Optoelectronics constitutes a very important group of elements used in all modern appliances. Without optoelectronics it is hard to imagine both operation of simple commodity products and professional medical, military equipment or industrial automatic devices. Competition in this group of components is very fierce. One of the optoelectronics manufacturers equipment is Citizen whose offer is presented below. All described elements are available in TME’s Internet shop.
Optoelectronic elements have been divided into several groups due to their purpose. They consist of both electronic and various mechanical elements that facilitate mounting and even improve functional properties of the optoelectronics itself.
LED in SMD enclosures
Citizen products overview starts with CL-824 type miniature LED with white luminescence. They are manufactured in several groups of color temperatures: 2700, 3000, 3500, 4000, 5000 and 6300 K. Thanks to a small and compact SMD 0816 enclosure, CL-824 led are used in lighting modules emitting uniform light. They can also be used as signalling elements mounted directly on printed circuit boards of electronic devices. The light intensity obtained by them is different for various performance versions and is within the range of 1650 up to 2430 mcd.
The CL-824 luminosity angle is 120° which means that the decrease in luminosity brightness by
half takes place at the angle of ± 60° measured from the element centre line. Directional characteristics of CL-824 led are presented in figure 1. Typical conduction current at the 3,2V led is 20mA. These elements can operate in the temperature range between -30 … +85°C.
LEDs replace more and more often bulbs in lighting fittings. LED production is becoming more and more dynamic. The function of a bulb with tungsten fibre is fulfilled by several or even several dozen of LED’s. This trend is mainly owing to world legal regulations, but such decisions are also taken as a result of multiple analyses of various parameters of alternative sources of light. Much better efficiency and long life are the features in favour of LEDs. Unfortunately, determination of this parameter is not easy, mainly because of its value. An additional difficulty is made by the dependence of LED durability on many factors, mainly on conduction current and temperature. In real life, special tests are used (IES LM-80) for which measuring conditions have been very accurately specified. Those tests help to determine the life time of a given element without the necessity of its actual “killing” which could last several or even several dozen years. In most cases LED diodes are not suddenly damaged but gradual deterioration of its lighting can be observed, which results from degradation of its structure. The test whose purpose is to determine LED durability cannot be shorter than 6000 hours (250 days). The light intensity of the tested element is checked every 1000 hours, and based on this its parameter characteristics in time function is determined. At the LED initial operating period, its light intensity remains on an almost unchanged level (decreases very slowly). After some time, one can observe clear collapse of the characteristics, after which the light intensity deteriorates at a much quicker rate. In the LM-80 test two characteristic points were assumed which were determined for light intensity drop down to the level of 91,8%
and 94,1% of the initial light intensity after 6000 hours of continuous lighting. They correspond to an estimated drop of light intensity to 70% of the initial value, after 25000 and 35000 hours respectively. The diagram of light intensity changes made for CL-824 LED is presented in figure 2. As it can be seen, after 6000 hours, even for the temperature of 85°C, the curve goes above the threshold of 94,1%, which means light intensity drop to 70% of the initial value will take place for sure after the time not shorter than 35000 hours (approximately 4 years of continuous lighting). However, it should be remembered that the test does not determine this time ideally, those are just estimates. There is one more, essential nuance related to this parameter. In the catalogues of many manufacturers, LED life is given for the temperature of 25°C, which is not at all reflected in practical applications. Element structure is always subject to a warm up to a much higher temperature which considerably reduces its life. Citizen specifies this parameter for the temperature of 85°C measured at the enclosure. It means that LED structure is heated up to 125°C.
Citizen also manufactures LED lighting in PLCC4 enclosures marked with the CL-L270 symbol. They also exist in one or two-matrix versions in one structure. In both cases, lighting angle is 120°.
Those LED’s emit white light with the following color temperature: 2700, 3000, 3500, 4000, 5000 or 6300 K. The scope of those LED’s applications is similar as the one discussed above, however, they operate with higher conduction currents (typically it is 60mA), and luminous flux obtained by them achieves the value from 16,2 to 20,5 lm.
When comparing this parameter with classical bulbs made of tungsten fibres, it could be said that there is still a long way ahead of LED manufacturers to achieve comparable performance. For example, luminous flux of a classical bulb 100W/230V is equal to approx. 1360 lm, but its efficiency is only 13,6 lm/W. Meanwhile, CL-L270 LED obtains the efficiency of approximately from 80 to 102 lm/W.
The next group of Citizen lighting LEDs are CL-L251 family elements. These are high-voltage power LEDs manufactured in the Emitter version with the power of 4 and 5W. The enclosure with flat lens has the following dimensions: 13,5×13×1,4mm. Conduction current at the voltage of 9,3V is equal to 480 and 720mA respectively, and the luminous flux, depending on the version, is within the range from 255 up to 625 lm. The lighting angle is 120°. Those LEDs are used for production of LED bulbs, ceiling fittings, spot lights etc. They are available in the following color temperatures: 2700, 3000, 3500, 4000 and 5000 K. This parameter, however, does not clearly specify the ability of giving up colors, which results from different distribution of radiation even in LED’s with the same color of light. It can be proved by comparing subjective feelings while watching different objects in the sunlight and in artificial light. For example, an object that in the sunlight is of a yellow color, after using red light source, is perceived as orange or even red. Each non-uniformity of light source spectral characteristics will therefore lead to a different manner of color rendering. CL-L251 LED spectral characteristics are presented in figure 3. In order to enable more accurate comparison of source lights against color rendering, the catalogues provide a CRI parameter (Color Rendering Index), marked with a Ra symbol. If its value is equal to zero it means that the source is monochromatic, whereas,
for an ideal white light the parameter obtains the value of 100. A general principle states that the higher the CRI parameter, the better is the rendering of colors by the source of light. There are even norms specifying minimum CRI values for sources of light used in various institutions, e.g. offices, surgeries, schools, libraries, etc.
