A Canned Ham Ham Antenna

November 16, 2023 by Dan Maloney 29 Comments

If you’d have asked us for odds on whether you could successfully turn a canned ham into an amateur radio antenna, we’d have declined the offer. Now, having seen [Ben Eadie (VE6SFX)]’s “hamtenna” project, we’d look at just about any “Will it antenna?” project with a lot less skepticism than before.

To be painfully and somewhat unnecessarily clear about [Ben]’s antenna, the meat-like product itself is not in the BOM for this build, although he did use it as sustenance. Rather, it was the emptied and cleaned metal can that was the chief component of the build, along with a few 3D printed standoffs and the usual feedline and connectors. This is a slot antenna, a design [Ben] recently experimented with by applying copper foil tape to his car’s sunroof. This time around, the slot was formed by separating the top and bottom of the can using the standoffs and electrically connecting them with a strip of copper tape.

Connected to a stub of coax and a BNC connector, a quick scan with a NanoVNA showed a fantastic 1.26:1 SWR in the center of the 70-cm ham band, and a nearly flat response all the way across the band. Results may vary depending on the size of canned ham you sacrifice for this project; [Ben]’s can measured just about 35 cm around, a happy half-wavelength coincidence. And it actually worked in field tests — he was able to hit a local repeater and got good signal reports. All that and a sandwich? Not too shabby.

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Robot Hand Has Good Bones

November 16, 2023 by Al Williams 8 Comments

What do you get when you mix rigid and elastic polymers with a laser-scanning 3D printing technique? If you are researchers at ETH Zurich, you get robot hands with bones, ligaments, and tendons. In conjunction with a startup company, the process uses both fast-curing and slow-curing plastics, allowing parts with different structural properties to print. Of course, you could always assemble things from multiple kinds of plastics, but this new technique — vision-controlled jetting — allows the hands to print as one part. You can read the full paper from Nature or see the video below.

Wax with a low melting point encases the entire structure, acting as a support. The researchers remove the wax after the plastics cure.

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No TP? No Problem!

November 16, 2023 by Jenny List 42 Comments

Among First World Problems, there can be few worse than running out of toilet paper. The horror! If you’re not able to do as we did yesterday and borrow a pack until more can be bought, then you’re not without options. A handy copy of the Daily Mail could be cut into squares and hung up in your Smallest Room, or you can even make your own with the help of this handy instructional video from [whoisandrewfahmy]. It appears from a casual search to be one of many such guides that appeared during the pandemic when the bog roll supply was seen as endangered, but it’s still interesting simply as a diversion into how something is made.

The process is surprisingly straightforward, starting with scrap paper, which is shredded and soaked before being boiled to break down to pulp. The pulp is then emulsified, and some body oil is added to remove the sandpaper-on-the-butt experience before being spread between a sheet and a piece of window screen to be ironed dry. It’s an energy-intensive process, so the Daily Mail is likely to be an easier stopgap if no friends can lend you a few rolls, but it’s left us here curious about papermaking. The butts of Hackaday may be safe from homemade TP, but that’s not to say that it wouldn’t be interesting to make other paper products. Check out the video below.

Of course, back in April 2020 we had our own solution to the pandemic toilet paper shortage. After you make your bespoke dunny roll, how can you wind it into a nice roll? Don’t worry. We got you.

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ColorReplica Is A Rainbow At Your Fingertips

November 16, 2023 by Kristina Panos 15 Comments

Have you ever wanted to match paint to the color of a pillow, or make a website where the primary color matches your favorite shade of electrolytic capacitor? Then ColorReplica is the project for you.

At the heart of this build are two ESP32s, one of which controls the color picker, and the other lights up the 18 WS2812 LEDs and displays information on the OLED screen.

ColorReplica has two modes, ColorPicker and ColorCube. In ColorPicker mode, you just choose what color you want, adjust the brightness level, and choose between static and dynamic modes for the LEDs. [CiferTech] used the ESP32 touch pins extended to pads on the PCB to control different menu variables, which is a nice touch.

