Category Archives: tachometer

PLA Foils Homemade Tachometer

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[Integza] built a Tesla turbine and wanted to know how fast it was spinning. However, he didn’t have a tachometer, and didn’t want to buy one. After a false start of trying to analyze the audio to measure the speed, he decided to use a tried-and-true method. Let the wheel break an infrared (IR) optointerruptor and count the spokes of the wheel as they go by. If you know the spacing between the spokes, you can compute the speed. There was only one problem: it didn’t work.

Turns out, PLA is at least somewhat transparent to IR. Knowing that it …read more

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Tachometer Uses Light, Arduinos

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To measure how fast something spins, most of us will reach for a tachometer without thinking much about how it works. Tachometers are often found in cars to measure engine RPM, but handheld units can be used for measuring the speed of rotation for other things as well. While some have mechanical shafts that must make physical contact with whatever you’re trying to measure, [electronoobs] has created a contactless tachometer that uses infrared light to take RPM measurements instead.

The tool uses an infrared emitter/detector pair along with an op amp to sense revolution speed. The signal from the IR …read more

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The Tachometer Inside Your Smartphone

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It’s the latest in instrumentation for the well-appointed shop — an acoustically coupled fast Fourier transform tachometer. Sounds expensive, but it’s really just using a smartphone spectrum analyzer app to indirectly measure tool speeds. And it looks like it could be incredibly handy.

Normally, non-contact tachometers are optically coupled, using photoreceptors to measure light flashing off of a shaft or a tool. But that requires a clear view of the machine, often putting hands far too close to the danger zone. [Matthias Wandel]’s method doesn’t require line of sight because it relies on a cheap spectrum analyzer app to listen …read more

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Nixie Tachometer Displays in Style

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Nixietach II is a feature-rich tachomoter [Jeff LaBundy] built for his 1971 Ford LTD. It displays RPM with an error rate of only 0.03 RPM at 1,000 RPM

The latest iteration of a long-running project, [Jeff] approached it with three goals: the tachometer had to be self-contained and easy to install, the enclosure had to be of reasonable size, and it had to include new and exciting features over the first two versions.

The finished project consists of an enclosure mounted under the dash with a sensor box in the engine bay connected to the ignition coil. He can also …read more

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Art With Steppers And STM32

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Automotive dashboards are something that largely go untouched in the average car’s life. Other than the occasional wipe with a damp cloth, they’re generally reliable for the life of the car and considered too tricky to repair as age sets in. Nevertheless, some hackers find themselves tinkering with them, and learn skills in the process, such as how to control stepper motors and talk to the CAN bus. Having done some projects in the past, [Dan] had some old tachometers lying around and decided to turn them into a piece of art.

The build is powered by an STM32 – …read more

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How To Use a Photo Tachometer

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If you’re into anything even vaguely mechanical on the broad hacking spectrum, you’ve come into contact with things that spin. Sometimes, it’s important to know precisely how fast they are spinning! When you’ve got the need to know angular speed, you need a device to measure it. That device is a tachometer. And the most useful tachometer is the non-contact photo-tachometer.


The basic principle of operation of a photo-tachometer is quite simple. The device contains a light source – typically a laser, which can create a focused, coherent beam of light. This beam of light is capable of bouncing off …read more

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Quick Arduino Hack Lets Tach-less Car Display Shift Points

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A tachometer used to be an accessory added to the dash of only the sportiest of cars, but now they’re pretty much standard equipment on everything from sleek coupes to the family truckster. If your daily driver was born without a tach, fear not – a simple Arduino tachometer is well within your reach.

The tach-less vehicle in question is [deepsyx]’s Opel Astra, which from the video below seems to have the pep and manual transmission that would make a tach especially useful. Eschewing the traditional analog meter display or even a digital readout, [deepsyx] opted to indicate shift points …read more

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Analog Guts Display GPS Velocity in this Hybrid Speedometer

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A digital dash is cool and all, but analog gauges have lasting appeal. There’s something about the simplicity of a purely mechanical gauge connected directly to a vehicle’s transmission. Of course that’s not what’s hapenning here. Instead, this build is an analog display for GPS-acquired speed data.

The video below does a good job at explaining the basics of [Grant Stephens]’ build. The display itself is a gutted marine speedometer fitted with the movement from a motorcycle tachometer. The tach was designed to take a 4-volt peak-to-peak square wave input signal, the frequency of which is proportional to engine speed. …read more

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