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Arcus Technology has developed an all-in-one NEMA 11 microstep motor with Renishaw’s AM256 magnetic encoder chip, as well as a driver and a controller, integrated into the motor’s back cap.

This is intended to minimise external electronics and wiring.

Launched at the 2009 Lab Automation show, the DMX-K-SA-11 stepper motor uses the Renishaw encoder chip for real-time position verification.

The small package size of the magnetic encoder chip allows the motor to stay within the 1.1in (2.8cm) square form factor of the NEMA 11 standard.

The DMX-K-SA-11 stepper motor is suitable for size-sensitive biomedical, optical and semiconductor applications requiring open-loop microstep motion with real-time position confirmation.

The integrated DMX-K-SA-11 is a 16-microstep driver that is capable of full, half, quarter or one-sixteenth microsteps in three different stack sizes.

Arcus developed this design as an alternative to typical step motors that run open loop with sensors to detect position values after the move.

The DMX-K-SA-11 is designed for customers and applications that require a position verification signal from the motor as well.

By incorporating the Renishaw AM256 magnetic encoder chip into the back cap, Arcus was able to add this capability with no change in size or add-on external components or encoders.

The electronics inside the back cap have a maximum ambient operating temperature of 85C (185F).

The standalone control uses Windows-based programming language similar to Basic and is said to be easy to program.

The DMX-K-SA-11 motor features RS-485 communication with a baud rate of 9,600bps to 115Kbps.

It has a trapezoidal acceleration profile control, a 12VDC to 24VDC voltage input and a driver current from 100mA to 1.5A.

It includes opto-isolated +Limit/-Limit/Home inputs and opto-isolated digital output.

Its homing routine uses home input or limit input.

Renishaw’s AM256 8-bit encoder chip is a solid-state, compact magnetic solution for non-contact angular position encoding over 360 degrees, providing incremental, parallel, serial SSI and analogue sinusoidal output options.

The encoder’s integrated circuit senses the angular position of a diametrically polarised, cylindrical magnet placed above it.

A circular array of Hall sensors around the centre of the IC detects the magnetic flux density distribution at the surface of the silicon and delivers a voltage representation of the magnetic field distribution.

Sine and cosine voltage outputs from the Hall sensors vary with magnet position and are converted to absolute position with a fast 8-bit flash interpolator.

Relative changes of angle position are output as incremental A quad B signals with 8-bit/256 counts per revolution.

With an operational range of -40C to +125C, high resistance to shock and vibration and a rotational speed capability up to 60,000rpm, the AM256 is claimed to combine the ruggedness and performance needed for harsh environments.

Working closely with its associate company RLS, Renishaw offers a line of solid-state magnetic encoder chips based on the Onaxis Hall sensor technology, ranging from the AM256 8-bit to the AM8192B programmable 13-bit chip.

Renishaw also custom designs solid-state encoder solutions for motor original equipment manufacturers (OEMs).

Onaxis encoders are suitable for non-contact incremental or absolute position or velocity measurements for motion-control applications in robotics, servo and step motors, semiconductors, medical applications, agriculture and military applications.


A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

A world leader in engineering technologies, Renishaw’s core skills in measurement and precision machining serve sectors as diverse as dimensional metrology, spectroscopy, machine calibration, motion control, dentistry and surgical robotics.

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