The LM393 Motor Speed Measuring Sensor Module is a simple IR-based speed detection board used to measure the rotation speed (RPM) of motors, wheels, and rotating objects. It works using an infrared emitter and receiver pair placed in a slot, where a rotating encoder disc or object interrupts the IR beam to generate pulses. These pulses can be counted by a microcontroller to calculate RPM, making it perfect for robotics, automation, and DIY tachometer projects.
Core Sensor Specifications
• Sensor Type: IR slot sensor (photo interrupter) module
• Comparator IC: LM393
• Measurement Type: Speed / RPM measurement using pulse counting
• Detection Method: Interrupt IR beam with rotating disc/object
Electrical & Interface
• Operating Voltage: 3.3 V – 5 V DC
• Output Type: Digital pulse output (DO)
• Interface Pins: VCC, GND, DO
• Sensitivity / Threshold: Adjustable via onboard potentiometer
• Indicator LED: Output LED for pulse detection
Performance Characteristics
• Generates clean pulses for accurate speed calculation
• Fast response time for high-speed rotations
• Stable output for interrupt-based reading
• Works best with encoder disc or slotted wheel
Physical Characteristics
• Sensor Element: IR emitter + IR receiver slot type
• Module Type: Compact PCB with mounting hole
• Adjustment: Blue trimpot for signal threshold
• Lightweight design for easy mounting near motor shaft
Compatibility
• Arduino Uno / Nano / Mega
• ESP8266 / ESP32
• STM32 boards
• Robotics motor RPM monitoring
• DIY tachometer and speed feedback systems
Key Advantages
• Easy RPM measurement using pulse output
• Adjustable sensitivity for reliable detection
• Low-cost feedback sensor for motor control
• Ideal for closed-loop speed control projects
Technical Insights
• Use an interrupt pin for best pulse counting accuracy
• Add a slotted encoder disc for precise readings
• Keep sensor aligned with rotating disc for stable output
• Avoid direct sunlight or strong IR sources for best performance
Applications
• Motor RPM measurement
• Speed feedback for robot wheels
• DIY tachometer projects
• Conveyor belt speed monitoring
• Closed-loop motor control experiments
Pro Tip
• Start by adjusting the potentiometer until output LED blinks cleanly
• Use a black/white or slotted disc for stronger pulse detection
• Calculate RPM = (Pulses per second × 60) / pulses per revolution
• Secure mounting avoids vibration false triggers
Package Includes
• 1 × LM393 Motor Speed Measuring Sensor Module