerful elements, but on LED strips.

Decoding of the LED strip marking code

In order to understand how the tape is marked, you need to pay attention to the table:

Position in the code	Appointment	Designations	Explanation of designation
1	Light source	LED	Light-emitting diode
2	Glow color	R	Red
		G	Green
		B	Blue
		RGB	Any
		CW	White
3	Installation method	SMD	Surface Mounted Device
4	Chip size	3028	3.0 x 2.8mm
		3528	3.5 x 2.8 mm
		2835	2.8 x 3.5mm
		5050	5.0 x 5.0 mm
5	Number of LEDs per meter of length	30
		60
		120
6	Degree of protection:	IP	International Protection
7	From penetration of solid objects	0-6	According to GOST 14254-96 (IEC 529-89 standard) "Degrees of protection provided by enclosures (IP code)"
8	From liquid penetration	0-6

For example, let's take the specific marking LED CW SMD5050 / 60 IP68. From it you can understand that we have a white LED strip for surface mounting. The elements installed on it are 5x5mm in size, in the amount of 60 pcs / m. The degree of protection allows her to work under water for a long time.

What can you do with your own LEDs?

This is a very interesting question. And if you answer it in detail, then it will take a very long time. The most common use of LEDs is to illuminate suspended and suspended ceilings, a kitchen work area, or even a computer keyboard.

Expert opinion

Engineer-designer of ES, EM, EO (power supply, electrical equipment, interior lighting) LLC ASP North-West

Ask a specialist

“For such elements to work, you need a power stabilizer or controller. You can even take it from an old Chinese garland. Many "craftsmen" write that an ordinary step-down transformer is enough, but this is not so. In this case, the diodes will blink. "

Current stabilizer - what function does it perform

A stabilizer for LEDs is a power supply that steps down voltage and equalizes current. In other words, it creates conditions for the normal operation of the elements. At the same time, it protects against an increase or decrease in voltage on the LEDs. There are stabilizers that can not only regulate the voltage, providing smooth fading of the light elements, but also control the color or flicker modes. They are called controllers. Similar devices can be seen on garlands. They are also sold in electrical stores for switching with RGB tapes. These controllers are equipped with remote controls.

The scheme of such a device is not complicated, and if desired, the simplest stabilizer can be made by hand. This requires only a little knowledge in electronics and the ability to hold a soldering iron in your hands.

Daytime running lights on the car

The use of light diodes in the automotive industry is fairly common. For example, DRLs are made exclusively with their help. But if the car is not equipped with running lights, then purchasing them can hit the budget. Many car enthusiasts get by with cheap LED strip, but this is not a very good idea. Especially if the strength of its luminous flux is small. A good solution may be to purchase a self-adhesive tape based on Cree diodes.

It is quite possible to make DRL with the help of those already out of order, by placing new, powerful diodes inside the old cases.

Important! Daytime running lights are designed specifically to make the car noticeable during the day and not at night. It makes no sense to check how they will shine in the dark. DRLs should be visible in sunlight.

Flashing LEDs - what is it for?

A good use of such elements would be a billboard. But if it shines statically, it will not attract due attention. The main task is to assemble and solder the shield - this requires some skills, which are not difficult to acquire. After assembly, you can mount the controller from the same garland. The result is flashing ads that will clearly grab attention.

Color music on light diodes - is it difficult to make it

This job is no longer for beginners. In order to assemble a full-fledged color music with your own hands, you need not only an accurate calculation of the elements, but also knowledge of radio electronics. But still, its simplest version is quite within the power of everyone.

You can always find a sound sensor in electronics stores, and many modern switches have one (light on cotton). If you have an LED strip and a stabilizer, then you can achieve the desired result by running the "+" from the power supply to the strip through a similar cracker.

Voltage indicator: what to do if it burns out

Modern indicator screwdrivers consist of a light diode and resistors with an insulator. Most often it is an ebony insert. If the element inside burns out, it can be replaced with a new one. And the color will already be chosen by the craftsman himself.

Another option is to make chain continuity. To do this, you will need 2 penlight batteries, wires and a light diode. Having connected the batteries in series, we solder one of the element legs to the plus of the battery. The wires will go from the other leg and from the negative of the battery. As a result, when closed, the diode will light up (if the polarity is not reversed).

LED connection diagrams - how to do everything correctly

Such elements can be connected in two ways - in series and in parallel. It should not be forgotten that the light diode must be positioned correctly. Otherwise, the scheme will not work. In conventional elements with a cylindrical shape, this can be determined as follows: a flag is visible on the cathode (-), it is slightly larger than the anode (+).

How to calculate LED resistance

The calculation of the resistance of the LED is very important. Otherwise, the element will simply burn out, unable to withstand the value of the network current.

