EncodeRS

A dirt-cheap, minimal-component RS485 magnetic encoder designed to sit right on the back of a Nema 17 stepper motor.

Building a closed-loop stepper system or a FOC (Field Oriented Control) setup? This board gives you high-speed, noise-immune angle data without breaking the bank. By using RS485, it ignores the nasty electromagnetic interference (EMI) generated by the motor coils, even over long cables.

Key Features

• Ultra-Low Cost: Designed with minimal BOM in mind. No fancy or redundant components.
• Hand-Assembly Friendly: SMD components smaller than 0805 were avoided wherever possible, so you don't need eagle eyes or a microscope to build it yourself.
• Noise Immune: RS485 differential signaling ensures your angle data survives the electrically noisy environment right next to a spinning motor.
• 4-Wire Interface: Just provide +5V, GND, and the A/B differential pair.
• FOC Ready: Offloads the motor position sensing from the main controller.

Under the Hood

• Sensor: MT6816CT-ACD – SPI magnetic angle sensor.
• MCU: STM8S003F3P – Reads the SPI sensor and spits out UART.
• Transceiver: SP3485EN – Converts UART to robust RS485.
• LDO: HT75R33-1A – Drops the incoming 5V to a clean 3.3V for the logic.

Project Status

• Schematic design
• PCB routing
• Enclosure design
• Firmware development
• Testing on a real motor under heavy load

Acknowledgments

A big shoutout to dVNaNt for coming up with the perfect name for this project!