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AMBIENT_LIGHT_GNORING_OPTICAL_SENSOR

2014-11-21 20:07  
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AMBIENT_LIGHT_GNORING_OPTICAL_SENSOR
A resonance-tuned narrow-band amplifier reduces this optical object detector's sensitivity to stray light. C1 and L1 in IC2A's feedback loop cause the op amp to pass only those frequencies at or near the LED's 5-kHz modulation rate. IC2B's output increases when the received signal is sufficient to drop the negative voltage across C2 below the reference set by R2.