Feeling The Heat Of High-Frequency Trading

August 6, 2018 by Dan Maloney 45 Comments

It’s high summer here in North America, and for a lot of us, this one has been a scorcher. Media reports have been filled with coverage of heat wave after heat wave, with temperature records falling like dominoes.

But as they say, it’s not the heat, it’s the humidity, and that was painfully true in the first week of July as a slug of tropical air settled into the northeast United States. With dewpoints well into the 70s (25°C plus) and air temperatures pushing the century-mark (38°C), people suffered and systems from transportation to the electrical grid strained under the load. But as punishing as such soupy conditions are for people, there are other effects that are less well known but of critical importance to financial markets, where increased humidity can lead to billion-dollar losses for markets. Welcome to the weird world of high-frequency trading.

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Mouse Trap Game Used As An Actual Mouse Trap

August 6, 2018 by Tom Nardi 7 Comments

Just when you thought you had explored all the weird stuff on YouTube, along comes [Shawn Woods] with his channel dedicated to testing different types of mouse traps. His weekly videos demonstrate the construction and ultimate effectiveness of everything from primitive traps that can be made in the field from sticks and rocks to 3D printed creations sent in from viewers. But his latest video might just be the weirdest one yet, as he found a way to use the classic “Mousetrap” board game to capture an actual rodent.

Well, sort of. For one, [Shawn] admits the “trap” is completely impractical and is just for fun. Which should be pretty obvious considering the thing is enclosed in a box the size of a small refrigerator. Second, the lucky rodent that gets to test drive this Milton Bradley-powered gadget is actually the family’s pet chinchilla which is obviously rather calm and we dare say accustomed to these sort of shenanigans.

The key to the whole contraption comes via two traditional mousetraps, one on either end of the game’s more fanciful rendition of the same device. The first trap is used to pull the crank which gets the board game going when the mouse steps on the pad (a piece of wood with padding prevents the bar from actually hitting the animal). The game goes through its nostalgic routine featuring metal balls rolling down tracks and figurines on jumping boards, eventually triggering the second real mouse trap. In this case, the trap pulls a rope which closes a door at the opening of the box.

Assuming your target rodent is very patient and not startled by the cacophony of plastic machinery, the whole thing works perfectly. To use the parlance of his channel, this is what’s known as a “Live Catch” trap as it doesn’t hurt the mouse and lets you easily remove them after the fact. Which is the least you could do after humiliating it like this.

While likely the most unique, it surely isn’t the only mouse trap we’ve ever covered here at Hackaday. This clever soda bottle trap can be built cheaply and easily, but if you want something expensive and complex you can always use a Raspberry Pi.

[Thanks to Pete for the tip.]

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Rolling Out A Slick Rotary Phase Converter

August 6, 2018 by Dan Maloney 46 Comments

Home machinists can often find great deals on used industrial equipment, and many a South Bend lathe or Bridgeport milling machine has followed someone home. Then comes the moment to plug it in, and the new owner discovers that the three-phase plug needed to power the new beast is nowhere to be found in the shop. Thus commences the weeping and the gnashing of teeth.

Luckily, [Handmade Extreme] is ahead of the curve in terms of shop power, and built a rotary phase converter to power his machines. Industry generally runs on three-phase AC systems, mainly because three-phase electric motors are so much more efficient and compact than the equivalent single-phase motor. But residential electrical service is either split-phase or, in the UK where [Handmade Extreme] is based, single phase. A rotary phase converter is an electromechanical device that can generate the missing phases – in essence a three-phase motor that can run on one winding and generate the missing phases across the other windings. It needs some supporting control circuitry to do so, such as timers and contactors to switch the winding connections once the motor starts, plus capacitors for motor starting and for balancing the voltage across the phases. The control gear is DIN-rail mounted and neatly wired to a smart-looking control panel. Everything is housed in a sturdy enclosure that’s big enough to serve as a mobile tool cart. It’s a really nice job – watch the whole build in the video below.

If you’re interested in power distribution, we’ve got a primer that covers the basics. And if you’re in the market for machine tools, [Quinn]’s machine tool buyer’s guide will let you decide if a three-phase machine is worth the extra effort.

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Spot Welding …Plastic?

August 5, 2018 by Ben James 12 Comments

Plastic milk bottles, when your project or prototype needs an urgent source of plastic, they are often the first thing to hand. Convenient and flexible, but strong at the same time and usually free, they’re the ultimate source of material in a pinch. However, when it comes to actually manipulating the HDPE plastic they’re made from, there’s often a challenge. It’s easy to cut, but not so easy to join. Conventional glues can have a hard time, making it difficult to bond.

Enter [zimitt], and a spot welding solution for joining HDPE with ease. Ok, so ‘spot welding’ might be a little optimistic given the speed of this process, but it’s useful nonetheless. To heat the plastic, a cheap soldering iron is recommended. A low wattage, straight-to-the-wall one does well, especially as they commonly have the washer-style end shown in the picture. To protect the plastic from burning, a BBQ mat is used – they’re temperature resistant and usually made with a PTFE surface.

