Belt The Quarantine Blues Into A Homemade Mic

April 12, 2020 by Kristina Panos 15 Comments

If there’s any psychological good to be gleaned from quarantine, it’s that people are using the time to finish old projects while starting plenty of new ones. If you’re running out of ideas, or just want to feel better by doing some in-house recycling, dump out that bin and make a simple microphone.

All you need is some PETE #1 plastic, a piezo disk, and the right kind of tin can. The plastic gets heat-fused to the rolled edge of the can, and since it gets stretched and shrunk in the process, it forms a tight membrane that doubles as a percussion instrument.

You do your shouting into the other end, and your sound waves vibrate the membrane. The piezo picks up the vibrations and sends them to a 1/4″ jack so you can plug it into an amp.

Even if you are somehow sidestepping the blues, you can always use this to yell at people who threaten to get too close to you. This fun project is about as open as it gets, but we’re sure that you can think of ways around using a piezo disk. Let us know in the comments after you check out [Ham-made]’s music video.

We like [Ham-made]’s method for cutting down the juice jug without cutting into yourself. Just clamp a razor blade into your vise and move jug against it. Reminds us of another way to easily reuse plastic soda bottles by making them into rope.

Continue reading “Belt The Quarantine Blues Into A Homemade Mic” →

Impressive Lever-Press Espresso Machine Has Finesse

April 8, 2020 by Kristina Panos 8 Comments

Some people will do anything for a good cup of coffee, and we don’t blame them one bit — we’ve been known to pack up all our brewing equipment for road trips to avoid being stuck with whatever is waiting in the hotel room.

While this stylish lever-based industrial coffee machine made by [exthemius] doesn’t exactly make textbook espresso, it’s pretty darn close. Think of it like an Aeropress on steroids, or more appropriately, bulletproof coffee. As you can see in the demo after the break, the resulting coffee-spresso hybrid brew looks quite tasty.

Here’s how it works: finely-ground beans go in a pressurized portafilter basket that was scavenged from an entry-level prosumer espresso machine. Pour boiling water into the top of the cylinder, and pull the giant lever down slowly to force it through the portafilter. Presto, you’re in thin, brown flavor town.

We love the piston-esque plunger that [exthemius] made by layering washers and rubber gaskets up like a tiramisu. Although there are no plans laid out, there’s probably enough info in the reddit thread to recreate it.

If you ever do find yourself stuck with hotel house brand, soak it overnight to make it much more palatable.

Continue reading “Impressive Lever-Press Espresso Machine Has Finesse” →

Charging Pad Flips For Solar Power

April 3, 2020 by Lewin Day 10 Comments

Charging pads are now a common, popular way to charge small devices. They have the benefit of reducing wear on connectors and being easier to use. [bcschmi6] decided to build a solar powered charging pad, which should come in handy when out and about.

The build uses a 3 W square solar panel, hooked up to an Adafruit solar charging board. This charges a pair of 18650 lithium batteries. The batteries only put out a maximum of 4.2 V, so they’re hooked up to a boost converter to get the output a little higher, up to 5.2 V. The output of the boost converter is then hooked up to a charging pad harvested from an Anker charger, and it’s all wrapped up in a tidy 3D printed frame.

We imagine the device would be great for camping. It could be left charging in the sun during the day, before being flipped over and used as a charging pad at night. It would be easy to build a bigger version for charging several phones at once, too. If you want to build your own charging coils, that’s a thing, too. And if you’ve got your own solar project cooking up as we head into summer, be sure to let us know!

A 1950s Ampex Tape Recorder Microphone Preamplifier Restoration

March 28, 2020 by Jenny List 12 Comments

So often when we read of a modification on a classic piece of tube electronics we prepare to wince, as such work often results in senseless butchery of a well-preserved survivor. With [Frank Olson]’s work on a 1958 Ampex 601 tape recorder though we were pleasantly surprised, because while he makes a modification to allow its use as a stand-alone microphone preamplifier he also performs an extremely sympathetic upgrade to modern components and retains it in substantially the form it left the Ampex factory.

The video below the break is a satisfying wallow in pre-PCB-era construction for any of the generation who cut their teeth on tube, chassis, and tag strip electronics. We can almost smell the phenolic as he carefully removes time-expired capacitors and fits modern replacements complete with period features such as sheathing over their leads. The larger multiway can electrolytics are left in the chassis, with their modern miniaturised equivalents nestling underneath them out of sight. We all know that electronic components have become a lot smaller over the decades, but it’s still a bit of a shock to see just how tiny even a high voltage electrolytic has become.

The Ampex would have been a very high quality tape recorder when new, and while this one has a problem with its mechanism it’s that quality that makes it easier for him to do this work in 2020. There’s every chance that this one could be returned to service as a tape recorder if someone was of a mind to fix it, and meanwhile it will give Frank excellent service as a high quality pre-amp. This is how resto-mods should be done!

Ampex are very much still in existence making digital storage products, but back in the 1950s they were at the forefront of analogue magnetic tape technology. We’ve written in the past about how Bing Crosby had a hand in the development of high quality tape recorders, and also about Ampex’s part in the gestation of the video recorder.

