Speed Measuring RPM Sensor Module For Arduino

Speed Measuring RPM Sensor Module for Arduino is an optical tachometer and encoder module designed to measure rotational speed (RPM), motor velocity, and count passing objects with high precision. Built around a slotted infrared (IR) optocoupler transmission gate and the LM393 dual differential voltage comparator IC, this module detects when a physical encoder disk or slotted wheel interrupts the infrared light beam. Featuring a clean digital switching output, an active trigger indicator LED, and an included slotted encoder disc, it is an essential component for robotics wheel speed feedback, motor tachometers, conveyor belt counters, and closed-loop PID motor control systems.

Features

• Equipped with a sensitive slot-type infrared optical sensor (transmissive photo-interrupter) for non-contact object and speed detection
• Powered by the LM393 dual differential comparator chip providing clean, stable digital square-wave pulses
• High-resolution slotted encoder disc included in the kit for immediate RPM measurement setup
• Active indicator LEDs for power status (Red) and output signal triggering (Green/Blue)
• Standard 4-pin interface (VCC, GND, DO, AO) compatible with 3.3V and 5V microcontroller logic
• Fast response time capable of counting rapid motor shaft rotations and pulse transitions
• Compact PCB layout with a pre-drilled mounting hole for secure mechanical alignment near motor gearboxes
• Ideal sensor feedback element for building self-correcting line-following robots and differential drive rovers

Applications

• Measuring motor RPM and rotational velocity in DC gear motors and encoder gearboxes
• Wheel speed feedback for closed-loop PID control in autonomous line-following and obstacle-avoiding robots
• Industrial conveyor belt item counters, mechanical production batch counters, and position limit switches
• Fan speed monitoring, tachometer instruments, and rotational shaft stall detectors
• Polytechnic diploma, university engineering thesis, and Arduino/ESP32 robotics experimentation

Important Notes:

• Optical Alignment: Ensure that the rotating slotted encoder disk spins smoothly through the center of the optical sensor slot without rubbing against the plastic sides, which could cause motor drag or false optical triggering.
• Ambient Light Interference: While the infrared sensor operates on modulated infrared light, avoid placing the module in direct, intense sunlight or under high-intensity halogen spotlights, as ambient IR light can occasionally saturate the phototransistor receiver.
• Interrupt Programming: For accurate RPM counting in Arduino or ESP32, connect the digital output (DO) pin to an external interrupt-capable pin on your microcontroller and use rising/falling edge interrupt service routines (attachInterrupt).
• Logic Compatibility: Connect VCC to 3.3V or 5V matching your microcontroller logic level, and GND to system ground.

Package includes

• 1 x Slot-Type IR Speed Measuring Sensor Board (LM393)