Super bright white LEDs. White LED Light output, beam angle and LED power

Houseplants do not always have enough light at home. Without this, their development will be slow or incorrect. To avoid this, you can install LEDs for plants. It is this lamp that can provide the required spectrum of color. widely used for lighting greenhouses, conservatories, indoor gardens and aquariums. They replace sunlight well, do not require large expenditures and have a long service life.

Plant photosynthesis is a process that occurs with sufficient light. The following factors also contribute to the correctness: ambient temperature, humidity, light spectrum, length of day and night, carbon sufficiency.

Determining the sufficiency of light

If you decide to install lamps for plants, then you need to do it as correctly as possible. To do this, you need to decide which plants lack the ray, and which will be superfluous. If you are designing lighting in a greenhouse, then you need to provide zones with different spectrums. Next you need to determine the number of LEDs themselves. Professionals do this with a special device - a lux meter. You can also make the calculation yourself. But you will have to dig a little and design the desired model.

If the project is being done for a greenhouse, there is one universal rule for all types of light sources. When the height of the suspension increases, the illumination decreases.

LEDs

The spectrum of color radiation is of great importance. The optimal solution would be red and blue LEDs for plants in a two to one ratio. How many watts the device will have doesn't really matter.

But more often they use one-watt ones. If you need to install diodes yourself, it is better to purchase ready-made tapes. You can secure them with glue, buttons or screws. It all depends on the holes provided. There are a lot of manufacturers of such products; it is better to choose a well-known, rather than a faceless seller who cannot give a guarantee for his product.

Light wavelength

The spectrum of natural sunlight contains both blue and red colors. They allow plants to develop mass, grow and bear fruit. When irradiated only with a blue spectrum with a wavelength of 450 nm, the representative of the flora will be stunted. Such a plant cannot boast of a large green mass. It will also bear fruit poorly. When absorbing the red range with a wavelength of 620 nm, it will develop roots, bloom well and bear fruit.

Pros of LEDs

When a plant is illuminated, it goes all the way: from sprout to fruit. At the same time, during this time, only flowering will occur when the luminescent device is operating. LEDs for plants do not heat up, so there is no need to frequently ventilate the room. In addition, there is no possibility of thermal overheating of flora representatives.

Such lamps are irreplaceable for growing seedlings. The directionality of the radiation spectrum helps the shoots to grow stronger in a short time. Low energy consumption is also a plus. LEDs are second only to But they are ten times more economical LEDs for plants last up to 10 years. - from 3 to 5 years. Having installed such lamps, you will not have to worry about replacing them for a long time. Such lamps do not contain harmful substances. Despite this, their use in greenhouses is very preferable. The market today presents a large number of different designs of such lamps: they can be hung, mounted on a wall or ceiling.

Minuses

To increase the radiation intensity, LEDs are assembled into a large structure. This is a disadvantage only for small rooms. In large greenhouses this is not significant. The disadvantage can be considered the high cost compared to analogues - fluorescent lamps. The difference can reach eightfold. But diodes will pay for themselves after several years of service. They can significantly save energy. A decrease in glow is observed after the warranty period expires. With a large greenhouse area, more lighting points are needed compared to other types of lamps.

Radiator for lamp

It is necessary that heat is removed from the device. This would be better done by a radiator made of aluminum profile or steel sheet. The use of a U-shaped finished profile will require less labor. Calculating the radiator area is easy. It must be at least 20 cm 2 per 1 Watt. After all the materials have been selected, you can assemble everything into one chain. It is better to alternate LEDs for plant growth by color. This will ensure uniform lighting.

PhytoLED

The latest development, such as phyto-LED, can replace conventional analogues that glow in only one color. The new device combines the necessary spectrum of LEDs for plants in one chip. It is needed for all stages of growth. The simplest phytolamp usually consists of a block with LEDs and a fan. The latter, in turn, can be adjusted in height.

Fluorescent lamps

Fluorescent lamps have long remained at the peak of popularity in household gardens and vegetable gardens. But such lamps for plants do not fit the color spectrum. They are increasingly being replaced by phyto-LED or special-purpose fluorescent lamps.

Sodium

A light as strong in saturation as that of a sodium apparatus is not suitable for placement in an apartment. Its use is advisable in large greenhouses, gardens and greenhouses where plants are illuminated. The disadvantage of such lamps is their low performance. They convert two-thirds of the energy into heat and only a small part is used for light radiation. In addition, the red spectrum of such a lamp is more intense than the blue one.

We make the device ourselves

The easiest way to make a lamp for plants is to use a strip with LEDs on it. We need it in the red and blue spectra. They will connect to the power supply. The latter can be purchased in the same place as tapes - at a hardware store. You also need a fastening - a panel the size of the lighting area.

Manufacturing should begin by cleaning the panel. Next, you can glue the diode tape. To do this, remove the protective film and stick the sticky side to the panel. If you have to cut the tape, then its pieces can be joined using a soldering iron.

LEDs for plants do not require additional ventilation. But if the room itself is poorly ventilated, then it is advisable to install the tape on a metal profile (for example, made of aluminum). Lighting modes for flowers in a room can be as follows:

• for those growing far from the window, in a shaded place, 1000-3000 lux will be enough;
• for plants that need diffused light, the value will be up to 4000 lux;
• representatives of the flora that need direct lighting - up to 6000 lux;
• for tropical and those that bear fruit - up to 12,000 lux.

If you want to see indoor plants in a healthy and beautiful form, you must carefully satisfy their need for lighting. So, we have found out the advantages and disadvantages for plants, as well as the spectrum of their rays.

Ecology of consumption. Science and technology: What kind of lighting is needed to get a fully developed, large, fragrant and tasty plant with moderate energy consumption?

The intensity of photosynthesis under red light is maximum, but under red light alone, plants die or their development is disrupted. For example, Korean researchers have shown that when illuminated with pure red, the mass of grown lettuce is greater than when illuminated with a combination of red and blue, but the leaves contain significantly less chlorophyll, polyphenols and antioxidants. And the Faculty of Biology of Moscow State University has established that in the leaves of Chinese cabbage under narrow-band red and blue light (compared to illumination with a sodium lamp), the synthesis of sugars is reduced, growth is inhibited and flowering does not occur.

Rice. 1 Leanna Garfield Tech Insider - Aerofarms

What kind of lighting is needed to get a fully developed, large, fragrant and tasty plant with moderate energy consumption?

How to evaluate the energy efficiency of a lamp?

Basic metrics for assessing the energy efficiency of phytolight:

• Photosynthetic Photon Flux (PPF), in micromoles per joule, i.e., in the number of light quanta in the range of 400–700 nm emitted by a lamp that consumed 1 J of electricity.
• Yield Photon Flux (YPF), in effective micromoles per joule, i.e., in the number of quanta per 1 J of electricity, taking into account the multiplier - the curve McCree.

PPF always turns out a little higher than YPF(curve McCree normalized to one and in most of the range less than one), so the first metric is beneficial for lamp sellers. The second metric is more profitable to use for buyers, since it more adequately assesses energy efficiency.

Efficiency of DNAT

Large agricultural enterprises with extensive experience and counting money still use sodium lamps. Yes, they willingly agree to hang the LED lights provided to them over the experimental beds, but they do not agree to pay for them.

From Fig. 2 shows that the efficiency of a sodium lamp is highly dependent on power and reaches a maximum at 600 W. Characteristic optimistic value YPF for a sodium lamp 600–1000 W is 1.5 eff. µmol/J. Sodium lamps 70–150 W are one and a half times less efficient.

Rice. 2. Typical spectrum of a sodium lamp for plants (left). Efficiency in lumens per watt and in effective micromoles of commercial sodium greenhouse light brands Cavita, E-Papillon, "Galad" and "Reflex" (on right)

Any LED lamp with an efficiency of 1.5 eff. µmol/W and reasonable price, can be considered a worthy replacement for a sodium lamp.

The questionable effectiveness of red-blue phytolights

In this article we do not present the absorption spectra of chlorophyll because it is incorrect to refer to them in a discussion of the use of light flux by a living plant. Chlorophyll invitro, isolated and purified, only really absorbs red and blue light. In a living cell, pigments absorb light in the entire range of 400–700 nm and transfer its energy to chlorophyll. The energy efficiency of light in a sheet is determined by the curve " McCree 1972"(Fig. 3).

