TinyTacho: Rotational Speed Measurement Without The Bulk

An electronic tachometer is a straightforward enough device, in which the light reflections from a white spot on a rotating object are detected and counted over time, measuring the revolutions per minute (RPM). It’s a technique that has its roots in analogue electronics where the resulting pulses would have fed a charge pump, and it’s a task well suited to a microcontroller that simply counts them. But do you need an all-singing, all-dancing chip to do the job? [Stefan Wagner] has done it with a humble ATtiny13.

His TinyTacho is a small PCB with an IR LED and photodiode on one end, a small OLED display on its front, and a coin cell holder on its rear. The electronics may be extremely simple, but there’s still quite some effort to get it within the ATtiny’s meagre resources. Counting the revolutions is easy enough, but the chip has no I2C interface of its own and some bitbanging code is required. You can find all the design files and software you need in a GitHub repository, and he’s put up a video of the device in action that you can see below the break.

Tachometers are a popular project hereabouts, and we’ve featured a lot of them over the years. Perhaps the best place to direct readers then is not to another project, but to how to use a tachometer.

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The Swiss Army Knife Of Bench Tools

[splat238] had a ton of spare sensors laying around that he had either bought for a separate project or on an impulse buy, so he knew he had to do something with them. He decided to build his own digital multi-tool focusing on sensors that would be particularly useful in a workshop setting. Coincidentally, he was inspired by a previous hack that we covered a while back.

He’s equipped his device with a bubble level, tachometer, IR thermometer, protractor, laser pointer, and many, many more features that would make great additions to any hacker’s workspace. There’s a good summary of each sensor, making his Instructable somewhat of a quick guide to common sensing modalities for hardware designers. The tachometer, thermometer, laser pointer, and a few other capabilities are notable upgrades from the project we highlighted previously. We also appreciate the bigger display, allowing for more detailed user feedback particularly in using the compass and bullseye digital level among other features.

The number of components in [splat238’s] build is too extensive to detail one-by-one in this article, so please see his Instructable linked above for all the details. [splat238] made his own PCB for mounting each sensor and did a good job making the design modular so you wouldn’t need to add certain components if you don’t need them. Most of the components take some through-hole soldering with only a handful of 0805 resistors required otherwise. The housing was designed such that the user can handle the tool with one hand and can switch between each function with a push of a button.

Finally, the device is powered using a rechargeable lithium-polymer battery making it very reusable. And, if there weren’t enough features already, the battery can be charged via USB or through two solar panels mounted into the housing unit. Okay, solar charging might be a case of featuritis, but still a cool build either way.

Check out some other handy DIY tools on Hackaday.

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Steampunk Brushless Motor Demo Pushes All The Maker Buttons

We’ll be honest right up front: there’s nothing new in [David Cambridge]’s brushless motor and controller build. If you’re looking for earth-shattering innovation, you’d best look elsewhere. But if you enjoy an aimless use of just about every technique and material in the hacker’s toolkit employed with extreme craftsmanship, then this might be for you. And Nixies — he’s got Nixies in there too.

[David]’s build started out as a personal exploration of brushless motors and how they work. Some 3D-printed parts, a single coil of wire, and a magnetic reed switch resulted in a simple pulse motor that performed surprisingly well. This morphed into a six-coil motor with Hall-effect sensors and a homebrew controller. This is where [David] pulled out all the stops on tools — a lathe, a plasma cutter, a welder, a milling machine, and a nice selection of woodworking tools went into making parts for the final motor as well as an enclosure for the project. And because he hadn’t checked off quite all the boxes yet, [David] decided to use the 3D-printed frame as a pattern for casting one from aluminum.

The finished motor, with a redesigned rotor to deal better with eddy currents, joined the wood and metal enclosure along with a Nixie tube tachometer and etched brass control plates. It’s a great look for a project that’s clearly a labor of self-edification and skill-building, and we love it. We’ve seen other BLDC demonstrators before, but few that look as good as this one does.

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Laser Tachometer Knows How Fast You Were Spinning Back There

Does your drill go as fast as the manufacturer says it will? Well, you’d need a tachometer to figure that out. They’re not that expensive to buy, but as [Elite Worm] shows, they’re not that expensive to make, either — about $10 total if you get your parts from the right places. Lucky for you, he has links to everything.

