How to make two phases BLDC Motor?

Below is a practical guide focused on hobbyist-friendly approaches:

Option 1: Modify a PC Cooling Fan (Easiest)

Most small PC fans are 2-phase BLDC motors with unipolar windings.
Steps:

1. Salvage a Fan: Disassemble a 40–120mm DC fan (e.g., 12V).

2. Identify Components:

   • Stator: 4 electromagnet poles (2 phases, center-tapped).

   • Rotor: 4-pole ring magnet.

   • Hall Sensors: Two sensors (90° apart).

3. Extract Electronics: Remove the original controller.

4. Build Your Own Driver (See Option 3 below).

Option 2: Build a Prototype Motor (Advanced)

Materials Needed:

Assembly Steps:

1. Wind Stator Phases:

   • Phase A: Wind coil pairs in slots 1-4 and 5-8.

   • Phase B: Wind coil pairs in slots 2-5 and 6-1 (shifted 45°).

   • Center Tap: Split each phase into two halves (connect midpoint to GND).
     //www.electronicdesign.com/sites/electronicdesign.com/files/uploads/2015/09/Fig_01.gif

2. Build Rotor:

   • Glue magnets to rotor hub with alternating polarity.

   • Ensure clearance between rotor/stator (0.5–1 mm).

3. Mount Hall Sensors:

   • Position sensors facing rotor magnets at 0° and 90° electrical angles.

Option 3: Build the Drive Circuit (Essential)

Unipolar Driver (4 MOSFETs):

Circuit Diagram:

                           Vcc (12-24V)
                              │
           ┌───────────┬─────┴─────┬───────────┐
           │           │           │           │
         [FET1]      [FET2]      [FET3]      [FET4]   (N-channel MOSFETs)
           │           │           │           │
Phase_A1 ──┤           ├─ Phase_A2 │           │
           │           │           │           │
Phase_B1 ──┤           ├─ Phase_B2 │           │
           │           │           │           │
CT_A ──────┴───────────┘           └───┬───┬───┘
CT_B ──────────────────────────────────┘   │
                                          GND

Components:

• MOSFETs: 4x IRFZ44N (with heatsinks).

• Flyback Diodes: 4x 1N5819 (across each FET's drain-source).

• Microcontroller: Arduino Nano.

• Gate Drivers: 4x TC4427 (optional but recommended).

Arduino Code (Simplified):

// Pins: HA=A0, HB=A1, FET1=2, FET2=3, FET3=4, FET4=5
void setup() {
  pinMode(2, OUTPUT); // FET1 (Phase A+)
  pinMode(3, OUTPUT); // FET2 (Phase A-)
  pinMode(4, OUTPUT); // FET3 (Phase B+)
  pinMode(5, OUTPUT); // FET4 (Phase B-)
}

void loop() {
  int HA = analogRead(A0) > 512 ? 1 : 0; // Hall A (digital)
  int HB = analogRead(A1) > 512 ? 1 : 0; // Hall B (digital)

  // Commutation logic
  if (!HA && !HB) { // 0°: A+ and B-
    digitalWrite(2, HIGH); digitalWrite(5, HIGH);
    digitalWrite(3, LOW);  digitalWrite(4, LOW);
  } else if (!HA && HB) { // 90°: A+ and B+
    digitalWrite(2, HIGH); digitalWrite(4, HIGH);
    digitalWrite(3, LOW);  digitalWrite(5, LOW);
  } else if (HA && HB) { // 180°: A- and B+
    digitalWrite(3, HIGH); digitalWrite(4, HIGH);
    digitalWrite(2, LOW);  digitalWrite(5, LOW);
  } else if (HA && !HB) { // 270°: A- and B-
    digitalWrite(3, HIGH); digitalWrite(5, HIGH);
    digitalWrite(2, LOW);  digitalWrite(4, LOW);
  }
}

Key Challenges & Solutions

1. Torque Ripple:

   • Add rotor/stator skewing (tilt magnets/teeth by 10–15°).

   • Use PWM current control to smooth phase transitions.

2. Sensor Alignment:

   • Power coils briefly and adjust Hall sensor positions until rotor "locks" smoothly.

3. Overheating MOSFETs:

   • Use heatsinks and limit current to 2–3A (for IRFZ44N).

   • Add current-sensing resistors for overload protection.

When to Avoid This Design

• High-torque applications: Use 3-phase BLDC instead.

• Low-noise needs: Torque ripple causes audible vibration.

• Precision control: Sensorless 2-phase control is unreliable.

Final Recommendation

For learning: Modify a PC fan + build your own controller.
For practicality: Buy a 2-phase BLDC motor (e.g., from small appliances) and focus on the driver.
For performance: Use a 3-phase motor – they’re cheaper and better for most applications!

? Pro Tip: Start with a small 5V fan and Arduino to test your driver before scaling up.