A quick brush over the part with some sand paper and it quickly transforms from obviously plastic to metallic.

Learn Resin Casting Techniques: Cold Casting

July 14, 2016 by Gerrit Coetzee 36 Comments

Sometimes we need the look, feel, and weight of a metal part in a project, but not the metal itself. Maybe you’re going for that retro look. Maybe you’re restoring an old radio and you have one brass piece but not another. It’s possible to get a very metal like part without all of the expense and heat required in casting or the long hours in the metal fabrication shop.

Before investing in the materials for cold casting, it’s best to have practical expectations. A cold cast part will not take a high polish very well, but for brushed and satin it can be nearly indistinguishable from a cast part. The cold cast part will have a metal weight to it, but it clinks like ceramic. It will feel cool and transfers heat fairly well, but I don’t have numbers for you. Parts made with brass, copper, and iron dust will patina accordingly. If you want them to hold a bright shine they will need to be treated with shellac or an equivalent coating afterward; luckily the thermoset resins are usually pretty inert so any coating used on metal for the same purpose will do.

It is best to think of the material as behaving more or less like a glass filled nylon such as the kind used for the casing of a power tool. It will be stiff. It will flex a relatively short distance before crazing and then cracking at the stress points. It will be significantly stronger than a 3D printed part, weaker than a pure resin part, and depending on the metal; weaker than the metal it is meant to imitate.

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A Drone Photosphere Is Worth 4000 Times Pi Words

July 14, 2016 by Al Williams 13 Comments

One of the problems with a cheap drone is getting good video, especially in real time. Cheap hobby quadcopters often have a camera built-in or mounted in a fixed position. That’s great for fun shots, but it makes it hard to get just the right shot, especially as the drone tilts up and down, taking the camera with it. Pricey drones often have a gimbal mount to keep the camera stable, but you are still only looking in one direction.

Some cheap drones now have a VR (virtual reality) mode to feed signal to a headset or a Google Cardboard-like VR setup. That’s hard to fly, though, because you can’t really look around without moving the drone to match. You can mount multiple cameras, but now you’ve added weight and power drain to your drone.

MAGnet Systems wants to change all that with a lightweight spherical camera made to fit on a flying vehicle. The camera is under 2.5 inches square, weighs 62 grams, and draws less than 3 watts at 12 volts. It picks up a sphere that is 360 degrees around the drone’s front and back and 240 degrees centered directly under the drone. That allows a view of 30 degrees above the horizon as well as directly under the drone. There is apparently a different lens that can provide 280 degrees if you need that, although apparently that will add size and weight and be more suitable for use on the ground.

The software (see video below) runs on Windows or Android (they’ve promised an iOS version) and there’s no additional image processing hardware needed. The camera can also drive common VR headsets.

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Riding Shotgun In The Apollo 12 Lunar Lander

July 14, 2016 by Gregory L. Charvat 8 Comments

Last week we had a walk through of the Lunar Module’s source code with Don Eyles, who wrote the landing programs. Now you can take a rather thrilling ride to see Don’s code in action.

Below is an annotated video of the Apollo 12 landing, in real-time. It’s worth setting aside a quarter-hour to check it out. In an age where everyone is carrying around an HD (or way better) camera in their pocket, following along with radio broadcasts, still images, and small slivers of video might not sound that awesome. But it is!

The video takes us from Powered Descent Initiation through touchdown on the Moon with Pete Conrad and Alan Bean. As the audio plays out the video has annotations which explain what is going on and that translate the jargon used by the team. With the recently celebrated push to publish the source code you can even follow along as the video displays which program is running at that time. Just search for the program code and you’ll find it, like this screenshot of the P63 routine. The code comments are more than enough to get the gist of it all.

If you enjoy this, the description of the YouTube video below includes links to similar videos for Apollo 11, 14, 15, 16, and 17.

http://www.youtube.com/watch?v=8WEEFHJsZ0k

[Thanks to Paul Becker for sending along this video]

Nirvana Like You’ve Never Heard Them Before

July 13, 2016 by Jenny List 20 Comments

If you were an early 1990s youth, the chances are [Nirvana]’s Smells Like Teen Spirit is one of those pieces of music that transports you straight back to those times. As your writer it evokes a student radio studio and the shelves of its record library, and deafening badly-lit discos with poorly adjusted PA systems and unpleasantly sticky dance floors.

One of our finds this morning therefore comes as an evocative diversion, Smells Like Teen Spirit on [SileNT]’s Floppotron. The Floppotron is a music player composed of a huge array of floppy drives, hard drives, and a couple of flatbed scanners. The scanners are controlled by off-the-shelf Arduino boards and the hard drives have ATMega16s with H-bridge drivers.

This build is the most refined floppy drive organ we’ve seen yet. The floppies are divided into single-voice blocks of eight controlled by an ATMega16, with dynamic volume envelopes mad possible by the number of simultaneously running drives, so the sounds can fade in and out like “natural” musical instruments. The hard drives and scanners are run against their mechanical stops, providing percussion. All the boards are daisychained via SPI to an Arduino that acts as a PC interface, and the PC schedules the performance with a Python script.