Rice. 3. V(λ) - visibility curve for humans; RQE- relative quantum efficiency for the plant ( McCree 1972); σ r And σ fr- absorption curves of red and far-red light by phytochrome; B(λ) - phototropic efficiency of blue light

Note: the maximum efficiency in the red range is one and a half times higher than the minimum efficiency in the green range. And if you average the efficiency over a somewhat wide band, the difference becomes even less noticeable. In practice, the redistribution of part of the energy from the red range to the green range sometimes, on the contrary, enhances the energy function of light. Green light passes through the thickness of the leaves to the lower tiers, the effective leaf area of ​​the plant increases sharply, and the yield of, for example, lettuce increases.

The energy feasibility of lighting plants with common LED white light lamps was studied in the work.

The characteristic shape of the spectrum of a white LED is determined by:

• the balance of short and long waves, correlating with color temperature (Fig. 4, left);
• the degree of spectral occupancy, which correlates with color rendering (Fig. 4, right).

Rice. 4. Spectra of white LED light with the same color rendering, but different color temperature CCT (left) and with the same color temperature and different color rendering R a(on right)

The differences in the spectrum of white diodes with the same color rendering and the same color temperature are subtle. Consequently, we can evaluate spectrum-dependent parameters only by color temperature, color rendering and luminous efficiency - parameters that are written on the label of a conventional white light lamp.

The results of the analysis of the spectra of serial white LEDs are as follows:

1. In the spectrum of all white LEDs, even with a low color temperature and maximum color rendering, like sodium lamps, there is very little far-red (Fig. 5).

Rice. 5. White LED spectrum ( LED 4000K R a= 90) and sodium light ( HPS) in comparison with the spectral functions of plant sensitivity to blue ( B), red ( A_r) and far red light ( A_fr)

Under natural conditions, a plant shaded by a canopy of alien foliage receives more distant red than near red, which in light-loving plants triggers the “shade avoidance syndrome” - the plant stretches upward. Tomatoes, for example, at the growth stage (not seedlings!) need far red to stretch, increase growth and the total occupied area, and therefore the harvest in the future.

Accordingly, under white LEDs and under sodium light the plant feels like it is under the open sun and does not stretch upward.

2. Blue light is needed for the “sun tracking” reaction (Fig. 6).

Examples of using this formula:

A. Let us estimate for the basic values ​​of the parameters of white light what the illumination should be in order to provide, for example, 300 eff. for a given color rendering and color temperature. µmol/s/m2:

It can be seen that the use of warm white light with high color rendering allows the use of slightly lower illumination levels. But if we take into account that the luminous efficiency of warm light LEDs with high color rendering is somewhat lower, it becomes clear that by choosing color temperature and color rendering there is no energetically significant win or loss. You can only adjust the proportion of phytoactive blue or red light.

B. Let's evaluate the applicability of a typical general purpose LED grow light for growing microgreens.

Let a lamp measuring 0.6 × 0.6 m consume 35 W and have a color temperature of 4000 TO, color rendition Ra= 80 and luminous efficiency 120 lm/W. Then its efficiency will be YPF= (120/100)⋅(1.15 + (35⋅80 − 2360)/4000) eff. µmol/J = 1.5 eff. µmol/J. Which, when multiplied by the consumed 35 W, will be 52.5 eff. µmol/s.

If such a lamp is lowered low enough above a bed of microgreens with an area of ​​0.6 × 0.6 m = 0.36 m 2 and thereby avoiding light loss to the sides, the lighting density will be 52.5 eff. µmol/s / 0.36m 2 = 145 eff. µmol/s/m2. This is approximately half the usually recommended values. Therefore, the power of the lamp must also be doubled.

Direct comparison of phytoparameters of different types of lamps

Let's compare the phytoparameters of a conventional office ceiling LED lamp produced in 2016 with specialized phytoluminaires (Fig. 7).

Rice. 7. Comparative parameters of a typical 600W sodium lamp for greenhouses, a specialized LED phytolight and a lamp for general indoor lighting

It can be seen that an ordinary general lighting lamp with the diffuser removed when lighting plants is not inferior in energy efficiency to a specialized sodium lamp. It is also clear that the red-blue light phyto-lamp (the manufacturer is deliberately not named) is made at a lower technological level, since its total efficiency (the ratio of the power of the luminous flux in watts to the power consumed from the network) is inferior to the efficiency of an office lamp. But if the efficiency of red-blue and white lamps were the same, then the phytoparameters would also be approximately the same!

It is also clear from the spectra that the red-blue phyto-luminaire is not narrow-band, its red hump is wide and contains much more far-red red than that of the white LED and sodium lamp. In cases where far-red is required, using such a luminaire alone or in combination with other options may be advisable.

Assessment of the energy efficiency of the lighting system as a whole:

The plant's response to light: the intensity of gas exchange, consumption of nutrients from solution and synthesis processes is determined in the laboratory. The responses characterize not only photosynthesis, but also the processes of growth, flowering, and the synthesis of substances necessary for taste and aroma.

In Fig. Figure 14 shows the plant's response to changes in the wavelength of light. The intensity of sodium and phosphorus intake from the nutrient solution was measured by mint, strawberries and lettuce. Peaks in such graphs are signs that a specific chemical reaction is being stimulated. The graphs show that excluding some ranges from the full spectrum for the sake of saving is the same as removing part of the piano keys and playing a melody on the remaining ones.

Rice. 14. The stimulating role of light for nitrogen and phosphorus consumption in mint, strawberries and lettuce.

The principle of the limiting factor can be extended to individual spectral components - for a full result, in any case, the full spectrum is needed. Removing some ranges from the full spectrum does not lead to a significant increase in energy efficiency, but the “Liebig barrel” may work - and the result will be negative.
Examples demonstrate that ordinary white LED light and specialized “red-blue phytolight” have approximately the same energy efficiency when lighting plants. But broadband white comprehensively satisfies the needs of the plant, which are expressed not only in stimulating photosynthesis.

Removing green from the continuous spectrum so that the light turns from white to violet is a marketing ploy for buyers who want a “special solution” but are not qualified customers.

White light adjustment

The most common general purpose white LEDs have poor color rendering Ra= 80, which is due primarily to the lack of red color (Fig. 4).

The lack of red in the spectrum can be compensated by adding red LEDs to the lamp. This solution is promoted, for example, by the company CREE. The logic of the “Liebig barrel” suggests that such an additive will not harm if it is truly an additive and not a redistribution of energy from other ranges in favor of red.

Interesting and important work was done in 2013–2016 by the Institute of Biomedical Problems of the Russian Academy of Sciences: they studied how the addition of 4000 white LEDs to the light affects the development of Chinese cabbage TO / Ra= 70 light narrowband red LEDs 660 nm.

And we found out the following:

• Under LED light, cabbage grows about the same as under sodium light, but it has more chlorophyll (the leaves are greener).
• The dry weight of the crop is almost proportional to the total amount of light in moles received by the plant. More light - more cabbage.
• The concentration of vitamin C in cabbage increases slightly with increasing illumination, but increases significantly with the addition of red light to white light.
• A significant increase in the proportion of the red component in the spectrum significantly increased the concentration of nitrates in the biomass. It was necessary to optimize the nutrient solution and introduce part of the nitrogen in ammonium form so as not to exceed the maximum permissible concentration for nitrates. But in pure white light it was possible to work only with the nitrate form.
• At the same time, an increase in the proportion of red in the total light flux has almost no effect on the weight of the crop. That is, replenishment of the missing spectral components affects not the quantity of the crop, but its quality.
• The higher moles per watt efficiency of a red LED means that adding red to white is also energetically efficient.

Thus, adding red to white is advisable in the special case of Chinese cabbage and quite possible in the general case. Of course, with biochemical control and the correct selection of fertilizers for a specific crop.

Options for enriching the spectrum with red light

The plant does not know where the quantum from the white light spectrum came from, and where the “red” quantum came from. There is no need to make a special spectrum in one LED. And there is no need to shine red and white light from one special phyto-lamp. It is enough to use general-purpose white light and additionally illuminate the plant with a separate red light lamp. And when a person is near the plant, the red light can be turned off using a motion sensor to make the plant look green and pretty.

