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Machine Design

Interface options for rotary encoders

A new combined interface for Optocode absolute rotary encoders allows simultaneous communication of both absolute and incremental rotary position data. The interface provides cost-effective point-to-point communications between encoders and many popular types of programmable logic controllers (PLCs).

Data is reported to the PLC through a synchronous serial-interface (SSI) standard, operating over an RS-422/485 communication link. The encoder simultaneously transmits a series of electronic pulses as the shaft rotates – up to 16,384 pulses/rotation. As an option, an index pulse can be sent once every complete rotation. Incremental pulses can be sent over an RS-422/485 link, or via a push/pull connection. These “dual-personality” encoders are useful for motor-control applications or monitoring rotating machinery such as wind turbines, as they provide accurate real-time measurement of the rotational velocity while also providing access to absolute rotary position data in response to a request from the controller.

Additional new features include enhanced diagnostic reporting via case-mounted LEDs or via the SSI connection, and an optional case-mounted push-button that lets operators reset the zero-position of the absolute position readout. Available as solid, hollow and hub shaft versions, the units can be supplied with a connector or a cable exit.

Fraba Inc.
1800 East State St., Suite 148
Hamilton, NJ 08609
(609) 750-8705

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