Turning A Rotary Tool Into A CNC

November 16, 2018 by Brian Benchoff 32 Comments

Now that 3D printers are everywhere, electronics are cheap, and open source software is extremely capable, just about anyone can build a CNC machine. That’s exactly what [Nikodem] did by turning a Dremel tool into an extremely capable CNC machine that’s able to cut MDF and acrylic and can engrave aluminum.

The electronics for the build are just an Arduino Uno, a motor driver sheld running GRBL, a relay for the Dremel, a few motor drivers, and a big ‘ol 30 A power supply. The build uses NEMA 17 motors, two on the Y-axis and one each on the X and Z. The CNC has a fantastically strong frame despite the 3D printed parts. It is constructed out of aluminum extrusion, with the carriages riding on some nice straight rods.

As for how well this CNC machine works, it’s pretty good. With the Gcode to cut an 80mm diameter circle out of MDF, this machine managed to cut a circle that was 80.02 mm in diameter. That’s pretty good, and getting into the territory that the error is probably in the cheap set of calipers, not the finished part itself. It’s an awesome build, and [Nikodem] has everything documented in his four-part video series. You can check the end of that out below.

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Supercon: Designing Your Own Diffractive Optics

November 16, 2018 by Brian Benchoff 15 Comments

Kelly Peng is an electrical and optical engineer, and founder of Kura AR. She’s built a fusion reactor, a Raman spectrometer, a DIY structured light camera, a linear particle accelerator, and emotional classifiers for likes and dislikes. In short, we have someone who can do anything, and she came in to talk about one of the dark arts (pun obviously intended): optics.

The entire idea of Kura AR is to build an immersive augmented reality experience, and when it comes to AR glasses, there are two ways of doing it. You could go the Google Glass route and use a small OLED and lenses, but these displays aren’t very bright. Alternatively, you could use a diffractive waveguide, like the Hololens. This is a lot more difficult to manufacture, but the payoff will be a much larger field of view and a much more immersive experience.

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Delta Bot Plucks Out Tunes On A Mandolin

November 16, 2018 by Dan Maloney 22 Comments

Is there no occupation safe from the scourge of robotic replacement? First it was the automobile assemblers, then fast food workers, and now it’s the — mandolin players?

Probably not, unless [Clayton Darwin]’s mandolin playing pluck-bot has anything to say about it. The pick-wielding delta-ish robot can be seen in action in the video below, plucking out the iconic opening measures of that 70s prom-theme favorite, “Colour My World.” The robot consists of two stepper motors connected to a hinged wooden arm by two pushrods. We had to slow the video down to catch the motion, but it looks like [Clayton] has worked out the kinematics so that the pick can be positioned in front of any of the mandolin’s eight strings. A quick move of the lower stepper then flicks the pick across a string and plucks it. [Clayton] goes into some detail about how he built the motion-control part in an earlier video; he also proves that steppers are better musicians than we’ll ever be with a little “Axel F” break.

It’s only a beginning, of course, but the complexity of the kinematics just goes to show how simple playing an instrument isn’t. Unless, of course, you unleash an endless waterfall of marbles on the problem.

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Smooth Moves From Cheap Motors

November 16, 2018 by Bryan Cockfield 36 Comments

Building an electric motor isn’t hard or technically challenging, but these motors have very little in the way of control. A stepper motor is usually employed in applications that need precision, but adding this feature to a motor adds complexity and therefore cost. There is a small $3 stepper motor available, but the downside to this motor is that it’s not exactly the Cadillac of motors, nor was it intended to be. With some coaxing, though, [T-Kuhn] was able to get a lot out of this small, cheap motor.

To test out the motors, [T-Kuhn] built a small robotic arm. He began by programming his own pulse generating algorithm that mimics a sine wave in order to smooth out the movement of the motor. An Arduino isn’t fast enough to do these computations, though, so he upgraded to using the ESP32. He also was able to implement the inverse kinematics on his own. The result of all this work for a specific platform and motor type is a robotic arm that has a very low cost but delivers performance of much more expensive hardware.