But the opposite solution is also justified - by selecting the composition of the phosphor, expand the spectrum of the white LED towards long waves, balancing it so that the light remains white. And you get white light with extra-high color rendering, suitable for both plants and humans.

It is especially interesting to increase the proportion of red, increasing the overall color rendering index, in the case of city farming - a social movement to grow plants necessary for humans in the city, often combining the living space, and therefore the light environment of humans and plants.

Open questions

It is possible to identify the role of the ratio of far and near red light and the advisability of using the “shade avoidance syndrome” for different crops. One can argue into which areas during analysis it is advisable to divide the wavelength scale.

It can be discussed whether the plant needs wavelengths shorter than 400 nm or longer than 700 nm for stimulation or regulatory function. For example, there is a private report that ultraviolet radiation significantly affects the consumer qualities of plants. Among other things, red-leaved varieties of lettuce are grown without ultraviolet radiation, and they grow green, but before sale they are irradiated with ultraviolet light, they turn red and are sent to the counter. And is the new metric correct? PBAR (plant biologically active radiation), described in the standard ANSI/ASABE S640, Quantities and Units of Electromagnetic Radiation for Plants (Photosynthetic Organisms, prescribes taking into account the range of 280–800 nm.

Conclusion

Chain stores choose more shelf-stable varieties, and then the buyer votes with rubles for brighter fruits. And almost no one chooses the taste and aroma. But as soon as we become richer and begin to demand more, science will instantly provide the necessary varieties and recipes for the nutrient solution.

And in order for the plant to synthesize everything that is needed for taste and aroma, it will require lighting with a spectrum containing all the wavelengths to which the plant will react, i.e., in the general case, a continuous spectrum. Perhaps the basic solution will be white light with high color rendering.

Literature
1. Son K-H, Oh M-M. Leaf shape, growth, and antioxidant phenolic compounds of two lettuce cultivars grown under various combinations of blue and red light-emitting diodes // Hortscience. – 2013. – Vol. 48. – P. 988-95.
2. Ptushenko V.V., Avercheva O.V., Bassarskaya E.M., Berkovich Yu A., Erokhin A.N., Smolyanina S.O., Zhigalova T.V., 2015. Possible reasons for a decline in the growth of Chinese cabbage under combined narrowband red and blue light in comparison with illumination by high- pressure sodium lamp. Scientia Horticulturae https://doi.org/10.1016/j.scienta.2015.08.021
3. Sharakshane A., 2017, Whole high-quality light environment for humans and plants. https://doi.org/10.1016/j.lssr.2017.07.001
4. C. Dong, Y. Fu, G. Liu & H. Liu, 2014, Growth, Photosynthetic Characteristics, Antioxidant Capacity and Biomass Yield and Quality of Wheat (Triticum aestivum L.) Exposed to LED Light Sources with Different Spectra Combinations
5. Lin K.H., Huang M.Y., Huang W.D. et al. The effects of red, blue, and white light-emitting diodes on the growth, development, and edible quality of hydroponically grown lettuce (Lactuca sativa L. var. capitata) // Scientia Horticulturae. – 2013. – V. 150. – P. 86–91.
6. Lu, N., Maruo T., Johkan M., et al. Effects of supplemental lighting with light-emitting diodes (LEDs) on tomato yield and quality of single-truss tomato plants grown at high planting density // Environ. Control. Biol. – 2012. Vol. 50. – P. 63–74.
7. Konovalova I.O., Berkovich Yu.A., Erokhin A.N., Smolyanina S.O., O.S. Yakovleva, A.I. Znamensky, I.G. Tarakanov, S.G. Radchenko, S.N. Lapach. Justification of optimal plant lighting regimes for the Vitacycle-T space greenhouse. Aerospace and environmental medicine. 2016. T. 50. No. 4.
8. Konovalova I.O., Berkovich Yu.A., Erokhin A.N., Smolyanina S.O., Yakovleva O.S., Znamensky A.I., Tarakanov I.G., Radchenko S.G., Lapach S.N., Trofimov Yu.V., Tsvirko V.I. Optimization of the LED lighting system of a vitamin space greenhouse. Aerospace and environmental medicine. 2016. T. 50. No. 3.
9. Konovalova I.O., Berkovich Yu.A., Smolyanina S.O., Pomelova M.A., Erokhin A.N., Yakovleva O.S., Tarakanov I.G. The influence of light regime parameters on the accumulation of nitrates in the above-ground biomass of Chinese cabbage (Brassica chinensis L.) when grown with LED irradiators. Agrochemistry. 2015. No. 11.

If you have any questions on this topic, ask them to the experts and readers of our project.

Now, probably, only the deaf have not heard about LED lamps and super-bright LEDs. Among radio amateurs, the ultra-bright LED has long been the object of close study and the main element of home-made innovative devices. Yes, this is no wonder, super-bright LEDs are interesting primarily for their efficiency and good light output characteristics. LEDs have good mechanical strength and are not afraid of vibration and shaking. It’s no wonder that high-power LEDs are increasingly used in the automotive industry.

Another important positive quality of LEDs is that they begin to emit instantly after power is applied. Fluorescent lamps, for example, are inferior to LEDs in this regard. For long-term operation of a fluorescent lamp, a hot start is recommended, when the filaments are preheated. The lamp turns on after a few seconds.

In the early nineties, Nichia introduced the world's first blue and white LEDs. Since then, a technological race has begun in the production of ultra-bright, high-power LEDs.

An LED by itself cannot emit white light, since white light is the sum of all colors. Light emitting diode emits light in a strictly defined manner wavelength. The color of the LED radiation depends on the width of the energy gap of the transition, where the recombination of electrons and holes occurs.

The width of the energy gap, in turn, depends on the semiconductor material. To obtain white light onto the crystal blue LED A layer of phosphor is applied, which, when exposed to blue radiation, emits yellow and red light. The result of mixing blue, yellow and red is white light.

This is one of several widely used technologies for producing white light using light-emitting diodes.

The supply voltage for ultra-bright white LEDs typically ranges from 2,8 before 3,9 volt. The exact characteristics of the LED can be found in the description (datasheet).

Powerful, ultra-bright white LEDs, although available, are still expensive compared to red and green indicator LEDs, so care should be taken when using them in lighting installations high-quality LED power supply.

Despite the fact that the resource of LEDs is quite long, any light-emitting semiconductor Very sensitive to overcurrent. As a result of overloads, the LED may remain operational, but its light output will be significantly less. In some cases, a partially working LED can cause failure of the other LEDs connected with it.

To prevent overloading of LEDs, and, consequently, their failure, power drivers on specialized microcircuits. The power driver is nothing more than a stabilized current source. To adjust the brightness of LEDs, it is recommended to use pulse modulation.

It is possible that soon manufacturers of high-power LEDs will integrate a current stabilizer chip directly into the design of a high-power LED, similar to flashing LEDs ( blinking led ), which have a built-in pulse generator chip.

An LED can operate for decades, provided that the light-emitting crystal does not become very hot due to the flow of current. In modern high-power LEDs, the supply current can reach more than 1000 mA(1 Ampere!) at a supply voltage of 2,5 before 3,6 – 4 volt. For example, high-power LEDs have these parameters. Lumileds . To remove excess heat in such LEDs, an aluminum radiator is used, structurally integrated with the LED crystal. Manufacturers of high-power white LEDs also recommend installing them on additional radiators. The conclusion is obvious - if you want long-term LED operation, ensure good heat dissipation.

When installing high-power LEDs, you need to remember that the heat-conducting base of the LED is not electrically neutral. In this regard, it is necessary to ensure electrical insulation of the LED bases when mounted on a common radiator.

Since the typical supply voltage for ultra-bright LEDs is 3,6 volts, then such LEDs can be easily used for LED flashlights in conjunction with rechargeable batteries of the format A.A.. To power the LED, you will need 3 rechargeable batteries connected in series with a voltage of 1,2 volt. The total voltage will be just the required 3,6 volt. In this case, no voltage converters are needed.