Continue reading “A 1950s Ampex Tape Recorder Microphone Preamplifier Restoration” →

Whirling Shutters On This Field Mill Measure Electrostatic Charges At Distance

March 26, 2020 by Dan Maloney 34 Comments

Hardly a person hasn’t experienced the sudden, sharp discharge of static electricity, especially on a crisp winter’s day. It usually requires a touch, though, the classic example being a spark from finger to doorknob after scuffing across the carpet. But how would one measure the electrostatic charge of an object without touching it? Something like this field mill, which is capable of measuring electrostatic charge over a range of several meters, will do the trick.

We confess to not having heard of field mills before, and found [Leo Fernekes]’ video documenting his build to be very instructive. Field mills have applications in meteorology, being used to measure the electrostatic state of the atmosphere from the ground. They’ve also played a role in many a scrubbing of rocket launches, to prevent the missile from getting zapped during launch.

[Leo]’s mill works much like the commercial units: a grounded shutter rotates in front of two disc-shaped electrodes, modulating the capacitance of the system relative to the outside world. The two electrodes are fed into a series of transimpedance amplifiers, which boost the AC signal coming from them. A Hall sensor on the shutter allows sampling of the signal to be synchronized to the rotation of the shutter; this not only generates the interrupts needed to sample the sine wave output of the amplifier at its peaks and troughs, but it also measures whether the electrostatic field is positive or negative. Check out the video below for a great explanation and a good looking build with a junk-bin vibe to it.

Meteorological uses aside, we’d love to see this turned toward any of the dozens of Tesla coil builds we’ve seen. From the tiny to the absurd, this field mill should be able to easily measure any Tesla coil’s output with ease.

Continue reading “Whirling Shutters On This Field Mill Measure Electrostatic Charges At Distance” →

Ingenious Hacks That Brought The Original Prince Of Persia To Life

March 23, 2020 by Roger Cheng 6 Comments

For many 8-bit computing veterans, the original Prince of Persia game was our first exposure to fluid life-like animation on screen. This groundbreaking technical achievement earned the game’s place in nostalgia and history. Ars Technica invited its original creator [Jordan Mechner] to sit in front of a camera and talk through many technical and game design challenges he had to solve. (Video embedded below. Bonus: correct pronunciation of Karateka directly from the creator’s mouth.)

Enjoy the journey back in time as [Jordan] broke down the convoluted process behind Prince of Persia‘s rotoscope animation. Starting with VCR footage, to film negatives, to tracing out with black markers and white correction fluid to generate a high contrast reference suitable for the (then) state-of-the-art digitizer. But generating those frames was just the beginning! They consumed majority of an Apple II’s memory, thus fighting memory constraints was a persistent headache. Fortunately for us, that limitation also motivated memorable elements such as our “Shadow Man” alter ego.

This Prince of Persia feature is the latest episode of Ars Technica’s “War Stories” series, inviting people behind notable games to talk about their work behind the scenes. The creators of Myst put a lot of effort into minimizing the impact of CD-ROM seek times, an entirely theoretical endeavour as they had no CD burner for verification. The creators of Crash Bandicoot paged in game content from CD in 64kb chunks as a player progressed, allowing creation of levels too large to fit in a PlayStation’s memory all at once. Read over these and other short synopsis of episodes so far or go straight to their YouTube playlist.

If this talk of wrangling bits with 6502 assembly code has whet your appetite for more, the source code for Prince of Persia is available for digging into. Don’t worry if you have long since lost track of your Apple II (or never had one) as the code can run in an emulator.

Continue reading “Ingenious Hacks That Brought The Original Prince Of Persia To Life” →

Classic Macintosh Gets An IPad Infusion

March 23, 2020 by Tom Nardi 19 Comments

We know the classic Mac fans in the audience won’t be happy about this one, but the final results are simply too clean to ignore. With a laser-cut adapter and a little custom wiring, [Travis DeRose] has come up with a repeatable way to modernize a Compact Macintosh (Plus, SE, etc) by swapping out all of its internals for an iPad mini.

He goes over the whole process in the video after the break, while being kind enough to spare our sensitive eyes from having to see the Mac’s enclosure stripped of its original electronics. We’ll just ~~pretend~~ hope that the computer was so damaged that repair simply wasn’t an option.

Anyway, with a hollow Mac in your possession, you can install the adapter that allows the iPad to get bolted in place of the original CRT monitor. You won’t be able to hit the Home button anymore, but otherwise it’s a very nice fit.

Those with some first hand iPad experience might be wondering how you wake the tablet up once the Mac is all buttoned back up. That’s an excellent question, and one that [Travis] wrestled with for awhile. In the end he came up with a very clever solution: he cuts into a charging cable and splices in a normally-closed momentary push button. Pushing the button essentially “unplugs” the iPad for a second, which just so happens to wake it up. It’s an elegant solution that keeps you from having to make any modifications to that expensive piece of Apple hardware.

If there’s one thing we’re not thrilled with, it’s the empty holes left behind where the ports, switches, and floppy drive were removed. As we’ve seen in the past, you can simply cut the ports off of a motherboard and glue them in place to make one of these conversions look a little more convincing. If you’re going to do it, might as well go all the way.

Continue reading “Classic Macintosh Gets An IPad Infusion” →