This can be done using the formula:

R \u003d (VS - VL) / I, where

• VS - supply voltage;
• VL – rated voltage for LED;
• I - LED current (usually 0.02 A, which is equal to 20 mA).

Anything is possible if you wish. The scheme is quite simple - we use a power supply from a broken mobile phone or any other. The main thing is that it has a rectifier. It is important not to overdo it with the load (with the number of diodes), otherwise there is a risk of burning the power supply. A standard charger can handle 6-12 cells. You can mount a colored backlight for a computer keyboard by taking 2 blue, white, red, green and yellow elements. It turns out pretty nice.

Helpful information! The voltage that the power supply produces is 3.7 V. This means that the diodes must be connected in series in parallel in pairs.

Parallel and serial connection: how they are done

According to the laws of physics and electrical engineering, when connected in parallel, the voltage is distributed evenly over all consumers, remaining unchanged on each of them. With sequential installation, the flow is divided and at each of the consumers it becomes a multiple of their number. In other words, if you take 8 light diodes connected in series, they will work normally from 12 V. If you connect them in parallel, they will burn out.

Connecting 12V light diodes as the best option

Any LED strip is designed to be connected to a stabilizer that produces 12 or 24 V. Today, a huge range of products from various manufacturers with these parameters is presented on the shelves of Russian stores. But nevertheless, tapes and controllers of exactly 12 V predominate. This voltage is safer for humans, and the cost of such devices is lower. We talked about independent connection to the 12 V network a little above, but there should be no problems with connecting to the controller - a diagram is attached to them, which even a student can figure out.

Finally

The popularity that light diodes are gaining cannot but rejoice. After all, this makes progress move forward. And who knows, perhaps, in the near future, new LEDs will appear, which will be an order of magnitude higher in characteristics than the existing ones.

We hope our article was useful to the dear reader. If you have any questions on the topic, please ask them in the discussions. Our team is always ready to answer them. Write, share your experience, because he can help someone.

Video: how to connect the LED correctly

Everywhere there is a replacement of conventional lamps with LEDs. It is by far the best lighting solution for cars and homes, more durable and easier to replace. So, what is the principle of the LED and how to choose it correctly?

LED and how it works

An LED is a special electrical device that converts current into some kind of glow. Today, LEDs are more commonly known as LED, which stands for light emitting diode.

The device is a semiconductor device and consists of a crystal chip, a housing, pins and an optical device. The light comes from the crystal, and its color may vary depending on the material used. The brightness of the LED, as well as its color, can also be different. So, for example, for a greater light effect, several crystals are often inserted into one lamp, producing a monochromatic light, which together forms a bright glow.

The brightness of the device directly depends on the strength of the electric current supplied to it. In turn, an excessively powerful flow of electricity causes a rapid overheating of the inner crystal and disables it. In view of this, the design of the LED is somewhat costly in terms of the cost of materials, which somewhat negatively affects the choice of such lamps.

By brightness, LEDs are usually divided into categories:

• ultra-bright, their minimum power is 1 W;
• high brightness LEDs - up to 20 mW;
• standard lamps.

Today, a LED block is widely used, which is built into a lamp. Thanks to it, the choice of the optimal glow mode is also possible.

The advantage of LEDs over other types of lighting

LED is the best choice of lighting type today, which has several advantages:

• Durability.
• Adjustable lamp color and brightness.
• Color saturation, the ability to match red, blue, green LEDs or make the color change.
• Possibility of electronic control.
• Environmentally friendly materials that do not contain heavy substances that are harmful to the environment and hazardous if not properly disposed of.
• Low power consumption, several times more light is generated per watt.
• The light is pure and as close to natural as possible.
• They do not overheat thanks to a competent light outlet.
• Reliability and durability.

Why have LEDs become popular in the auto industry? This type of lighting is ideal for vehicles, gradually replacing halogen and xenon bulbs. Its positive qualities:

• the ability to direct the lighting behind the steering wheel - the creation of adaptive headlights;
• looks aesthetically better than other types of headlights;
• increased safety through improved visibility on the road;
• vibration resistance;
• often LEDs are installed in a housing where moisture does not penetrate;
• reaching the working condition is faster, for this reason the brake lights work better.

Of course, these advantages are inherent only in really high-quality products, so it is not worth saving on them, especially since the period of their operation has been significantly increased compared to Chinese products. Additionally, the service life of LED lamps, when compared with conventional ones, is also much longer.

Classification of LEDs

There are 2 main types of LEDs - for backlighting (indicator) and for lighting. Their strength and durability depend on the supply of electric current, therefore, the second type of LEDs serves a shorter period, since the crystal wears out faster. However, these lighting devices are very durable and last several thousand hours.

