72 Tranducers For Acoustic Levitation

November 28, 2018 by 9 Comments

Levitation has a way of arousing curiousity and wonder wherever it appears. There’s a multitude of ways to do it, each with their own strengths and weaknesses and ideal use cases. [Julius Kramer] tried his hand at acoustic levitation, and decided to share his build.

The build relies on an astounding number of ultrasonic transducers – 72, in fact. The device operates at 40 kHz to be well above the human range of hearing. 36 each are placed in the top and bottom shells of the device’s 3D printed chassis. Through careful construction, the transducers are placed an integer multiple of half the wavelength apart. This allows the device to create a standing wave, with several low-energy nodes in which small objects can be levitated. In this case, [Julius] uses small scraps of styrofoam, but notes that water droplets can also be used if one is careful to avoid spilling any on the electronics.

The transducers are energised with a square wave generated by an Arduino Nano. This allows the possibility of the frequency and phase of the wave to be altered, which can help tune the device and allow some movement in the vertical axis. Unfortunately, movement in the other axes isn’t possible as the transducers appear to be connected in parallel. However, this could be a good upgrade in a later revision.

This project shows that a device relying on incredibly precise measurement and control can now be constructed at home with a 3D printer and some off the shelf electronics.

Now that you’ve whet your whistle, perhaps you’d like to tackle laser levitation?

[Thanks to Baldpower for the tip!]

 

A Daylight-Readable Bar Graph Display In The 70s Wasn’t Cheap

November 11, 2018 by 4 Comments
The driver board with display attached; the row of lamps is visible on the right hand side.

LEDs weren’t always an easy solution to displays and indicators. The fine folks at [Industrial Alchemy] shared pictures of a device that shows what kind of effort and cost went into making a high brightness bar graph display in the 70s, back when LEDs were both expensive and not particularly bright. There are no strange materials or methods involved in making the display daylight-readable, but it’s a peek at how solving problems we take for granted today sometimes took a lot of expense and effort.

The display is a row of 28 small incandescent bulbs, mounted in a PCB and housed in a machined aluminum frame. Holes through which to view the bulbs are on both the top and front of the metal housing, which allows the unit to be mounted in different orientations. It was made as a swappable module, its 56 machined gold pins mate to sockets on the driver board. The driver board itself consists of 14 LM119 dual comparators, each of which controls two bulbs on the display.

An example of a Wamco minitron bar graph display. Each window contains an incandescent filament. [Source: industrialalchemy.org]
[Industrial Alchemy] believes that the display unit itself may have been a bit of a hack in its own way. Based on the pin spacing and dimensions of the driver board, they feel that it was probably designed to host a row of modular units known as the Wamco minitron bar graph display. An example is pictured here; they resembled DIP chips and could be stacked side-by-side to make a display of any length. Each window contained an incandescent filament in a reflective well, and each light could be individually controlled.

These minitron bar graph units could only be viewed from the top, and were apparently high in cost and low in availability. Getting around these limitations may have been worth creating this compatible unit despite the work involved.

Display technology has taken many different turns over the years, and you can see examples of many of them in one place in the Circus Clock, which tells the time with a different technology for each digit: a nixie, a numitron, a 7-segment thyratron tube, a VFD, an LED dot display, and a rear projection display.

Soviet-Era 7-Segment Display, Built Like A Tank

November 6, 2018 by 36 Comments

In a way, all 7-segment displays are alike; at least from the outside looking in. On the inside it can be quite another story, and that’s certainly the case with the construction of this Soviet-era 7-segment numerical display. From the outside it may look a bit sturdier than usual, but it’s still instantly recognizable for what it is. On the inside is an unusual mixture of incandescent bulbs and plastic light guides.

The black-coated blocks of plastic on the left (shown from the rear) act as light guides. The holes are for nesting the incandescent bulbs. Note the puzzle-like arrangement of the uniquely shaped pieces.

The rear of the display is a PCB with a vaguely hexagonal pattern of low-voltage incandescent bulbs, and each bulb mates to one segment of the display. The display segments themselves are solid blocks of plastic, one for each bulb, and each a separate piece. These are painted black, with the only paint-free areas being a thin segment at the top for the display, and a hole in the back for the mating bulb.

The result is that each plastic piece acts as a light guide, ensuring that a lit bulb on the PCB results in one of the seven thin segments on the face being lit as well. An interesting thing is that the black paint is the only thing preventing unwanted light from showing out the front, or leaking from one segment to another; usually some kind of baffle is used for this purpose in displays from this era.

More curiously, each plastic segment is a unique shape apparently unrelated to its function. We think this was probably done to ensure foolproof assembly; it forms a puzzle that can only fit together one way. The result is a compact and remarkably sturdy unit that shows how older and rugged tech isn’t necessarily bulky. Another example of small display tech from the Soviet era is this tiny 7-segment display of a completely different manufacture, which was usually used with an integrated bubble lens to magnify the minuscule display.

7 Segment Clockwork Display Made From Cardboard

October 31, 2018 by 25 Comments

We’ve seen a variety of oddball 7-segment displays in the past, but this one uses a new material: both for the display and the mechanical mechanism that drives it; cardboard. Yup, the whole thing is made from cardboard, wood and a few rubber bands. [The Q] shows how he put together in this nice video, starting from first principles that show how the segments are made: simple pieces of cardboard painted on one side with fluorescent paint. A piece of wood pushes the element out to blank it, and each element is connected to a cam wheel that pushes the wood in or out.

