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Controlling the Speed of a 28BYJ-48 Stepper Motor with a Potentiometer T174

In this tutorial, we’ll show you how to turn a simple potentiometer into a real-time speed controller for the 28BYJ-48 stepper motor using an Arduino. Rather than a fixed, “one-speed” step sequence, you’ll learn how to read an analog knob and translate its position into a variable delay between coil steps—giving you smooth, twist-to-control motion. All the full Arduino sketch is provided below the article; here we’ll focus on the key concepts and code highlights you saw in the video.

When we jump to 02:31 Wiring Explained, you’ll see the straightforward hookup: the 28BYJ-48 driver’s four inputs go to four digital pins on the Arduino, and the potentiometer’s wiper goes to A0 (with its ends tied to 5 V and GND). A second digital pin simply feeds 5 V to the pot, so everything shares a common ground. This five-wire setup gives you both the motor stepping interface and a live analog control signal.

At 05:38 Code Explained, the sketch’s structure becomes clear:

• Desired Speed Baseline

  A variable desiredValue represents the target seconds per full revolution (e.g. 20 s). A helper function converts that into a maximum delay (N) between individual half-steps—so you can dial in any slowest speed without hard-coding magic numbers.

• Analog-to-Delay Mapping

  Inside loop(), we read analogRead(A0) (0–1023) and use map() to scale it into the range 1…N milliseconds. That mapped value becomes the delay() after each step, so turning the pot from minimum to maximum smoothly sweeps the speed from its slowest crawl up to its fastest spin.

• Half-Step Drive Sequence

  Rather than rely on a library, the code defines four arrays—one per coil—encoding an 8-step half-drive pattern. A small helper function driveStepper(stepIndex) sets the four output pins accordingly, energizing the coils in the correct order for smooth motion.

By organizing the sketch around these pieces—baseline delay computation, real-time mapping, and a clean drive function—you get full analog control in just a few dozen lines of code.

In 12:25 Motor Speed Formula Explained, we break down the math: the 28BYJ-48’s internal gearbox means 2048 half-steps per output revolution. To achieve any RPM, you calculate the total steps per minute and derive a per-step delay. Our calcDelayfromTime() function generalizes this so you can simply pick “10 s per rev,” “20 s per rev,” etc., without re-deriving the math each time.

Finally, at 15:03 Demonstration of speed control, you’ll see how responsive the system feels: twist the pot slowly and the motor inches forward; crank it to maximum and you’ll approach around 60 RPM. The serial monitor even echoes the mapped delay or RPM in real time, so you can confirm the mapping is linear and jitter-free.

All of the code snippets and helper functions mentioned here—calcDelayfromTime(), driveStepper(), the mapping logic, and the half-step arrays—are included in full below. Feel free to copy, tweak your desiredValue, or experiment with different step patterns.

🎬 Video Chapters

00:00 – Start

00:39 – Introduction

02:31 – Wiring Explained

05:38 – Code Explained

12:25 – Motor Speed Formula Explained

15:03 – Demonstration of speed control