A lighting LED is a device that provides reliable and powerful light. It is widely used in design, creating the desired level of illumination.

According to the type of case, it is customary to distinguish LEDs in the form of "Star", "Piranha" and SMD. Among them, the most popular are "Piranhas", as their luminous flux seems to be of higher quality. Their design feature is the shape of a rectangle with leads along the edges, with the help of them, a rigid adhesion to the surface is provided. In addition, the device's substrate has excellent heat dissipation properties. These devices are widely used in automobiles and advertising. They come in various sizes and colors: red, white, green, blue LED.

Indicator LEDs have a simpler design, their light is not as strong and are used to illuminate displays and dashboards. Round, oval and rectangular indicator LEDs are distinguished in shape.

Lenses also differ from each other, they can be built into lighting, and in some are designed to diffuse light (the vast majority of these devices), others - for focusing, thanks to a directed beam of light produced. Moreover, in the second group, lenses are distinguished: flat, conical and round.

By the color of the lens, LEDs are:

• colorless transparent;
• colored transparent;
• painted matt.

In addition, the color scheme of the device is now very diverse. There is yellow, red, blue, green LED, etc. These colors are skillfully combined to create an even wider spectrum. The most difficult, oddly enough, to get a pure white.

A white LED is obtained in three ways:

• using red, blue and green in the right proportions at the same time gives the impression of white;
• the use of a blue diode with an admixture of yellow;
• the third method requires the use of fluorescent materials, which converts ultraviolet light, acting like a fluorescent lamp.

White LED is the most common, although somewhat difficult to obtain. It can be cold and warm. On a light bulb, this parameter is usually indicated in kelvin, the lower the indicator, the yellower and warmer the color will be. Manufacturers recommend opting for an average parameter, although cold, bluish light can also quickly get used to.

Choosing a lamp for home

The choice of a lamp for the home includes several stages, where it is necessary to determine the type of network, the diameter of the base and the appearance of the lighting device itself.

The 220 volt LED is produced in the most common types of caps - E27 and E14. The numbers indicate the thread diameter in millimeters. The first type of lamp is often found in the form of a ball, the second - a ball or corn.

What are their main advantages? Firstly, it is the ability to block and adjust the brightness of the glow yourself. Secondly, it is the choice of color lighting and the ability to remotely control it. Thirdly, the durability of operation and increased reliability.

When choosing a shape, you need to pay attention to the fact that corn lamps, although they have quite good characteristics, are still unsafe. Their contacts go out, and manufacturers have recently refused to release devices of this form.

Less powerful lamps are used to illuminate non-residential premises or bathrooms, so if you do not need to use a 220 volt LED, you can do with small flat devices with a G53 and GX53 base. These are round lamps that use multiple diodes.

When purchasing a lamp, pay attention to the following characteristics:

• the number of diodes - the brightness of the lamp depends on how many LEDs are in the lamp, especially with a long period of use, when they begin to fade and burn out;
• operating temperature mode - it must be borne in mind that when choosing a lamp for the street, it must be effective even in possible frosts, this is usually indicated in the device's passport;
• the possibility of pulsations - blinking is found in cheap lamps, usually when buying an expensive one, it is minimized;
• operating conditions sometimes require increased protection of the device, for example, resistance to moisture, you need to ask the seller about this parameter;
• when choosing a manufacturer, you need to pay attention to the diameter of the base, since not all foreign developers produce a 220V LED;
• the required luminous flux, which is measured in Lumens, is lighting or indicator lamps.

Manufacturer's choice

There are many manufacturers on the market who demonstrate different levels of quality. Accordingly, their supplier pricing also differs significantly.

The main disadvantage of LEDs is their cost. Therefore, if you are already paying a lot of money for a product, it is necessary that it be really high quality. Therefore, it is worthwhile to take a responsible approach to the choice of a manufacturer and supplier.

Manufacturers can be conditionally divided into 5 groups.

1. Chinese cheap brands unknown to anyone.
2. Well-known Chinese and Asian manufacturers. The most popular are Selecta, Camelion, LG. They use modern equipment, and the quality of the products produced by these companies is quite high, so a fairly large segment of the domestic market is occupied by goods from Asia. Separately, it is worth noting LG LEDs, which since 2016 have significantly reduced the price of their goods due to the use of new technologies in production. Moreover, the quality remains the same. There is no doubt about that. The company specializes in medium-power lamps and shows itself quite well relative to analogues.
3. Domestic manufacturers who make a high quality product, but their technology is quite expensive, so the price of lamps is corresponding. Unfortunately, on the territory of Russia it was late to learn about the wide possibilities of LEDs and there are not so many domestic manufacturers yet. These are, for example, Optoman and Gauss. These companies have their own product line and are available throughout the country.
4. European manufacturers are represented mainly by German firms Philips, Osram, Bioledex, which have vast experience in the production of lamps. Perhaps Philips remains the leader in this market segment, although it is relatively expensive.
5. Sino-Russian projects such as Ecola, Newera are also brands of good quality and price, which are much younger than competing firms.

