Get A Fresh Build Plate At The Push Of A Button

September 6, 2023 by 22 Comments

For best results, a build sheet for a 3D printer’s print bed should be handled and stored by the edges only. To help make that easier, [Whity] created the Expandable Steel Sheet Holder system that can store sheets efficiently without touching their main surfaces, and has a clever mechanism for ejecting them at the push of a button.

Pushing the button (red, bottom left) pivots the section at the top right, ejecting the plate forward for easy retrieval.

The design is 3D printable and made to be screwed to the bottom of a shelf, which is great for space saving. It can also be extended to accommodate as many sheets as one wishes, and there’s a clever method for doing that.

Once the first unit is fastened to a shelf, adding additional units later is as simple as screwing them to the previous one with a few M3 bolts, thanks to captive nuts in the previously-mounted unit. It’s a thoughtful feature that makes it easy to expand after the fact. Since build sheets come in a variety of different textures and surfaces for different purposes, one’s collection does tends to grow.

Interested, but want it to fit some other manufacturer’s sheets? The design looks easy to modify, but before you do that, check out the many remixes and you’re likely to find what you’re looking for. After all, flexible magnetic build sheets are useful in both resin and filament-based 3D printing.

Mining And Refining: Quartz, Both Natural And Synthetic

September 6, 2023 by 17 Comments

So far in this series, pretty much every material we’ve covered has had to undergo a significant industrial process to transform it from its natural state to a more useful product. Whether it’s the transformation of bauxite from reddish-brown clay to lustrous aluminum ingots, or squeezing solid sulfur out of oil and natural gas, there haven’t been many examples of commercially useful materials that are taken from the Earth and used in their natural state.

Quartz, though, is at least a partial exception to this rule. Once its unusual electrical properties were understood, crystalline quartz was sent directly from quarries and mines to factories, where they were turned into piezoelectric devices with no chemical transformation whatsoever. The magic of crystal formation had already been done by natural processes; all that was needed was a little slicing and dicing.

As it turns out, though, quartz is so immensely useful for a technological society that there’s no way for the supply of naturally formed crystals to match demand. Like copper before it, which was first discovered in natural metallic deposits that could be fashioned into tools and decorations more or less directly, we would need to discover different sources for quartz and invent chemical transformations to create our own crystals, taking cues from Mother Nature’s recipe book on the way.

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It’s Numbers All The Way Down With This Tape Measure Number Station Antenna

September 6, 2023 by 12 Comments

For all their talk of cooperation and shared interests, the nations of the world put an awful lot of effort into spying on each other. All this espionage is an open secret, of course, but some of their activities are so mysterious that no one will confirm or deny that they’re doing it. We’re talking about numbers stations, the super secret shortwave radio stations that broadcast seemingly random strings of numbers for the purpose of… well, your guess is as good as ours.

If you want to try to figure out what’s going on for yourself, all you need is a pair of tape measures and a software defined radio (SDR), as [Tom Farnell] demonstrates. Tape measure antennas have a long and proud history in amateur radio and shortwave listening, being a long strip of conductive material rolled up in a convenient package. In this case, [Tom] wanted to receive some well-known numbers stations in the 20- to 30-meter band, and decided that a single 15-meter conductor would do the job. Unlike other tape measure antennas we’ve seen, [Tom] just harvested the blades from two 7.5-meter tape measures, connected them end-to-end, and threw the whole thing out the window in sort of a “sloper” configuration. The other end is connected to an RTL-SDR dongle and a smartphone running what appears to be SDRTouch, which lets him tune directly into the numbers stations.

Copying the transmissions is pretty simple, since they transmit either in voice or Morse; the latter can be automatically decoded on a laptop with suitable software. As for what the long strings of numbers mean, that’ll remain a mystery. If they mean anything at all; we like to think this whole thing is an elaborate plan to get other countries to waste time and resources intercepting truly random numbers that encode nothing meaningful. It would serve them right.

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Finally, A Machine To Organize Resistors!

September 6, 2023 by 37 Comments

Perhaps it’s a side-effect of getting older, but it seems like reading the color bands on blue metal-film resistors is harder than it was on the old brown carbon ones. So often the multimeter has to come out to check, but it’s annoying. Thus we rather like [Mike]’s Resistorganizer, which automates the process of keeping track of the components.

