| 摘要 |
A system and method for adjusting the LED current of an optical sensor that does not decrease the effectiveness of the optical sensor or the length of its operating life, or significantly increase the cost due to hardware requirements. The LED current of an optical sensor is adjusted using a high frequency pulse-width modulated signal generated from a microcontroller. Based on feedback provided by the photo-detector, the duty cycle of the signal can be adjusted by the microcontroller. The signal passes through a low pass filter which averages the modulated signal into a DC voltage, which is then used to control a current amplifier circuit that provides current to the LED of the optical sensor. This adjustability enables the system to compensate for variations in sensor LED's and the LED brightness reduction to due aging and/or build-up of contaminants on the photo-detector and/or LED.
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