Thus, among such an abundance of manufacturers, it is sometimes quite difficult to choose a worthy brand, therefore it is especially important and necessary to pay attention mainly to the characteristics of the product and its operating conditions.

Approximate algorithm of actions when installing the LED

If you have even the slightest knowledge of electrics and had experience installing any lamps, you can try to install the LED yourself. First you need to make sure the lamps are working. The sequence of actions should be as follows:

• studying technical characteristics and calculating how many volts one LED consumes;
• drawing up a connection diagram taking into account voltage;
• calculation of the power consumption of the electrical circuit;
• then you need to choose a power supply that would fit in power, it can also be a driver;
• the LED legs indicate the polarity to which you need to solder the wires;
• connecting the power supply;
• installation of diodes and their fastening;
• if everything is in order, it is necessary to measure such characteristics as the amount of energy consumed, heating, electric current;
• correction of electric current;
• warming up for half an hour - so that nothing happens during the initial installation and in order to prevent overheating, it is better to buy LEDs on a star-shaped substrate.

During operation, especially if these are Chinese products, sometimes it is necessary to replace the LEDs. Instead of contacting specialists, the replacement can be done independently if you have the necessary tools. After spinning the lamp, the diodes ring out with a digital multimeter. These, in turn, are dimly highlighted, and some of them may not work. Unnecessary diodes are soldered off and replaced with new ones. Of course, this happens when spare LEDs are available, for this you can take an old lamp.

Today, a popular addition is the Arduino program. The LED, connecting to it, can be made to blink. The Arduino board has many possibilities, I / O, and you can connect almost any device to it. This program is able to receive signals from various devices, which makes them act. It is an easy and convenient programming environment that is easy to handle even for an ordinary user.

Choice of LEDs for the car

Car owners are increasingly switching to a new type of lighting in their car. This is a really good decision not only in terms of the operating mode, but also in terms of the appearance of the car. The car will significantly change, attracting the glances of passing drivers. All lamps used in the car can be safely replaced with lighting.

How to choose the dimensions and light for the front brake lights?

Most of the automotive industry uses lamps without a base, installed in the gap between the headlights. The advantage of LEDs is their resistance to any temperature, since they are located close to the main lighting lamp, overheating of the crystal and its premature failure is possible. In view of this, when choosing lighting, you need to pay attention to the additional protection of LEDs - the presence of an electric current stabilizer.

When choosing lamps, you need to pay attention to their series, for example, the SF series, although it does not have a stabilizer, is quite suitable for a car, since it has a large number of diodes and works in a wide range, perfectly illuminating the space.

It is also necessary to pay attention to the dimensions of the lamp, so the above example SF is a fairly large device. You need to think carefully about everything before buying lighting.

Also popular is the series for dimensions - SMD, which has excellent characteristics, but also costs a lot of money.

Rear car lighting

It is customary to equip rear brake lights with base two-pin LEDs. The most popular series: MSD, 14HP and 3x1W. They have a slightly different operating mode, differ in the number of diodes. But they all have fairly high rates. These LEDs are bright, provide rich light and long life.

The most affordable are SF series lamps.

Interior LEDs

Before choosing lamps for the interior, you must decide on the type of lighting and the size of the shade.

In the salon, you need to select a festoon-type lamp - these are oblong devices, 31-41 mm in size. There are 3 types of interior LEDs.

1. Installed in the plafond connector instead of the old conventional light bulb. In size, such LEDs are almost identical to conventional lighting devices, they are used when it is impossible to use another lamp due to the small size of the plafond.
2. Larger LEDs than a standard bulb. Before installing the required one, make sure whether such a device fits under the ceiling. Due to the larger size, the number of diodes in the lamp also increases. Thus, the lighting becomes much brighter than usual.
3. Matrix containing a large number of diodes. If the plafond is large enough to accommodate a rectangular matrix, then this type of lighting will be the brightest and most saturated.

The interior lighting uses SF or SMD lamps.

In addition, replacement of fog lamps with LED lamps is widely used in cars. Special attention should be paid to motorists who want to stand out among others, to the backlighting with LED strips and to "angel eyes".

Summarizing

LED is a great alternative to old light bulbs, which helps to solve the problem of insufficient lighting in the room. Even at a higher cost than a conventional lamp, this is an excellent investment, as the LED can last for more than one year and give a bright light to your home and car.