The robot arm was built by [T-Kuhn] too, and all of the details on that build, as well as all the schematics and code, are available on the project site if you need a low-cost robot arm or a good stepper motor controller for a low cost. There are many other ways of getting the most out of other types of low-cost motors as well.

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How’s A Gyro Work?

November 15, 2018 by Al Williams 25 Comments

It wasn’t long ago that a gyro — or gyroscope — was an exotic piece of electronics gear. Most of us only saw them as children’s toys that would balance on your finger. That’s changed, though, thanks to microelectronics. Now your game controller, your phone, and your drone all probably use little ICs that are actually three-axis gyroscopes. Ever wonder how they work and what they do? [RCModelReviews] has a video that covers three kinds of gyros: old mechanical gyros, modern MEMS gyros, and even an exotic laser-based gyro. (YouTube, embedded below.)

Gyroscopes allow you to detect orientation by detecting linear forces on a rotating element. They are used in everything from spacecraft to submarines. The device has many origins dating back to antiquity. But the modern gyro showed up around 1800 or so. The children’s toy appeared in 1917 and is still made today.

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Magnets And Printed Parts Make Quick-Disconnect Terminals

November 15, 2018 by Dan Maloney 19 Comments

The Apple MagSafe power connector is long gone from their product line, but that doesn’t mean that magnetic connectors aren’t without their charms. It just takes the right application, and finding one might be easier with these homebrew magnetic connectors.

We’ll admit that the application that [Wesley Lee] found for his magnetic connectors is perhaps a little odd. He’s building something called Linobyte, a hybrid art and electronics project that pays homage to computing history with very high-style, interactive core memory modules. The connectors are for the sense wire that is weaved through the eight toroids on each module, to program it with a single byte. Each connector has a 3D-printed boot that holds a small, gold-plated neodymium magnet with the sense wire soldered to it. A socket holds another magnet to the underside of a PCB. The magnet in the boot sticks to the PCB and makes contact with pads, completing the circuit. We know what you’re thinking: heating a magnet past the Curie point is a great way to ruin it. [Wesley] admits that happens, but it just makes the connection a little weaker, which works for his application. The short video below shows how he puts them together.

We can think of a couple of ways these connectors would be useful, and we really like the look of the whole project. It’ll be interesting to see where it goes, but in the meantime, brushing up on how magnets work could be fun. Continue reading “Magnets And Printed Parts Make Quick-Disconnect Terminals” →

Measuring The Cooling Effect Of Transformer Oil

November 15, 2018 by Steven Dufresne 36 Comments

Transformer oil has long served two purposes, cooling and insulating. The large, steel encased transformers we see connected to the electrical grid are filled with transformer oil which is circulated through radiator fins for dumping heat to the surrounding air. In the hacker world, we use transformer oil for cooling RF dummy loads and insulating high voltage components. [GreatScott] decided to do some tests of his own to see just how good it is for cooling circuits.

He started with testing canola oil but found that it breaks down from contact with air and becomes rancid. So he purchased some transformer oil. First, testing its suitability for submerging circuits, he found that he couldn’t see any current above his meter’s 0.0 μA limit when applying 15 V no matter how close together he brought his contacts. At 1 cm he got around 2 μA with 230 VAC, likely from parasitic capacitance, for a resistance of 115 Mohm/cm.

Moving on to thermal testing, he purchased a 4.7 ohm, 100 watt, heatsink encased resistor and attached a temperature probe to it with Kapton tape. Submerging it in transformer oil and applying 25 watts through it continuously, he measured a temperature of 46.8°C after seven minutes. The same test with distilled water reached 35.3°C. Water’s heat capacity is 4187 J/kg∙K, not surprisingly much better than the transformer oil’s 2090 J/kg∙K which in turn is twice as good as air’s 1005 J/kg∙K.

He performed a few more experiments but we’ll leave those to his video below.

We’ve run across a number of tests running boards submerged in various oils before. For example, we’ve seen Raspberry Pi’s running in vegetable oil and mineral oil as well as an Arduino running in a non-conductive liquid coolant, all either overclocked or under heavy load.

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