The CRI indicator for the family of CL-L251 has the following values: 67, 85 and 90, depending on the performance.
Citizen also offers several other families of power led. For example, 13 Watt CL-L233 are manufactured in enclosures with the dimensions of 23×17,5×1,4mm. Conduction current at the voltage of 18,6V is equal to 720mA. The luminous flux depending on the version is within the range of 710 to 1400 lm. The CL-L330 (1960 and 2800 lm) and CL-L340 (3060 and 4390 lm) families are characterized by even higher brightness. This is related to higher power of those elements, 26 and 41W respectively.
The CL-L330 and CL-L340 LEDs are used in modern spotlights, ceiling fittings, warehouse and manufacturing buildings lighting systems. They are manufactured in color temperatures 3000 and 5000 K and the CRI coefficient of 67.
While looking through Citizen’s LED catalogue parameters, it is worth paying attention to a certain detail. In the column specifying the maximum permissible temperature of connection (Tj) one can find LEDs operating up to 120°C and up to 150°C. Operating conditions of the latter (Tj < 150°C) can be, in some cases, exceeded. Users with strong nerves can “turn up” LEDs, similarly to what is often practiced with PC processors. “Turning up” LEDs means that nominal conduction current of a LED is exceeded with simultaneous maintenance of limitations concerning maximum permissible of each of the parameters (in particular current and temperature). A user should take complete responsibility for all the effects of such proceeding, which not always is cost-effective, because among Citizen LEDs one can find such whose efficiency, despite of considerable power, is higher than 100 lm/W. LED Modules
Optoelectronic elements manufactured by Citizen include also LED module, e.g. CL-L103. There are also matrices constituting several dozen LEDs mounted on boards with the dimensions of 500×70×1,35mm. The total power of such module is equal to 3 or 6W at the conduction current of 9,3V. Should this be necessary, a radiator can be mounted onto the board in order to improve cooling conditions. The obtained luminous flux, is within the range of 190 to 720 lm, and the color temperature can be equal to: 2700, 3000, 3500, 4000 and 5000 K. Modules of this kind are used in street and decorative lighting, and also as the element of interiors main lighting.
Such applications result among others from a very high efficiency, which in the 6W version is within the scope from approx. 79 up to 110 lm/W, whereas in the 3 W version, it is approx. 89 up to 116 lm/W. Modules used to illuminate interiors (with warm color) have high CRI which is 85. This parameter in modules designed for external lighting applications is 65.
Other group of Citizen LED modules comprises of L-CM family. TME offers three variations of such modules with different combinations of power, brightness and conduction current. Among them, there are modules with the powers of 6 and 13W and luminous flux of 605 and 1205lm respectively. The versions with the conduction current of 9,6V or 19,2V are available. The board’s dimensions are 290×15×5,63mm. Modules glow with white color and the color temperature of 5000 K. They fit perfectly as surroundings lighting emphasizing specific climate and mood of rooms. They are also used to achieve special illumination effects.
The L-CM modules also offer high efficiency which is about 90lm/W. Color rendering indicator Ra of 70 ranks them among good light sources in 2A class, for which the Ra parameter can have the value from 70 to 79. In very good sources, the following classes are distinguished: 1A (Ra ≥ 90) and 1B (Ra=80…89).
LED Modules designed for a 230V direct power supply
One of Citizen’s newest products are modules designed to be directly supplied from the AC 220…240V/50…60 Hz. Presently, there are two versions of such modules: LMC10B-23L180A-11 with color temperature of 3000 K and luminous flux of 1100 lm and LMC10B-23W180A-11 with color
temperature of 4000 K and luminuous flux of 1000 lm. An inovative technology of LED control – SCD (Selective Current Diversion) has been used.
It is characterized with high efficiency and low interferences introduced to the network. Modules consume the power of 22W at the power coefficient of 0,97. LEDs flickering frequency is equal to 100Hz, which is practically unnoticed by a human being. Due to operation at high voltages, enclosures have been made of material with high resistance to puncture.
Optoelectronics additional elements
Optoelectronics offer is completed by components used for the assembly of light-emitting diodes and additional collimators.
L250-HOLDER is a special LED enclosure facilitating its mounting (figure 4), whereas, the L250-LENS15 element is an external collimator for the family of CL-L250 diodes (figure 5). This collimator is used to correct light radiation characteristics.
Among discussed Citizen optoelectronic elements, it is easy to choose those which will meet the requirements of developed lighting applications. All presented diodes and LED modules glow with white color of different temperatures. They can be selected depending on individual needs and likings. Appliances developed by their means can fulfill decorative functions with a subtle, dispersed light intensity, but also appropriate elements can be selected in order to obtain a sharp and pointwise light in order to emphasize single elements of interiors equipment. Long life of Citizen LEDs guarantees a long, failure-free operation of lighting systems in which those elements are implemented.
More information available at:
Transfer Multisort Elektronik
Tel.: +48 42 645 54 44
Fax: +48 42 645 54 70