Translating And Broadcasting Spoken Morse Code

January 24, 2023 by Bryan Cockfield 24 Comments

When the first radios and telegraph lines were put into service, essentially the only way to communicate was to use Morse code. The first transmitters had extremely inefficient designs by today’s standards, so this was more a practical limitation than a choice. As the technology evolved there became less and less reason to use Morse to communicate, but plenty of amateur radio operators still use this mode including [Kevin] aka [KB9RLW] who has built a circuit which can translate spoken Morse code into a broadcasted Morse radio signal.

The circuit works by feeding the signal from a microphone into an Arduino. The Arduino listens for a certain threshold and keys the radio when it detects a word being spoken. Radio operators use the words “dit” and “dah” for dots and dashes respectively, and the Arduino isn’t really translating the words so much as it is sending a signal for the duration of however long each word takes to say. The software for the Arduino is provided on the project’s GitHub page as well, and uses a number of approaches to make sure the keyed signal is as clean as possible.

[Kevin] mentions that this device could be used by anyone who wishes to operate a radio in this mode who might have difficulty using a traditional Morse key and who doesn’t want to retrain their brain to use other available equipment like a puff straw or a foot key. The circuit is remarkably straightforward for what it does, and in the video below it seems [Kevin] is having a blast using it. If you’re still looking to learn to “speak” Morse code, though, take a look at this guide which goes into detail about it.

Thanks to [Dragan] for the tip!

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Casting Metal With A Microwave And Vacuum Cleaner

September 29, 2022 by Bryan Cockfield 38 Comments

Metalworking might conjure images of large furnaces powered by coal, wood, or electricity, with molten metal sloshing around and visible in its crucible. But metalworking from home doesn’t need to use anything more fancy than a microwave, at least according to [Denny] a.k.a. [Shake the Future]. He has a number of metalworking tools designed to melt metal using a microwave, and in this video he uses them to make a usable aluminum pencil with a graphite core.

Before getting to the microwave kiln, the pencil mold needs to be prepared. A 3D-printed pencil is first created with the graphite core, and then [Denny] uses a plaster of Paris mixture to create the mold for the pencil. The 3D printed plastic is left inside the mold and placed in the first microwave kiln, which is turned on just enough to melt the plastic out of the mold, leaving behind the graphite core. From there a second kiln goes into the microwave to melt the aluminum.

Once the molten aluminum is ready, it is removed from the kiln and poured in the still-warm pencil mold. This is where [Denny] has another trick up his sleeve. He’s using a household vacuum cleaner to suck the metal into place before it cools, creating a rudimentary but effective vacuum forming machine. The result is a working pencil, at least after he wears down a few razor blades attempting to sharpen the metal pencil. For more information about how [Denny] makes these microwave kilns, take a look at some of his earlier projects.

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Remembering NICAM: Deep-Dive Into A Broadcasting Legacy

July 10, 2022 by Maya Posch 17 Comments

Although for many the introduction of color television would have seemed to be the pinnacle of analog broadcast television, the 1970s saw the development of stereo audio systems to go with TV broadcasts, including the all-digital NICAM. With NICAM broadcasts having ceased for about a decade now, the studio equipment for encoding and modulating NICAM can now be picked up for cheap. This led [Matthew Millman] to not only buy a stack of Philips NICAM studio gear, but also tear them down and set up a fully working NICAM encoding/decoding system with an Arcam Delta 150 as receiver and Philips PM5687 encoder.

Finally, the Philips PM5688 test receiver is analyzed. This is the component that studios would have used to ensure that the NICAM encoding and modulating systems were working properly. Although public NICAM broadcasts started in the late 1980s, the system was originally developed to enable point to point transfers of audio data within a transmission system. This was made very easy due to the digital nature of the system, and made enabling it for public broadcasts relatively straightforward once receivers became affordable enough.

Of note is that NICAM was only ever used in Europe and some Asian-Pacific countries, with others using the German Zweikanalton. This was a purely analog (two FM channels) system, and the US opted to use its MTS system, that was quite similar to the German system in terms of transmitting multiple FM channels alongside the TV signal. With digital TV gradually overtaking analog TV transmissions, the future of NICAM, MTS and others was sealed, leaving us with just these time capsules we can build up using old studio equipment.

Casting Parts In Urethane: Tips From A Master

June 21, 2022 by Elliot Williams 11 Comments

When you want a couple copies of a thing, you can 3D print ’em. When you want a ton of them, you might consider making a mold. If those are the shoes you’re in, you should check out this video from [Robert Tolone] (embedded below). Or heck, just check out all of his videos.

Even just in this single video from a couple years back, there are a ton of tips that’ll help you when you’re trying to pour resin of just the right color into a silicone mold. Mostly, these boil down to testing everything out in small quantities before pouring it in bulk, because a lot changes along the way. And that’s where [Robert]’s experience shines through — he knows all of the trouble spots that you need to test for.

