The use of a magnetic chip encoder enabled Arcus Technology to develop an “all-in-one micro stepmotor that meets the 1.1-in.2 form factor of the NEMA 11 standard. The DMX-K-SA-11 NEMA 11 microstep motor integrates the driver, controller, and encoder into the motor’s back cap, minimizing external electronics and wiring. The encoder is Renishaw’s magnetic AM256 magnetic encoder chip, which delivers position verification in real-time.
The DMX-K-SA-11 is a 16-microstep driver capable of full, 1/2, 1/4, or 1/16 microsteps in three different stack sizes. Arcus Technology developed this design as an alternative to typical stepmotors that run open loop with sensors to detect position values after the move. By incorporating the Renishaw magnetic encoder chip into the back cap, Arcus engineers were 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 85° C (185° F).
The stand-alone control uses a Windows-based programming language similar to BASIC. The motor features RS-485 communication with a baud rate of 9600 to 115 Kbps. It has a trapezoidal acceleration profile control, 12 to 24 Vdc voltage input and driver current from 100 mA to 1.5 A. It includes opto-isolated +Limit/-Limit/Home inputs and opto-isolated digital output. Its homing routine uses home input or limit input.
The AM256 8-bit chip encoder is a solid state, compact magnetic unit for non-contact angular position encoding over 360°. It offers incremental, parallel, serial SSI, and analog sinusoidal output options. The encoder’s integrated circuit senses the angular position of a diametrically polarized, cylindrical magnet placed above it. A circular array of Hall sensors around the center 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.
Operational range of the encoder is from -40° C to 125° C. It has high resistance to shock and vibration, and delivers rotational speed capability up to 60,000 rpm. These OnAxis encoders suit non-contact incremental or absolute position or velocity measurements for motion control applications in robotics, servo and step motors, semiconductor, medical, agriculture, as well as military applications.
Filed Under: Factory automation, Motion control • motor controls, Motors • stepper
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