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EnDat 3 interface is designed for digital manufacturing

21 July, 2021

The German sensor-maker Heidenhain has released the third generation of its EnDat serial communications interface, specifically designed to meet the needs of digital manufacturing. EnDat 3 is said to offer faster data transmission, improved reliability and improved diagnostics, combined with additional sensor data (from encoders or other external devices).

Previous versions of EnDat have been limited to point-to-point or master/slave topologies. EnDat 3 supports bus topologies that can link multiple devices. It also offers enhanced functional safety to SIL 3, and can be used with hybrid cables to create a single, standardised cable between servodrives and motors, thus cutting cabling and installation costs.

EnDat 3 can be applied to a variety of devices – mainly position encoders – and supports a wide range of measuring and scanning technologies, including absolute and incremental, photoelectric, inductive and magnetic types. Connections can be made via a bus, hybrid cables or sensor boxes, with the ability to add extra internal or external sensors.

High performance is ensured by 15µs cycle times with low position-measurement jitter and a 12.5Mbit/s bandwidth for 100m-long cables (or 25 Mbits/s for 40m lengths). The diagnostic performance has been enhanced by using electronic ID labels that support automated system installation, online encoder diagnostics, and improved condition monitoring and predictive maintenance.

One of the first manufacturers to take advantage of EnDat 3 is the German motion controls manufacturer Stober, which has used it to enhance its one-cable solution (OCS) technology, allowing users to connect servomotors and drives over distances of up to 100m. The single-cable connection means that machine-builders no longer need to use separate cables to power the motor and to transmit encoder data.

Continuous testing has shown that encoder signals can be read and evaluated without errors, even after five million cycles. The new OCS – which is compatible with Stober’s SC6 and SI6 controllers – also removes the need to use output chokes up to 50m. A new transceiver chip in the drives, as used in Heidenhain’s EnDat 3 encoder, makes Stober the first drive specialist to use the OCS in combination with this encoder system. The OCS works with Stober’s EZ and EZS synchronous servomotors, which can also be attached directly to gearboxes, resulting in compact geared drives suitable for digital production and robotics applications.

Heidenhain launched its first EnDat protocol in 1995 to meet the need for a fast, reliable interface for data transfer in applications involving absolute linear and rotary encoders. It operated as a bi-directional interface.

One of the first applications for the EnDat 3 protocol is in Stober’s OCS single-cable technology, which can link drives and motors up to 100m apart

In 2003, EnDat 2.2 arrived, offering faster communications with clock speeds of up to 16MHz (compared to a maximum of 2MHz with EnDat 2.1), making it suitable for use in closed-loop systems. Advances in encoder technology allowed absolute position values to be derived in the encoder, avoiding the need for extra electronics to process the serial and incremental signals. Other enhancements included single-cable support for servomotors, capable of carrying power and brake signals to the motor, as well as encoder data back to the drive.

The imminent arrival of EnDat 3 was first revealed at the 2019 SPS trade show in Germany.

“The arrival of EnDat 3 is another step along the road to enhanced digital manufacturing which will bring major benefits in the field of data transfer with added reliability and improved performance all round,” says Heidehain (GB)’s sales manager, Philip Lodge.


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