Rupin Chheda
Problem Statement & Decomposition
The Problem:
Stepper motors, though common and cheap, come with a learning curve. This is especially true for the 28BYJ-48 unipolar stepper, which is widely available and very affordable, but not very beginner-friendly when it comes to wiring, sequencing, and control logic.
To add to the difficulty:
-
You often need a microcontroller and some level of programming knowledge.
-
A driver board is typically needed to interface between motor and microcontroller.
-
Even with hardware in place, writing or adapting stepper motor code can be overwhelming for non-technical users.
-
Configuring motion patterns like oscillations or synchronizing multiple motors becomes even more complex.
Decomposing the Need:
From a design perspective, the challenge can be broken down into a few key problems:
-
Ease of Use: Users shouldn't have to understand H-bridges, pulse sequences, or lookup tables.
-
Configurable Motion: The system should support both continuous and oscillating motion, ideally with live tuning.
-
Standalone Control: Motion should be easily initiated and adjusted without a PC or development board.
-
Scalability: Multiple motors should be able to run in sync, and optionally be triggered by external events or sensors.
-
Compact and Drop-in Friendly: The hardware should be compact, self-contained, and easy to integrate into small spaces or enclosures.
This decomposition became the guiding framework for the final design — from microcontroller choice to UI and feature set.
Project Idea & Features
The Unipolar Stepper Motor Controller is a 43mm x 32mm PCB that houses a CH32V003 microcontroller, driver circuitry, a rotary encoder for real-time control, and an intuitive interface that supports both manual and automated motor control. While it is optimized for the 28BYJ-48 stepper motor, it works with any unipolar stepper.
Here’s what makes it special:
🔧 1. Built Around the CH32V003 MCU
At the heart of the controller is the CH32V003, a rising star in the ultra-low-cost microcontroller world. Despite its small price tag and footprint, it offers:
-
Adequate I/O for stepper control.
-
Fast interrupt handling for rotary encoder inputs.
-
Support for I2C communication.
-
Low power consumption, making it ideal for embedded, standalone systems.
Using CH32V003 also makes this project replicable and modifiable by other hardware hackers without resorting to high-cost components.
🎛 2. Rotary Encoder as a Natural UI
The controller includes a rotary encoder, which acts as a human-friendly interface for all key operations:
-
Rotate CW/CCW to turn the stepper motor in either direction.
-
Press to save configurations or trigger motion.
-
Navigate through modes like Continuous or Arc without the need for serial terminals or software tools.
It’s a small addition, but it turns the product into a plug-and-play device rather than a development kit.
🔁 3. Continuous and Arc Modes
There are two main modes for using the motor:
-
Continuous Mode: Spin continuously in CW or CCW direction. Great for things like rotating displays, kinetic sculptures, or simple mechanisms.
-
ARC Mode: Here’s where it gets interesting. In ARC mode, the user can define left and right extents by manually rotating the motor to each endpoint using the encoder. Once set, the motor automatically oscillates between these positions. This opens the door to:
-
Windshield-wiper style motion
-
Linkage animations
-
Scanner head sweeps
-
Servo-like behavior with a stepper
-
🧩 4. I2C Daisy Chain Support
Want multiple motors working in sync or responding to a central controller like a Raspberry Pi, ESP32, or another CH32 board?
The onboard I2C interface allows multiple controller boards to be daisy-chained. This supports master-slave configuration, enabling advanced behaviors like:
-
Coordinated multi-axis movement
-
Sequenced motion (domino-style animations)
-
Centralized triggering...
Jan Neumann
John Taylor
Andy Geppert
Scott Duckworth