When you select a stepper motor, you see a “step angle” specification (e.g., 1.8°). This represents the physical angle the motor will move for every one pulse it receives in “full-step” mode. A 1.8° motor, therefore, requires 200 steps to complete one 360° revolution.
However, the motor’s actual motion—its smoothness, noise, and resolution—is not determined by the motor alone. It is controlled by the stepper motor driver and its “step mode.” The driver dictates how current is delivered to the motor’s coils.
Let’s explore the three most common drive modes: Full-Step, Half-Step, and Microstepping.
1. Full-Step Mode
Full-step is the most basic and simplest mode of driving a stepper motor. As the name implies, for every pulse from the controller, the motor moves one full “basic” step (e.g., 1.8°).
In practice, full-step operation comes in two forms:
- Single-Phase Full-Step (Wave Drive):The driver energizes only one phase (winding) at a time, cycling in a sequence like A → B → A’ → B’. This method has the lowest power consumption, but because only one coil is working, it also produces the lowest torque (approx. 70% of rated torque) and is rarely used.
- Dual-Phase Full-Step (High-Torque Mode):This is the most common full-step mode. The driver energizes two phases simultaneously at all times (e.g., A+B → B+A’ → A’+B’ → B’+A’). By using both coils, this mode provides 100% of the motor’s rated torque at every step position.
Advantages:
- Maximum Torque: In dual-phase mode, the motor delivers its full rated holding torque.
- Simple Control: The driver logic is the simplest.
Limitations:
- Low Resolution: The motor can only operate at its coarsest resolution (e.g., 200 steps/revolution).
- Vibration and Noise: The motor “jumps” from one 1.8° position to the next. This creates a rough motion and can cause significant vibration and noise, especially at certain speeds (resonance).
2. Half-Step Mode
Half-stepping is a simple way to increase the resolution of a full-step motor. It works by alternating between energizing a single phase and two phases.
The energizing sequence looks like this: (A+B) → (B) → (B+A’) → (A’) → (A’+B’) …
Advantages:
- Doubled Resolution: The step angle is now half of the full step (e.g., 1.8° → 0.9°). A 200-step motor now has 400 steps per revolution.
- Smoother Motion: Because the step size is smaller, the motor’s operation is much smoother than full-step, significantly reducing vibration and noise.
Limitations:
- Torque Ripple: This is the primary drawback of half-stepping. When two phases are on (like A+B), the motor outputs 100% torque. But when only one phase is on (like B), it outputs only ~70% torque. This alternating high-low torque can cause operational instability or “ripple,” especially under load.
Note: Some advanced drivers can compensate for this by increasing the current (e.g., to 141%) during the single-phase steps, but this is essentially a primitive form of microstepping.
3. Microstepping Mode
Microstepping is the most advanced and widely used drive mode today. It abandons simple “on/off” current control. Instead, it supplies a precisely proportioned sine/cosine current to both motor phases, dividing a single full step into many much smaller “microsteps.”
Common subdivisions include 1/4, 1/8, 1/16, 1/32, or even 1/256.
How it Works: Instead of jumping from (100% current in Phase A, 0% in B) to (0% in A, 100% in B), the driver smoothly transitions: (100% A, 0% B) → (98% A, 20% B) → (92% A, 38% B) … This smooth current change allows the rotor to rest at stable “micro-positions” between the full steps.
Advantages:
- Extremely High Resolution: A 200-step motor in 1/16 microstep mode has 200 * 16 = 3,200 steps/revolution. This can often replace expensive mechanical gearboxes.
- Extremely Smooth and Quiet: The motion is “silky smooth,” virtually eliminating the vibration and noise common in other modes.
- Eliminates Resonance: By smoothly “gliding” through the low-speed resonance points, it vastly improves low-speed performance.
Limitations (Key Practical Considerations):
- Torque and Accuracy are Not Linear: Microstepping provides excellent resolution, but not always equivalent accuracy. The motor’s maximum holding torque only exists at the full-step positions. At the “micro-step” positions, the holding torque is lower. If the load is too high, it can “pull” the motor to the nearest full-step, reducing accuracy.
- Current Requirement: To achieve smooth motion, the driver is more complex and typically requires a higher total current to maintain torque.
How to Choose: Drive Mode Comparison
| Feature | Full-Step (Dual-Phase) | Half-Step | Microstepping |
| Resolution | Standard (e.g., 200 steps) | High (e.g., 400 steps) | Extremely High (e.g., 3200+ steps) |
| Smoothness | Poor | Medium | Excellent |
| Noise & Vibration | High (Prone to resonance) | Medium | Very Low |
| Torque Output | 100% Rated Torque | Torque Ripple (70%-100%) | Smooth, but reduced torque at micro-positions |
| Positional Accuracy | Good | Fair (Affected by ripple) | Good (Depends on load & subdivision) |
| Best For… | Simple, low-speed, high-torque tasks where noise is not a concern. | A simple way to double resolution. | The vast majority of modern applications (3D Printing, CNC, Medical, Automation) |
Conclusion
- Full-Step is for simple indexing tasks where you only care about maximum holding torque and are not concerned with noise or vibration.
- Half-Step is an outdated compromise. Its benefits are almost entirely surpassed by microstepping.
- Microstepping is the standard choice for all modern stepper applications. It provides unmatched smoothness and high resolution, making it the preferred solution for precise, quiet motion control. When choosing, you simply need to select an appropriate microstep division (e.g., 1/8 or 1/16) that meets your load and precision needs.