Hackaday Podcast 235: Licorice For Lasers, Manual Motors, And Reading Resistors

Name one other podcast where you can hear about heavy 3D-printed drones, DIY semiconductors, and using licorice to block laser beams. Throw in homebrew relays, a better mouse trap, and logic analyzers, and you’ll certainly be talking about Elliot Williams and Al Williams on Hackaday Podcast 235.

There’s also contest news, thermoforming, and something that looks a little like 3D-printed Velcro. Elliot and Al also have their semi-annual argument about Vi vs. Emacs. Spoiler alert: they decided they both suck.

Missed any of their picks? Check out the links below, and as always, tell us what you think about this episode in the comments!

Download it yourself. You can even play it backwards if you like.

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Fitting 3D Prints In A Snap

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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[Thomas Sanladerer]’s YouTube Channel Goes In The Toilet

We like [Thomas Sanladerer], so when we say his channel has gone in the toilet, we mean that quite literally. He had a broken toilet and wanted to compare options for effecting a 3D printed repair. The mechanism is a wall-mounted flush mechanism with a small broken plastic part. Luckily, he had another identical unit that provided a part that wasn’t broken.

The first attempt was to 3D scan the good part. The first scanner’s software turned out to be finicky, and [Thomas] finally gave up on it. He finally used a handheld scanner which took about a half hour. It wasn’t, of course, perfect, so he also had to do some more post-processing.

The next step was to make measurements and draw the part in CAD. It took the same amount as the scan, and it is worth noting that the part had curves and angles — it wasn’t just a faceplate. The printed results were good, although a measurement error made the CAD model bind a bit instead of pivoting the way it should. The scan, of course, got it right.

A quick revision of the design solved that problem but, of course, it added some time to the process. At the end, he noticed that the scanned “good” part was also broken but in a different way. He added the additional part, which didn’t seem to bother the function. The scanned object required a little trimming but nothing tremendous.

In the end, the scanning was a bit quicker, partly because it didn’t suffer from the measurement error. However, [Thomas] noted that it was more fun to work in CAD. We thought the results looked better, anyway. [Thomas] thinks the scanners, at least the budget ones, are probably better for just getting reference objects into CAD to guide you when you create the actual objects to print.

It isn’t hard to make a cheap scanner. Some of the open designs are quite sophisticated.

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Triso Fuel And The Rolls Royce Of Nuclear Reactors

Bangor University scientists think that the way to go big with nuclear power is to, in fact, go small. Their tiny nuclear fuel pellets called triso fuel are said to be the size of poppy seeds and are meant to power a reactor by Rolls Royce the size of a “small car.” We aren’t sure if that’s a small Rolls Royce or a small normal car.

The Welsh university thinks the reactor has applications for lunar bases, here on Earth, and even on rockets because the reactor is so small. We can’t tell if the fuel from Bangor is unique or if it is just the application and the matching reactor that is making the news. Triso fuel — short for tri-structural isotropic particle fuel — was developed in the 1960s, and there are multiple projects worldwide gearing up to use this sort of fuel.

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The Computer That Controlled Chernobyl

When you think of Chernobyl (or Chornobyl, now), you think of the nuclear accident, of course. But have you ever considered that where there is a nuclear reactor, there is a computer control system? What computers were in control of the infamous reactor? [Chornobyl Family] has the answer in a fascinating video documentary you can see below.

The video shows a bit of the history of Soviet-era control computers. The reactor’s V-30M computer descended from some of these earlier computers. With 20K of core memory, we won’t be impressed today, but that was respectable for the day. The SKALA system will look familiar if you are used to looking at 1970s-era computers.

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3D Printed — Um — Hook And Loop Fasteners

[Teaching Tech’s] latest video discusses “3D printed Velcro.” But as even he admits, Velcro is a trademark, so we think it is more appropriate to talk about hook and loop fasteners. In fact, you can see the good-natured official video about the trademark below [Teaching Tech’s] video. Regardless, his experiments with several 3D-printed Vel… fastener designs are worth watching.

Some of the designs were rather large, like we would have expected. However, some of the designs were fairly small and looked almost like real Velcro. However, since the pattern is not as random as the fabric portions of the real deal, it seems like alignment between parts is more critical when you are joining the two halves.

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If You Aren’t Making Your Own Relays…

We’ve all been there. Someone will say something like, “I remember when we had to put our programs on a floppy disk…” Then someone will interrupt: “Floppy disk? We would have killed for floppy disks. We used paper tape…” After a few rounds, someone is talking about punching cards with a hand stylus or something. Next time someone is telling you about their relay computer, maybe ask them if they are buying their relays already built. They will almost surely say yes, and then you can refer them to [DiodeGoneWild], who shows how he is making his own relays.

While we don’t seriously suggest you make your own relays, there are a lot of fun techniques to pick up, from the abuse of a power drill to the calculation of the coil parameters. Even if you don’t learn anything, we get the desire to make as much as you can.

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