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Stepper motors are beneficial in applications that require precise movement. However, they need a closed-loop feedback system to determine if the move command was successful. One example is Anton Khrustalev's CLN17 compact open source closed-loop driver for NEMA 17 stepper motors. Closed Loop Stepper
CLN17 fits on the back of a NEMA 17 motor. The publication NEMA ICS 16-2001 standardizes many aspects of stepper motor design. For example, a NEMA 17 motor's faceplate measures 1.7 by 1.7 inches (43 by 43 millimeters.) That size works well for CLN17 since it is only 38 x 38 millimeters.
Packed into that relatively small circuit board is a microcontroller, a 15-bit encoder, a motor driver, a CAN driver, a 6-axis IMU, and a DC-DC converter.
The microcontroller is an STMicroelectronics STM32G431. It has an Arm-Cortex M4 core running at 170 MHz. The STM32 also provides CLN17's interfaces. Those include I2C, CAN, UART, and a generic enable/direction/step control.
Stepper motors are well known for their ability to sing when actuated. The Trinamic TMC2209 driver provides ultra-silent (and smooth) operation. These drivers also enable passive braking, stall detection (current feedback), and microstepping.
The closed-loop part of CLN17's name primarily comes from the Infineon TLE5012 magnetic encoder. This angle sensor provides a 15-bit value of the absolute angle of the motor's shaft. This detail lets the microcontroller know if the stepper motor moved as expected.
One seemingly unique addition is an LSM6DSO. This sensor is a six-axis IMU. CLN17 uses this to detect some motion and vibration of the assembly. It could also provide detection for non-motor events like collisions.
An onboard DC-DC convert provides flexible options for powering CLN17. The two- and six-pin XH2.5 connectors accept five to 25 volts and has reverse polarity protection. Alternatively, you can use a USB-C power supply that supports Power Delivery for up to 20 volts and five amps.
Khrustalev already completed a prototype and has testing of the, hopefully, final prototype underway. Once testing is complete, The plan is to provide design details under an open license and launch a Kickstarter.
In the future, Khrustalev may also offer expansions for CLN17 and driver boards for larger motors. Learn more details about its design and when it is available on the CLN17 website.
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