《MK_LED senses and displays ambient-light intensity 中文》.pdf

LED senses and displays ambient-light intensity LED 感受并显示周围光线的强度 Two identical LEDs, closely spaced in a light-shielded housing, form a photovoltaic-characterization fixture. Choose resistor R and voltage source V to apply nominal forward current to the illuminating LED. 两个相同的led 近距离的摆放在一个光纤封闭的房间里，作为光伏转 换的参照性特征。选择电阻和电源构建一个典型的Led 发光电路。 Figure 2 Connecting one of the microcontroller’s outputs, Pin 2, to the LED’s cathode applies reverse bias that charges the LED’s internal capacitance to the supply voltage. Connecting the LED’s cathode to Input Pin 3 attaches a high-impedance load to the LED. (Note that pin numbers are representative only and not actual pinnumbers.) 连接单片机的输出引脚2 到LED 的阴 极，用来提供方向偏置电压给LED 的 内部电容充电电压。链接LED 的阳极 至为高阻负载状态输入引脚 3 。记录 中的引脚数仅仅是典型的，不是实际 的引脚数 In addition to their customary roles as indicators and illuminators,modern LEDs can also serve as photovoltaic detectors (references 1 and 2). Simply connecting a red LED to a multimeter and illuminating the LED with a source of bright light, such as a similar red LED, produce a reading of more than 1.4V (Figure 1). One model for a reverse-biased LED comprises a charged capacitor that connects in parallel with a light-dependent current source (Reference 1). Increasing the incident light increases the current source and more rapidly discharges the e