Reverse Engineering A Two-Wire Intercom

October 27, 2019 by 13 Comments

There was a time when an intercom was simply a pair of boxes with speakers joined by a couple of wires, with an audio amplifier somewhere in the mix. But intercoms have like everything else joined the digital age, so those two wires now carry a load of other functionality as digital signalling. [Aaron Christophel] installs these devices for a living, and has posted a fascinating reverse engineering video that we’ve also placed below the break.

Power for the system is present as a constant 24V DC, and the audio is still an old-fashioned analogue signal that we’ll all be familiar with. On that 24V DC though are imposed a series of pulse trains to trigger the different alarms and other functions, and he describes extracting these with an oscilloscope before showing us the circuitry he’s used to send and receive pulses with an Arduino. The bulk of the video is then devoted to the software on the Arduino, which you can also find in a GitHub repository.

The result is an interesting primer for anyone who fancies a bit of serial detective work, even if they don’t have a intercom to hand.

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Restoring A Rusty Rebar Cutter

October 27, 2019 by 16 Comments

We’ve all probably come across hunks of junk that used to be tools, long-neglected and chemically welded into a useless mass of solid rust. Such items are available for a pittance at the local flea market, or more likely found in an old barn or rotting on a junk pile. They appear to be far beyond salvage, but with the proper application of elbow grease and penetrating lubricants, even a nasty old seized-up rebar cutter can live again.

We honestly almost passed up on the video below when it came across our feed. After all, a rebar cutter is a dead-simple device, and half the fun of restoration videos like those made by [my mechanics] is seeing all the parts removed, restored, and replaced. But it ended up being far more interesting than we expected, and far more challenging too.

The cutter was missing its original handle and looked for all the world like it had been cast from a solid piece of iron oxide. [my mechanics] was able to get the main pivot bolts free with a combination of leverage, liberal application of penetrating oil, drilling, and the gentle persuasion of a hydraulic press.

These efforts proved destructive to both bolts, so new ones were made on the lathe, as were a number of other parts beyond saving. New cutters were fabricated from tool steel and a new handle was built; before anyone comments on anyone’s welding skills, please read [Jenny]’s recent article on the subject.

The finished product is strikingly dissimilar to the starting lump of oxidized junk, so there’s going to to be some debate in calling this a “restoration” in the classical sense. The end result of a [my mechanics] video is invariably a tool or piece of gear that looks far better than it did the day it was made, and any one of them would get a place of honor on our shelf. That said, he’d probably be swiftly shown the door if he worked at the Smithsonian.

Whatever you want to call these sort of videos, there are tons of them out there. We’ve featured a few examples of the genre, from the loving rehabilitation of classic Matchbox cars to rebuilding an antique saw set. They’re enough to make us start trolling garage sales. Or scrap yards.

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Turntable Spins Color And Sound Together

October 27, 2019 by 5 Comments

If you can’t grow your own synesthesia, buying electronics to do it for you is fine. Such is the case with the CHROMATIC by [Xavier Gazon], an artist who turns all kinds of electronics into circuit-bent musical art pieces. His project turns an old Philips Music 5120 turntable into a colorful MIDI sequencer, inspired by older 20th century instruments such as the Optophonic Piano and the Luminaphone.

The CHROMATIC uses colored pucks placed on a converted turntable to perform a looping sequence of chords in a given musical scale, generating MIDI data as output. Where its inspirations used primitive optics as their medium, this project employs a Teensy microcontroller and two modern optical sensors to do the work. One of these is a simple infrared sensor which tracks a white spot on the edge of the turntable, generating a MIDI clock signal to keep everything quantized and in sync. The other is a color sensor mounted on the tone arm, which can tell what color it sees and the height of the arm from the turntable.

While the instrument is still in beta testing phase details on how notes are generated aren’t yet given, though the general idea is that they are dictated by the color the tone arm sees and its position above the platter. Moving the tone arm changes which pucks it tracks, and the speed of the turntable can also be adjusted, changing how the melody sounds.​

The CHROMATIC is a very interesting project, but it’s not the first optical-based turntable hack we’ve seen here. We’ve also seen a much weirder use for a color sensor, too. Check out the video of this one in action after the break.

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An All-Electric Plane Takes To The Skies

October 27, 2019 by 89 Comments

With climate protests and airline strikes occurring around the world, there is more awareness than ever before for the necessity of environmental sustainability. More importantly, there is more discussion around the immense carbon footprint left by the airline industry, perhaps one of the largest contributors to climate change worldwide.

The Slovenian-based Pipistrel ALPHA Electro is one of the leading electric planes today, with bragging rights as the world’s first mass-produced electric aircraft. While NASA may have announced their X-57 Maxwell, the plane is still undergoing testing for its first planned flight in 2020. The ALPHA Electro, marketed as a trainer plane for flight students and recreational flyers, features a 34’6″ wingspan and low running costs.