The still high price of high-power LEDs is due to the complexity of manufacturing a high-power LED. The cost of modern technological installations, which produce high-power LED crystals using epitaxial technology, is 1.5 - 2 million dollars!

Structurally, a powerful LED is a rather complex device.

The figure shows the device of the ultra-bright Luxeon III LED from Lumileds, with a power 5 Watt .

As can be seen from the figure, modern ultra-bright LED is a complex device that requires many technological steps in manufacturing.

Currently, high-power LED manufacturers are trying different LED manufacturing technologies using different materials and components. All this is aimed at reducing the cost of LEDs and ensuring the required quality of the product.

It should be noted that a powerful LED, manufactured in violation of the technological process and using low-quality materials, after some time of operation loses its calculated light output. As a rule, such LEDs are cheaper than their analogues. Cheap LEDs for the first time 4000 hours of operation lose their brightness by 35% . This is due to the fact that the epoxy material of the LED bulb turns yellow, and the emissivity of the blue LED chip and the phosphor layer applied to it decreases. High-quality LEDs for 50 000 hours of operation, the brightness decreases by no more than 20% .

A band with a maximum in the yellow area (the most common design). The emission of the LED and phosphor, when mixed, produce white light of various shades.

Encyclopedic YouTube

1 / 5

✪ Short white LEDs

✪ White LED vs Red Blue White LED Grow Test - Amazon Lights (Intro)

✪ Cool White Vs Neutral White LED"s In Flashlights (Thrunite TN12 Models)

✪ White LED vs Red/Blue LED Grow light Grow Test - Part 1 (Educational) 2016

✪ White LED vs Red Blue White LED Grow Test w/Time Lapse - Lettuce Ep.1

Subtitles

History of invention

The first red semiconductor emitters for industrial use were obtained by N. Kholonyak in 1962. In the early 70s, yellow and green LEDs appeared. The light output of these, at that time still inefficient, devices reached one lumen by 1990. In 1993, Shuji Nakamura, an engineer at Nichia (Japan), created the first high-brightness blue LED. Almost immediately, LED RGB devices appeared, since blue, red and green colors made it possible to obtain any color, including white. White phosphor LEDs first appeared in 1996. Subsequently, the technology developed rapidly, and by 2005, the luminous efficiency of LEDs reached 100 lm/W or more. LEDs appeared with different shades of glow, the quality of light made it possible to compete with incandescent lamps and already traditional fluorescent lamps. The use of LED lighting devices in everyday life, in indoor and outdoor lighting, has begun.

RGB LEDs

White light can be created by mixing emissions from LEDs of different colors. The most common trichromatic design is made from red (R), green (G) and blue (B) sources, although bichromatic, tetrachromatic and more multi-chromatic variants are found. A multicolor LED, unlike other RGB semiconductor emitters (luminaires, lamps, clusters), has one complete housing, most often similar to a single-color LED. The LED chips are located next to each other and share a common lens and reflector. Since semiconductor chips have a finite size and their own radiation patterns, such LEDs most often have uneven angular color characteristics. In addition, to obtain the correct color ratio, it is often not enough to set the design current, since the light output of each chip is unknown in advance and is subject to changes during operation. To set the desired shades, RGB lamps are sometimes equipped with special control devices.

The spectrum of an RGB LED is determined by the spectrum of its constituent semiconductor emitters and has a pronounced line shape. This spectrum is very different from the spectrum of the sun, therefore the color rendering index of the RGB LED is low. RGB LEDs allow you to easily and widely control the color of the glow by changing the current of each LED included in the “triad”, adjusting the color tone of the white light they emit directly during operation - up to obtaining individual independent colors.

Multicolor LEDs have a dependence of luminous efficiency and color on temperature due to the different characteristics of the emitting chips that make up the device, which results in a slight change in the color of the glow during operation. The service life of a multicolor LED is determined by the durability of the semiconductor chips, depends on the design and most often exceeds the service life of phosphor LEDs.

Multicolor LEDs are used primarily for decorative and architectural lighting, in electronic signage and video screens.

Phosphor LEDs

Combining a blue (more often), violet or ultraviolet (not used in mass production) semiconductor emitter and phosphor converter allows you to produce an inexpensive light source with good characteristics. The most common design of such an LED contains a blue gallium nitride semiconductor chip modified with indium (InGaN) and a phosphor with maximum re-emission in the yellow region - yttrium-aluminum garnet doped with trivalent cerium (YAG). Part of the power of the initial radiation of the chip leaves the LED body, dissipating in the phosphor layer, the other part is absorbed by the phosphor and re-emitted in the region of lower energy values. The re-emission spectrum covers a wide region from red to green, but the resulting spectrum of such an LED has a pronounced dip in the green-blue-green region.

Depending on the composition of the phosphor, LEDs with different color temperatures (“warm” and “cold”) are produced. By combining different types of phosphors, a significant increase in color rendering index (CRI or R a) is achieved. As of 2017, there are already LED panels for photography and filming, where color rendering is critical, but such equipment is expensive, and manufacturers are few and far between.

One of the ways to increase the brightness of phosphor LEDs while maintaining or even reducing their cost is to increase the current through the semiconductor chip without increasing its size - increasing the current density. This method is associated with a simultaneous increase in requirements for the quality of the chip itself and the quality of the heat sink. As the current density increases, the electric fields in the volume of the active region reduce the light output. When limiting currents are reached, since sections of the LED chip with different impurity concentrations and different band gap widths conduct current differently, local overheating of the chip sections occurs, which affects the light output and the durability of the LED as a whole. In order to increase the output power while maintaining the quality of spectral characteristics and thermal conditions, LEDs are produced containing clusters of LED chips in one housing.

One of the most discussed topics in the field of polychrome LED technology is its reliability and durability. Unlike many other light sources, an LED changes its light output (efficiency), radiation pattern, and color tint over time, but rarely fails completely. Therefore, to estimate the useful life, for example for lighting, a level of reduction in luminous efficiency of up to 70% of the original value (L70) is taken. That is, an LED whose brightness has decreased by 30% during operation is considered to be out of order. For LEDs used in decorative lighting, a dimming level of 50% (L50) is used as a life estimate.

The service life of a phosphor LED depends on many parameters. In addition to the manufacturing quality of the LED assembly itself (the method of attaching the chip to the crystal holder, the method of attaching the current-carrying conductors, the quality and protective properties of the sealing materials), the lifetime mainly depends on the characteristics of the emitting chip itself and on changes in the properties of the phosphor over the course of operation (degradation). Moreover, as numerous studies show, the main factor influencing the service life of an LED is temperature.

Effect of temperature on LED service life

During operation, a semiconductor chip emits part of the electrical energy in the form of radiation and part in the form of heat. Moreover, depending on the efficiency of such conversion, the amount of heat is about half for the most efficient emitters or more. The semiconductor material itself has low thermal conductivity; in addition, the materials and design of the case have a certain non-ideal thermal conductivity, which leads to the heating of the chip to high temperatures (for a semiconductor structure). Modern LEDs operate at chip temperatures in the region of 70-80 degrees. And a further increase in this temperature when using gallium nitride is unacceptable. High temperature leads to an increase in the number of defects in the active layer, leads to increased diffusion, and a change in the optical properties of the substrate. All this leads to an increase in the percentage of non-radiative recombination and absorption of photons by the chip material. An increase in power and durability is achieved by improving both the semiconductor structure itself (reducing local overheating), and by developing the design of the LED assembly, and improving the quality of cooling of the active area of ​​the chip. Research is also being conducted with other semiconductor materials or substrates.

The phosphor is also susceptible to high temperatures. With prolonged exposure to temperature, re-emitting centers are inhibited, and the conversion coefficient, as well as the spectral characteristics of the phosphor, deteriorate. In early and some modern polychrome LED designs, the phosphor is applied directly to the semiconductor material and the thermal effect is maximized. In addition to measures to reduce the temperature of the emitting chip, manufacturers use various methods to reduce the influence of chip temperature on the phosphor. Isolated phosphor technologies and LED lamp designs, in which the phosphor is physically separated from the emitter, can increase the service life of the light source.

