Detailed description of LED SMD 2835
The SMD2835 LED is a high efficiency semiconductor artificial light emitter. It belongs to the group of super-bright. If ordinary brightness LEDs are used for decorative or auxiliary lighting, then super-bright ones are used as the main one.
LEDs with a power of 40-80 W provide a light flux of about 6000 Lm. Light output is from 150 to 75 lm/W, which is 6-12 times better than incandescent lamp.
For example, a 200 W incandescent lamp gives a light flux of 2500 Lm, i.e. its light output, measured in lm/W, is 12.5. The SMD3528 LED has a light output of 7-8 lm / W, and the SMD2835 - 20-22 lm / W, i.e. about 2.7-2.8 times better than SMD3528.
What is 2835 SMD LED
For the SMD2835 LED in the international classification:
- 2835 - the width and length of the LED body, expressed in tenths of a millimeter: 2.8 mm and 3.5 mm. Case height - 0.8 mm.
- SMD is an abbreviation derived from the English Surface Mounted Device - a surface mount device.
- LED is an abbreviation for the name of the LED in English - Light-emitting diode, light emitting diode, LED.
The SMD2835 LED is a light emitting semiconductor device. It is based on a p-n junction formed at the boundary of two semiconductor metals of p and n types of conductivity. In a p-metal, this is the bulk "hole" conductivity of atoms that have lost an electron and become a "hole". There is a movement of conditional positive particles - holes. In an n-metal, the carriers are electrons. When electricity is applied, holes and electrons move towards each other.
A moving electron has a high energy potential. Attracted to the hole, it occupies an empty place in the atom, their recombination occurs and a light quantum is formed, emerging from the end of the p-n junction. The process of glow, the release of quanta, will continue as long as the transition is supplied with electricity.
In the national economy, several models of SMD2835 are used - with a power of 0.09 W; 0.2; 0.5 and 1 W.
Appearance and dimensions
Externally, the housings of the SMD2835 and SMD3528 LEDs are almost the same, they have the same length and width - 3.5 x 2.8 mm.
However, there are external features.
SMD2835 is more powerful and gives three times more luminous flux, it is distinguished by a yellow phosphor, which almost completely covers its outer front side. The USMD3528 phosphor has the appearance of a round spot and occupies a smaller area.
The reverse side of the cases is also different.SMDZ528 has two narrow contact strips for soldering to the contact pads of the board, removal and passive dissipation of heat generated in the working LED crystal.
The SMD2835 also has two strips on the bottom of the case, but they are wider and occupy almost the entire area of the bottom. Therefore, they remove much more heat for passive dissipation by the printed tracks of the board.
Some technical characteristics of the SMD3528 and SMD2835 devices are shown in the table.
| LED Model | Size, mm - length, width, height | Light emission area, sq. mm | heat sink | Light scattering angle, deg. | Light output, Lm/W |
|---|---|---|---|---|---|
| SMD 3528 | 3,5*2,8*1,9 | 4,5 | Hardly ever | 90 | 7-8 |
| SMD 2835 | 2,8*3,5*0,8 | 9.18 | big | 120 | 20-22 |
SMD3528 are available in single or triple chip. The first is filled with a yellow phosphor, gives white light of different shades. The second can have three crystals of the same color or an RGB triad. With digital color management, it can give 16 million combinations. Three-crystal has four contacts - a common one and one for each crystal.
The polarity of the SMD2835 and SMD3528 LEDs is determined by the terminals of the anode, which is connected to the "+" voltage, and the cathode "-". The anode of the LED on the electrical circuits is indicated by a triangle, the cathode by a cross line. On the transparent cover of the case, it is marked with a “key” that looks like a cut corner. On both types of devices, such keys designate the leads of the cathodes.
Characteristics of the LED and the whole strip
The characteristics of super-bright SMD2835 include:
- Case material - plastic or ceramic.
- Electrical characteristics - operating current, forward voltage, rated power.
- Light (light quality characteristics): luminous flux - brightness or luminous intensity, index or color rendering index CRI or Ra - determines the correctness of the transmission of shades, color temperature - the shade of the glow of white light, expressed in the temperature of a completely black body, measured in degrees Kelvin, the color of the glow is red, yellow, blue, orange, white with many shades, etc.
- Climatic characteristics - operating temperature of the crystal, maximum and minimum air temperatures during operation, humidity.
- The characteristics of the tape include: supply voltage and current strength, level of dust and moisture protection (sealing), types of cases and sizes of LEDs, placement density, length, glow color or white light shade, controllability - dimmability, control of white light shade or glow color, special devices - "running fire", side glow.
