Author: Al Williams

3652 Articles

Manual Supports For 3D Printing

April 21, 2024 by 14 Comments

[MakerSpace] wanted to 3D print an RFID card holder. On one side is a slot for a card and on the other side has recesses for the RFID antenna. They used these to control access to machines and were milling them out using a CNC machine. Since there were no flat surfaces, he had to turn on supports in the slicer, right? No. He does use supports, but not in the way you might imagine.

Inspired by creating cast iron using sand casting, he decided to first 3D print a reusable “core” using PETG. This core will support future prints that use PLA. When printing the actual item, the printer lays down the first few layers and pauses. This allows you to stick the core in and resume the print. After the print completes, you can remove the core, and the results look great, as you can see in the video below.

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Measuring An Unknown Velocity Factor

April 19, 2024 by 14 Comments

When is the speed of light not the speed of light? Of course, that’s a trick question. The speed of light may be constant, but just as sound travels at different speeds in different media, electronic signals move through transmission lines at a reduced speed. When you have a known cable, you can look up the velocity factor and use it to approximate the length of cable to have a given effective length. But what if you don’t know what kind of cable you have? [More Than Electronics] used a scope to measure it. You can see what he did in the video below.

For example, RG-8/U has a factor of 0.77. Even air isn’t exactly a factor of 1, although it is close enough that, in practice, we pretend that it is. If you wonder why it matters, consider stubs. Suppose you have a 300 MHz signal (handy because that’s 1 meter in wavelength; well, OK, pick 299.792 MHz if you prefer). If you have a quarter wavelength piece of coax shorted at one end, it will attenuate signals at 300 MHz. To understand why, picture the wave on the stub. If the close end of the stub is at 0 volts, then the other end — because it is a quarter wavelength away — must be at the maximum positive voltage or the minimum negative voltage. If either of the extremes is at the close end, then the far end must be at zero volts. That means the maximum current flows only when the signal is at 300 MHz.

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Crystal Radio Kit From The 1970s

April 19, 2024 by 19 Comments

If you read the December 1970 issue of Mechanix Illustrated, you’d be treated to [Len Buckwalter]’s crystal radio build. He called out Modern Radio Labs as the supplier for parts. That company, run by [Elmer Osterhoudt], got so many inquiries that he produced a kit, the #74 crystal set. [Michael Simpson] found an unopened kit on eBay and — after a bidding war, took possession of the kit. The kit looked totally untouched. The crystal detector was still in the box, and there were period-appropriate newspaper wrappings.

The kit itself isn’t that remarkable, but it is a classic. An oatmeal box serves as a coil form. There’s a capacitor, a crystal detector, and headphones. The original cost of the parts was $7, but we imagine the eBay auction exceeded that by a large amount.

If the name [Len Buckwalter] sounds familiar, he was quite prolific in magazines like Electronics Illustrated and also wrote several books about transistors. [Michael] also shows off his innovative coil winder made from plastic cups and a coat hanger.

We’d love to find some old kits like this, although, from one way of thinking, it is almost a shame to build them after all these years. With an added audio amplifier and fiddling with the cat whisker, it sounded just fine.

If you don’t like oatmeal, you could fire up the 3D printer. While the basic circuit is simple, you can make it more complex if you like.

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Hackaday Podcast Episode 267: Metal Casting, Plasma Cutting, And A Spicy 555

April 19, 2024 by 3 Comments

What were some of the best posts on Hackaday last week? Elliot Williams and Al Williams decided there were too many to choose from, but they did take a sampling of the ones that caught their attention. This week’s picks were an eclectic mix of everything from metal casting and plasma cutters to radio astronomy and space telescope budgets. In between? Some basic circuit design, 3D printing, games, dogs, and software tools. Sound confusing? It won’t be, after you listen to this week’s podcast.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Download an audiophile-quality oxygen-free MP3 file here.

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PC Watercooling Prototype Is Pumpless

April 18, 2024 by 23 Comments

Watercooling is usually more efficient than air cooling for the same volume of equipment, and — important for many people — it is generally quieter. However, you still have water pump noises to deal with. [Der8auer] got a Wieland prototype cooler that doesn’t use a pump. Instead, it relies on the thermosiphon effect. In simple terms, the heat moves water — possibly boiling it — upwards to a radiator. Once the water is cool, it falls down back to the heat exchanger again.

It looks like any other AIO, but the block is extremely flat compared to normal coolers, which have the pump on top of the plate. As you might expect, orientation matters, and you can’t have tight bends in the hoses. The system also has to be totally airtight to function properly. The test was meant to be against a commercial AIO unit with the same number of fans. However, there was a problem, and the final test was done with a larger radiator with one of its three fans removed.

The prototype performed fine and was quiet. It didn’t do as well as the commercial cooler, but it wasn’t bad. Of course, this is a prototype. Maybe a final product will do better. Around the ten-minute mark, the IR camera came out, and it didn’t show any major unexpected hot spots.

We’ve seen water-cooled printer hotends, and pumping is a problem there. We wondered if this technology might work there. The whole thing reminded us of heat pipes without the internal wick to move cold working fluid. We’ve even seen a water-cooled calculator.

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Computing Via (Virtual) Dominos

April 18, 2024 by 6 Comments

Back in 2012, [Matt Parker] and a team built a computer out of dominos for the Manchester Science Festival. [Andrew Taylor], part of the team that built the original,  has built a series of virtual domino puzzles to help explain how the computer worked. He also links to a video from the event, but be warned: the video contains some spoilers for the puzzles. If you are ready for spoilers, you can watch the video below.

The original computer could add two three-bit numbers and provide a four-bit result. We don’t want to give away the answers, but the inverter is quite strange. If you don’t want to puzzle it out, you can press the “reveal answer” to see [Andrew’s] solutions. Press “play” and watch the dominos fall.

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Early CD Player Teardown

April 18, 2024 by 16 Comments

While CD players are nothing new today, they were the height of high-tech in the early 1980s. [w1ngsfly] shows us the inside of a Phase Linear 9500 player from 1983. Not only does it have many components, but it is also mechanically unusual.

The CD loads into a toaster-like slot and even pops out like a piece of toast. The tracking mechanism is quite complex, and there’s something that looks suspiciously like a dial string from an old slide rule tuner radio. Apparently, the unit was made by Kyocera and is internally similar to a Kyocera DA-01.

There’s a “head position” indicator that is actually just an LED connected to the tracking mechanism. The front panel controls look great but also allow you to control the head position exactly. As [w1ngsfly] mentions, it is almost like moving a turntable’s tonearm where you can drop it anywhere you want.

If we recall, they were about $600 to $1,000 new. If Phase Linear doesn’t ring a bell, they were well known in their day. Founded by [Bob Carver] and [Steve Johnston], the company was bought by Pioneer before the introduction and, later, by Jensen before the introduction of the 9500. [Bob] would go on to found Carver Corporation. You can find plenty of history about the company online.

We’ve seen CD players that look older. These days, CD drives are cheap and they are easy enough to control.

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