How to achieve fast, precise, and low power position sensing for real- time control Written by Jeff Shepard
Figure 1: 3D Hall effect position sensors can be placed on-axis or coplanar to the magnetic field to measure distance and angular movement. Image source: Texas Instruments
This article reviews the fundamentals of 3D Hall effect position sensors and describes their use in robotics, tamper detection, human interface controls, and gimbal motor systems. It then presents examples of high-precision, linear 3D Hall effect position sensors from Texas Instruments, along with associated evaluation boards and implementation guidance to speed the development process. What are 3D Hall effect sensors? 3D Hall effect sensors can gather information about the complete
The use of three-dimensional (3D) position sensing for real- time control is growing across a variety of Industry 4.0 applications, ranging from industrial robots and automated systems to robot vacuums and security. 3D Hall effect position sensors are a good option for these applications as they provide high repeatability and reliability, and can also be used with windows, doors and enclosures for intrusion or magnetic tampering detection. Still, designing an effective and safe 3D sensing system using a Hall effect sensor can be a complex and time-consuming process. The Hall effect sensor needs to interface with a microcontroller (MCU) powerful enough to act as an angle calculation engine and to perform measurement averaging, as well as gain and offset compensation to determine magnet orientations and 3D positions. The MCU also needs to handle a variety of diagnostics including monitoring
the magnetic field, system temperature, communication, continuity, internal signal path, and the power supply. In addition to hardware design, software development can be complex and time-consuming, further delaying time to market. To address these challenges, designers can use integrated Hall effect 3D position sensor ICs with an internal calculation engine. These ICs simplify software design and reduce the system processor’s load by as much as 25%, enabling the use of a low- cost, general-purpose MCU. They can also provide fast sample rates and low latency for accurate real- time control. In battery-powered devices, 3D Hall effect position sensors can be operated with duty cycles of 5 Hertz (Hz) or less to minimize power consumption. In addition, integrated functions and diagnostics maximize design flexibility and system safety and reliability.
magnetic field, enabling the use of distance and angular measurements for position
determination in 3D environments. The two most common placements for these sensors are on-axis and coplanar with the magnetic polarization (Figure 1). When placed on the axis of polarization, the field provides a unidirectional input to the sensor that can be used for position determination. Coplanar placement produces a field vector that is parallel to the magnet face regardless of the range to the sensor, also enabling position and
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