Really, the links are just the tip of the iceberg here as far as the gifts that [Elite Worm] bestows upon those who choose to undertake this project. The build video (after the break, as usual; our favor to you) is fantastic, and would be perfect for a beginner because of the entrancing speed at which he builds it. The video is straight up relaxing to watch, whether you want to build one or not.

It’s a fairly simple circuit — just push the momentary switch, and the laser diode and sensor pair count the revolutions over one second. The Arduino Nano multiplies this number by 60 and displays the RPM on the OLED screen. What we absolutely love about this build is the care that taken in designing the case. There’s a designated spot for each component, and the ones without their own special holder are kept in place with printed crossbar pieces. [Elite Worm] says this has a higher refresh rate than his store-bought tacho, and we say it looks way cooler, too.

Still don’t want to make one yourself? Well, okay. Before you buy one, try using your phone to calculate RPM.

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Hacking A Cheap EBay Frequency Counter

eBay is a wondrous land, full of Star Wars memorabilia in poor condition, old game consoles at insane markups, and a surprising amount of DIY electronics. [TheHWCave] found himself tinkering with a common frequency counter kit, and decided to make a few choice improvements along the way (Youtube link, embedded below).

The frequency counter in question is a common clone version of [Wolfgang “Wolf” Büscher]’s minimalist PIC design. Using little more than a PIC16F628 and some seven-segment displays, it’s a competent frequency counter for general use. Clone versions often add a crystal oscillator tester and are available on eBay for a fairly low price.

[TheHWCave] found that the modifications were less than useful, and developed a way to turn the tester components into a more useful signal preamp instead. Not content to stop there, custom firmware was developed to both improve the resolution and also add a tachometer feature. This allows the device to display its output in revolutions per minute as opposed to simply displaying in hertz. By combining this with an optical pickup or other RPM signal, it makes a handy display for rotational speed. If you’re unfamiliar with the theory, read up on our phototachometer primer. If you’re looking to modify your own kit, modified firmware is available on Github.

We’ve seen other eBay kit specials modified before. Being cheap and using commodity microcontrollers makes them a ripe platform for hacking, whether you just want to make a few tweaks or completely repurpose the device.

[Thanks to Acesoft for the tip!]

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Arduino Tachometer Clock Fires On All Cylinders

We’re certainly no strangers to unique timepieces around these parts. For whatever reason, hackers are obsessed with finding new and interesting ways of displaying the time. Not that we’re complaining, of course. We’re just as excited to see the things as they are to build them. With the assumption that you’re just as enamored with these oddball chronometers as we are, we present to you this fantastic digital tachometer clock created by [mrbigbusiness].

The multi-function digital gauge itself is an aftermarket unit which [mrbigbusiness] says you can get online for as little as $20 from some sites. All he needed to do was figure out how to get his Arduino to talk to it, and come up with some interesting way to hold it at an appropriate viewing angle. The mass of wires coming out of the back of the gauge might look intimidating, but thanks to his well documented code it shouldn’t be too hard to follow in his footsteps if you were so inclined.

Hours are represented by the analog portion of the gauge, and the minutes shown digitally were the speed would normally be displayed. This allows for a very cool blending of the classic look of an analog clock with the accuracy of digital. He’s even got it set up so the fuel indicator will fill up as the current minute progresses. The code also explains how to use things like the gear and high beam indicators, so there’s a lot of room for customization and interesting data visualizations. For instance, it would be easy to scrap the whole clock idea and use this gauge as a system monitor with some modifications to the code [mrbigbusiness] has provided.

The gauge is mounted to a small project box with some 3D printed brackets and bits of metal rod, complete with a small section of flexible loom to cover up all the wires. Overall it looks very slick and futuristic without abandoning its obvious automotive roots. Inside the base [mrbigbusiness] has an Arduino Nano, a DS1307 RTC connected via I2C, a voltage regulator, and a push button to set the time. It’s a perfectly reasonable layout, though we wonder if it couldn’t be simplified by using an ESP8266 and pulling the time down with NTP.

We’ve seen gauges turned into a timepiece before, but we have to admit that this is probably the most practical realization we’ve seen of the idea yet. Of course if you want to outfit the garage with something a bit more authentic, you can always repurpose a Porsche brake rotor.

PLA Foils Homemade Tachometer

[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 was a simple matter to fix some tape to the wheel that would block IR and that made things work much better. If you missed the video where he built the turbine, you might want to watch it first.

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