Left: kids stomping spiders projected on a driveway. Right: the setup.

Make This Halloween A Spider-Stomping Good Time

We can count on one hand the number of times that we haven’t needed a coat on Halloween night around here. Even if it was fair and sunny the day before, you can count on Halloween being appropriately windy, cold, and spooky. Trick-or-treating only keeps a kid so warm, and we would have loved to happen upon a house with a spider-stomping sugar-burning good time of a game going on in the driveway.

[Kyle Maas] built this game a few years ago, and it has proved quite popular ever since. It’s so popular, in fact, that they have to have someone on duty with a vaudeville hook to yank spectators off the playing field. The point is to stomp as many spiders as you can in a set amount of time, though you only need to stomp one to win. It can handle one to four players, depending on the size of the projection, but [Kyle] says it’s kind of hard to track more than two at a time.

The setup is fairly simple, provided you can reliably affix your projector to something sturdy. [Kyle] used a Structure sensor for the 3D scanner, but you could easily use a Kinect instead. Conversely, the calibration was challenging. [Kyle] ended up using a DSP math trick known as the inverse bilinear transform to be able to calibrate the system using the 3D scanner itself.

If you’re more into scaring the children, just rig up a coffin bell. Either way, don’t forget about our Halloween Hackfest contest, running now through Monday, October 11th. There are more details over on IO. While you’re there, why not check out the list of entries?

3D Objects Without Scanning

There are many scanners — both commercial and homemade — that can take a variety of scans or images of a 3D object and convert it into something like a 3D printable file. When the process works, it works well, but the results can be finicky at best and will require a lot of manual tuning. According to [Samuel Garbett], you might as well just draw your own model using Blender. He shows you how using a Red Bull can which, granted, isn’t exactly the most complicated thing ever, but it isn’t the simplest either.

He does take one photo of the can, so there is a camera involved at some point. He also takes measurements using calipers, something you probably already have laying around.

Since it is just a can, there aren’t many required pictures or measurements as, say, a starship model. Once you have the measurements, of course, you could use the tool of your choice and since we aren’t very adept with Blender, we might have used something we think is easier like FreeCAD or OpenSCAD. However, Blender has a lot of power, so we suspect making the jump from can to the USS Enterprise might be more realistic for a Blender user.

Besides, it is good to see how other tools work and we were surprised that Blender could be relatively simple to use. Every time we see [Jared’s] channel, we think we should learn more about Blender. But if you have your heart set on a real scanner, there are plenty of open source designs you can print.

a very slapdash x-ray machine on a table

Building An X-Ray Machine

While we typically encourage hackers to make their own tools or machines when practical, x-ray machines don’t usually make that list. Despite the risk of radiation, [William Osman] has done just that and built a homemade x-ray machine. After receiving an eye-watering medical bill, [William] resolves to make his own x-ray machine in the hopes of avoiding future bills. Thanks to his insurance, the total owed was smaller but still ridiculous to those who live in single-payer health care countries, but it got William thinking. What if he could make an x-ray machine to do cheap x-rays?

Armed with a cheap high voltage DC power supply he acquired from an online auction house, he started to power up his x-ray vacuum tube. A smaller power supply energizes the cathode and forms an electron beam. Then the high voltage (30-150kv) is applied as a tube voltage, accelerating the electrons into x-rays. Safety measures are taken somewhat haphazardly with Geiger counters and lead sheets. With a finger bone cast in ballistic shell [William] made his first x-ray with a long exposure on a DSLR. The next items to go in the x-ray “chamber” were a phone and a hand. The results were actually pretty decent and you can clearly see the bones.

We’ve seen homemade X-Ray machines here at Hackaday before, but not one that is constructed perhaps so haphazardly — his approach makes this obvious: don’t try this at home. Video after the break.

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New Part Day: DLP300s The Next Big Thing For Low Cost Resin Printing?

The majority of non-SLA resin 3D printers, certainly at the hacker end of the market, are most certainly LCD based. The SLA kind, where a ultraviolet laser is scanner via galvanometers over the build surface, we shall consider no further in this article.

What we’re talking about are the machines that shine a bright ultraviolet light source directly through a (hopefully monochrome) LCD panel with a 2, 4 or even 8k pixel count. The LCD pixels mask off the areas of the resin that do not need to be polymerised, thus forming the layer being processed. This technique is cheap and repeatable, hence its proliferance at this end of the market.

