Why Choose the A3144 for Brushless Motor RPM Sensing?

Digital Output (TTL) – Provides clean ON/OFF pulses for easy microcontroller interfacing.
Low Cost – Typically under $1 per unit, making it budget-friendly.
Robust Design – Works in harsh environments (dust, moisture, vibrations).
High Speed – Can detect RPMs up to 100,000+ (depends on magnet arrangement).
Easy to Use – Only 3 pins: VCC (5V), GND, and OUTPUT.

How to Set It Up

1. Hardware Connections

Attach a Magnet to the motor’s rotating part (shaft, rotor, or gear).
Mount the A3144 near the magnet (1–5 mm gap recommended).

Wiring:

text

  A3145 Pinout:
    VCC → 5V (Arduino/STM32)
    GND → GND
    OUT → Digital Pin (e.g., D2 on Arduino) + 10kΩ pull-up resistor

2. Code Example (Arduino)

cpp

const int hallPin = 2;  // Interrupt-capable pin (D2)
volatile unsigned long pulseCount = 0;
unsigned long lastTime = 0;
const int PPR = 1;      // Pulses per revolution (adjust if using multiple magnets)

void setup() {
  pinMode(hallPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(hallPin), countPulse, FALLING); // Triggers on magnet pass
  Serial.begin(9600);
}

void loop() {
  if (millis() - lastTime >= 1000) {  // Update RPM every second
    detachInterrupt(digitalPinToInterrupt(hallPin)); // Avoid race conditions
    float rpm = (pulseCount * 60.0) / PPR;
    Serial.print("RPM: "); Serial.println(rpm);
    pulseCount = 0;
    lastTime = millis();
    attachInterrupt(digitalPinToInterrupt(hallPin), countPulse, FALLING);
  }
}

void countPulse() {
  pulseCount++;
}

Key Considerations

Magnet Type: Use a neodymium magnet (e.g., 5x5mm N52) for strong signal detection.
Noise Immunity: Add a 0.1µF capacitor between VCC and GND near the sensor.
Multiple Magnets: Increase PPR (Pulses Per Revolution) for higher resolution (e.g., 4 magnets = PPR=4).

Alternatives

US1881 – Latching version (detects direction).
SS49E – Analog output (if precise field strength measurement is needed).

Troubleshooting

No Signal? Check magnet polarity (A3144 responds to one pole).
Erratic Readings? Ensure stable power supply and proper grounding.

The A3144 is a simple, reliable choice for brushless motor RPM sensing. For advanced applications (e.g., direction detection), consider latching Hall sensors like the US1881.

Why Choose the A3144 for Brushless Motor RPM Sensing? And How to Set It Up?