Understanding MotorCell

When working on projects that require high-speed motion in a compact form factor, traditional brushless motors can be difficult to integrate due to their size and complexity. This is why MotorCell is unique as it combines the rotor, stator, and driver into a single, ultra-compact module.

In this post, we’ll explore the MotorCell’s design, driver functionality, and integration into your projects.

What is a MotorCell?

MotorCell is the smallest coreless high-speed PCB motor with planar PCB windings and built-in sensorless control, eliminating the need for extra sensors! By integrating everything into a single module, it provides a tiny and compact solution for makers and developers working on applications requiring high speed motor control.

Designed for low-torque, high-speed applications, MotorCell supports PWM-based speed control and works seamlessly with the MotorCell library, which includes prebuilt PID control for CodeCell and other ESP32-based devices.

How Does MotorCell Work?

It's PCB stator is made from a 6-layer FR4 board, that has 6 copper windings connected in a star-shape configuration. This makes the motor a 3-phase axial-flux brushless motor. These type of motors need to be powered with specific timings to generate a commutation waveform and rotate the magnetic rotor on top. 

This is why MotorCell also utilizes the BD67173NUX chip as its three-phase back-EMF controller, enabling a sensorless commutation, so no Hall sensors required. This driver allows speed adjustments via the input signal PWM duty cycle, with a resolution of around 1,000 RPM increments. The IN pin is by defaults low, running the motor at the maximum speed when pulled high (2.5V–5V).

If the motor is forced to stop, it enters a 5-second lock protection mode, which can be instantly resets when PWM is set to 0% and restarted - this is automatically managed by the MotorCell library’s Spin function.

Key Features

• Ultra-Compact & Shaftless: With a 3.3mm thin aluminum rotor, the MotorCell allows direct press-fit attachment to the rotor’s teeth.
• High-Speed Performance: Spins up to 30,000 RPM at no-load.
• Durable & Lightweight: The rotor integrates four arc-magnets, an iron back-plate to enchance the magnetic field and a ceramic-hybrid ball bearings.
• PCB Integration: The open PCB stator design enables integration into a PCB, allowing for better customization.
• Sensorless Operation: Reduces components and size, making the setup easier.
• PWM Speed Control & Feedback: Provides speed feedback through the OUT pin.

Important Notes

• MotorCell is designed for light loads. Speed decreases with load. Maximum spinning load: 12g at a radius of 18mm.
• High-Speed Caution: Keep hands away from moving parts and wear protective eyewear.
• OUT Pin Pull-Up Resistor: The MotorCell library automatically enables an internal pull-up on the OUT pin. If using a different microcontroller, ensure the pull-up remains enabled or add an external one.
• Disassembly & Handling: MotorCell has precision-machined parts that are super-tiny and easy to lose. If reassembling, it is recommended to torque the bolted-shaft to 0.15 Nm.
• Soldering Precautions: The soldering iron may be attracted to the rotor’s magnets—handle with care.
• Press-Fit 3D Printed Parts: Recommended inner diameter: 16.4mm–16.6mm, depending on 3D printer tolerances. Parts can be press-fit or secured with superglue.

Open Stator

We believe the exciting advantage of PCB motors lies in their ability to integrate seamlessly with electronics, eliminating the need for additional PCBs. That’s why we’ve made it simpler to incorporate the Stator directly into your custom PCB, thanks to its Open Source Design - available here.

However, building a high-speed rotor remains a complex challenge. To make things easier, you can purchase the rotor separately, allowing you to effortlessly add a PCB motor to your board for a more compact design while ensuring a reliable rotor configuration!

Setting Up Your MotorCell 

Connecting Your MotorCell

• IN: 10kHz-50kHz PWM input for speed control (or connect to VDD for full speed)
  
• OUT: Speed frequency feedback (requires a pull-up resistor if not implemented through software)
• FR: Optional direction control (connect to VDD, GND, or control with GPIO)
  
• GND: Ground connection
• VDD: Power input (2.5V–5V)
  

Installing the MotorCell Library

To get started with Arduino:

1. Open the Arduino IDE.
2. Navigate to Sketch > Include Library > Manage Libraries.
3. Search for “MotorCell” and install it.

Conclusion

With the MotorCell library installed, you can easily control speed, direction, and monitor its RPM, explained in more detail in our other tutorials.

Ready to start experimenting? Grab a MotorCell today and check out the MotorCell GitHub Repository for more code examples and technical documentation!