The really clever bit is that [The Q] mapped digits 0 – 9 onto a matrix for which of the 7 segments is “on” or “off”. He then used this information to create a stack of 7 cams on a central axle. As you rotate the axle, the cams turn, moving the wooding arms. The arms then cause the elements to flip as they count up through the digits. In essence, he engineered a physical decimal to 7 segment decoder, much like the electronic one inside the SN74LS47. The whole assembly is capped by a knob that indicates which digit is currently displayed. If mechanical displays like this are your thing, check out this one made from LEGO parts, or this awesome 3D printed creation.

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You’ll Flip For This 7404 IC Motherboard Fix

October 20, 2018 by 35 Comments

We often lament that the days of repairable electronics are long gone. It used to be you’d get schematics for a piece of gear, and you could just as easily crack it open and fix something as the local repairman — assuming you had the knowledge and tools. But today, everything is built to be thrown away when something goes wrong, and you might as well check at the end of a rainbow if you’re searching for a circuit diagram for a new piece of consumer electronics.

But [Robson] writes in with an interesting story that gives us hope that the “old ways” aren’t gone completely, though they’ve certainly changed for the 21st century. After blowing out his laptop’s USB ports when he connected a suspect circuit, he was desperate for a fix that would fit his student budget (in other words, nearly zero). Only problem was that he had no experience fixing computers. Oh, and it takes months for his online purchases to reach him in Brazil. Off to a rocky start.

His first bit of luck came with the discovery he could purchase schematics for his laptop online. Now, we can’t vouch for the site he used (it sure isn’t direct from Dell), but for under $5 USD [Robson] apparently got complete and accurate schematics that let him figure out what part was blown on the board without even having to open up the computer. All he had to do was order a replacement IC (SY6288DAAC), and solder it on. It took two months for the parts to arrive, and had to do it with an iron instead of a hot air station, but in the end, he got the part installed.

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Teardown: D50761 Aircraft Quick Access Recorder

October 15, 2018 by 37 Comments

Everyone’s heard of the “black box”. Officially known as the Flight Data Recorder (FDR), it’s a mandatory piece of equipment on commercial aircraft. The FDR is instrumental in investigating incidents or crashes, and is specifically designed to survive should the aircraft be destroyed. The search for the so-called “black box” often dominates the news cycle after the loss of a commercial aircraft; as finding it will almost certainly be necessary to determine the true cause of the accident. What you probably haven’t heard of is a Quick Access Recorder (QAR).

While it’s the best known, the FDR is not the only type of recording device used in aviation. The QAR could be thought of as the non-emergency alternative to the FDR. While retrieving data from the FDR usually means the worst has happened, the QAR is specifically designed to facilitate easy and regular access to flight data for research and maintenance purposes. Its data is stored on removable media and since the QAR is not expected to survive the loss of the aircraft it isn’t physically hardened. In fact, modern aircraft often use consumer-grade technology such as Compact Flash cards and USB flash drives as storage media in their QAR.

Through the wonders of eBay, I recently acquired a vintage Penny & Giles D50761 Quick Access Recorder. This was pulled out of an aircraft which had been in service with the now defunct airline, Air Toulouse International. Let’s crack open this relatively obscure piece of equipment and see just what goes into the hardware that airlines trust to help ensure their multi-million dollar aircraft are operating in peak condition.

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3D Printed Catamaran Eats Benchy’s Lunch

October 10, 2018 by 18 Comments

If we’ve learned anything, it’s that 3D printers are exceptionally well suited to printing little boats. According to the Internet, 3D printers are at their best when pumping out cute PLA boats in all the colors of the rainbow; perfect for collecting dust on a shelf somewhere. Ask not what your Benchy can do for you, ask what you can do your Benchy.

But this 3D printed boat isn’t so cute and cuddly. In fact, it’s an absolute beast. Built by [Wayne Andrews], this nearly meter long 3D printed racing catamaran looks more Batman than Popeye. In the video after the break you can see a recent run of the boat on the lake, and we think you’ll agree it definitely has the performance to back up its fierce looks.

Impressively, the hull isn’t printed out of some expensive high-tech filament. It’s the cheapest PLA [Wayne] could get his hands on, and glued together with nothing more exotic than Loctite Super Glue Gel. The secret is the internal “West System” fiberglass cloth and resin work, which is the same stuff used on real boat hulls. It took about 5 days of continuous printing to produce all the pieces needed to assemble the hull, which is a scaled up version of a design by [Thomas Simon].

The internal layout is about what you’d expect in a fast RC boat. It’s running on a 1900 Kv motor powered by dual 6S batteries and a water cooled 180 A Seaking ESC which provides 5 BHP to the Octura x452 propeller. On the business end of his boat, [Wayne] used a commercial aluminum strut and rudder unit. Running gear printed out of something strong like nylon would be an interesting experiment, but perhaps a tall order for this particular motor.

We recently covered a 3D printed jet boat that’s no slouch either, but if you’re looking for a more relaxed ride you could always 3D print a FPV lifeboat.

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