The LED housing, made of optically transparent silicone plastic or epoxy resin, is subject to aging under the influence of temperature and begins to dim and yellow over time, absorbing part of the energy emitted by the LED. Reflective surfaces also deteriorate when heated - they interact with other elements of the body and are susceptible to corrosion. All these factors together lead to the fact that the brightness and quality of the emitted light gradually decreases. However, this process can be successfully slowed down by ensuring efficient heat removal.

Phosphor LED design

A modern phosphor LED is a complex device that combines many original and unique technical solutions. The LED has several main elements, each of which performs an important, often more than one function:

All LED design elements experience thermal stress and must be selected taking into account the degree of their thermal expansion. And an important condition for a good design is manufacturability and low cost of assembling an LED device and installing it in a lamp.

Brightness and quality of light

The most important parameter is not even the brightness of the LED, but its luminous efficiency, that is, the light output from each watt of electrical energy consumed by the LED. The luminous efficiency of modern LEDs reaches 190 lm/W. The theoretical limit of the technology is estimated at more than 300 lm/W. When assessing, it is necessary to take into account that the efficiency of a lamp based on LEDs is significantly lower due to the efficiency of the power source, the optical properties of the diffuser, reflector and other design elements. In addition, manufacturers often indicate the initial efficiency of the emitter at normal temperature, while the temperature of the chip during operation is much higher. This leads to the fact that the actual efficiency of the emitter is 5-7% lower, and that of the lamp is often twice as low.

The second equally important parameter is the quality of the light produced by the LED. There are three parameters to assess the quality of color rendering:

Phosphor LED based on an ultraviolet emitter

In addition to the already widespread combination of a blue LED and YAG, a design based on an ultraviolet LED is also being developed. A semiconductor material capable of emitting in the near ultraviolet region is coated with several layers of a phosphor based on europium and zinc sulfide activated by copper and aluminum. This mixture of phosphors gives re-emission maxima in the green, blue and red regions of the spectrum. The resulting white light has very good quality characteristics, but the efficiency of such conversion is still low. There are three reasons for this [ ]: the first is due to the fact that the difference between the energy of the incident and emitted quanta is lost during fluorescence (turns into heat), and in the case of ultraviolet excitation it is much greater. The second reason is that part of the UV radiation not absorbed by the phosphor does not participate in the creation of the luminous flux, unlike LEDs based on a blue emitter, and an increase in the thickness of the phosphor coating leads to an increase in the absorption of luminescent light in it. And finally, the efficiency of ultraviolet LEDs is significantly lower than that of blue ones.

Advantages and disadvantages of phosphor LEDs

Considering the high cost of LED lighting sources compared to traditional lamps, there are compelling reasons to use such devices:

But there are also disadvantages:

Lighting LEDs also have features inherent in all semiconductor emitters, taking into account which the most successful application can be found, for example, the direction of radiation. The LED shines only in one direction without the use of additional reflectors and diffusers. LED luminaires are best suited for local and directional lighting.

Prospects for the development of white LED technology

Technologies for producing white LEDs suitable for lighting purposes are under active development. Research in this area is stimulated by increased public interest. The prospect of significant energy savings is attracting investment in process research, technology development and the search for new materials. Judging by the publications of manufacturers of LEDs and related materials, specialists in the field of semiconductors and lighting engineering, it is possible to outline development paths in this area:

see also

Notes

1. , p. 19-20.
2. MC-E LEDs from Cree, containing red, green, blue and white emitters Archived November 22, 2012.
3. LEDs VLMx51 from Vishay, containing red, orange, yellow and white emitters(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
4. Multicolor LEDs XB-D and XM-L from Cree(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
5. LEDs XP-C from Cree, containing six monochromatic emitters(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
6. Nikiforov S.“S-class” of semiconductor lighting technology // Components and Technologies: magazine. - 2009. - No. 6. - pp. 88-91.
7. Truson P. Halvardson E. Advantages of RGB LEDs for lighting devices // Components and Technologies: magazine. - 2007. - No. 2.
8. , p. 404.
9. Nikiforov S. Temperature in the life and operation of LEDs // Components and Technologies: magazine. - 2005. - No. 9.
10. LEDs for interior and architectural lighting(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
11. Xiang Ling Oon. LED solutions for architectural lighting systems // Semiconductor lighting technology: magazine. - 2010. - No. 5. - pp. 18-20.
12. RGB LEDs for use in electronic scoreboards(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
13. High CRI LED Lighting  | Yuji LED (undefined) . yujiintl.com. Retrieved December 3, 2016.
14. Turkin A. Gallium nitride as one of the promising materials in modern optoelectronics // Components and Technologies: Journal. - 2011. - No. 5.
15. LEDs with high CRI values(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
16. Cree EasyWhite technology(English) . LEDs Magazine. Retrieved November 10, 2012. Archived November 22, 2012.
17. Nikiforov S., Arkhipov A. Features of determining the quantum yield of LEDs based on AlGaInN and AlGaInP at different current densities through the emitting crystal // Components and Technologies: Journal. - 2008. - No. 1.
18. Nikiforov S. Now electrons can be seen: LEDs make electric current very visible // Components and Technologies: magazine. - 2006. - No. 3.
19. LEDs with a matrix arrangement of a large number of semiconductor chips(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
20. Service life of white LEDs(English) . U.S. Department of Energy. Retrieved November 10, 2012. Archived November 22, 2012.
21. Types of LED defects and analysis methods(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
22. , p. 61, 77-79.
23. LEDs from SemiLEDs(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
24. GaN-on-Si Silicon LED Research Program(English) . LED Professional. Retrieved November 10, 2012.
25. Cree's isolated phosphor technology(English) . LED Professional. Retrieved November 10, 2012. Archived November 22, 2012.
26. Turkin A. Semiconductor LEDs: history, facts, prospects // Semiconductor Lighting Engineering: magazine. - 2011. - No. 5. - pp. 28-33.
27. Ivanov A.V., Fedorov A.V., Semenov S.M. Energy-saving lamps based on high-brightness LEDs // Energy supply and energy saving - regional aspect: XII All-Russian meeting: materials of reports. - Tomsk: St. Petersburg Graphics, 2011. - pp. 74-77.
28. , p. 424.
29. Reflectors for LEDs based on photonic crystals(English) . Led Professional. Retrieved February 16, 2013. Archived March 13, 2013.
30. XLamp XP-G3(English) . www.cree.com. Retrieved May 31, 2017.
31. White LEDs with high light output for lighting needs(English) . Phys.Org™. Retrieved November 10, 2012. Archived November 22, 2012.

The times when LEDs were used only as indicators for turning on devices are long gone. Modern LED devices can completely replace incandescent lamps in household, industrial and. This is facilitated by the various characteristics of LEDs, knowing which you can choose the right LED analogue. The use of LEDs, given their basic parameters, opens up a wealth of possibilities in the field of lighting.

A light-emitting diode (denoted as LED, LED, LED in English) is a device based on an artificial semiconductor crystal. When an electric current is passed through it, the phenomenon of emission of photons is created, which leads to a glow. This glow has a very narrow spectral range, and its color depends on the semiconductor material.

LEDs with red and yellow emission are made from inorganic semiconductor materials based on gallium arsenide, green and blue ones are made on the basis of indium gallium nitride. To increase the brightness of the luminous flux, various additives are used or the multilayer method is used, when a layer of pure aluminum nitride is placed between semiconductors. As a result of the formation of several electron-hole (p-n) transitions in one crystal, the brightness of its glow increases.

There are two types of LEDs: for indication and lighting. The former are used to indicate the inclusion of various devices in the network, and also as sources of decorative lighting. They are colored diodes placed in a translucent case, each of them has four terminals. Devices emitting infrared light are used in devices for remote control of devices (remote control).

In the lighting area, LEDs are used that emit white light. LEDs are classified by color into cool white, neutral white and warm white. There is a classification of LEDs used for lighting according to the installation method. The SMD LED designation means that the device consists of an aluminum or copper substrate on which the diode crystal is placed. The substrate itself is located in a housing, the contacts of which are connected to the contacts of the LED.

Another type of LED is designated OCB. In such a device, many crystals coated with phosphor are placed on one board. Thanks to this design, a high brightness of the glow is achieved. This technology is used in production with a large luminous flux in a relatively small area. In turn, this makes the production of LED lamps the most accessible and inexpensive.

