LiDAR Sensor TFmini: Distance Measurement Beyond Ultrasonic

When ultrasonic sensors hit their limits — range too short, accuracy too coarse, outdoor sunlight causing interference — LiDAR sensors like the TFmini step in. The TFmini measures distances from 30 cm to 12 metres with ±1 cm accuracy at 100 readings per second, using an infrared laser pulse and time-of-flight measurement. At ₹2,000-4,000, it costs more than an HC-SR04 but opens up applications in drone altitude hold, precision mapping, and high-speed obstacle detection that ultrasonic sensors simply cannot handle.

LiDAR vs Ultrasonic: When to Upgrade

Upgrade to LiDAR when you need: longer range (>4m), faster sampling (>20 Hz), narrow beam for precision targeting, or reliable outdoor operation.

TFmini Specifications

The TFmini by Benewake emits a modulated infrared laser (850 nm wavelength, Class 1 — eye-safe) and measures the time-of-flight of the reflected pulse. Key specifications:

• Range: 0.3-12 m (indoor), 0.3-7 m (outdoor, high ambient light)
• Accuracy: ±1 cm at 0.3-6 m, ±2% at 6-12 m
• Frame rate: 100 Hz (default)
• Interface: UART (115200 baud default)
• Power: 5V, ~120 mA
• Weight: 6.1 g
• Size: 42×15×16 mm

Wiring to Arduino and ESP32

The TFmini uses a 4-pin connector: 5V, GND, TX, RX. It communicates via UART at 115200 baud.

Note: On Arduino Uno, SoftwareSerial at 115200 baud is unreliable. Use an Arduino Mega (with hardware Serial1/Serial2) or ESP32 for best results. If you must use Uno, change the TFmini’s baud rate to 9600 via its configuration commands.

Arduino Code for Distance Reading

// For Arduino Mega (using Serial1) or ESP32 (using Serial2)
// For Uno, use SoftwareSerial at 9600 baud after reconfiguring TFmini

#define TFMINI_SERIAL Serial1  // Arduino Mega Serial1

void setup() {
  Serial.begin(115200);
  TFMINI_SERIAL.begin(115200);
  Serial.println("TFmini LiDAR Ready");
}

void loop() {
  static uint8_t buf[9];
  static int idx = 0;

  while (TFMINI_SERIAL.available()) {
    uint8_t b = TFMINI_SERIAL.read();

    if (idx == 0 && b != 0x59) continue; // Wait for header byte 1
    if (idx == 1 && b != 0x59) { idx = 0; continue; } // Header byte 2

    buf[idx++] = b;

    if (idx == 9) {
      idx = 0;

      // Verify checksum
      uint8_t checksum = 0;
      for (int i = 0; i  100 && distance < 1200) { // Valid reading
        Serial.print("Distance: ");
        Serial.print(distance);
        Serial.print(" cm | Signal: ");
        Serial.println(strength);
      }
    }
  }
}

Drone Altitude Hold Project

The TFmini’s 100 Hz update rate and lightweight design (6.1g) make it ideal for drone altitude hold. Point it downward and feed the distance reading to your flight controller’s altitude PID loop. Advantages over barometric altitude (BMP280):

• Absolute ground distance — barometric altitude drifts; LiDAR gives actual height above ground
• Works during descent — propwash doesn’t affect LiDAR (but disrupts barometric readings)
• Precise landing — critical in the final 1-2 metres of landing where barometric altitude is too coarse

Limitation: over water, glass, or very dark surfaces, the laser reflection may be too weak. The signal strength value (buf[4-5]) indicates reading reliability — ignore readings with strength below 100.

Other LiDAR Projects

2D Mapping with Spinning LiDAR

Mount a TFmini on a continuously rotating servo (or a slip-ring motor) and take distance readings at each angle. Plot the results in polar coordinates to create a 2D map of the room. This is the same principle used by robotic vacuum cleaners and autonomous vehicles.

Vehicle Speed Measurement

Point the TFmini at a road. When a vehicle passes, the distance reading changes rapidly. By tracking the distance profile over time (at 100 Hz), you can calculate the vehicle’s speed. Mount two sensors 1 metre apart and measure the time delay between detections for even more accurate speed estimation.

Precision Level Measurement

For industrial tanks, silos, and hoppers where ultrasonic sensors struggle (dust, temperature extremes, long distances), the TFmini provides reliable level measurement up to 12 metres. Its narrow 2° beam avoids sidewall reflections that plague ultrasonic sensors in narrow containers.

Gesture Detection

At 100 Hz, the TFmini can detect hand movements in front of it. Track distance changes to recognise swipe-in, swipe-out, and hover gestures. Useful for touchless interfaces — relevant in post-COVID public installations like kiosks and elevator controls.

Frequently Asked Questions

Is the TFmini laser safe for eyes?

Yes. The TFmini uses a Class 1 infrared laser (850 nm), which is the safest classification. It’s the same safety level as TV remotes and optical mice. However, don’t deliberately stare into the lens at close range — standard optical safety practice.

Can the TFmini work outdoors in sunlight?

Yes, but with reduced range. Indoor range is 12 metres; outdoor range drops to 5-7 metres depending on sunlight intensity and target reflectivity. The TFmini Plus variant has improved outdoor performance up to 12 metres even in sunlight.

What’s the difference between TFmini and VL53L0X?

The VL53L0X is a time-of-flight sensor with a much shorter range (up to 2 metres) but at a lower price (₹200-400). It’s better for close-range gesture detection and proximity sensing. The TFmini offers 12-metre range for applications that need longer reach. For intermediate range, the VL53L1X covers up to 4 metres.

Can I connect multiple TFmini sensors?

Each TFmini needs its own UART connection. On an Arduino Mega, you have Serial1, Serial2, and Serial3 (3 sensors). On ESP32, you have 3 hardware UARTs. For more sensors, use UART multiplexers or an I2C-to-UART bridge (SC16IS750). Alternatively, the TFmini-I2C variant uses I2C protocol and supports multiple sensors with different addresses.

Why does the reading show 0 or maximum range on some surfaces?

Highly reflective surfaces (mirrors, polished metal) can cause multi-path reflections that confuse the sensor. Very dark surfaces (black fabric, tyres) absorb too much light. Transparent surfaces (glass, clear water) pass the laser through. Check the signal strength value — readings with strength below 100 are unreliable.

Conclusion

The TFmini LiDAR sensor fills the gap between basic ultrasonic sensors and expensive industrial LiDAR systems. At ₹2,000-4,000, it’s accessible for serious hobbyist projects — drone altitude hold, room mapping, and precision distance measurement. If your project needs more than 4 metres of range, faster than 20 Hz sampling, or outdoor reliability, the TFmini is the natural upgrade from the HC-SR04.

Find LiDAR sensors and precision distance modules at Zbotic’s sensor collection.