OCB100-KIT Datasheet, PDF (5/24 Pages) OPTEK Technologies – Auto-Calibration Design Kit

THEORY OF OPERATION OCB100
The OCB100 series is designed to minimize the change of optical de-
vices due to manufacturing variance, temperature change, and device
aging. This system can be used to calibrate either reflective or inter-
ruptive devices to provide a consistent output, thus eliminating the
need to confirm either the LED drive resistance or the phototransistor
load resistance. With the OCB100, the design engineer can reduce
the sensor to sensor variation present in many systems. By providing a
pre-calibrated sensor to the system design, the engineer can enhance
the reliability and consistency. Degradation of the LED or phototransis-
tor is compensated for each time the system is calibrated allowing the
system to provide a known, consistent output level resulting in years ₅
of consistent quality. The OCB100 series is designed to maintain the
calibrated setting even if power is lost, thus allowing faster startup
without the need for calibration every time the device is initiated. The
designer can initiate the calibration procedure at any time by momen-
tarily grounding J1-Pin-4 (green wire). This allows the device to be re-
motely calibrated, and then mounted in the equipment.
The PCBoard has a set of shorting pins allowing the user to change
the phototransistor load resistor. By arranging the shorting bar to the
appropriate location (see table on pg. 9) you can change the load re-
sistance from approximately 2.5K to 27K ohms. Increasing the load
resistor increases the device sensitivity.
When the “Calibrate” pin (#4) is momentarily grounded, the sys-
tem begins its calibration process and raises the current through the
LED, from 0 mA to 14 mA, until the phototransistor reaches the preset
calibration point. A green calibration light will blink 3 times when the
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