Note! Comparing lamps based on SMD and COB LEDs, it can be noted that the former can be repaired by replacing a failed LED. If a COB LED lamp does not work, you will have to change the entire board with diodes.

LED characteristics

When choosing a suitable LED lamp for lighting, you should take into account the parameters of the LEDs. These include supply voltage, power, operating current, efficiency (luminous output), glow temperature (color), radiation angle, dimensions, degradation period. Knowing the basic parameters, it will be possible to easily select devices to obtain a particular illumination result.

LED current consumption

As a rule, a current of 0.02A is provided for conventional LEDs. However, there are LEDs rated at 0.08A. These LEDs include more powerful devices, the design of which involves four crystals. They are located in one building. Since each of the crystals consumes 0.02A, in total one device will consume 0.08A.

The stability of LED devices depends on the current value. Even a slight increase in current helps to reduce the radiation intensity (aging) of the crystal and increase the color temperature. This ultimately leads to the LEDs turning blue and failing prematurely. And if the current increases significantly, the LED immediately burns out.

To limit the current consumption, the designs of LED lamps and luminaires include current stabilizers for LEDs (drivers). They convert the current, bringing it to the value required by the LEDs. In the case when you need to connect a separate LED to the network, you need to use current-limiting resistors. The resistor resistance for an LED is calculated taking into account its specific characteristics.

Helpful advice! To choose the right resistor, you can use the LED resistor calculator available on the Internet.

LED voltage

How to find out the LED voltage? The fact is that LEDs do not have a supply voltage parameter as such. Instead, the voltage drop characteristic of the LED is used, which means the amount of voltage the LED outputs when the rated current passes through it. The voltage value indicated on the packaging reflects the voltage drop. Knowing this value, you can determine the voltage remaining on the crystal. It is this value that is taken into account in the calculations.

Given the use of various semiconductors for LEDs, the voltage for each of them may be different. How to find out how many volts an LED is? You can determine it by the color of the devices. For example, for blue, green and white crystals the voltage is about 3V, for yellow and red crystals it is from 1.8 to 2.4V.

When using a parallel connection of LEDs of identical ratings with a voltage value of 2V, you may encounter the following: as a result of variations in parameters, some emitting diodes will fail (burn out), while others will glow very faintly. This will happen due to the fact that when the voltage increases even by 0.1V, the current passing through the LED increases by 1.5 times. Therefore, it is so important to ensure that the current matches the LED rating.

Light output, beam angle and LED power

The luminous flux of diodes is compared with other light sources, taking into account the strength of the radiation they emit. Devices measuring about 5 mm in diameter produce from 1 to 5 lumens of light. While the luminous flux of a 100W incandescent lamp is 1000 lm. But when comparing, it is necessary to take into account that a regular lamp has diffused light, while an LED has directional light. Therefore, the dispersion angle of the LEDs must be taken into account.

The scattering angle of different LEDs can range from 20 to 120 degrees. When illuminated, LEDs produce brighter light in the center and reduce illumination towards the edges of the dispersion angle. Thus, LEDs illuminate a specific space better while using less power. However, if it is necessary to increase the illumination area, diverging lenses are used in the design of the lamp.

How to determine the power of LEDs? To determine the power of an LED lamp required to replace an incandescent lamp, it is necessary to apply a coefficient of 8. Thus, you can replace a conventional 100W lamp with an LED device with a power of at least 12.5W (100W/8). For convenience, you can use the data from the table of correspondence between the power of incandescent lamps and LED light sources:

Incandescent lamp power, W	Corresponding power of LED lamp, W
100	12-12,5
75	10
60	7,5-8
40	5
25	3

When using LEDs for lighting, the efficiency indicator is very important, which is determined by the ratio of luminous flux (lm) to power (W). Comparing these parameters for different light sources, we find that the efficiency of an incandescent lamp is 10-12 lm/W, a fluorescent lamp is 35-40 lm/W, and an LED lamp is 130-140 lm/W.

Color temperature of LED sources

One of the important parameters of LED sources is the glow temperature. The units of measurement for this quantity are degrees Kelvin (K). It should be noted that all light sources are divided into three classes according to their glow temperature, among which warm white has a color temperature of less than 3300 K, daylight white - from 3300 to 5300 K, and cool white over 5300 K.

Note! The comfortable perception of LED radiation by the human eye directly depends on the color temperature of the LED source.

The color temperature is usually indicated on the labeling of LED lamps. It is designated by a four-digit number and the letter K. The choice of LED lamps with a certain color temperature directly depends on the characteristics of its use for lighting. The table below displays options for using LED sources with different glow temperatures:

LED color		Color temperature, K	Lighting Use Cases
White	Warm	2700-3500	Lighting for domestic and office premises as the most suitable analogue of an incandescent lamp
	Neutral (daytime)	3500-5300	The excellent color rendition of such lamps allows them to be used for lighting workplaces in production.
	Cold	over 5300	Mainly used for street lighting, and also used in hand-held lanterns
Red		1800	As a source of decorative and phyto-lighting
Green		-
Yellow		3300	Lighting design of interiors
Blue		7500	Illumination of surfaces in the interior, phyto-lighting

The wave nature of color allows the color temperature of LEDs to be expressed using wavelength. The marking of some LED devices reflects the color temperature precisely in the form of an interval of different wavelengths. The wavelength is designated λ and is measured in nanometers (nm).

Standard sizes of SMD LEDs and their characteristics

Considering the size of SMD LEDs, devices are classified into groups with different characteristics. The most popular LEDs with standard sizes are 3528, 5050, 5730, 2835, 3014 and 5630. The characteristics of SMD LEDs vary depending on the size. Thus, different types of SMD LEDs differ in brightness, color temperature, and power. In LED markings, the first two digits indicate the length and width of the device.

Basic parameters of SMD 2835 LEDs

The main characteristics of SMD LEDs 2835 include an increased radiation area. Compared to the SMD 3528 device, which has a round working surface, the SMD 2835 radiation area has a rectangular shape, which contributes to greater light output with a smaller element height (about 0.8 mm). The luminous flux of such a device is 50 lm.

The SMD 2835 LED housing is made of heat-resistant polymer and can withstand temperatures up to 240°C. It should be noted that the radiation degradation in these elements is less than 5% over 3000 hours of operation. In addition, the device has a fairly low thermal resistance of the crystal-substrate junction (4 C/W). The maximum operating current is 0.18A, the crystal temperature is 130°C.

Based on the color of the glow, there are warm white with a glow temperature of 4000 K, daytime white - 4800 K, pure white - from 5000 to 5800 K and cool white with a color temperature of 6500-7500 K. It is worth noting that the maximum luminous flux is for devices with cool white glow, the minimum is for warm white LEDs. The design of the device has enlarged contact pads, which promotes better heat dissipation.

Helpful advice! SMD 2835 LEDs can be used for any type of installation.

Characteristics of SMD 5050 LEDs

The SMD 5050 housing design contains three LEDs of the same type. LED sources of blue, red and green colors have technical characteristics similar to SMD 3528 crystals. The operating current of each of the three LEDs is 0.02A, therefore the total current of the entire device is 0.06A. To ensure that the LEDs do not fail, it is recommended not to exceed this value.

LED devices SMD 5050 have a forward voltage of 3-3.3V and a light output (mains flux) of 18-21 lm. The power of one LED is the sum of three power values ​​of each crystal (0.7 W) and amounts to 0.21 W. The color of the glow emitted by the devices can be white in all shades, green, blue, yellow and multi-colored.

The close arrangement of LEDs of different colors in one SMD 5050 package made it possible to implement multi-color LEDs with separate control of each color. To regulate luminaires using SMD 5050 LEDs, controllers are used, so that the color of the glow can be smoothly changed from one to another after a given amount of time. Typically, such devices have several control modes and can adjust the brightness of the LEDs.

Typical characteristics of SMD 5730 LED

SMD 5730 LEDs are modern representatives of LED devices, the housing of which has geometric dimensions of 5.7x3 mm. They belong to ultra-bright LEDs, the characteristics of which are stable and qualitatively different from the parameters of their predecessors. Manufactured using new materials, these LEDs are characterized by increased power and highly efficient luminous flux. In addition, they can work in conditions of high humidity, are resistant to temperature changes and vibration, and have a long service life.

