Scan Your Caliper For Physical Part Copies

May 9, 2025 by 60 Comments

We’ve certainly seen people take a photo of a part, bring it into CAD, and then scale it until some dimension on the screen is the same as a known dimension of the part. We like what [Scale Addition] shows in the video below. In addition to a picture of the part, he also takes a picture of a vernier caliper gripping the part. Now your scale is built into the picture, and you can edit out the caliper later.

He uses SketchUp, but this would work on any software that can import an image. Given the image with the correct scale, it is usually trivial to sketch over the image or even use an automatic tracing function. You still need some measurements, of course. The part in question has a vertical portion that doesn’t show up in a flat photograph. We’ve had good luck using a flatbed scanner before, and there’s no reason you couldn’t scan a part with a caliper for scale.

This is one case where a digital caliper probably isn’t as handy as an old-school one. But it would be possible to do the same trick with any measurement device. You could even take your picture on a grid of known dimensions. This would also allow you to check that the distances at the top and bottom are the same as the distances on the right and left.

Of course, you can get 3D scanners, but they have their own challenges.

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Hacky Shack? The TRS-80 Model I Story

May 8, 2025 by 44 Comments

The 1970s saw a veritable goldrush to corner the home computer market, with Tandy’s Z80-powered TRS-80 probably one of the most (in)famous entries. Designed from the ground up to be as cheap as possible, the original (Model I) TRS-80 cut all corners management could get away with. The story of the TRS-80 Model I is the subject of a recent video by the [Little Car] YouTube channel.

Having the TRS-80 sold as an assembled computer was not a given, as kits were rather common back then, especially since Tandy’s Radio Shack stores had their roots in selling radio kits and the like, not computer systems. Ultimately the system was built around the lower-end 1.78 MHz Z80 MPU with the rudimentary Level I BASIC (later updated to Level II), though with a memory layout that made running the likes of CP/M impossible. The Model II would be sold later as a dedicated business machine, with the Model III being the actual upgrade to the Model I. You could also absolutely access online services like those of Compuserve on your TRS-80.

While it was appreciated that the TRS-80 (lovingly called the ‘Trash-80’ by some) had a real keyboard instead of a cheap membrane keyboard, the rest of the Model I hardware had plenty of issues, and new FCC regulations meant that the Model III was required as the Model I produced enough EMI to drown out nearby radios. Despite this, the Model I put Tandy on the map of home computers, opened the world of computing to many children and adults, with subsequent Tandy TRS-80 computers being released until 1991 with the Model 4.

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Understanding Linear Regression

May 8, 2025 by 7 Comments

Although [Vitor Fróis] is explaining linear regression because it relates to machine learning, the post and, indeed, the topic have wide applications in many things that we do with electronics and computers. It is one way to use independent variables to predict dependent variables, and, in its simplest form, it is based on nothing more than a straight line.

You might remember from school that a straight line can be described by: y=mx+b. Here, m is the slope of the line and b is the y-intercept. Another way to think about it is that m is how fast the line goes up (or down, if m is negative), and b is where the line “starts” at x=0.

[Vitor] starts out with a great example: home prices (the dependent variable) and area (the independent variable). As you would guess, bigger houses tend to sell for more than smaller houses. But it isn’t an exact formula, because there are a lot of reasons a house might sell for more or less. If you plot it, you don’t get a nice line; you get a cloud of points that sort of group around some imaginary line.

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DIY Driving Simulator Pedals

May 8, 2025 by 8 Comments

In the driving simulator community, setups can quickly grow ever more complicated and expensive, all in the quest for fidelity. For [CNCDan], rather than buy pedals off the shelf, he opted to build his own.