Current and voltage parameters
Several variants of SMD2835 devices are industrially produced with different power parameters: 0.09 W - operating current 25 mA; 0.2 W - 60 mA; 0.5 W - 0.15 A and 1 W - 0.3 A.
High electrical and lighting performance obtained by gradual improvements in the mass production SMD3528 LED - one of the first in the group of super-bright, but with traditional dimensions.
The following changes were made to the design:
- the area of the yellow phosphor is increased, which converts the blue light of the semiconductor light-emitting crystal into white, i.e. a circle with a diameter of 2.4 mm and an area of 4.5 sq. mm was converted into a rectangle having an area of 9.18 sq. mm;
- case height was reduced from 1.95 mm to 0.8 mm;
- increased the rated operating current from 20 mA to 60 mA or more;
- expanded the contact area on the bottom of the housing for soldering and heat removal from 2.32 sq. mm to 2 x 1.8, i.e. up to 3.6 sq. mm.
This made it possible to increase the luminous flux of SMD2835 by 2.5-3 times compared to SMD3528.
Where and how is the 2835 SMD LED strip applied?
Tapes of this type have a high luminosity. That is why they are used as sources of main light in residential and work premises, public buildings, shopping and entertainment centers, in decorative, interior and exterior lighting. Sealed devices illuminate landscape elements, gazebos, paths, MAFs - small architectural forms, and more. other. They are widely used in illuminated advertising - volumetric luminous letters, inscriptions, signs, road signs, fountains, pools, etc.
We can say that SMD2835 tapes are applicable in all areas of life.
Wiring diagram
The SMD3528 and SMD2835 LEDs, as well as all other light emitting semiconductor diodes, cannot be connected directly to a traditional power supply. The reason is the insignificant internal resistance of an open semiconductor p-n junction. Direct inclusion will lead to the flow of a large current through the crystal, its rapid heating, which will end with an avalanche-like overheating and thermal breakdown of the p-n junction in the form of ordinary combustion. Therefore, it is necessary to limit the current by connecting a resistor in series with the diode. The disadvantage of this method is the useless conversion of "expensive" and high-quality electricity from power sources into heat, which must be removed and dissipated.
High-quality power supplies for LEDs convert the mains voltage of 220 V AC, often 50 Hz, into a constant voltage. It must have a high level of stabilization and filtering of mains voltage ripples.In addition, several types of power supply protection are provided.
With medium and high power LEDs, this leads to very noticeable power losses. Therefore, the current through the LEDs began to be limited in two ways:
- at low power diodes - their serial connection from 3 to 6, 9 and even 12 pcs. to one constant voltage through a current-limiting resistor;
- for powerful light emitters - using drivers.
When connected in parallel, each diode is connected through a resistor that quenches excess voltage. With series - the voltage on the chain of diodes is equal to the sum of all the diodes. The excess is extinguished, equal to the difference between the supply voltage and the sum of the voltages across the diodes.
The LED, depending on the materials, the color of the glow and other factors, has an operating direct voltage at the p-n junction from 1.63 V (red) to 3.7 (blue) and 4 (green). When diodes are connected in series, for example, in the diagram - LED5-LED8, the excess voltage of the power source is “quenched” and dissipated in the form of heat on the resistor R5.
When diodes are connected in parallel, a common quenching resistor is not allowed. The spread of diode parameters is 50-80%. The diodes will have different voltages due to the spread of operating currents.
The difference between SMD2835 LED strip and 3528
The main difference between SMD2835 tape and SMD3528 tape is the brightness of the glow. The difference is almost threefold in favor of the product based on SMD2835.
On the off tapes, you can see LEDs with yellow phosphor zones on the cases - rectangular (SMD2835) or round (SMD3528).
We advise you to see: Differences between LED strip 5050 and 2835
Another difference is that SMD2835 tapes shine only with white light, and SMD3528 can be red, yellow, green, and other colors, or RGB with a changeable color. They shine statically, without changing the magnitude of the luminous flux or with adjustable brightness and color tone. The brightness of the glow is regulated by a manual or electronic dimmer.
Tapes are flexible and can be mounted on flat and curved surfaces. To increase the luminous flux, LEDs are placed on a tape with a normal or increased density.
Two-, three-, and four-row tapes have even greater brightness. Such products get very hot during operation. Therefore, special aluminum mounting profiles have been developed for them.
On the tape, yellow elements are LEDs, black ones are current-limiting resistors, pairs of brown stripes are places where the tape is cut into autonomous segments - “pixels”. Pairs of pads are needed for soldering conductors or connecting connectors. Stylized images of scissors are usually placed on these places.
