Motor Tachometer
Measure motor speed in RPM with a slotted disc and photo-interrupter.
Overview
A disc with slots spins between the interrupter's LED and detector. Each slot breaks the beam, an interrupt counts it, and the board converts pulses per second into RPM.
Build Steps
Make the disc
Cut a card disc with 10 evenly spaced slots and mount it on the motor shaft so it runs in the sensor slot.
Wire the sensor
Photo-interrupter to 5 V and ground with the output on an interrupt pin; add a pull-up if the module lacks one.
Count pulses
Count interrupts over a one-second window, then RPM = pulses × 60 ÷ slots.
Display and smooth
Show RPM on the TM1637 and average a few windows so the reading stops jumping around.
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