Fun With Fire: Oxy-Acetylene Basics

November 14, 2016 by Dan Maloney 30 Comments

If generations of Hollywood heist films have taught us anything, it’s that knocking off a bank vault is pretty easy. It usually starts with a guy and a stethoscope, but that never works, so the bad guys break out the cutting torch and burn their way in. But knowing how to harness that raw power means you’ve got to learn the basics of oxy-acetylene, and [This Old Tony]’s new video will get your life of crime off on the right foot.

In another well-produced video, [Tony] goes into quite a bit of detail on the mysteries of oxygen and acetylene and how to handle them without blowing yourself up. He starts with a tour of the equipment, including an interesting look at the internals of an acetylene tank — turns out the gas is stored dissolved in acetone in a porous matrix inside the tank. Working up the hoses, he covers the all-important flashback arrestors, the different styles of torches, and even the stoichiometry of hydrocarbon combustion and how adjusting the oxygen flow results in different flame types for different jobs. He shows how oxy-acetylene welding can be the poor man’s TIG, and finally satisfies that destructive urge by slicing through a piece of 3/8″ steel in under six seconds.

We’ve always wanted a decent oxy-acetylene rig, and [Tony] has convinced us that this is yet another must-have for the shop. There’s just so much you can do with them, not least of which is unsticking corroded fasteners. But if a blue wrench is out of your price range and you still want to stick metal together, you’ll want to learn how to braze aluminum with a propane torch.

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How Not To Build A CPU Hand Warmer

November 12, 2016 by Brian Benchoff 50 Comments

Winter is coming, along with mittens, cold hands, snow, and jackets. Now that we’re all carrying around lithium batteries in our pocket, wouldn’t it be a great idea to build an electronic hand warmer? That’s what [GreatScott!] thought. To build his electronic hand warmer, he turned to the most effective and efficient way to turn electricity into heat: a ten-year-old AMD CPU.

Building an electronic hand warmer is exceptionally simple. All you need is a resistive heating element (like a resistor), a means to limit current (like a resistor), and a power supply (like a USB power bank). Connect these things together and you have a hand warmer that is either zero percent or one hundred percent efficient. We haven’t figured that last part out yet.

Because more power and more retro is more betterer, [GreatScott] pulled an AMD Sempron out of an old computer. Finding and reading data sheets is for wimps, apparently, so [GreatScott] just poked some pins with a variable power supply until the CPU was drawing about 500mA at 5V.

The video continues with some Arduino-based temperature measurement, finding some new pins to plug the power leads into, and securing all the wires on this heating element with hot glue. For anyone in the comments ready to say, ‘not a hack’, we assure you, this qualifies.

With the naive method of building a CPU hand warmer out of the way, here’s the pros and cons of this project, and how it can be made better. First off, using an old AMD processor was a great idea. These things are firestarters, and even though this processor preceded the 100+ W TDP AMD CPUs, it should work well enough.

That said, this is not how you waste power in a CPU. Ideally, the processor should do some work, with more active gates resulting in higher power consumption. If this were an exceptionally old processor, a good, simple option would be freerunning the chip, or having the CPU count up through its address space. This can be done by tying address lines low or high, depending on the chip. That’ll waste a significant amount of power. Randomly poking pins hoping for the right power consumption is not the way to get the most heat out of this CPU.

Of course, the above paragraph is just theory. The eating is in the pudding, or some other disfigured colloquialism, so here’s a quad-core 386 coffee warmer. This project from [magnustron] uses four 80386 CPUs powered via USB to make a nice desktop hotplate for your cuppa. Of course being powered by USB means there’s only 500mA to go around, and the ΔT is comparable to [GreatScott]’s AMD and hot glue hand warmer. Thus we get to the crux of the issue: 5V and 500mA isn’t very hot. Until cheap USB-C power banks, with ten or twelve Watts flood in from China, the idea of a USB powered heater is a fool’s errand. It does make for some great AMD firestarter jokes, though, so we have to give [GreatScott] credit for that.

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Retrotechtacular: The Golden Book Of Chemistry Experiments

November 11, 2016 by Al Williams 33 Comments

Back in “the old days” (that is, when I was a kid), kids led lives of danger and excitement. We rode bikes with no protective gear. We stayed out roaming the streets after dark without adult supervision. We had toy guns that looked like real ones. Dentists gave us mercury to play with. We also blew things up and did other dangerous science experiments.

If you want a taste of what that was like, you might enjoy The Golden Book of Chemistry Experiments. The book, first published in 1960, offers to show you how to set up a home laboratory and provides 200 experiments. The colorfully illustrated book shows you how to do some basic lab work as well as offering some science history and terminology.

Want to make oxygen? There’s several methods on page 27. Page 28 covers making hydrogen. To test the hydrogen for purity, the suggest you collect a test tube full, invert it, and stick a match up to the tube. If the hydrogen is pure it will burn with a pop noise. If air is mixed it, it will explode. Yeah, that sound safe to us.

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When A CRT Isn’t Retro Enough: LEDs

November 8, 2016 by Jenny List 31 Comments

When we think of an old-style computer terminal, it has a CRT screen: either one of the big 1970s VDUs with integrated keyboard, or maybe one from a later decade with more svelte styling. You would have found other displays in use in previous decades though, and one of them came our way that we think it worthy of sharing.

