Building A LEGO Pneumatic Engine

Pneumatic engines aren’t something we use every day, but they’re compelling things to see working in practice. [Nico71] built an eye-catching example out of LEGO Technic, and it’s remarkably fully-featured.

The build relies on a single pneumatic cylinder driving a flywheel. Flow to the cylinder is determined by camshaft-controlled valves. The valves themselves are custom-built, composed of hose loops that are kinked to shut off flow. In addition to the basic operating components, the engine also features a throttle valve which uses the same kinked-hose principle. The main control valves are installed in a housing that can be rotated relative to the engine’s frame to vary the timing of the valves relative to the flywheel’s rotation. A gear system allows fine adjustment of the timing. The throttle and timing controls are accessible on a tidy control panel complete with a idle-adjust mechanism.

Those wishing to build one themselves can rejoice, for [Nico71] provides instructions for a small fee. We’ve seen other air engines before, too, often of the 3D-printed variety.

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Logic Via DNA

We often say you can make logic gates out of nearly anything. [Steve Mould] would agree as he just finished playing naughts and crosses (tic tac toe if you are an American) with a tray full of DNA. You can see the resulting game and how it works in the video below.

The use of DNA isn’t really significant as it simply implements a logic equation for each of the nine cells. So, for example, each cell is taken by an X (the DNA) only when certain other squares have been taken by O or not taken by O. So you essentially create an AND/OR gate using the state of each cell and its inverse.

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Hackaday supercon badge PCB showing illuminated activity lights after being loaded with a punch card

Supercon Badge Reads A “Punch” Card

This year’s Hackaday Supercon, the first since 2019 thanks to the pandemic, was a very similar affair to those of the past. Almost every hardware-orientated hacker event has its own custom electronic badge, and Supercon was no different. This year’s badge is a simulation platform for a hypothetical 4-bit CPU created by our own [Voja Antonic], and presented a real challenge for some of the attendees who had never touched machine code during their formative years. The challenge set was to come up with the most interesting hack for the badge, so collaborators [Ben Hencke] and [Zach Fredin] set about nailing the ‘expandr’ category of the competition with their optical punched card reader bolt-on.

Peripheral connectivity is somewhat limited. The idea was to build a bolt-on board with its own local processing — using a PixelBlaze board [Ben] brought along — to handle all the scanning details. Then, once the program on the card was read, dump the whole thing over to the badge CPU via its serial interface. Without access to theirPrinted paper faux punch card showing read LEDs and an array of set and reset bits of the encoding usual facilities back home, [Ben] and [Zach] obviously had to improvise with whatever they had with them, and whatever could be scrounged off other badges or other hardware lying around.

One big issue was that most people don’t usually carry photodiodes with them, but luckily they remembered that an LED can be used as a photodiode when reverse-biased appropriately. Feeding the signal developed over a one Meg resistance, into a transconductance amplifier courtesy of a donated LM358 there was enough variation for the STM32 ADC to reliably detect the difference between unfilled and filled check-boxes on the filled-in program cards.

The CPU required 12-bit opcodes, which obviously implies 12 photodiodes and 12 LEDs to read each word. The PixelBlaze board does not have this many analog inputs. A simple trick was instead of having discrete inputs, all 12 photodiodes were wired in parallel and fed into a single input amplifier. To differentiate the different bits, the illumination LEDs instead were charlieplexed, thus delivering the individual bits as a sequence of values into the ADC, for subsequent de-serialising. The demonstration video shows that it works, with a program loaded from a card and kicked into operation manually. Such fun!

Punch cards usually have a hole through them and can be read mechanically, and are a great way to configure testers like this interesting vacuum valve tester we covered a short while back.

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Amphibious Dragster Drives On Water

Dragsters are typically about peak performance on a tarmac drag strip. [Engineering After Hours] took a different tack, though, building a radio-controlled amphibious dragster intended to cross small bodies of water.

