Overview

The HM3301 (Seeed Studio Grove Laser PM2.5 Sensor) is an optical particulate matter (PM) sensor engineered for real-time air quality monitoring. Housed in a compact metallic shielding case with a 4-pin Grove $I^2C$ connector, it integrates a semiconductor laser diode, an internal miniature air fan, light scattering collection optics, and a photo-detector.

Operating on the principle of light scattering, the sensor continuously draws ambient air across the laser beam. As airborne particles ($0.3\ \mu\text{m}$ to $10.0\ \mu\text{m}$) pass through the beam, scattered light signals are processed by internal algorithms to compute real-time mass concentrations of PM1.0, PM2.5, and PM10 (in $\mu\text{g/m}^3$) over an $I^2C$ bus (0x40).

Quick reference

Pinout (Grove 4-Pin Connector Header)

Specifications

$I^2C$ Telemetry Frame Structure

When reading 29 bytes from $I^2C$ address 0x40, the HM3301 returns binary data formatted as 16-bit big-endian integers:

• Bytes 0–1: Sensor Sensor Head / Checksum ID.
• Bytes 6–7: PM1.0 Standard concentration ($\mu\text{g/m}^3$).
• Bytes 8–9: PM2.5 Standard concentration ($\mu\text{g/m}^3$).
• Bytes 10–11: PM10 Standard concentration ($\mu\text{g/m}^3$).
• Bytes 12–13: PM1.0 Atmospheric concentration ($\mu\text{g/m}^3$).
• Bytes 14–15: PM2.5 Atmospheric concentration ($\mu\text{g/m}^3$).
• Bytes 16–17: PM10 Atmospheric concentration ($\mu\text{g/m}^3$).
• Byte 28: Checksum byte (8-bit sum of bytes 0 through 27).

Wiring

Example (Seeed_PM2_5_sensor_HM3301 Library)

#include <Wire.h>
#include <Seeed_HM3301.h>

HM3301 sensor;
uint8_t buf[30];

void setup() {
  Serial.begin(115200);
  Wire.begin();

  Serial.println("HM3301 Laser PM2.5 Sensor Test");

  if (sensor.init()) {
    Serial.println("HM3301 initialization failed! Check I2C wiring.");
    while (1);
  }
}

void loop() {
  if (sensor.read_sensor_value(buf, 29)) {
    Serial.println("Error reading HM3301 data");
  } else {
    // Parse 16-bit big-endian PM values from buffer
    uint16_t pm1_0 = (uint16_t)buf[12] << 8 | buf[13];
    uint16_t pm2_5 = (uint16_t)buf[14] << 8 | buf[15];
    uint16_t pm10  = (uint16_t)buf[16] << 8 | buf[17];

    Serial.print("PM1.0: "); Serial.print(pm1_0); Serial.print(" µg/m³");
    Serial.print(" | PM2.5: "); Serial.print(pm2_5); Serial.print(" µg/m³");
    Serial.print(" | PM10: "); Serial.print(pm10); Serial.println(" µg/m³");
  }

  delay(2000);
}

Common mistakes

• Blocking airflow intakes: The metal casing has specific air inlet and outlet vents. Blocking or enclosing the air vents in a sealed box prevents ambient air flow, leading to zero particle readings.
• Reading before 30-second warm-up: The internal air fan requires 30 seconds to establish stable laminar airflow over the laser beam.

Notes

• HM3301 vs PMS5003 vs SDS011: HM3301 uses $I^2C$ (0x40) with a Grove connector; PMS5003 and SDS011 use UART serial communication.