user Electronics Engineer

city Innovuze Solution Inc.

  • AS5311 Magnetic and Linear Position Sensor

  • Created: Aug 23, 2016

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The magnetic linear encoders is a position sensing device that uses hall effect elements like a multi-pole magnetic strip or ring to convert the encoded position into an analog signal or digital signal. The AS5311 is a high-resolution contactless magnetic linear encoder for accurate linear motion and off-axis rotary sensing with a resolution down to <0.5um. It is also immune to external magnetic stray fields.

The design has a microcontroller, USB interface, 128x32 graphical LCD display, incremental indicators, and PWM output LED. The circuit can be powered through USB or an externally supplied 9V battery. A multi-pole magnetic strip or ring with a pole length of 1.0mm is required to sense the rotational or linear motion. It is placed above the AS5311 at a distance of 0.3mm. An absolute position can be read from the AS5311 using its serial output. To use this feature, SW1 must be on position INT. The EXT position is for external AS5311, which is connected on header J6. The LED that is connected to the PWM output of the AS5311 is proportional to the position of a pole-pair of the magnet. The brightness of the PWM LED follows the absolute position, moving the magnet to the left increases the brightness of the PWM, while it would be opposite the other way around. The MagINCn and MagDECn is the magnetic field change indicator that indicates if the magnetic field strength increase or decrease through variation of the distance between the magnet and the device. The phase shift between channel A and B indicates the direction of the magnet movement. Channel A leads channel B during a right-to-left movement of the magnet by 90 electrical degrees. Channel B leads channel A during a left-to-right movement.

The use of a multi-pole strip magnet and a multi-pole ring magnet depends on the application. The magnetic and linear position sensor is applicable in motor speed and motion control for off axis applications, replacement of linear and rotary optical sensor system, and robotic systems.



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