Commutation encoder simplifies BLDC motor setup time

October 08, 2014 // By Graham Prophet
CUI has an addition to its next-generation modular encoder series that generates standard U/V/W commutation signals for vectoring current to brushless motors: the capacitive technology enables a combination of durability and flexibility.

Positional information for the AMT31 series is generated using CUIs capacitive code generation system coupled with a proprietary ASIC. The technology suits the encoder for use in brushless dc motor applications subject to vibration and contaminants - such as dust, dirt and oil - that typically stop optical encoders from working effectively. The AMT31 series also delivers accuracy figures of ±12 arcmin (±0.2 mechanical degrees).

The digital nature of the encoder designenables a 'One Touch Zero' feature, allowing for time saving during the motor installation process. Installing a commutation optical encoder onto a brushless dc motor (BLDC) can otherwise be an iterative and time-consuming process as the optical disk must be physically and precisely rotated to align with the correct motor windings. Once aligned, the assembly must then be checked via back EMF to ensure mounting accuracy and this process can take upwards of 15 minutes per motor. The AMT, being ASIC and MCU based, reduces this time consuming process to a few seconds via the One Touch Zero feature, saving time and cost during the manufacturing process.

Commutation output can accommodate brushless motors with 2, 4, 6, 8, 10, 12 or 20 pole pairs, selectable from the factory or via CUI's AMT Viewpoint graphical user interface. The AMT31 also offers supplementary incremental A, B, and Z channels for various servo positioning and startup sequences. 20 programmable resolutions are available with a range of 48 to 4096 PPR, again adjustable at the factory or via CUI's AMT Viewpoint. For quick analysis during design or in the field, the AMT31 implements an onboard diagnostic system, allowing access to a range of parameters.

The compact series measures 28.58 x 37.25 x 10.34 mm and has a -40 to 105°C operating temperature range. A current draw of 10 mA at 5 Vdc suits the AMT31 series to mobile and battery-driven equipment. An input range of 4.5~5.5 Vdc is standard, with options for CMOS