Study of Magnetic Encoder Sensors for Motion Control Applications

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Dr. Sütő Zoltán
Department of Automation and Applied Informatics

The task of my final project is the study of magnetic encoders. In the first part of my work I present the literature of rotary encoders. I have studied the working principle of encoders and I have chosen two sensors (AS5045B and AS5115) on which the examination is based. After that I built up a test environment for testing the sensor.

For the first step I designed two Printed Circuit Boards (PCB), using KiCad software, for the chosen sensors. The PCB-s were manufactured by Sos PCB Kft. based on my design plans. The necessary circuit elements were soldered on the surface of the PCB. A magnet was attached to the shaft of a motor, which can operate at maximum 5 Volts, with ~1mm air gap to the sensor. The angular position of the magnet is determined by integrated Hall elements in the sensor. Measurements were made to identify the output signals of the sensor

By the AS5045 sensor the angular information is sent out on incremental and absolute channel as well. It generates quadrature signals by incremental method and it generates a digital signal with 4096 position / rotation by absolute method. The digital signal is available by serial communication (using SSI) and by a pulse width modulated signal (PWM). To determine the angular position, I wrote a program for a microcontroller, to process the signals from the SSI output.. An oscilloscope was used to visualize the signals on the other channels and with those signals I calculated the motor’s rotational speed and determined the angular position as well. Further, I wrote a program, which is able to measure the time period of one rotation, using the signal from the quadrature reference channel.

By the AS5115 sensor the position of the magnet is translated into analog output voltages. By measuring this signal’s frequency, the rotational speed of the motor was calculated and a comparison was made between these results and the results measured by the other sensor.

The results of my measurements are realistic and can be used for further applications.


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