Page 382 - The Mechatronics Handbook

FIGURE 19.5 The Fairchild semiconductor QVA11234 photointerrupter.

FIGURE 19.6 The Fairchild semiconductor QRB1114 photoreflective sensor.

FIGURE 19.7 A position sensitive detector (PSD), UDT Sensors, Inc.

Photointerrupters and photoreflectors can be bought prepackaged or constructed separately from an
infrared LED and a photodiode or phototransistor, after making certain the detector is sensitive to the
wavelength produced by the LED.
Photoreflector units are also available with more advanced position sensitive detectors (PSDs), which
report the location of infrared light incident on the sensing surface (Fig. 19.7). The fixed location of the
LED relative to the PSD, as well as the location of the image of the infrared light on the PSD, allows the

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