Rotor Position Encoder
dev_motor_controller_4808 incorporates an integrated rotor position encoder based on the Austria Micro AS5047p magnetic encoder. The AS5047p device returns 14 bits of rotational position at a maximum rate of 28k RPM.
Encoder Target
AS5047p magnetic target
The AS5047p returns the position of a diametrically magnetised cylindrical magnet mounted to a rotating structure at a fixed distance from the surface of the sensor.
| Magnet type | Cylindrical diametrically magnetised Neodymium Iron Boron (NdFeB) N35 |
| Potential part number | Radial Magnets Inc 9042, Digikey 469-1070-ND |
Magnet mounting requirements
In practice the AS5047p is quite tolerant to magnet misalignment and in most cases will produce a reasonable output. Mounting guidelines are presented below.
| Vertical mounting distance | Between 0.5mm and 1.8mm from the surface of the sensor |
| Suggested magnet size | 6mm diameter, >= 2.5mm height |
| Bz (Orthogonal magnetic field strength) | 35mT - 70mT peak field strength at a radius of 1.1mm |
For further detailed information consult the AustriaMicroSystems AS5047p datasheet. Although it is a different sensor the AS5040 datasheet also offers useful mounting guidelines.
WARNING:
Ensure the magnet is fixed well to the rotating magnet mount. Any movement of the magnet in its mounting feature can result in erratic motor behaviour. It is recommended to glue or stake the magnet into its fixture.
Magnet mounting example