There are two types of devices: SMD 5730-0.5 with a power of 0.5 W and SMD 5730-1 with a power of 1 W. A distinctive feature of the devices is the ability to operate on pulsed current. The rated current of SMD 5730-0.5 is 0.15A; during pulse operation, the device can withstand current up to 0.18A. This type of LEDs provides a luminous flux of up to 45 lm.

SMD 5730-1 LEDs operate at a constant current of 0.35A, in pulsed mode - up to 0.8A. The light output efficiency of such a device can be up to 110 lm. Thanks to the heat-resistant polymer, the device body can withstand temperatures up to 250°C. The dispersion angle of both types of SMD 5730 is 120 degrees. The degree of luminous flux degradation is less than 1% when operating for 3000 hours.

Cree LED Specifications

The Cree company (USA) is engaged in the development and production of ultra-bright and most powerful LEDs. One of the Cree LED groups is represented by the Xlamp series of devices, which are divided into single-chip and multi-chip. One of the features of single-crystal sources is the distribution of radiation along the edges of the device. This innovation made it possible to produce lamps with a large luminous angle using a minimum number of crystals.

In the XQ-E High Intensity series of LED sources, the beam angle ranges from 100 to 145 degrees. Having small geometric dimensions of 1.6x1.6 mm, the power of ultra-bright LEDs is 3 Volts, and the luminous flux is 330 lm. This is one of the newest developments from Cree. All LEDs, the design of which is developed on the basis of a single crystal, have high-quality color rendering within CRE 70-90.

Related article:

How to make or repair an LED garland yourself. Prices and main characteristics of the most popular models.

Cree has released several versions of multi-chip LED devices with the latest power types from 6 to 72 Volts. Multichip LEDs are divided into three groups, which include devices with high voltage, power up to 4W and above 4W. Sources up to 4W contain 6 crystals in MX and ML type housings. The dispersion angle is 120 degrees. You can buy Cree LEDs of this type with white warm and cool colors.

Helpful advice! Despite the high reliability and quality of light, you can buy powerful LEDs of the MX and ML series at a relatively low price.

The group over 4W includes LEDs made from several crystals. The largest in the group are the 25W devices represented by the MT-G series. The company's new product is XHP model LEDs. One of the large LED devices has a 7x7 mm body, its power is 12W, and the light output is 1710 lm. High voltage LEDs combine small dimensions and high light output.

LED connection diagrams

There are certain rules for connecting LEDs. Taking into account that the current passing through the device moves only in one direction, for long-term and stable operation of LED devices it is important to take into account not only a certain voltage, but also the optimal current value.

Connection diagram for LED to 220V network

Depending on the power source used, there are two types of circuits for connecting LEDs to 220V. In one of the cases it is used with limited current, in the second - a special one that stabilizes the voltage. The first option takes into account the use of a special source with a certain current strength. A resistor is not required in this circuit, and the number of connected LEDs is limited by the driver power.

To designate LEDs in the diagram, two types of pictograms are used. Above each schematic image there are two small parallel arrows pointing upward. They symbolize the bright glow of the LED device. Before connecting the LED to 220V using a power supply, you must include a resistor in the circuit. If this condition is not met, this will lead to the fact that the working life of the LED will be significantly reduced or it will simply fail.

If you use a power supply when connecting, then only the voltage in the circuit will be stable. Considering the insignificant internal resistance of an LED device, turning it on without a current limiter will lead to the device burning out. That is why a corresponding resistor is introduced into the LED switching circuit. It should be noted that resistors come in different values, so they must be calculated correctly.

Helpful advice! The negative aspect of circuits for connecting an LED to a 220 Volt network using a resistor is the dissipation of high power when it is necessary to connect a load with increased current consumption. In this case, the resistor is replaced with a quenching capacitor.

How to calculate the resistance for an LED

When calculating the resistance for an LED, they are guided by the formula:

U = IxR,

where U is voltage, I is current, R is resistance (Ohm’s law). Let's say you need to connect an LED with the following parameters: 3V - voltage and 0.02A - current. So that when connecting an LED to 5 Volts on the power supply it does not fail, you need to remove the extra 2V (5-3 = 2V). To do this, you need to include a resistor with a certain resistance in the circuit, which is calculated using Ohm’s law:

R = U/I.

Thus, the ratio of 2V to 0.02A will be 100 Ohms, i.e. This is exactly the resistor needed.

It often happens that, given the parameters of the LEDs, the resistance of the resistor has a value that is non-standard for the device. Such current limiters cannot be found at points of sale, for example, 128 or 112.8 ohms. Then you should use resistors whose resistance is the closest value compared to the calculated one. In this case, the LEDs will not function at full capacity, but only at 90-97%, but this will be invisible to the eye and will have a positive effect on the life of the device.

There are many options for LED calculation calculators on the Internet. They take into account the main parameters: voltage drop, rated current, output voltage, number of devices in the circuit. By specifying the parameters of LED devices and current sources in the form field, you can find out the corresponding characteristics of resistors. To determine the resistance of color-coded current limiters, there are also online calculations of resistors for LEDs.

Schemes for parallel and serial connection of LEDs

When assembling structures from several LED devices, circuits for connecting LEDs to a 220 Volt network with a serial or parallel connection are used. At the same time, for correct connection, it should be taken into account that when LEDs are connected in series, the required voltage is the sum of the voltage drops of each device. While when LEDs are connected in parallel, the current strength is added up.

If the circuits use LED devices with different parameters, then for stable operation it is necessary to calculate the resistor for each LED separately. It should be noted that no two LEDs are exactly alike. Even devices of the same model have minor differences in parameters. This leads to the fact that when a large number of them are connected in a series or parallel circuit with one resistor, they can quickly degrade and fail.

Note! When using one resistor in a parallel or series circuit, you can only connect LED devices with identical characteristics.

The discrepancy in parameters when connecting several LEDs in parallel, say 4-5 pieces, will not affect the operation of the devices. But if you connect a lot of LEDs to such a circuit, it will be a bad decision. Even if LED sources have a slight variation in characteristics, this will cause some devices to emit bright light and burn out quickly, while others will glow dimly. Therefore, when connecting in parallel, you should always use a separate resistor for each device.

As for the series connection, there is economical consumption here, since the entire circuit consumes an amount of current equal to the consumption of one LED. In a parallel circuit, the consumption is the sum of the consumption of all LED sources included in the circuit.

How to connect LEDs to 12 Volts

In the design of some devices, resistors are provided at the manufacturing stage, which makes it possible to connect LEDs to 12 Volts or 5 Volts. However, such devices cannot always be found on sale. Therefore, in the circuit for connecting LEDs to 12 volts, a current limiter is provided. The first step is to find out the characteristics of the connected LEDs.

Such a parameter as the forward voltage drop for typical LED devices is about 2V. The rated current of these LEDs corresponds to 0.02A. If you need to connect such an LED to 12V, then the “extra” 10V (12 minus 2) must be extinguished with a limiting resistor. Using Ohm's law you can calculate the resistance for it. We get that 10/0.02 = 500 (Ohm). Thus, a resistor with a nominal value of 510 Ohms is required, which is the closest in the range of E24 electronic components.

In order for such a circuit to work stably, it is also necessary to calculate the power of the limiter. Using the formula based on which power is equal to the product of voltage and current, we calculate its value. We multiply a voltage of 10V by a current of 0.02A and get 0.2W. Thus, a resistor is required, the standard power rating of which is 0.25W.

If it is necessary to include two LED devices in the circuit, then it should be taken into account that the voltage dropped across them will already be 4V. Accordingly, the resistor will have to extinguish not 10V, but 8V. Consequently, further calculation of the resistance and power of the resistor is done based on this value. The location of the resistor in the circuit can be provided anywhere: on the anode side, cathode side, between the LEDs.

How to test an LED with a multimeter

One way to check the operating condition of LEDs is to test with a multimeter. This device can diagnose LEDs of any design. Before checking the LED with a tester, the device switch is set in the “testing” mode, and the probes are applied to the terminals. When the red probe is connected to the anode and the black probe to the cathode, the crystal should emit light. If the polarity is reversed, the device display should display “1”.

