Low-Cost Tachometer

The Low-Cost Tachometer system operates by combining mechanical rotation with optoelectronic sensing to measure rotational speed accurately. At the heart of the setup is a rotating disk featuring a single hole or slot, which is mechanically coupled to the motor shaft whose speed you wish to measure. Positioned on opposite sides of the disk's path is an optical sensor, typically consisting of an infrared emitter and a photodetector. As the motor spins, the disk rotates along with it, causing the solid portions of the disk to block the optical beam, while the hole or slot allows the light to pass through momentarily once per revolution. Each time the light beam is interrupted and restored, the optical sensor generates a pulse-like electrical signal. This signal is fed into the digital input pins of the Arduino board. A sketch running on the Arduino counts these incoming pulses over a defined time interval, mathematically converting the pulse frequency into revolutions per minute (RPM). Once calculated, the Arduino transmits this real-time speed data using communication protocols to an OLED display, which visually renders the numerical RPM value for the user. Power is supplied to both the microcontroller and the display through an independent power supply, ensuring stable operation during continuous data collection.