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Reflective Switch Employed in Wind Turbines for RPM Sensing

The OPB732 Series long distance infrared reflective switch from TT electronics OPTEK Technology (Carrollton, TX) has been employed in a 6kW wind turbine for RPM sensing. Placed at the turbine rotor, the switch is used internally to sense RPMs, and that data is then transmitted to a customer-accessible Web site via GPRS.

The OPB732 Series switch has a reflective distance of more than one inch, depending on circuitry. The reflective switch configuration includes an infrared LED and phototransistor, and uses an opaque housing to reduce the sensor's ambient light sensitivity. The infrared LED features an 850nm wavelength and a power dissipation of 100mW. Maximum forward current is 50mA and maximum forward voltage is 1.8V.

When infrared light strikes the phototransistor, it becomes forward biased and is considered to be in the "on" state, providing an IC(ON) current proportional to the light striking the phototransistor. When the infrared light from the LED is not reflected to the phototransistor, the device turns "off," minimizing the IC(ON) current.

Accurately monitoring turbine RPMs is crucial for their safe and efficient operation. In addition to wind turbines, the OPB732 reflective switch is ideal for use in assembly line and machine automation, equipment security, door sensor, machine safety, end of travel sensor, and non-contact reflective object sensor applications.

(TT electronics OPTEK Technology)