Precision Pressure In A Piston

May 9, 2017 by Brian Benchoff 26 Comments

[Scott] is building a DIY yeast reactor for his aquarium. What’s a yeast reactor? [Scott] wants to pump carbon dioxide into his aquarium so his aquatic plants grow more. He’s doing this with a gallon of sugary, yeasty water bubbling into a tank of plants and fish. In other words, [Scott] is doing this whole thing completely backward and utilizing the wrong waste product of the yeast metabolism.

However, along the way to pumping carbon dioxide into his aquarium, [Scott] created a very high precision pressure sensor. It’s based on a breakout board featuring the MS5611 air pressure sensor. This has a 24-bit ADC on board, which translates into one ten-thousandths of a pound per square inch of pressure.

To integrate this pressure sensor into the aquarium/unbrewery setup, [Scott] created a pressure meter out of a syringe. With the plunger end of this syringe encased in epoxy and the pointy end still able to accept needles, [Scott] is able to easily plug this sensor into his yeast reactor. The data from the sensor is accessible over I2C, and a simple circuit with an ATmega328 and a character LCD displays the current pressure in the syringe.

We’ve seen these high-resolution pressure sensors used in drones and rockets as altimeters before, but never as a pressure gauge. This, though, is a cheap and novel solution for measuring pressures between a vacuum and a bit over one atmosphere.

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Powerful, Professional Brushless Motor From 3D-Printed Parts

May 8, 2017 by Dan Maloney 23 Comments

Not satisfied with the specs of off-the-shelf brushless DC motors? Looking to up the difficulty level on your next quadcopter build? Or perhaps you just define “DIY” as rigorously as possible? If any of those are true, you might want to check out this hand-wound, 3D-printed brushless DC motor.

There might be another reason behind [Christoph Laimer]’s build — moar power! The BLDC he created looks more like a ceiling fan motor than something you’d see on a quad, and clocks in at a respectable 600 watts and 80% efficiency. The motor uses 3D-printed parts for the rotor, stator, and stator mount. The rotor is printed from PETG, while the stator uses magnetic PLA to increase the flux and handle the heat better. Neodymium magnets are slipped into slots in the rotor in a Halbach arrangement to increase the magnetic field inside the rotor. Balancing the weights and strengths of the magnets and winding the stator seem like tedious jobs, but [Cristoph] provides detailed instructions that should see you through these processes. The videos below shows an impressive test of the motor. Even limited to 8,000 rpm from its theoretical 15k max, it’s a bit scary.

Looking for a more educational that practical BLDC build? Try one cobbled from PVC pipes, or even this see-through scrap-bin BLDC.

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Anatomically Correct Plotter Avoids Back Scratch Fever

May 7, 2017 by Dan Maloney 15 Comments

Everybody needs somebody sometimes, even if it’s just for when your back itches. But directing your itchy interlocutor to the correct spot can be a spatial relations challenge: “Right in the middle… no, down a bit… left… no, the other left! Harder! Wait, not that hard!” Why bother with all that messy interpersonal communication and human contact when you can build an automated, precision-guided back scratcher?

[VijeMiller] has aluminum extrusion tastes on a cardboard budget, but don’t let that put you off this clever build. The idea is pretty simple: a two-axis plotter that moves a rotary-action business end to any point within a V-shaped work envelope. The Arduino in the base talks to a smartphone app that lets you point to exactly the spot in need of attention on what for most of us would be an incredibly optimistic photorealistic map of the dorsal aspect of the body (mildly NSFW photo in the link above dips below the posterior border). Point, click, sweet relief.

The video below shows the rig in action, along with the Thespian skills we’ve come to know and love from [VijeMiller] with such classics as the fake floating 19th green, the no-idling-while-texting alert, and the more recent ker-sploosh fighting foam filled toilet. It does seem like he changed his name from [TVMiller] somewhere along the line, but he can’t throw us off the trail that easily.

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Remotely Controlling A Not-So-Miniature Hot Air Balloon

May 7, 2017 by Dan Maloney 17 Comments

Calling [Matt Barr]’s remote controlled hot air balloon a miniature is a bit misleading. Sure, it’s small compared with the balloons that ply cold morning skies with paying passengers and a bottle of champagne for the landing. Having been in on a few of those landings, we can attest to the size of the real thing. They’re impressively big when you’re up close to them.

