Day: September 8, 2023

Fitting 3D Prints In A Snap

September 8, 2023 by 27 Comments

The good news is that 3D printing lets you iterate on your design until it is just right. The bad news is that you often have to iterate your design over and over to get things to fit together. It is a little easier if you are designing both parts, but matching sizes and positions on a printed part that fits something that already exists can be a pain. Sure, you can grab the calipers and make fidgety measurements — but [Maker Tales] has a different approach. As you can see in the video below, he takes a photo, imports it into CAD, scales it, and then uses it as a reference.

If you have one, you could, of course, scan the existing part. However, if you’ve ever tried that, results vary wildly, especially with cheap hardware. [Maker Tales] just takes a picture with his phone, trying to get as straight as possible and from a distance. Once in CAD, he makes one measurement and scales the image to the correct size.

This is one of those things that should be obvious, but you don’t always think it through. Of course, it is possible to measure everything precisely or — even better — if you have the original CAD or drawing for the part that has exact measurements. But compared to making numerous precise measurements, this method is a lot less work and gives good results.

If you are creating mating parts, think about shadow lines. Many commercial parts now have CAD models as STEP files if you want to skip the scanning.

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This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack

September 8, 2023 by 8 Comments

There has been a rash of cryptocurrency thefts targeting some unexpected victims. Over $35 million has been drained from just over 150 individuals, and the list reads like a who’s-who of the least likely to fall for the normal crypto scams. There is a pattern that has been noticed, that almost all of them had a seed phrase stored in LastPass this past November when the entire LastPass database was breached.

The bulletproof security of the LastPass system depends in part on the rate limiting of authenticating with the LastPass web service. Additionally, accounts created before security improvements in 2018 may have had master passwords shorter than 12 characters, and the hash iterations on those accounts may have been set distressingly low. Since attackers have had unrestricted access to the database, they’ve been able to run offline attacks against accounts with very low iterations, and apparently that approach has been successful.

Microsoft’s Signing Key

You may remember a story from a couple months ago, where Microsoft found the Chinese threat group, Storm-0558, forging authentication tokens using a stolen signing key. There was a big open question at that point, as to how exactly an outside group managed to access such a signing key.

This week we finally get the answer. A crash log from 2021 unintentionally included the key, and Microsoft’s automated redaction system didn’t catch it. That crash dump was brought into development systems, and an engineer’s account was later accessed by Storm-0558. That key should not have worked for enterprise accounts, but a bug in a Microsoft key validation allowed the consumer systems key to work for enterprise accounts. Those issues have been fixed, but after quite a wild ride. Continue reading “This Week In Security: LastPass Shoe Drops, Keys Lost, And Train Whistles Attack” →

Wien Bridge Oscillator Drives Distortion Into The Floor

September 8, 2023 by 12 Comments

It’s not often that a single photo can tell you pretty much everything you need to know about a project, but the spectrum analyzer screenshot nearby is the perfect summary of this over-the-top low-distortion audio oscillator build. But that doesn’t mean there’s not a ton of interesting stuff going on with this one, so buckle up.

One spike at the fundamental and not much more.

The project is by [Basin Street Design], who doesn’t really offer much by way of inspiration for this undertaking, nor a discussion on what this will be used for. But the design goals are pretty clear: build an oscillator with as little distortion as possible across the audio frequency range.

The basic circuit is the well-known Wien bridge oscillator where the R-C pairs are switched in and out of the feedback loop to achieve frequency range control. This was accomplished with rotary switches rebuilt from their original configuration in a Heathkit IG-18 sine/square wave generator, a defunct instrument that was gutted and used as an enclosure for this build. There are a lot of other treats here, too, like the automatic gain control (AGC) that uses a homebrew voltage-controlled resistor made from an incandescent lamp and a cadmium sulfide photoresistor glued inside a piece of brake line, and an output attenuator made from discrete resistors that drops the output in 10 dB steps while maintaining an overall 75-Ohm impedance.

But at the end of the day, it all comes down to that single spike on the spectrum analyzer, with no apparent harmonics. To make sure there wasn’t something hiding down in the noise, [Basin Street] added a notch filter to lower the fundamental by 60 dB, allowing the spectrum analyzer sensitivity to be cranked way up. Harmonics were visible, but so far down into the noise — as low as -115 dBc — that it’s hardly worth mentioning.

There’s a lot more detail in this one, so dive in and enjoy. If you want another take on Wien bridge circuits, check out this recent LM386-based oscillator. Just don’t expect such low distortion with that one.

An aluminum box sits on a workbench. It is open and has a message saying "I Love You!" inserted in a wooden slot. There is a switch with a yellow LED on the front and a small compartment to the left of the wooden slot to store paper.

Share Your Feelings Like A Spy

September 8, 2023 by 13 Comments

While hackers can deftly navigate their way through circuit diagrams or technical documentation, for many of us, simple social interactions can be challenge. [Simone Giertz] decided to help us all out here by making a device to help us share our feelings.

Like an assignment in Mission: Impossible, this aluminum box can convey your confessions of love (or guilt) and shred them after your partner (or roommate) reads the message. The box houses a small shredder and timer relay under a piece of bamboo salvaged from a computer stand. When the lid is opened, a switch is depressed that starts a delay before the shredder destroys the message. The shredder, timer, and box seem almost made for each other. As [Giertz] says, “Few things are more satisfying than when two things that have nothing to do with each other, perfectly fit.”

While seemingly simple, the attention to detail on this build really sets it apart. The light on the front to indicate a message is present and the hinged compartment to easily clean out shredded paper really make this a next-level project. Our favorite detail might be the little space on the side to store properly-sized paper and a marker.

While the aluminum box is very industrial chic, we could see this being really cool in a vintage metal lunch box as well. If you’re looking for other ways to integrate feelings and technology, checkout how [Jorvon Moss] brings his bots to life or how a bunch of LEDs can be used to express your mood.

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