Helpful advice! Before testing the LED for functionality, it is recommended to dim the main lighting, since during testing the current is very low and the LED will emit light so weakly that in normal lighting it may not be noticeable.

Testing LED devices can be done without using probes. To do this, insert the anode into the holes located in the lower corner of the device into the hole with the symbol “E”, and the cathode into the hole with the indicator “C”. If the LED is in working condition, it should light up. This testing method is suitable for LEDs with sufficiently long contacts that have been cleared of solder. The position of the switch does not matter with this method of checking.

How to check LEDs with a multimeter without desoldering? To do this, you need to solder pieces of a regular paper clip to the tester probes. A textolite gasket, which is placed between the wires and then treated with electrical tape, is suitable as insulation. The output is a kind of adapter for connecting probes. The clips spring well and are securely fixed in the connectors. In this form, you can connect the probes to the LEDs without removing them from the circuit.

What can you make from LEDs with your own hands?

Many radio amateurs practice assembling various designs from LEDs with their own hands. Self-assembled products are not inferior in quality, and sometimes even surpass their manufactured counterparts. These can be color and music devices, flashing LED designs, do-it-yourself LED running lights and much more.

DIY current stabilizer assembly for LEDs

To prevent the LED's life from being exhausted ahead of schedule, it is necessary that the current flowing through it has a stable value. It is known that red, yellow and green LEDs can cope with increased current load. While blue-green and white LED sources, even with a slight overload, burn out in 2 hours. Thus, for the LED to operate normally, it is necessary to resolve the issue with its power supply.

If you assemble a chain of series- or parallel-connected LEDs, you can provide them with identical radiation if the current passing through them has the same strength. In addition, reverse current pulses can negatively affect the life of LED sources. To prevent this from happening, it is necessary to include a current stabilizer for the LEDs in the circuit.

The qualitative characteristics of LED lamps depend on the driver used - a device that converts voltage into a stabilized current with a specific value. Many radio amateurs assemble a 220V LED power supply circuit with their own hands based on the LM317 microcircuit. The elements for such an electronic circuit are low cost and such a stabilizer is easy to construct.

When using a current stabilizer on LM317 for LEDs, the current is adjusted within 1A. A rectifier based on LM317L stabilizes the current to 0.1A. The device circuit uses only one resistor. It is calculated using an online LED resistance calculator. Available devices are suitable for power supply: power supplies from a printer, laptop or other consumer electronics. It is not profitable to assemble more complex circuits yourself, since they are easier to purchase ready-made.

DIY LED DRLs

The use of daytime running lights (DRL) on cars significantly increases the visibility of the car during daylight hours by other road users. Many car enthusiasts practice self-assembly of DRLs using LEDs. One of the options is a DRL device of 5-7 LEDs with a power of 1W and 3W for each block. If you use less powerful LED sources, the luminous flux will not meet the standards for such lights.

Helpful advice! When making DRLs with your own hands, take into account the requirements of GOST: luminous flux 400-800 cd, luminous angle in the horizontal plane - 55 degrees, in the vertical plane - 25 degrees, area - 40 cm².

For the base, you can use a board made of aluminum profile with pads for mounting LEDs. The LEDs are fixed to the board using a thermally conductive adhesive. Optics are selected according to the type of LED sources. In this case, lenses with a luminous angle of 35 degrees are suitable. Lenses are installed on each LED separately. The wires are routed in any convenient direction.

Next, a housing is made for the DRLs, which also serves as a radiator. For this you can use a U-shaped profile. The finished LED module is placed inside the profile, secured with screws. All free space can be filled with transparent silicone-based sealant, leaving only the lenses on the surface. This coating will serve as a moisture barrier.

Connecting the DRL to the power supply requires the mandatory use of a resistor, the resistance of which is pre-calculated and tested. Connection methods may vary depending on the car model. Connection diagrams can be found on the Internet.

How to make LEDs blink

The most popular flashing LEDs, which can be purchased ready-made, are devices that are controlled by the potential level. The blinking of the crystal occurs due to a change in power supply at the terminals of the device. Thus, a two-color red-green LED device emits light depending on the direction of the current passing through it. The blinking effect in the RGB LED is achieved by connecting three separate control pins to a specific control system.

But you can make an ordinary single-color LED blink, having a minimum of electronic components in your arsenal. Before you make a flashing LED, you need to choose a working circuit that is simple and reliable. You can use a flashing LED circuit, which will be powered from a 12V source.

The circuit consists of a low-power transistor Q1 (silicon high-frequency KTZ 315 or its analogues are suitable), a resistor R1 820-1000 Ohms, a 16-volt capacitor C1 with a capacity of 470 μF and an LED source. When the circuit is turned on, the capacitor is charged to 9-10V, after which the transistor opens for a moment and transfers the accumulated energy to the LED, which begins to blink. This circuit can only be implemented when powered from a 12V source.

You can assemble a more advanced circuit that works in a similar way to a transistor multivibrator. The circuit includes transistors KTZ 102 (2 pcs.), resistors R1 and R4 of 300 Ohms each to limit the current, resistors R2 and R3 of 27000 Ohms each to set the base current of the transistors, 16-volt polar capacitors (2 pcs. with a capacity of 10 uF) and two LED sources. This circuit is powered by a 5V DC voltage source.

The circuit operates on the “Darlington pair” principle: capacitors C1 and C2 are alternately charged and discharged, which causes a particular transistor to open. When one transistor supplies energy to C1, one LED lights up. Next, C2 is smoothly charged, and the base current of VT1 is reduced, which leads to the closing of VT1 and the opening of VT2 and another LED lights up.

Helpful advice! If you use a supply voltage above 5V, you will need to use resistors with a different value to prevent failure of the LEDs.

DIY LED color music assembly

To implement fairly complex color music circuits on LEDs with your own hands, you must first understand how the simplest color music circuit works. It consists of one transistor, a resistor and an LED device. Such a circuit can be powered from a source rated from 6 to 12V. The operation of the circuit occurs due to cascade amplification with a common radiator (emitter).

The VT1 base receives a signal with varying amplitude and frequency. When signal fluctuations exceed a specified threshold, the transistor opens and the LED lights up. The disadvantage of this scheme is the dependence of blinking on the degree of the sound signal. Thus, the effect of color music will appear only at a certain level of sound volume. If you increase the sound. The LED will be on all the time, and when it decreases, it will flash slightly.

To achieve a full effect, they use a color music circuit using LEDs, dividing the sound range into three parts. The circuit with a three-channel audio converter is powered from a 9V source. A huge number of color music schemes can be found on the Internet at various amateur radio forums. These can be color music schemes using a single-color strip, an RGB LED strip, as well as a scheme for smoothly switching LEDs on and off. You can also find diagrams of running LED lights online.

DIY LED voltage indicator design

The voltage indicator circuit includes resistor R1 (variable resistance 10 kOhm), resistors R1, R2 (1 kOhm), two transistors VT1 KT315B, VT2 KT361B, three LEDs - HL1, HL2 (red), HLЗ (green). X1, X2 – 6-volt power supplies. In this circuit, it is recommended to use LED devices with a voltage of 1.5V.

The operating algorithm of a homemade LED voltage indicator is as follows: when voltage is applied, the central green LED source lights up. In the event of a voltage drop, the red LED located on the left turns on. An increase in voltage causes the red LED on the right to light up. With the resistor in the middle position, all transistors will be in the closed position, and voltage will only flow to the central green LED.

Transistor VT1 opens when the resistor slider is moved up, thereby increasing the voltage. In this case, the voltage supply to HL3 stops, and it is supplied to HL1. When the slider moves down (voltage decreases), transistor VT1 closes and VT2 opens, which will provide power to the LED HL2. With a slight delay, LED HL1 will go out, HL3 will flash once and HL2 will light up.

Such a circuit can be assembled using radio components from outdated equipment. Some assemble it on a textolite board, observing a 1:1 scale with the dimensions of the parts so that all elements can fit on the board.

The limitless potential of LED lighting makes it possible to independently design various lighting devices from LEDs with excellent characteristics and a fairly low cost.