They do suffer from a few drawbacks however. Firstly, optical convergence in the panel causes a degree of smearing at the resin interface, which reduces effective resolution somewhat. The second issue is one of thermal control – the LCD will transmit less than 5% of the incident light, so for a given exposure at the resin, the input light intensity needs to be quite high, and this loss in the LCD results in significant internal heating and a need for active cooling.  Finally, the heating in the LCD combined with intense UV radiation degrades the LCD over time, making the LCD itself a consumable item.

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Better 3D Scans Through A Slowed Down Turntable

3D scanners aren’t cheap, and the last thing you want to see after purchasing one is bad data. But that’s what [Dave Does] and others were getting from their Revopoint POP scanners until some communal brainstorming uncovered the reason: the motorized turntable that came with the Kickstarter edition of the product was spinning too fast for the software to accurately keep track of the object. So he decided to replace the stepper motor controller in his turntable and document the process for anyone else who’s scanner might be struggling.

Plenty of room for expansion.

In the video below, [Dave] pops open the plastic case of the turntable and reveals a pretty sparse interior. There’s an incredible amount of empty space inside, and even some mounting studs to screw down new components, should you want to get into some hardcore upgrades. But for his purposes, a generic stepper motor controller that featured a potentiometer to adjust the speed was enough. He found a suitable board online for around $5 USD, and got to designing a 3D printed bracket that mates up to the existing screw holes on the turntable.

But it’s not exactly a drop-in replacement. For one thing, you’ve got to pop a hole in the side of the enclosure for the potentiometer knob to stick out of. You’ve also got to solder wires coming from the original DC jack and power switch to the new board to get it hooked up, but at least the motor plugs right in. In the video below, you can see [Dave] demonstrate the impressively deep throttle capability of the new driver.

If you’d rather build than buy, we’ve covered some impressive DIY turntables in the past that could fit the bill nicely, from automatic models that handle camera control to fully 3D printed versions that you’ve got to crank yourself.

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Ask Hackaday: What Is Amazon Thinking By Entering The Palm-Reading Business?

Have you heard about this One? At least three United States senators have, and they want to know what Amazon plans to do with all the biometric data collected by the Amazon One program. It’s their new contactless payment method that uses your unique palm print instead of cards or phones to make purchases, gain access to venues of work and play, and enter or pay in whatever other spaces Amazon can invade down the line. The idea is that one day, we’ll all be able to leave our homes without any form of money or ID of any kind, because we’ll all be stored away in Bezos’ big biometric file cabinet.

We tossed this one around in the writer’s room back when the Amazon One concept was nothing but a pile of buzzwords and a render or two, but these kiosks are now active in 50+ Whole Foods and Amazon 4-Star locations across the US. Here’s the deal: you can only sign up at a participating store that has a kiosk, because they have to scan your palms into the system. We were worried that the signup kiosk could easily take fingerprint scans at the same time, but according to the gifs in Morning Brew’s review, it just uses another of their point-of-sale palm scanners along with a touch screen and a card reader. But you still have to hover your entire hand over it, so who’s to say that the scan ends where the fingers begin?

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Cobbled together proof-of-concept vaccination verification system, showing a dot-matrix receipt printer, a webcam for QR code scanning, and an old laptop running the software

Manitoban Makes Open Software Demo Of Proprietary Vaccine Verification Systems

[Mark Jenkins] wasn’t impressed with the Covid 19 vaccination verification systems that restaurants in Manitoba are required to use. Patrons must present a QR code, which must be verified by a mobile app available only from Apple or Google. With help from his local hackerspace, he came up with a bash script solution requiring only kilobytes vs the 50 MB of the mobile apps. [Mark] isn’t pleased with the exclusivity of the apps availability and the lack of an open API. His concern isn’t entirely theoretical, either — Google mysteriously pulled their app from the Play Store for over a week.

The interim result, shown in the video below, is a demonstration system called Alexandra. It consists of a receipt printer, a webcam being used as a QR scanner, and a 2005-era laptop running the script. This is merely a proof of concept, as [Mark] clearly notes. There is still some work to be done — for example, the method used to authenticate with the Google server is transient. But eventually [Mark] hopes to have a free software alternative soon, suitable for restaurant owners to use in their establishments.

What kinds of vaccination verifications systems, if any, are used in your part of the world? Is the system open or proprietary? Let us know in the comments below.

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