NanoVNA Tests Antenna Pattern

January 11, 2020 by Al Williams 6 Comments

When [Jephthai] wanted to build his own Yagi antenna, he turned to MMANA software for antenna modeling. This is an antenna analysis program that uses the moment method to calculate parameters for different antenna geometries. After building the Yagi, the predicted tuning and impedance matched the real antenna nicely. But what about the radiation pattern? To test that, he used a NanoVNA and a clever test setup.

He needed a test spot out of the antenna’s near field so he set up his workstation 18 feet away from the test antenna which was on a mount that could rotate. On the edge of the workstation table — affixed with painter’s tape — is a NanoVNA connected to a laptop.

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This Artist Drags His Feet Across Sand And Snow

January 11, 2020 by Sharon Lin 10 Comments

You may have seen Simon Beck’s work a few years back. The snow artist, known for creating large-scale works of art with nothing but snowshoes, has been creating geometrically inspired fractals and mathematical forms for years. An orienteer and map-maker by day, he typically plans out his works in advance and chooses sites based on their flat terrain. The lack of slopes prevents skiers from traversing the area beforehand and helps with measuring the lines needed to create the drawing.

He starts off by measuring the distance he has to be from the center by using a compass and walking in a straight line towards a point in the distance, making curves based on relative position to other lines. Once the primary lines are made, he measures points along the way using pace counting and joins secondary lines by connecting the points. The lines are generally walked three times to solidify them before filling in the shaded areas. The results are mesmerizing.

He has since expanded to sand art, using the same techniques that gained him fame in ski resorts and national parks on the sandy shores. Unfortunately, tidal patterns, seaweed, and beach debris make it slightly harder to achieve pristine conditions, but he has managed to create some impressive works of art nonetheless.

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Plucky Kalimba Plays Itself

January 11, 2020 by Kristina Panos 23 Comments

[Gurpreet] fell in love with the peaceful, floaty theme from the Avatar series and bought a kalimba so he could hear it resonate through his fingertips. He soon realized that although it’s nice to play the kalimba, it would be a lot cooler if it played itself. Then he could relax and enjoy the music without wearing out his thumbs.

After doing a bit of experimentation with printing tine-plucking extensions for the servo horns, [Gurpreet] decided to start the design process by mounting the servos on a printed base. The servos are slotted into place by their mounting tabs and secured with hot glue. We think this was a good choice — it’s functional and it looks cool, like a heat sink.

[Gurpreet]’s future plans include more servos to pluck the rest of the tines, and figuring out how feed it MIDI and play it real time. For the demo after the break, [Gurpreet] says he lapel mic’d the kalimba from the back and cut out the servo noise with Audacity, but ultimately wants to figure out how to quiet them directly. He’s going to try lubing the gears and making a sound-dampening enclosure with foam, but if you have any other ideas, let him know down below.

We don’t see too many kalimba projects around here, but here’s one connected to a Teensy-based looper.

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Printed Separator Separates Printed Pages

January 11, 2020 by Kristina Panos 17 Comments

We all know people trapped in aging bodies who can’t do all the things they used to do. It’s easy to accept that you may never move small furniture around by yourself again, but losing the ability to do something as simple as separating the pages of your newspaper to keep reading it is an end to enjoyment.

When [Randomcitizen4] visited his grandma over the holidays, she mentioned having trouble with this, among other things. He fired up his printer and got to work designing a device to help her get back to the funny pages. This simple gripper mechanism uses rubber bands for tension and flexible filament to get a firm grip on the paper. The jaws default to the open position so they’re ready to grab some newsprint, and a light squeeze of the handles slides the top page back from the stack, creating a gap for Grandma’s fingers. You can see a demo ~~on page 32~~ after the break.

Although the device does work on some books and magazines, he’d like to improve the design of the grips to make the device more universally useful. [Randomcitizen4] says he tried a few things already, but we wonder if a more complex surface pattern might do the trick — maybe less like fins and more like a tire tread pattern. All the STLs are available if you want to give it a go.

If Grandma’s newspaper ever goes out of print, she should still be able to read it on a tablet or an e-reader. Then maybe [Randomcitizen4] can build some kind of remote-controlled page turner for her.