[Dan] has been using some commercial pedals alongside his own DIY steering wheel and the experience is rather lackluster in comparison. The build starts with some custom brackets. To save on cost, they are flat with tabs to let you know where to bend it in a vise. Additionally, rather than three sets of unique brackets, [Dan] made them all the same to save on cost. The clutch and throttle are a simple hall effect sensor with a spring to provide feedback. However, each bracket provides a set of spring mounting holes to adjust the curve. Change up the angle of the spring and you have a different curve. The brake pedal is different as rather than measure position, it measures force. A load cell is perfect for this. The HX711 load cell sensor board that [Dan] bought was only polling at 10hz. Lifting a pin from ground and bodging it to VDD puts the chip in 80hz, which is much more usable for a driving sim setup.

[Dan] also cleverly uses a 3d printed bushing without any walls as resistance for the pedal. Since the bushing is just the infill, the bushing stiffness is controlled by the infill percentage. Aluminum extrusion forms the base so [Dan] can adjust the exact pedal positions. To finish it off, a bog standard Arduino communicates to the PC as a game controller.

The project is on GitHub. Perhaps the next version will have active feedback, like this DIY pedal setup.

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Edison Phonograph Plays The Cylinders

May 8, 2025 by 9 Comments

You might be old enough to remember record platters, but you probably aren’t old enough to remember when records were cylinders. The Edison Blue Amberol records came out in 1912 and were far superior to the earlier wax cylinders. If you had one today, how could you play it? Easy. Just build [Palingenesis’] record player. You can even hear it do its thing in the video below.

The cylinders are made of plaster with a celluloid wrapper tinted with the namesake blue color. They were more durable than the old wax records and could hold well over four minutes of sound.

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Let The Wookie Win With This DIY Holochess Table

May 8, 2025 by 9 Comments

If you have seen Star Wars, you know what is being referenced here. Holochess appeared as a diversion built into the Millennium Falcon in the very first movie, way back in 1977. While not quite as iconic a use of simulated holograms as tiny Princess Leia begging for hope, it evidently struck a chord with [Maker Mac70], given the impressive effort he’s evidently gone through to re-create the game table from the film.

The key component of this unit is a plate from Japanese firm ASKA3D that scatters light from displays inside the table in just such a way that the diverging rays are focused at a point above its surface, creating the illusion of an image hovering in space. Or in this case, hovering at the surface of a acrylic chessboard. Granted, this technique only works from one viewing angle, and so is not a perfect recreation of a sci-fi holoprojector. But from the right angle, it looks really good, as you can see in the video below.

There are actually six SPI displays, driven by an Arduino GIGA, positioned and angled to project each character in the game. Placing two of the displays on 3D printed gantries allows them to move, allowing two creatures to battle in the center of the table. As [Maker Mac70] admits, this is quite a bit simpler than the Holochess game seen in the film, but it’s quite impressive for real world hardware.

If this all seems a little bit familiar, we covered an earlier floating display by [Maker Mac70] last year. This works on similar principles, but uses more common components which makes the technique more accessible. If chess isn’t your forte, why not a volumetric display that plays DOOM? If you’re interested in real holograms, not Sci-Fi, our own [Maya Posch] did a deep dive you may find interesting. Continue reading “Let The Wookie Win With This DIY Holochess Table” →

The Owon HDS160 Reviewed

May 8, 2025 by 11 Comments

These days, if you are in the market for a capable digital voltmeter, you might as well consider getting one with an oscilloscope built-in. One choice is the Owon HDS160, which [Kerry Wong] covers in the video below. The model is very similar to the HDS120, but the multimeter in the HDS160 has more counts–60,000 vs 20,000 as you might expect from the model number.

The internal chip is an HY3131, which is rated at 50,000 counts which is odd since the meter is 60,000 counts, but presumably the meter uses some capability of the chip, possibly putting it out of spec. The oscilloscope is the same between the two models. Almost everything else works the same, other than the capacitance measuring feature, as the video shows.

The difference in cost between the two units isn’t much, so if you are shopping, the small extra cost is probably worth it. Not that a 20,000 count meter isn’t perfectly fine for most normal uses.

[Kerry] really likes scopemeters. He gets excited about bench scopes, too.

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