Speed Measuring Sensor Module (LM393)

Overview

The Speed Measuring Sensor Module (LM393) is a compact, high-precision speed sensor designed to measure rotational speed of motors, wheels, or any rotating object. Built around the reliable LM393 comparator, this module detects interruptions or reflections of an optical beam and translates them into a clean digital pulse output for straightforward RPM and speed calculations.

How it Works

This LM393 speed sensor uses either a transmissive or reflective optical sensing method. A light source and photodetector detect changes caused by a passing mark, slot, or reflective tape on the rotating object. The LM393 comparator converts the analog signal from the photodetector into a digital pulse each time the beam is interrupted or a reflection is detected. Counting these pulses over time lets you calculate RPM (pulses per second x 60) or other speed metrics.

Key Features

• Accurate optical detection with LM393 comparator for stable digital output
• Adjustable sensitivity via onboard potentiometer for different surfaces and lighting
• Digital pulse output compatible with Arduino, Raspberry Pi and other microcontrollers
• Compact footprint and clear pinout for quick GPIO hookup
• Easy mounting with pre-drilled holes for secure installation
• Wide operating temperature range suitable for most robotics and industrial projects

Specifications

• Sensor Type: Optical (Reflective or Transmissive)
• Comparator IC: LM393
• Output Type: Digital (Pulse)
• Power Supply: 5V DC
• Sensitivity Adjustment: Yes (Potentiometer)
• Mounting: Easy mounting holes
• Operating Temperature: -20°C to 70°C

Typical Applications

• Robotics wheel speed and odometry
• DC motor speed monitoring and control
• RPM measurement for fans, spindles and small rotating assemblies
• Feedback for closed-loop motor control
• Event counting and object detection in automation projects

Integration and Wiring

The module is designed for simple integration into microcontroller projects. Typical 3-pin connections are:

• VCC: 5V DC
• GND: Ground
• OUT: Digital pulse output to a GPIO or interrupt pin

To calculate RPM: measure the number of pulses per second and multiply by 60, or use pulses per revolution if your encoder mark provides one pulse per turn.

Arduino and Raspberry Pi Tips

• Use an interrupt-capable GPIO to capture pulses reliably at higher speeds.
• Debounce and filtering: if false pulses occur, adjust the potentiometer or add simple software debouncing.
• For analog fine-tuning, place a small reflective tape or mark on the rotor where the sensor can reliably detect it.

Installation and Best Practices

• Mount the sensor securely close to the rotating surface without touching it.
• Align the sensor and mark/slot for consistent detection; use reflective tape for better contrast.
• Adjust the onboard potentiometer while testing under actual lighting conditions for best results.
• Keep wiring short and use proper grounding to avoid electrical noise interfering with pulse detection.

What You Get and Notes

• Speed Measuring Sensor Module (LM393) with adjustable potentiometer and mounting holes
• Note: Images are for illustration only. Actual product appearance may vary slightly.