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An Arduino-Based Flute Playing Machine

January 11, 2020 by Sharon Lin 9 Comments

It’s one thing to be able to transcribe music from a flute, and it’s another to be able to make a flute play pre-written music. The latter is what [Abhilash Patel] decided to pursue in the flute player machine, an Arduino-based project that uses an air flow mechanism and PVC pipes to control the notes produced by a makeshift flute. It’s currently able to play 17 notes, just over two octaves starting from the lowest frequency of E.

In order to play songs, the tones have to either be directly coded and uploaded to the Arduino, composed with a random note generator, or detected from a microphone. While a real flute can be used for the machine, [Patel] uses a PVC flute, constructed with some knowledge of flute playing.

The resonant frequency is based on the effective length, hole sizes, and pipe diameter, so it is fairly difficult to correctly tune a homemade flute. Nevertheless, calculating the length as c/2f where c is the speed of sound (~345 m/s) and f is the frequency of the note can help with identifying the location of the holes. [Patel] cut the PVC pipe and sealed off one end, drilling a blowing hole at 1.5 x the pipe diameter. After playing the flute, the end of the pipe was filled until the frequency exactly matched the desired note.

The hole covering uses cuttings of pipe attached to a cable connecting to a servo. The motors are isolated inside a box to keep the wires clear and area all able to be powered with 5 V. As for the software, the code is primarily used to control when the fan is blowing and which holes are covered to produce a note.

Listen to the flute play “My Heart Will Go On” from Titanic in the video below. Now the next step might just be making the flute playing machine automatically play sheet music – imagine the possibilities!

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Stacks Of Spring Washers Power The Drawbar On This CNC Mill Conversion

January 11, 2020 by Dan Maloney 25 Comments

With Tormach and Haas capturing a lot of the entry-level professional market for CNC machines, we don’t see too many CNC conversions of manual mills anymore. And so this power drawbar conversion for a Precision Matthews mill really caught our eye.

What’s that, you say? Didn’t [Physics Anonymous] already build a power drawbar for a mill? They did, and it was quite successful. But that was based on a pneumatic impact wrench, and while it worked fine on a manual mill, the same approach would be a bit slow and cumbersome on a CNC mill. For this build, they chose a completely different approach to providing the necessary upward force to draw the collet into the collet holder and clamp down on the tool: springs. Specifically, Belleville spring washers, which are shaped like shallow cups and can exert tremendous axial force over a very short distance.

[PA] calculated that they’d need to exert 2,700 pounds (12,000 Newtons) of force over a length of a couple of inches, which seems outside the Belleville washer’s specs. Luckily, the springs can be stacked, either nested together in “series” to increase the load force, or alternating in “parallel” to apply the rated force over a greater distance. To compress their stack, they used a nifty multi-stage pneumatic cylinder to squash down the springs and release the collet. They also had to come up with a mechanism to engage to machine’s spindle only when a tool change is called for. The video below details the design and shows the build; skip to 11:32 to see the drawbar in action.

We’re looking forward to the rest of [Physics Anonymous]’ conversion. They’re no strangers to modifying off-the-shelf machines to do their bidding, after all – witness their improvements to an SLA printer.

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Building A Real Wooden Table Saw

January 11, 2020 by Sharon Lin 43 Comments

A table saw is one of those tools that aren’t strictly necessary to have, but immensely helpful if you do happen to have one around. The folks at [I Build It] have made a three part series that features a homemade table saw build, so you can finally get around to adding one to your makerspace.

The build uses a real table saw arbor and is made from Baltic birch plywood and solid wood, with some plastic sheets for the trunnions and top. The blade is housed in a blade lift made out wooden panels with a pivot point and slot for the lift mechanism. Bearings allow the blade the freedom of movement, while a curved cutout allows it to stay flat against the wall of the slot while the blade lift mechanism moves.

Meanwhile a reused motor from a previous table saw is dusted, cleaned, and rewired to run in reverse. While most table saws only need two trunnions, a third is used for supporting the motor, since it has to move with the lift and tilt. Once the lift/tilt mechanism is complete, the frame for the table saw is more straightforward, with many steps involving clamping, measuring, cutting, fitting, and painting the assembly. For the final few steps, a switched is mounted outside the table saw in a small box that connected to the power supply and motor, as well as a shop vac for handling dust collection from the saw. While the enclosure isn’t a metal box, as long as the connections are secured properly the wires shouldn’t come loose.

If you want to see other examples of homemade table saws, check out this teeny tiny saw and this kid-friendly table saw build.

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