The two-person flyer is equipped with a 60 kW electric motor, with a cruising speed of about 157 km/hr. A 21 kW battery provides the plane with enough energy for a 55 minute flight, with a half hour reserve, and takes about an hour to charge back up. An additional perk of flying an electric plane is the low noise and zero CO2 emissions, which allows the flights to take place near large cities with exhaust and noise emission standards.

With airplanes, a majority of the fuel is used for takeoff and landing, making short haul flights particularly troublesome – compare 107 lbs CO2 flying from New York to Boston versus 62 lbs CO2 driving. While refraining from frequent flights is still the best idea for reducing your carbon footprint, we’re hopefully headed towards more environmentally-friendly options for air travel.

Check out the ALPHA Electro’s teaser video below.

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Horse Racing Game Hits Trifecta Of Fun, Skill, And Competition

October 26, 2019 by 4 Comments

Out in the neon-painted desert of Las Vegas, if you know where to look, you can find an old, 1980s electromechanical horse racing game called Sigma Derby. In this group game, you and several drunk strangers sit around a machine the size of a pool table and bet on tiny horses at 25 cents a throw. There is no skill involved, it’s all chance. This is not that game.

[Alex Kov]’s electromechanical horse racing game is a unicorn compared to Sigma Derby, or at least a zebra. This game takes patience, skill, and cunning. And unlike Sigma Derby, you can easily replicate it at home with a few shakes of the old junk bin. You just need a couple of motors, transistors, electrolytic caps, and some passives.

The idea is simple — advance horse, be first, win prizes — but it’s not that easy. While the switch is unpressed, the circuit charges up a capacitor. Press it and the horse noses forward, draining the cap. There is never enough chooch in the cap to reach the finish line, so the real game is in building up more juice than the other guy, and then staying ahead or overtaking him with the next spurt. Place your bets and catch the action after the break.

A scoreboard would be a great addition to this game. If you want to keep it electromechanical, we have some tote board inspiration for you.

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It’s A TV-Scope-Guitar Amplifier!

October 26, 2019 by 8 Comments

Guitar amplifiers are a frequent project, and despite being little more than a simple audio amplifier on paper, they conceal a surprising quantity of variables in search of a particular sound. We’ve seen a lot of them, but never one quite like [Nate Croson]’s CRT TV guitar amplifier. The LM386 doesn’t just drive the speaker, he’s also using it to turn the TV into a crude oscilloscope to form a visualisation of the sound.

The video showing this feat is below the break, and it puts us in a quandary due to being short on technical information. He’s driving the horizontal coils with the TV’s 50 Hz sawtooth field timebase, and the vertical ones with the audio from the LM386. We aren’t sure whether he’s rotated the yoke or whether the connections have been swapped, but the result is certainly impressive.

So given that there’s not quite as much technical detail as we’d like, why has this project captured our interest? Because it serves as a reminder that a CRT TV is a bit more than a useless anachronism, it’s a complex analogue device with significant and unique hacking potential. The older ones in particular provide endless possibilities for modification and circuit bending, and make for a fascinating analogue playground at a very agreeable price. It’s worth pointing out however that some of the voltages involved can make them a hazardous prospect for the unwary hacker. If you’re interested though, take a look at our dive into an older model.

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LEGO And Minecraft Team Up For Custom Gaming PC Case

October 26, 2019 by 4 Comments

There are probably few parents who haven’t watched their kids sitting on the floor, afloat on a sea of LEGO pieces and busily creating, and thought, “If only they could make a living at that.” But time goes on and kids grow up, and parents soon sing the same refrain as the kids sit transfixed by the virtual equivalent of LEGO: Minecraft.

Finding a way to monetize either LEGO or Minecraft is a bit difficult for the young enthusiast; combining both obsessions into a paying proposition would be a dream come true. [Mike Schropp] did it, and this Minecraft-themed LEGO computer case was the result. Intel wanted a LEGO case for their new NUC mini-PC motherboard, and as a sponsor of the Minefaire event, the case needed to be Minecraft themed.

[Mike] chose the block that any Enderman would choose: the basic grass block. Each of the ten cases he made for the show had about 1000 of the smallest LEGO pieces available, to recreate the texture of the grass block in all its faux 8-bit glory. The 4″ x 4″ (10cm x 10cm) 8th Gen NUC board was a great fit for the case, which included slots for ventilation and SD card access, plus pop-out covers to access the board’s ports. It’s not exactly a screamer, but playing Minecraft on a grass block made from LEGO bricks is probably worth the performance hit.

We’ve seen [Mike]’s work a time or two here, most recently with a full-scale LEGO rack-mount server. Our hats off to him for another fun and creative build, and for proving that you’re never too old to LEGO. Or Minecraft.