First, place the two sheets of plastic face to face and sandwich top and bottom with the BBQ mat. Apply some heat to the mat with the soldering iron then, after a few seconds, remove the iron and provide pressure with a flat object to bond the plastic. [zimitt] used an espresso tamper for this which was ideal.

The results are impressive, and [zimitt] experiments with different plastics as well. Of course, you should exercise caution when attempting anything like this, given the health risks present when heating up different types of plastic.

HDPE is easy to recycle at home, and we’ve seen a lot of great uses: a plastic joiner’s mallet, plastic tiles, and even a filament extruder for 3D printing.

A Plasma Speaker Using A TL494

August 5, 2018 by Jenny List 23 Comments

We’re used to loudspeakers as circular components with a paper cone and a big magnet inside which is suspended a coil that is connected to our audio amplifier. But moving-coil speakers are not the only way to create sound from electricity, there are one or two other weapons in the audio designer’s arsenal.

One of the more spectacular and entertaining is the plasma speaker, and it’s one [Marcin Wachowiak] has been experimenting with. A continuous plasma in the form of a discharge between two electrodes is modulated with an audio signal, and the resulting rapid changes in the volume of plasma creates a sound. The value of a plasma speaker lies in the exceptionally low size and mass of the element producing the sound, meaning that while it can only effectively reproduce high frequencies it can do so from a much closer approximation to a point source than can other types of tweeter. For this reason it’s beloved of some audiophiles, and you will find a few commercially produced plasma tweeters at the high-end of the audio market.

[Marcin] isn’t in it for the audiophilia, instead he’s interested in the properties of the plasma. His plasma speaker does do the job well though, and in particular he’s put a lot of thought into the design of its drive circuit. At its heart is the ubiquitous TL494 PWM controller that you may be more familiar with in the context of switching power supplies, this one applies the audio drive as PWM to the gate of a MOSFET that switches the primary of a flyback transformer. He’s added refinements such as a gate discharge circuit and a second primary winding with a freewheel diode.

The result is an effective plasma speaker. It’s difficult to judge from his YouTube video below the break whether he’s achieved audiophile purity, but happily that’s not the point. We’ve shown you a few other plasma speakers in our time, if the subject interests you then take a look at this rotating plasma vortex, or a version using a 555 timer.

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Hackaday Links: August 5, 2018

August 5, 2018 by Brian Benchoff 18 Comments

Here’s something of historical interest. The daughter of Terry Holdt, project manager for the 6502, cleaned out a garage and found shelves full of MOS Technology binders, test results, notes, instructions for processes, letters to customers, and datasheets full of errata. Some of these documents have been posted on Twitter, and efforts are underway to collect, scan, upload, and preserve them. In the distance, a man in a fabulous suit is screaming, ‘donate them to the Internet Archive’.

This is a link to Defcad, the repository of 3D printable files for weapons. Under an agreement with the US Department of State, Defcad was set to go online on August 1st. This caused much handwringing in the tech journalist thoughtspace, with reporters calling to end the first amendment because they don’t like the second. Alyssa Milano chimed in. Defcad was ordered shut down by a federal judge in the western district of Washington before going live.

As you may well be aware, Printrbot ceased operations last month. It’s sad to see them go, but they made some acceptable machines and were really pushing the boundaries of what was possible with their infinite build volume prototype printer. But what about all those existing printrbots in the wild, you might ask. Well, good news for anyone who hasn’t changed their hotend over to an E3D yet: Ubis is going to be selling hotends. Get ’em while they’re hot (or not, I don’t know how this pun works).

File this one into the ‘awesome government auctions’ category. The city of Longmont, Colorado decommissioned their tornado sirens last year because they ‘self-activated’ and malfunctioned. These sirens were put up for auction, with a winning bid of $526. Someone bought the most annoying thing imaginable for just over five bills. The world of government auctions is amazing.

How To Run A Clock For A Century

August 5, 2018 by Rich Hawkes 53 Comments

What’s going to keep a clock running for a century, unattended? Well, whatever’s running it will have to sip power, and it’s going to need a power source that will last a long time. [Jan Waclawek] is looking into solar power for daytime, and capacitors for nighttime, to keep his clock running for a hundred years.

This project carries on from [Jan]’s previous project which looked at what kind of power source could power the gadgets around his house for a century without needing intervention – ie., no batteries to replace, no winding etc. [Jan] whittled his choices down to a combination of solar power and polypropylene film capacitors. Once the power had been sorted, a clock was chosen in order to test the power supply. The power consumption for a clock will be low during the night – it would only need a RTC circuit keeping track of the time – so a few low-leakage capacitors can be used. When daylight returns or a light is switched on, the solar circuit would power the clock’s display.

At the moment, [Jan] has a proof of concept circuit working, using the ultra-low-power microcontroller on a STM32L476 DISCOVERY board and a few 10 μF 0805 size capacitors, when fully charged by the solar panel, the clock’s display lasts for about two minutes.

Take a look at [Jan]’s project for more details, and check out his previous project where he narrowed down the components for a hundred-year power supply. [Jan]’s prototype can be seen in action after the break. Also take a look at this master clock that signals slave clocks and runs for a year on a single AA battery.