Homemade Digital Tachometer

Written by isaac mckinney
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A revolution per minute, or rpm, is a unit of measurement used to track the number of cycles completed by a revolving object in 1 minute. Digital tachometers are devices that measure the rpm of a spinning object and display the result on a screen. Assembling a homemade tachometer requires circuitry and computer programming skills. The parts can be found at electronics parts suppliers or purchased via the Internet.

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The base of a tachometer is its circuit board. The circuit board provides a backbone to connect wires and internal parts.


A proximity sensor detects any reflective element moving in front of it. Sensors broadcast energy to a device and measure the length of time for that energy to be reflected back. The energy can be in the form of infrared light, sound waves or magnetism.


A microcontroller collects information by counting the pulses from the sensor to calculate the rpm of the revolving object. Microcontrollers are small microchips that can be used to create small computer devices.


A math algorithm is stored within the microcontroller to calculate the rpm of the rotating object. An algorithm is a series of commands written in an algorithm language. Commonly used algorithm languages include Visual Basic, Perl and C++.


A digital tachometer requires an output display to show the results of the calculations. The display is an alphanumeric LCD screen small enough to fit on the circuit board or attach to the microcontroller.

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