Double rotating module and built-in electronics.

thingiverse

This module is designed to enhance the Fischertechnik building blocks, offering a compact unit with double rotation capabilities. Each stage features an integrated quadrature decoder and home point detection system, utilizing Hall detectors for precise measurements. The AH3144E Hall detector stands out due to its compatibility with various hardware setups, functioning effectively on voltages ranging from 4.5V to 24V. The output is configured as an open collector type, while each stage is powered by a 9V XS motor. The upper axis includes a pivoting block with 20 teeth, perfectly adapted to work in conjunction with the worm gear of FT without significant backlash. Notably, small holes are provided on the rotating block's contours for applying a neodymium magnet D2x3mm, which serves as a calibration point for home detection. On the worm shaft, a small disk encoder featuring 5 magnets offers 20 pulses per revolution through quadrature detection, resulting in an angle adjustment accuracy of 1/400 or 0.9 degrees. The total angular rotation is slightly more than 180 degrees, while the lower turntable's gear boasts 44 teeth and can rotate 360 degrees with an accuracy of 1/880 = 0.41 degrees. The worm shaft also incorporates an encoder disk with 5 magnets (20 pulses/rotation), meticulously adapted to prevent slippage on the shaft. All necessary STL files are available for download, ensuring seamless integration and customization. During testing, hall detectors were successfully mounted and signals measured, revealing a natural quadrature detection phase shift of 90 degrees without requiring any adjustments. The XS motor utilizes its standard reduction block and achieves approximately 140 revolutions per minute on the worm (2.35 rec/sec). Each encoder pulse corresponds to roughly 21 milliseconds; thus, your quadrature decoder must process these pulses within this timeframe or even better, 15 milliseconds due to potential deviations in phase shift (90° +/- 20%). To enhance the overall design, an original FT grip module was mounted on the upper rotation arm, with plans to replace it with a more compact version featuring built-in electronics. For 3D printing, PolyMaker polyMax PLA filament is consistently used, demonstrating exceptional strength comparable to ABS and clean printed parts that slide smoothly over each other. A heated table is not required; instead, the printing plate is warmed under water before printing. Standard settings on the FlashForge Finder with a temperature of 210° are employed for optimal results.