At its heart is a fairly simple concept, with the microcontroller reading the value of a resistor by measuring the voltage from a potential divider. The Resistorganizer extends this using an array of analogue multiplexer chips, and is designed to plug into one side of a breadboard with the idea being that each line can have a resistor connected to earth through it. Of course it’s not quite as simple as that, because to maintain a readable range a set of resistors must be switched in and out to form the other half of the divider for different ranges. Thus another multiplexer chip performs that task.

Finally a set of digital multiplexers handles an LED to see which of the many resistors is currently selected through a pair of buttons, and a dot-matrix LCD display delivers the value. We want one already!

Streaming Video From An ESP32

September 5, 2023 by 11 Comments

The ESP32, while first thought to be little more than a way of adding wireless capabilities to other microcontrollers, has quickly replaced many of them with its ability to be programmed as its own platform rather than simply an accessory. This also paved the way for accessories of its own, such as various sensors and even a camera. This guide goes over taking the input from the camera and streaming it out over the network to multiple browsers.

On the server side of things, the ESP32 and its attached camera are set up with MQTT, a lightweight communications protocol which uses a publish/subscribe model to send information. The ESP32 is configured to publish its images only, but not subscribe to any other nodes. On the client side, the browser runs a JavaScript program which is able to gather these images and stitch them together into a video.

This can be quite a bit of data to send out over the ESP32’s compact hardware, so there are some tips and tricks for getting more out of these little devices, including using an external antenna for better Wi-Fi signal, or omitting it entirely in favor of Ethernet. As far as getting a lot out of a tiny microcontroller, though, leveraging MQTT really helps the ESP32 go a long way. These chips have come along way since they were first introduced; they’re powerful enough to act as 8-bit gaming consoles too.

Thanks to [Surfskidude] for the tip!

Electro-Optical Control Of Lasers With A Licorice Twist

September 5, 2023 by 8 Comments

You’ve got to hand it to [Les Wright]; he really knows how to dig into optical arcana and present topics in an interesting way. Case in point: an electro-optical control cell that’s powered by ouzo.

OK, the bit about the Greek aperitif may be stretching things a bit, but the Kerr Cell that [Les] builds in the video below does depend on anethole, the essential component of aniseed extract, which lends its aromatic flavor to everything from licorice to Galliano and ouzo. As [Les] explains, the Kerr effect uses a high-voltage field to rapidly switch light passing through a medium on and off. The most common medium in Kerr cells is nitrobenzene, a “distressingly powerful organic solvent” with such fun side effects as toxicity, flammability, and carcinogenicity.

Luckily, [Les] found a suitable substitute in the form of anethole — a purified sample, not just an ouzo nip. The solution went into a plain glass cuvette equipped with a pair of aluminum electrodes, which got connected to one of the high-voltage supplies we’ve seen him build before for his nitrogen laser. A pair of polarizing filters go on either end of the cuvette, and are adjusted to blank out the light passing through it. Applying 45 kilovolts across the cell instantly turns the light back on. Watch it in action in the video below.

There’s a lot of room left for experimentation on this one, including purification of the anethole for potentially better results. We’d also be curious if plain ouzo would show some degree of Kerr effect. For science, of course.

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Clean Up Your Resin-Printing Rinse With Dialysis

September 5, 2023 by 64 Comments

There’s a lot to like about resin 3D printing. The detail, the smooth surface finish, the mechanical simplicity of the printer itself compared to an FDM printer. But there are downsides, too, not least of which is the toxic waste that resin printing generates. What’s one to do with all that resin-tainted alcohol left over from curing prints?

How about sending it through this homebrew filtering apparatus to make it ready for reuse? [Involute] likens this process to dialysis, and while we see the similarities, what’s going on here is a lot simpler than the process used to filter wastes from the blood in patients with failing kidneys — there are no semipermeable membranes used here. Not that the idea suffers from its simplicity, mind you; it just removes unpolymerized resin from the isopropyl alcohol rinse using the same photopolymerization process used during printing. Continue reading “Clean Up Your Resin-Printing Rinse With Dialysis” →