IR speed measurement optocoupler module for slotted optical encoders. The slot uses an infrared LED and an NPN phototransistor with a 5.9 mm gap. When a non-transparent object passes the slot (compatible with a motor encoder wheel), it generates a low TTL level output. Technical data - Operating voltage: 3.3 V to 5 V - Output: digital switching (0 and 1) - Power indicator lights when VCC and GND are connected - Inactive state: OUT is low and the indicator is off - Output can drive a relay to form a limit switch or connect to an active buzzer module to form an alarm Programming and interfacing - OUT can be connected directly to an MCU IO port - Typically used with an external interrupt to detect sensor pulses - Example: connect to a motor encoder wheel to measure speed - The OUT port serves as an external interrupt source whenever the infrared beam is present or occluded Measurement method - Output is a pulse signal; each slot passage interrupts the beam - The infrared beam weakens when active; the interrupt is configured for low-level handling - SPEED MEASUREMENT: count external interrupts per second using an MCU timer to determine speed Applications - Motor or rotor speed sensing with an encoder wheel - Limit switch or alarm circuits by wiring to a relay or buzzer - Robotics and automation where slot-based optical speed monitoring is needed