Machine Design

Sensor Sense: Optical Data Transmission Handles Remote Video

A flexible and resilient alternative to Wi-Fi, RF, or hard-wired data transfer is optical data transmission (ODT). Wi-Fi and RF are vulnerable to noise interference and can exhibit varying transfer speeds based on the location and the amount of metal nearby. The result can be a significant drop in the transfer rate. Hard-wired data transfer typically employs drag cables or slip rings — both prone to mechanical wear, inflexibility, and noise interference.

Optical data transmission offers a simple means of sending information without these common drawbacks. It uses a modulated infrared light beam for wireless data transfer. Each ODT sensor consists of a transmitter and receiver. The sensors are used in pairs aimed at each other along a line-of-sight axis. Typically, one sensor is stationary, while the other travels along the axis towards or away from the stationary sensor.

As the method of data transfer uses light, optical data couplers do not incur physical wear, need no recalibration, and operate without problems in electrically noisy environments. High-speed versions handle Ethernet communications and can even transfer live video. This is especially useful where remote video is needed for diagnostic or feedback purposes.

For example, an automated storage and retrieval system (ASRS) stacker crane creates an overhang when it doesn’t correctly place a pallet in an overhead bay. It then becomes necessary to shut down the line and physically reposition the pallet at the trouble spot. High-speed Ethernet optical data transmission lets a camera sit on the moving crane and provide live video of the crane and bays. The live video signal lets operators at a remote control room analyze the problem and correctly reposition the errant pallet within minutes. The optical data couplers transmit the video to the control room as well as instructions from the control room to the crane for repositioning the pallet. MD

Pepperl+Fuchs supplied information for this column.

Edited by Robert Repas, Associate Editor

© 2011 Penton Media, Inc.

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