Reflected light intensity detecting circuit CD4052B CD4011B

Posted on Mar 28, 2007

As shown for the intensity of reflected light detection circuit. The circuit consists of an infrared light-emitting diodes, photodiodes, CMOS analog switches, operational ampli

Reflected light intensity detecting circuit CD4052B CD4011B
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fiers and other components. When the circuit to work, first the infrared light-emitting diode (LED) does not light, the photodiode received external interference signal converted to an electrical signal applied to the negative direction integration circuit, provided this period is T1; then make the LED light, the photodiode the received optical signal is converted to an electrical signal applied to the positive direction of the integrating circuit, this period is set T2. Let T1 T2. The circuit is displayed and held external interference signal, and are based reflected light intensity. Hold signal this time is called hold time, referred to as T3. Integrator reset the corresponding time corresponding to T4. At the operating frequency (50Hz or 60Hz), the order to effectively avoid the interference of external synchronization, it is preferable that T1 T2 N/f (N an integer, f is the operating frequency), or take T1 T2 1/f. The circuit structure is simple, using the output power of 5 ~ 10mW infrared light-emitting diodes and photodiodes, can be detected at a distance of 10 ~ 100mm intensity of reflected light. Circuit op amps input bias current should be much less than the photocurrent. Circuit gain depends on integration time and integration capacitor Ci. This can eliminate the interference detection circuit in addition to the intensity of the reflected light (reflected light ratio), it can also be used to detect the distance, tilt, and pass rates, especially for detection of various intensity. In addition, the circuit can be used for measuring magnetic Hall element and other measurements.

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