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1、Fabrication of photoelectric sensors发信人: Death (44death), 信区 Robocon:标 题: 光电传感器的制作 (转自中科大bbs)发信站: 北京科大幻想空间站 (Wed Aug 13 01: 06: 50, 2004)光电传感器探头的制作光电传感器探头由发光二极管和接收管组成.一.元件介绍1.发光二极管 的介绍 (LED).做传感器的led要求亮度高, 颜色合适, 光斑形状合适.为了防止led损坏, 应该注意: 1.led的伏安特性曲线很陡, 测试和使用时一定要串联电阻限制电流或使用内阻很大的废旧电池. 2.氮化镓材料的高亮度led容易被
2、反向电压, 静电或电源尖峰击穿损坏, 电源电压较高时不可反接.不同的管子允许的工作电流不同.红外的平均电流最大可以用到100毫安, 用作调制时几十微秒的窄脉冲峰值甚至可以接近1安.3毫米的白色高亮度管子是最大电流20毫安(不记得是平均值还是峰值).5毫米的允许电流要大一些, 但一般也不超过50毫安.一般低亮度的管子要小一些.工作电流的限制一是发热限制平均电流, 二是高电流下亮度饱和限制峰值电流.有些管子电流大了之后还会变色.常用的led有红外, 红, 橙, 黄, 黄绿, 纯绿, 蓝, 紫, 紫外, 白等颜色.作为成品销售的 变色led 是在一个管壳 (通常是乳白色的, 用于使光线混合均匀) 里
3、封装了多个不同颜色的led, 如果有红, 绿, 蓝三色则非常适合作颜色传感器的照明.红外线led配合红外接收管抗干扰能力强, 但是不适合用于识别颜色, 因为物体在可见光下的颜色不能很好的代表它对于红外线的反射率.验钞用的管子发光含有紫色光和紫外线, 点亮时不要正对着眼睛, 也不要靠近观看或长时间观看.管壳无色透明的管子透光性能好一些, 散射小, 更适合做传感器 (变色管除外, 乳.白色管壳比无色透明管壳好.) 管壳有色的管子适合做指示灯.直径5毫米的管子品种较多, 亮度较高, 发出的光束比直径3毫米的管子要集中 (顶角小), 照在物体上光斑小, 适合用来识别白线.直径3毫米或者贴片的管子适合用
4、来做电路板上的指示灯.红外对管的发射管和接收管是平行的, 容易引起镜面反射, 只适用于接近开关.Led的伏安特性曲线很陡, 可以作稳压用, 给电路提供基准电压.红色的大约1.8v, 蓝色的可以超过3v.购买的时候一般到城隍庙的 临江, 这里品种比较多.天香家具城里面的一家电子商店有超高亮度橙红的管子.2.接收管的介绍.常用的接收管有硅光电二极管, 硅光电三极管, 光敏电阻三种.光电二极管产生的电流小 (微安级), 需要高倍放大, 但是速度很高, 可以高频调制.识别: 在遮光状态下的特性类似普通二极管.使用: 加反向电压或不加电压, 输出与光照强度近似成正比的光电流.光电三极管一般基极不引出,
5、只有两根管脚, 购买的时候叫做光敏管.光电三极管产生的电流较大 (几百微安以上), 无需前置高倍放大, 但是速度较低,调制频率低于100khz.识别: 遮光状态下正反向电阻都很大, 用强光 (比如台灯) 照射, 可以测出一个方向的电阻明显变小, 这个方向是正向.Use: forward voltage 1V, output light intensity and light approximately proportional to the current.The photoelectric receiving tube shell is colorless and transparent a
6、nd black two, black shell almost only through infrared and infrared.Supporting the use of luminous tube.The electrical characteristics of the photosensitive resistance is not a constant flow resistance, light resistance is greatly reduced, the output current isA large number of similar level, photot
7、riode. The working frequency is generally low, but also a high. The most important in the regionDont lie in the photosensitive resistor receive light is a plane, no shell and tube condenser, directional difference. In general do not distinguish betweenThe light direction or to reduce the cost of the
8、 circuit.3. receiving tube and distinguish the appearance of the launch tube.Colorless and transparent receiving tube core guard:From the head to look inside, the tube core is black, with a white spot. The tube core area is very large, almost filled theThe vision, and the tube core around without re
9、flector.The LED core is generally around a relatively large area of the metal reflector, the center of the square of the small things die. Black shellThe tube is mostly the infrared receiving tube. Also has the infrared emission tube, but the tube is generally not all black color.4. advanced materia
10、ls and spectral characteristics.(1) LED material, color and brightness.The principle of LED light is a semiconductor pn junction in the recombination of electrons and holes generated photons. Different materials due to bandwidthDifferent colors and lead to the turn-on voltage of different. In additi
11、on, the luminous efficiency of different materials (generally in quantum efficiencyMeasure the photon number / emission quantum efficiency = electron number flows) also have great difference.The color of luminescence quantum efficiency (related to the process, here is typical)GaAs GaAs infrared high
12、, 30%GaAsP 10% (red phosphorus GaAs, the purchase is called common)Orange, yellow phosphorus content increased with decreasing efficiency, shorter wavelength.Nitrogen doped GaP:N green gap is low, less than 1% (at the time of purchase is called common)Zinc Oxide GaP:ZnO doped gallium phosphide red t
13、o yellow in the low (buy called general)AlGaAs (high aluminum gallium arsenide red when buying called high brightness)AlGaInP orange (30% AlGaInP high, buy called high brightness)Gan GaN (including In) from pure green to ultraviolet, 20% (at the time of purchase is called high or super high brightne
14、ss)GaN, the tube core coated with a fluorescent powder purple + yellow = white high (at the time of purchase is called high or super high brightness)Different materials and colors of the tube core is not energized when the color is different, can be used to recognize the tube.Material / color tube c
15、ore colorGaAs/ infrared, GaAsP/ red, red black AlGaAs/GaP/ GaP-ZnO/ green, yellow, red, AlGaInP/ ultra high brightness orange light brownGaN/ from pure green to ultraviolet white, with two metal wire chipGaN core is coated with a fluorescent powder in a large white / yellow and white, the invisible chip, with two metal wire(2) receiving the spectral characteristics of tube.The photodiode and phototransistor are semiconductor pn junction photovoltaic element on the photoelectr