For instance? Color matching. Resin dyes are incredibly concentrated, so getting the right amount is tricky. Mixing the color at a high concentration first and then sub-diluting it slowly allows for more control. But even then, the dried product is significantly lighter than the mixture, so some experimentation is necessary. [Robert] sneaks up on just the right color of seafoam green and then pours some test batches. And then he pours it in the exact shape of the mold just to be sure.

That’s just one of the tips in this video, which is just the tip of the mold-casting iceberg. Pour yourself a coffee, settle down, and you’ll learn something for sure. If you’re into more technical parts and CNC machining, we still love the Guerilla Guide after all these years.

Much thank to [Zane] for tipping us off to this treasure trove.

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A Rotocasting Machine Sized For The Home Shop

June 3, 2022 by Dan Maloney 5 Comments

If you’ve ever wondered how large, hollow plastic structures like tanks and drums are formed, you’re in luck: [Andy] not only fills us in on the details of rotational casting and molding, but he also built this sweet little rotational casting machine to help him with his DIY projects.

Granted, [Andy]’s build won’t be making anything too large, like a car fuel tank or a kayak. Not only is it sized more for smallish parts, but those structures are generally made with the related process of rotational molding. Both processes use an enclosed multipart mold that’s partially filled with plastic resin, and then rotate the mold around two axes to distribute a thin layer of resin around the inside of the mold. The difference is that roto-molding uses a thermoplastic resin, whereas roto-casting uses resins like polyurethane and silicone that set at room temperature.

The machine looks simple, but only because he took great pains to optimize it. The videos below cover the build in detail — feel free to skip to the 11:38 mark of the second video if you just want to see it in action. Though you’ll be missing some juicy tidbits, like welding a perfect 90° joint in square tubing. There’s also the custom tool [Andy] built to splice the beaded chain he used to drive the spinning of the mold, which was pure genius.

Using the machine and a complex nine-piece mold, [Andy] was able to create remarkably detailed tires for RC cars from polyurethane resin. We’d love to see what else this rig is good for — almost as much as we want to see details on how the mold was made. We’ve seen other rotational casting machines before, but this one takes the cake for fit and finish.

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Maze Bolt Toy By Lost PLA Casting

May 5, 2022 by Anne Ogborn 8 Comments

Maze bolts, a bolt which has a maze along its shaft traversed by a pin on its nut, are great fun. Here’s a really beautiful metal version by [Robinson Foundry], made by a process more makers should know about – lost PLA casting.

His basic method is to 3D print in PLA, and then use more or less the same process as lost wax casting.

He 3D printed the part, along with the sprues and risers that go along with casting, in PLA, then dipped the parts in slurry ten (10) times. He heated in a kiln to 500°F (260°C), the PLA melted and ran out or burned away. With the PLA gone, after repairing a few cracks, he raised the temperature to 1500°F (815°C) and vitrified the slurry into a ceramic. He now had molds.

The nut is bronze. The bolt is aluminum. He poured the metal with the molds hot, held in heated sand, so the metal can flow into all the small details. The rest of the project is just cleanup, but we learned that you can vary the finish produced by glass bead blasting just by varying the air pressure.

A great demo of a useful technique and a fun toy at the end.

We covered a great technique for doing lost PLA casting using a microwave.

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3D Printed Molds For Casting Rose’s Metal

March 17, 2022 by Kristina Panos 21 Comments

Have you ever played with Rose’s metal? It’s a fusible alloy of bismuth, lead, and tin with a low melting point of around 100 °C. Historically, it’s been used as a solder for cast iron railings and things, and as a malleable pipe filler material to prevent crimping while a pipe is bent.

[Ben Healey] has been playing around with Rose’s metal and some PETG printed molds, making everything from Star Wars Imperial credits to chess pieces to leather stamping tools. In the video after the break, [Ben] takes us through the process, beginning with mold-making from STLs — something he picked up from another YouTuber.

He recommends adding registration marks to multi-part molds in order to keep everything lined up, and adding a small recess in the seam for easy separation with a flat-head screwdriver. So far, the molds have held up to multiple pours, though [Ben] did print them rather thick and is glad he did.

As far as making liquid metal, [Ben] used a cast iron pot with a convenient pour spout, and a blowtorch. He added graphite powder to the molds in an effort to make them give up the goods more easily. To finish the pieces, [Ben] cut the flashing with tin snips and used sandpaper and a Dremel to smooth the edges. Copper plating didn’t work out, but [Ben] is going to try it again because he thinks he screwed something up in the process. He’s also going to try printing with TPU, which we were just about to recommend for its flexibility.

There are many ways to cast metal on the (relatively) cheap. Have you considered Kinetic Sand?

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