While [Matt]’s balloon is certainly smaller, it’s not something you’d just whip together in an afternoon. Most of [Matt]’s build log concentrates mainly on the gondola and its goodies — the twin one-pound camp stove-style propane tanks, their associated plumbing, and the burner, a re-tasked propane weed torch from Harbor Freight. Remote control is minimal; just as in a full-size balloon, all the pilot can really do is turn the burner on or off. [Matt]’s approach is a high-torque RC servo to control the burner valve, which is driven by an Arduino talking to the ground over a 2.4-GHz RF link. The balloon is big enough to lift 30 pounds and appears to be at least 12 feet tall; we’d think such a craft would run afoul of some civil aviation rules, so perhaps it’s best that the test flight below was a tethered one.

Sadly, no instructions are included for making the envelope, which would be a great excuse for anyone to learn a little about sewing. And knowing how to roll your own hot air balloon might come in handy someday.

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Model Of A Transmission Line

May 3, 2017 by Manuel Rodriguez-Achach 16 Comments

Transmission lines are the kind of thing that seems to confuse beginners. After all, the fact that short-circuits can have infinite impedance and open-circuits can behave like a short is not intuitive at all!. That’s why we like [Tinselkoala]’s latest video that shows a nice model of a transmission line. It helps to understand the line as inductors and capacitors in series-parallel connection.

Any pair of wires used to transmit electrical power have tiny amounts of inductance and capacitance. This is not a problem with DC or low-frequency AC, but when the frequency is sufficiently high, weird things start to happen. The energy tends to escape as radio waves, and current reflects from discontinuities such as connectors and cable joints. For this reason, transmission lines for high frequency signals use specialized construction to minimize those effects and reduce power losses.

[Tinselkoala] has built a model of a transmission line using coils and capacitors to simulate the inductance and capacitance of the line, with LED’s placed between the coils. He feeds the system with the signal generator with frequencies from 10 kHz to 1 MHz. In his words, they act as simple “visual voltmeters” to show the peaks and nodes of the standing waves of voltage in the line.

It is relatively simple to build your own version if you want to experiment with this fascinating subject. You will only need some magnet wire, capacitors, resistors and LED’s. If the subject sounds interesting to you, here you can find an excellent introduction to transmission lines.

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Hack Your Hike With This Arduino Puzzle Geocache

May 3, 2017 by Dan Maloney 12 Comments

For those who love to hike, no excuse is needed to hit the woods. Other folks, though, need a little coaxing to get into the great outdoors, which is where geocaching comes in: hide something in the woods, post clues to its location online, and they will come. The puzzle is the attraction, and doubly so for this geocache with an Arduino-powered game of Hangman that needs to be solved before the cache is unlocked.

The actual contents of a geocache are rarely the point — after all, it’s the journey, not the destination. But [cliptwings]’ destination is likely to be a real crowd pleaser. Like many geocaches, this one is built into a waterproof plastic ammo can. Inside the can is another door that can only be unlocked by correctly solving a classic game of Hangman. The game itself may look familiar to long-time Hackaday readers, since we featured it back in 2009. Correctly solving the puzzle opens the inner chamber to reveal the geocaching goodness within.

Cleverly, [cliptwings] mounted the volt battery for the Arduino on top of the inner door so that cachers can replace a dead battery and play the game; strangely, the cache entry on Geocaching.com (registration required) does not instruct players to bring a battery along.

It looks like the cache has already been found and solved once since being placed a few days ago in a park north of Tucson, Arizona. Other gadget caches we’ve featured include GPS-enabled reverse caches, and a puzzle cache that requires IR-vision to unlock.

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Thermal Panorama One Pixel At A Time

May 2, 2017 by James Hobson 10 Comments

Inspiration can strike from the strangest places. Unearthing a forgotten Melexis MLX90614 thermopile from his ‘inbox,’ [Saulius Lukse] used it to build a panoramic thermal camera.

[Lukse] made use of an ATmega328 to control the thermal sensor, and used the project to test a pair of two rotary stage motors he designed for tilt and pan, with some slip rings to keep it in motion as it captures a scene. That said, taking a 720 x 360 panoramic image one pixel at a time takes over an hour, and compiling all that information into an intelligible picture is no small feat either. An occasional hiccup are dead pixels in the image, but those are quickly filled in by averaging the temperature of adjoining pixels.

The camera rig works — and it does turn out a nice picture — but [Lukse] says an upgraded infrared camera to captured larger images at a time and higher resolution would not be unwelcome.

Another clever use of a thermopile might take you the route of this thermal flashlight. if you don’t build your own thermal camera outright.

[Thanks for the tip, Imn!]