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  • The Mistakes use infrared LED in the security surveillance cameras

        Printing of some errors, the use of infrared LED cognitive Among the more important are:
        First, the importance of heat overlooked: the situation of the most common use too small heatsink or did not use the heat sink. To know: the heat bad cause high chip temperatures generated the infrared wavelength drift liter and photoelectric conversion efficiency lower results. Gone with the Wind and high wavelength, causing the camera CCD light sensor deterioration, poor night vision effect is more than 850nm. Low photoelectric conversion efficiency is bright enough. Often a few cents of the heat sink will produce the effect of NCTU.
        Second, the wrong hand touch test temperature: often been taken aback by their own manpower on more than 44 degrees Celsius (or cooling the body) shell less than 2-3 seconds can not stand, and therefore feel "too hot", in fact, this temperature is not high, will not harm the electronic components of the normal work. Moreover, the higher the temperature of the shell (or cooling body) explains: "hot" export more good. "Energy is eternal" --- envisaged: shell (or cooling body) is not hot "hot" to go there? Thermal conductivity could not stay on the chip, causing the chip work at high temperatures, night vision effect poor, the light fades, the short-lived.
        That the larger chip on certain relatively small chip "bright": large-size chip LED therefore often blind to the specified requirements. To know: brightness depending on the current, the current can be used and how much? Depending on the heat treatment, that is: heat determines the current and thus determine the brightness, rather than the size of the chip determines the brightness. Theoretically, the same brand of chip regardless of the size, if the current is the same, the voltage (the same power), the heat generated on the same problem: the same amount of heat is scattered on how much area? Scattered in the area of ​​the pinhole size and scattered on a slap in the size of the area, the difficulty of the heat treatment is very different. In dealing with heat dissipation, each due to the different techniques and different equipment, different from the heat sink material, therefore, individual on how much area, the ability to dispose of the same "hot".
        For example: if 1.2A current Epistar 28mil chip and 42mil chip, its voltage is substantially the same (1.7V), so the power substantially the same (about 2W), Of course, the heat generated is also come first problem is: this 2W heat scattered 42mil chip area, and relatively easy to handle, scattered 28mil chip difficult. To solid crystal using the traditional silver plastic encapsulation method, the thermal resistance is generally 20 ° C-30 ° C / W, use eutectic package, the thermal resistance is generally 6 ° C-10 ° C / W, which The cooling effect is very different. Drive current of more than two can be used to greatly different, the brightness will vary greatly.
        Of course, the choice of a small chip packaging, high-current drive with the advanced cooling technology also limited the above 2W heat on 10mil chip area, eutectic process package is also difficult to successfully complete the heat Export. Look forward to the future cooling technology, more advanced materials, may be able to use smaller chips, lower prices, but the night vision effect is still more advanced infrared LED.
        To sum up: the quality of large-size chip night vision effect may not be stronger than the small size chip, depending on heat treatment. Therefore the eutectic process of encapsulation technology is an important means of cost-effective progress, and future trends.

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