In ColorCube mode, there’s a secondary circuit with a color sensor an another ESP32. Once detected, it transmits the color data to the main device at the push of a button. The RGB LEDs turn that color, and shows the RGB, HEX, and HSV values on the OLED screen. If you’d like to make one of these yourself, everything is available on GitHub.

Want something a big more tangible? Check out this color picker that types HEX codes for you.

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Umbrella Antenna Protects You From Rain, But Not The Way You Think

November 16, 2023 by Dan Maloney 8 Comments

You never know when you’ll be called upon to [MacGyver] your way out of an emergency. We can’t imagine what kind of situation would call for whipping up a satellite ground station for NOAA weather satellites from junk, but hey, it could happen.

And when it does, you’ll be ready — as long as you have an umbrella, some foil tape, and various bits and bobs like wire and an RTL-SDR dongle. That’s what [saveitforparts] used for his field-expedient build, at least in the first instance; as you can imagine, builds like this take a lot of tweaking to get right. The umbrella and foil tape form the main reflector for the antenna, with a pie tin, a scrap of wire, and some random twigs being used to build the antenna’s helical feed. Attached to a SAWbird LNA/filter and an RTL-SDR plugged into a dodgy second-hand phone, he was able to get at least some kind of data from one of the GOES satellites, but it wasn’t great.

Switching the feed to a commercially available log periodic antenna worked much better, with some partial decodes of weather map data. Actually, getting anything at all with a setup like this is impressive enough for us to call it a win. It shows that the umbrella approach to antennas is valid; but then again, we already knew that.

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A 3D Printed Grinder For Printed Lens Blanks

November 16, 2023 by Dan Maloney 20 Comments

When one thinks of applications for 3D printing, optical components don’t seem to be a good fit. With the possible exception of Fresnel lenses, FDM printing doesn’t seem up to the job of getting the smooth surfaces and precision dimensions needed to focus light. Resin printing might be a little closer to the mark, but there’s still a long way to go between a printed blank and a finished lens.

That gap is what [Fraens] aims to fill with this homebrew lens grinding machine. It uses the same basic methods used to grind and polish lenses for centuries, only with printed components and lens blanks. The machine itself consists of a motorized chuck for holding the lens blank, plus an articulated arm to hold the polishing tool. The tool arm has an eccentric drive that wobbles the polishing tool back and forth across the blank while it rotates in the chuck. Lens grinding requires a lot of water and abrasive, so a large bowl is provided to catch the swarf and keep the work area clean.

Lens blanks are printed to approximately their finished dimensions using clear resin in an SLA printer. [Fraens] spent a lot of time optimizing the printing geometry to minimize the number of print layers required. He found that a 30° angle between the lens and the resin pool worked best, resulting in the clearest blanks. To polish the rough blanks, a lapping tool is made from polymer modeling clay; after baking it dry, the tool can hold a variety of pads and polishing compounds. From there it’s just a matter of running the blank through a range of abrasives to get the desired final surface.

Are the lenses fantastic? Well, they’re probably not going to make it into fine optical equipment, but they’re a lot better than you might expect. Of course, there’s plenty of room for improvement; better resins might result in clearer blanks, and perhaps degassing the uncured resin under vacuum might help with bubbles. Skipping the printed blanks and going with CNC-machined acrylic might be worth a try, too.

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Tech In Plain Sight: What Does A Yellow Light Mean?

November 16, 2023 by Al Williams 58 Comments

The traffic light is a ubiquitous feature of modern life and is quite old — dating back to 1868 London, although that device was a modified railroad semaphore operated by a policeman, but it was the same idea. The initial test of the signal proved disastrous.

The semaphore had gas lamps to illuminate the signs in the dark. A gas leak caused one of the lamps to explode, badly burning the operator and ending the nascent invention for a while. In 1910, American inventor Ernest Sirrine worked out an automatically controlled traffic signal. Two years later, Lester Wire, a police officer, developed a different version powered by overhead trolley wires to light the signal. A 1917 patent by William Ghiglieri also had two lights — red and green. But where was the yellow light?

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