Gearotons M17: A $20 Open-Source Servo for Pi Robots

Anyone who has built a 3D printer, CNC router or robot arm knows the wiring spaghetti that comes with stepper motors: a motor, a separate driver board, a motion controller and, for accurate positioning, an encoder bolted on the back. The Gearotons M17 from Move the Needle Ltd folds all four into a single standard NEMA 17 body, starting at just $20. CNX Software detailed the design on September 22, 2026, and Open Source For You followed on September 23.

• All-in-one: motor, driver, motion controller and encoder in a 42.2 by 42.2mm NEMA 17 footprint
• Four sizes: M17-34 to M17-60, rated from 0.28 to 0.65 N·m of torque
• Price: $20 to $35 depending on size, plus a $10 USB-to-RS-485 adapter
• Open source: firmware, KiCad hardware files and 3D files on GitHub, with Python and Arduino libraries

Gearotons M17 Specs at a Glance

Inside each motor, an STMicroelectronics STM32G0 Arm Cortex-M0+ microcontroller runs a closed-loop PID controller at 32kHz, reading the built-in encoder so the motor always knows exactly where it is. That closed loop is the key upgrade over a typical open-loop stepper, which can silently skip steps under load and lose its position.

• M17-60: 0.65 N·m, 59.7mm tall, 470g
• M17-48: 0.55 N·m, 48.7mm tall, 360g
• M17-40: 0.42 N·m, 40.1mm tall, 285g
• M17-34: 0.28 N·m, 33.5mm tall, 210g

All four run from 12 to 24V DC, top out at 560 RPM, and include over-current, over-voltage and over-temperature protection.

How Do You Control the M17 From a Raspberry Pi?

Every motor talks RS-485 at 230,400 baud, and the same bus daisy-chains from one motor to the next. Each unit carries a 64-bit factory ID plus a one-byte alias you assign, so a single cable run can address a whole robot's worth of joints. A Raspberry Pi, Arduino, ESP32, Mac or PC connects through the $10 USB adapter, and the Python library installs with pip.

CNX also notes an MCP server that lets AI assistants drive the motors directly, a fun twist for anyone experimenting with agent-controlled hardware on a single-board computer.

What Could You Build With It?

The obvious fits are desktop robot arms, camera sliders, pan-tilt heads, small CNC machines and lab automation rigs, the kind of maker project behind the Raspberry Pi Pico blood-research centrifuge we covered last week. Because each motor runs its own position loop, the host computer only sends high-level moves. That frees a Pi or microcontroller for vision, networking or user interface work instead of pulsing step signals.

Why an Open-Source Servomotor Matters for Makers

Integrated closed-loop steppers have mostly been aimed at industrial buyers, with configuration handled by vendor software. Publishing the firmware, schematics and mechanical files means makers can study, modify and repair the M17 rather than treat it as a black box. The KiCad files are also a useful reference design for anyone learning motor control, and at $20 for the smallest unit, an integrated closed-loop motor is priced for hobby builds.

The M17 is available to order now from the Gearotons website. If you are planning a robot that pairs these motors with an AI camera or a controller like the Arduino Ventuno Q, this is an easy way to cut the wiring down to a single bus. For more maker hardware, browse our mini computers coverage.

Sources: CNX Software — September 22, 2026; Open Source For You — September 23, 2026; Gearotons — September 2026.