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Reflective switch operates contaminated environs

Posted: 08 Dec 2006     Print Version  Bookmark and Share

Keywords:TT electronics  Optek  OPB725  IR  reflective switch 

TT electronics Optek Technology has developed a long-distance reflective switch with a sensing distance of up to 24 inches or more, depending on the object. This provides design engineers with a device capable of operating in contaminated environments. Designated the OPB725 Series, the reflective switch consists of an infrared LED and Photologic sensor in an opaque housing to reduce the sensors ambient light sensitivity.

According to Roland Chapa, VP of Optek's assemblies business unit, the components of the switch allow it to be used in a variety of applications. "The emitter and sensor are protected by a window that is transparent to near-infrared wavelengths, which allows it to operate in dusty environments," said Chapa. "Additionally, the Photologic sensor has an NPN open-collector output, making the switch suitable for use in a variety of applications."

Applications for the reflective switch include non-contact reflective object sensing, assembly line and machine automation, equipment security, door and end-of-travel sensing, and machine safety.

While an object is in the reflective path of a device, light from the LED will be reflected back to the housing, irradiating the surface of the Photologic sensor. This causes the output NPN transistor to turn on, providing a low output voltage when connected to the appropriate value pull-up resistor, Chapa explained. When the infrared light from the LED is not reflected to the Photologic sensor, the output transistor turns off, minimising the IC(ON) current and providing a high output.

The OPB725 Series long-distance reflective switch features an 850nm LED, and the assembly is offered with 48-inch AWG wires. The device features a power dissipation of 250mW, a maximum collector voltage of 30V and a collector DC current of 50mA. Operating temperature range is 0 to 50°C.

Pricing for the OPB725 Series reflective switch starts Rs.680.52 ($14.95) each in quantities of 5,000. Lead time, if stock is not available, is from six to eight weeks.

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