[Dan Julio] was given several tubes of Siemens DL1416B 4-digit 17-segment LED displays by a friend, and decided to use them as an unusual retro display for his terminal project. These devices are an alphanumeric display with a parallel interface that can show a subset of the ASCII character set as well as a cursor. He had 213 of them, so made plans for a 64 character by 16 line display, however on discovering a quantity of the parts were non-functional he had to scale back to 12 lines of 48 characters.

The displays are mounted on PCBs in groups of four, controlled by a PIC16F1459 and some shift registers. These boards are then daisy-chained via a TTL serial line. The whole display shares one of the three serial ports on a Teensy 3.1 with his retro keyboard that has its own PIC controller, the others serving a serial printer port and the terminal serial port. The Teensy software has two modes: serial terminal or a Tiny Basic interpreter, and the relevant repositories are linked from the project page.

Since each set of DL1416Bs takes 250 mA, the whole display consumes about 9 A at 5 volts. On top of that the keyboard uses another 500 mA, so a sufficiently powerful supply had to be incorporated. This is mounted along with the Teensy in a very well-made enclosure, and the whole is mounted on what looks like a surplus monitor stand for a very professional finish.

To take us through the terminal’s features he’s posted a YouTube video that we’ve placed below the break. It comes across as a surprisingly usable machine, as he logs into a Raspberry Pi and edits a file, and takes us through some features of the BASIC interpreter.

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Hollow State Receiver

November 7, 2016 by Al Williams 22 Comments

[Netzener] received a Radio Shack P-Box one tube receiver as a gift. However, at the time, his construction skills were not up to the task and he never completed the project. Years later, he did complete a version of it with a few modern parts substitutions. The radio worked, but he was disappointed in its performance. Turns out, the original Radio Shack kit didn’t work so well, either. So [Netzener] did a redesign using some some old books from the 1920’s. The resulting radio — using parts you can easily buy today — works much better than the original design.

The most expensive part of the build was a 22.5 V battery, which cost about $25. However, you can get away with using three 9 V batteries in series if you want to save some money. The battery provides the plate voltage for the 1T4 vacuum tube. A more conventional AA battery drives the tube’s filament. The original Radio Shack design relied on a variable inductor for tuning. These are difficult to find now, so [Netzener] uses a more conventional adjustable coil and a common tuning capacitor.

As an extra touch, [Netzener] painted the perf board to look as much like the original Radio Shack kit as possible. You can see from the pictures, it came out looking very good. If this isn’t challenging enough for you, maybe you want to roll your own tube. Or maybe you should just settle for the socket.

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A Vintage Interface For A Modern Radio

November 6, 2016 by Jenny List 10 Comments

The arrival of affordable software defined radio technologies over the last couple of decades has completely changed the way that radio amateurs and other radio enthusiasts approach the airwaves. There’s a minor problem with most software defined receivers though, being by their nature software driven they will usually rely on a host computer for their interface. Thus the experience is one of clicking mouse buttons or using keyboard shortcuts rather than the mechanical analogue dial interfaces that provided easy control of older radios.

This is a problem that has been addressed by [Jon Hudson, G4ABQ], with one of his SDRplay receivers. He’s mounted it and its control PC in the chassis of a very aged and non-functional Marconi CR100 communication receiver, and given it a control interface that only uses the Marconi’s front panel controls (YouTube link). A rotary encoder has been grafted onto the Marconi tuning capacitor with what looks like some Meccano, and in turn that feeds an Arduino which behaves as a keyboard for the benefit of the PC. Some extra buttons have been added for mode selection, spectrum zoom and shift, and care appears to have been taken to give their labels a period feel. Arduino code came courtesy of [Mike Ladd, KD2KOG]. The result is a very controllable SDR receiver, albeit one in a rather large case.

If you are interested in the project then we are told that it will be on the RS stand at Electronica in Munich next week, meanwhile we’ve put the video below the break.

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Rotary Cell Phone: Blast From A Past That Never Was

November 2, 2016 by Dan Maloney 32 Comments

The 1970s called and they want their rotary dial cell phone back.

Looking for all the world like something assembled from the Radio Shack parts department – remember when Radio Shack sold parts? – [Mr_Volt]’s build is a celebration of the look and feel of a hobbyist build from way back when. Looking a little like a homebrew DynaTAC 8000X, the brushed aluminum and 3D-printed ABS case sports an unusual front panel feature – a working rotary dial. Smaller than even the Trimline phone’s rotating finger stop dial and best operated with a stylus, the dial translates rotary action to DTMF tones for the Feather FONA board inside. Far from a one-trick pony, the phone sports memory dialing, SMS messaging, and even an FM receiver. But most impressive and mysterious is the dial mechanism, visible through a window in the wood-grain back. Did [Mr_Volt] fabricate those gears and the governor? We’d love to hear the backstory on that.

This isn’t the first rotary cell phone hybrid we’ve featured, of course. There was this GSM addition to an old rotary phone and this cell phone that lets you slam the receiver down. But for our money a rotary dial cell phone built from the ground up wins the retro cool prize of the bunch.

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