The build is based on a Traxxas Raptor RC car. However, it’s been heavily reworked from a pickup-like design to become a dragster with a motor mounted in the rear. It’s also been fitted with a foam underbody to allow it to float when stationary. The rear tires have been replaced with 3D-printed versions with large paddles, which provide propulsion in the water.

Initial tests showed the car struggled to make progress in the water, as the paddle tires tended to drag the rear end deeper under water. The tiny dragster tires up front didn’t help it steer, in water either. Large foam discs were added to the front tires to enable them to act as better rudders.

Fitted with its water tires and foam floatation aids, the car can only drive slowly on land, but [Engineering After Hours] points out this is enough to call it amphibious. It does a better job at skittering around on water, and it was able to cross a local pond at low speed.

We’ve seen some other creative techniques for making amphibious vehicles, like these crazy star-shaped wheels. Video after the break.

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Simple Plywood Lamp Has Neat Hidden Switch

Shortly after the development of the electric light came the light switch, presumably. Of course, obvious switches are old-hat, and this neat lamp build from [Giovanni Aggiustatutto] goes with a design that’s altogether more coy.

The lamp itself is a minimalist modern design, with a cube-like body constructed out of plywood. It was easily constructed by simply stacking up several layers of plywood to create the form. Inside the housing, a bulb holder was installed hooked up to a Shelly smart relay to enable the lamp to be used as a smart device. The relay also has a switch input for direct control. This is hooked up to a micro-switch that is tucked into the base. Tilting the lamp to one side triggers the micro-switch and turns the lamp on and off as desired.

Overall, it’s a simple build that is elegant and functional. It eschews switches on the lamp cord and other fussy details, while featuring both smart control and a direct switch as well. We’ve featured some other great lamps before, too. Video after the break.

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Madness Or Genius? FDM Printing With Resin

We aren’t sure what made him think of it, but [Proper Printing] decided to make an FDM printer lay down resin instead of filament. Why? We still aren’t sure, but we admire the effort nonetheless. In principle, extruding resin shouldn’t be much different than other liquid things you print like icing or concrete. Then you’d need to UV-cure the viscous liquid quickly. In fact, they wound up making up a paste-like resin using several chemicals and a filler.

Armed with the paste, it would seem like the big obstacles would be over. Instead of part cooling fans, the printer now has two laser heads focused on the print area. Printing in vase mode avoids some problems, but the first few attempts were not very successful.

With a bit of perseverance, the setup did work — for a while. More fine tuning got acceptable results. However, he eventually changed the filler material and got a passable Benchy to print. Nothing to be proud of, but recognizable. Honestly, we were surprised that the laser’s didn’t cure the material still inside the nozzle and cause terrible clogs.

Why put this much effort into doing this? We have no idea. Should you try it? Probably not. Of course, being able to print a paste has its own value. Perhaps delivering glue or solder paste, for example. But you generally won’t need to make tall prints with that kind of material. Then again, we’ve never been opposed to doing something “just because.”

After all, why make a musical instrument out of a Game Boy? Why make a modem with tin cans? You might as well extrude resin.

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TV Repair By Mail

I don’t think there was ever a correspondence school called the “Close Cover Before Striking School” but since book matches — which used to be a thing when most people smoked — always had that text on them anyway perhaps there should have been. There was a time when electronic magazines, billboards, and even book matches were constantly bombarding us with ads to have a career in electronics. Or computers. Or TV repair. So while we think of distance learning as a new idea, really it is just the evolution of these old correspondence schools which date back quite some time.

How far exactly? Hard to say. There’s evidence of some distance learning going back as far as 1728. In 1837, there was a correspondence course to learn shorthand. By 1858, the University of London started its external program for correspondence work and the University of Chicago had a home study division in 1892.  Radio was an early choice of topic, too. In the United States, the United Wireless Telegraph company started a training school — later the Marconi Institute — in 1909. However, it is doubtful that there was any correspondence training going on there until much later.

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