He’s provided a couple of pieces as YouTube videos, the floppy motors work particularly well for [Nirvana]’s grunge, but perhaps a bit more mechanical for Hawaii Five-O. This last track will be more evocative than the first if you attended a particular university in the North of England where it was the end-of night record played as the lights came up in one of the discos that had a much better-adjusted PA because the technician knew what she was doing. For those of you with different childhoods, there’s also the Imperial March.

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Hackaday Prize Entry: The World’s First Tampon Monitor

July 13, 2016 by Brian Benchoff 45 Comments

[Amanda], [Jacob], [Katherine], and [vyshaalij] had a class project for their ‘Critical Making’ class at UC Berkeley. The task was to design a ‘Neo-Wearable’ that would fulfill an unmet need. Realizing women make up about 50% of the population and experience monthly periods for about half of their lives, they decided to make what can only be described as a tampon monitor. It’s a small device that monitors the… uh… ‘fullness’ of a tampon. Yes, it’s wearable technology that is actually useful, and a great entry for the Hackaday Prize.

The my.Flow, as the team are calling it, uses mechanical means to measure the saturation level of a tampon. Why would anyone want to do this? Because of leakage, anxiety, and risk of Toxic Shock Syndrome (TSS).

A ‘smart’ tampon needs some electronics, and the team’s solution to this is rather ingenious. They’re using a small, flat, wearable clip that attaches to the user’s undergarments and is connected to the tampon by an elongated tail.

Already the team is seeing a lot of success – the market research for this product showed a whopping 82% of women are ready to buy a product that would help prevent TSS. This fledgling startup was picked up by the HAX accelerator and moved to China to bring this product to life. It’s a great idea, and also a great entry for the Hackaday Prize.

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Lightweight Game Console Packs A Punch

July 13, 2016 by James Hobson 9 Comments

Any maker worth their bits will look for new ways to challenge themselves. [Robert Fotino], a computer science student at the University of California, is doing just that: designing and building his own lightweight hobbyist game console that he has appropriately named Consolite.

[Fotino] wrote his own compiler in C++ that converts from C-like languages to a custom-designed assembler that he has dubbed Consolite Assembly. To test his code, he also wrote an emulator before loading it onto the Mimas V2 FPGA board. Presently, Consolite uses 64KiB of main memory and 48 KiB of video memory; a future version will have 32 bit support to make better use of the Mimas’ 64 MiB of on board ram, but the current 16-bit version is a functional proof of concept.

An SD card functions as persistent storage for up to 256 programs, which can be accessed using the hardware switches on the Mimas, with plans to add user access in the form of saving game progress, storage outside of main memory, etc. — also in a future update that will include audio support.

As it stands, [Fotino] has written his own versions of Breakout, Tetris, and Tron to show off his project.

Not wanting for diligence, [Fotino] has provided thorough documentation of nearly every step along the way in his blog posts and on GitHub if you are looking for guidelines for any similar projects you might have on the back burner — like an even tinier game console.

[via r/FPGA]

In Bed With An Arduino, Fighting Sleep Apnea

July 13, 2016 by Steven Dufresne 24 Comments

Sometimes the journey is as interesting as the destination, and that’s certainly the case with [Marc]’s pursuit of measuring his sleep apnea (PDF, talk slides. Video embedded below.). Sleep apnea involves periods of time when you don’t breathe or breathe shallowly for as long as a few minutes and affects 5-10% of middle-aged men (half that for women.) [Marc]’s efforts are still a work-in-progress but along the way he’s tried a multitude of things, all involving different technology and bugs to work out. It’s surprising how many ways there are to monitor breathing.

Debugging the Eeonyx conductive fabric approach

His attempts started out using a MobSenDat Kit, which includes an Arduino compatible board, and an accelerometer to see just what his sleeping positions were. That was followed by measuring blood O2 saturation using a cheap SPO2 sensor that didn’t work out, and one with Bluetooth that did work but gave results as a graph and not raw data.

Next came measuring breathing by detecting airflow from his nose using a Wind Sensor, but the tubes for getting the “wind” from his nose to the sensor were problematic, though the approach was workable. In parallel with the Wind Sensor he also tried the Zeo bedside sleep manager which involves wearing a headband that uses electrical signals from your brain to tell you what sleep state you’re in. He particularly liked this one as it gave access to the data and even offered some code.

And his last approach we know of was to monitor breathing by putting some form of band around his chest/belly to measure expansion and contraction. He tried a few bands and an Eeonyx conductive textile/yarn turned out to be the best. He did run into noise issues with the Xbee, as well as voltage regulator problems, and a diode that had to be bypassed.

But while [Marc]’s list of approaches to monitor sleep is long, he hasn’t exhausted all approaches. For example there’s monitoring a baby using lasers to detect whether or not the child is still breathing.

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