Misc Hacks

4173 Articles

Analysing National Budgets With File System Tools

April 15, 2019 by 20 Comments

Understanding a national budget can be difficult, with political interests and distorted talking points obscuring the truth. There’s no substitute for diving into the hard data yourself, but it can be difficult to know where to start. [D. Scott Williamson] wanted to do just that, and took an unconventional path – using file system tools to analyse the 2019 US budget.

The basic idea is simple. A file is created for every line item on the budget, and this file is filled with a $ for every million dollars that item costs. These files are sorted into folders for the relevant bureaus and agencies responsible, creating a Fiscal File System representation of the entire budget. The file system can then be analysed with standard tools to get a look at the overall make up of the budget – in this case, WinDirStat does a particularly good job.

It’s a novel way to go about budget analysis, and fills a gap in the market now that Time Plots aren’t producing their Death and Taxes infographics anymore. Pre-cooked file systems covering budgets back to 1977 are available for your perusal, should you need to investigate how things have changed over time.

Unsurprisingly, we haven’t covered the national budget before, but we’re always down to talk file systems.

A Peek Inside A Typical British Residential Power Panel

April 14, 2019 by 43 Comments

No matter what field you’re in, it’s interesting and instructive to find out how others practice it. That’s especially true with electrical distribution systems, where standards and practices differ from country to country and even between regions. This tour of a typical British residential electrical panel is a great example of the different ways that the same engineering problems can be solved, and the compromises that always attend any design.

We’re used to seeing [Big Clive] tearing interesting devices to bits, but rest assured that this electrical panel remains largely intact as it gives up its secrets. Compared to the distribution panels and circuit breakers common in North American residential construction, the British consumer unit is a marvel of neatness and simplicity. True, the unit on display hasn’t been put into service yet, and things will no doubt change once an electrician is through with it, but the fact that everything is DIN rail mounted is pretty cool. [Clive] explains a few of the quirks of the panel, such as the fact that what looks like a main breaker is in fact just an isolation switch, and that there are a pair of residual current devices (RCDs), which we call ground-fault circuit interrupters (GFCIs) in North America, that also don’t act as circuit breakers, despite appearances. A stout bus bar is provided to link the RCDs to adjacent circuit breakers, forming two groups that are separately protected from ground faults.

[Clive] notes with dismay that the lugs of the bus bar can actually be inserted behind the rising clamp terminal on the breaker, resulting in poor connections and overheating. Still, we wouldn’t mind some of these concepts brought to panels in North America, which we covered a bit in a discussion on circuit protection a while back.

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Electronics On Ice

April 12, 2019 by 6 Comments

We see all manner of electronics enclosures pass through these hallowed pages. Lasercut wooden builds with fancy kerf bending, expertly prepared acrylic boxes, and even the occasional device cast in concrete. [Mike Kohn] decided that all of these were too permanent, however, and chose a different material – ice.

[Mike] shares the ups and downs of his experiments with electronics and frozen water. Initial tests with a circuit sealed in DAP Ultra Clear were largely successful.  A tilt sensor was installed to allow the batteries to remain undrained during the freezing process, and once freed after a few hours of thawing, the circuit was operational. Later builds required some more work – the RC car in particular took a few attempts to avoid the mold leaking. The ice hands are a particular highlight, though – created with rubber gloves, these would be a remarkably spooky decoration come Halloween.

It’s a study in the techniques required to work with this ephemeral material, and there’s a few lessons to learn. Sealing electronics is good, and the best results are with simple circuits with a few LEDs that make everything glow nicely.

If you’re looking for other ideas, you could always create a frozen lens for photographical purposes. Video after the break.

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Flex PCBs Make Force-Mapping Pressure Sensor For Amputee

April 9, 2019 by 1 Comment

What prosthetic limbs can do these days is nothing short of miraculous, and can change the life of an amputee in so many ways. But no matter what advanced sensors and actuators are added to the prosthetic, it has to interface with the wearer’s body, and that can lead to problems.

Measuring and mapping the pressure on the residual limb is the business of this flexible force-sensing matrix. The idea for a two-dimensional force map came from one of [chris.coulson]’s classmates, an amputee who developed a single-channel pressure sensor to help him solve a painful fitting problem. [chris.coulson] was reminded of a piezoresistive yoga mat build from [Marco Reps], which we featured a while back, and figured a scaled-down version might be just the thing to map pressure points across the prosthetic interface. Rather than the expensive and tediously-applied web of copper tape [Marco] used, [chris] chose flexible PCBs to sandwich the Velostat piezoresistive material. An interface board multiplexes the 16 elements of the sensor array to a PIC which gathers and records testing data. [chris] even built a test stand with a solenoid to apply pressure to the sensor and test its frequency response to determine what sorts of measurements are possible.

We think the project is a great application for flex PCBs, and a perfect entry into our Flexible PCB Contest. You should enter too. Even though [chris] has a prototype, you don’t need one to enter: just an idea would do. Do something up on Fritzing, make a full EAGLE schematic, or just jot a block diagram down on a napkin. We want to see your ideas, and if it’s good enough you can win a flex PCB to get you started. What are you waiting for?

DIY Air Conditioner Built From Weird Donor Appliance

April 7, 2019 by 64 Comments

There are some parts of the world where living without air conditioning borders on unthinkable. But in more moderate climates, it isn’t all that unusual. [Josh’s] apartment doesn’t have central air conditioning — the kind that connects to a forced-air heating/cooling system. It does, though, have a water circuit for air conditioning, so he decided to hack a few experimental air conditioners.

He’s not starting completely from scratch. The two attempts he made at building his AC came from donor parts. The successful one started out as a hot water heater. The very first attempt didn’t quite work as well, using a refrigerator compressor and an evaporator from a baseboard heater. The flow control through the heat exchanger turns out to be very tricky, so [Josh] claims he mostly got ice right at the inlet and minimal cooling through the evaporator.

The more successful one works better but still has a problem with the evaporator freezing that he’s trying to solve. He’s looking for suggestions on how to make it work better. As much as we like a good hack, our advice is to move to a different apartment building.

We’ve seen other homemade coolers, but they are more like swamp coolers. If you just need to cool your desk, you might just get some ice in a metal can.

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But Can Your AI Recognize Slugs?

April 5, 2019 by 53 Comments

The common garden slug is a mystery. Observing these creatures as they slowly emerge from their slimy lairs each evening, it’s hard to imagine how much damage they can do. With paradoxical speed, they can mow down row after row of tender seedlings, leaving nothing but misery in their mucusy wake.

To combat this slug menace, [Tegwyn☠Twmffat] (the [☠] is silent) is developing this AI-powered slug busting system. The squeamish or those challenged by the ethics of slug eradication can relax: no slugs have been harmed yet. So far [Tegwyn] has concentrated on the detection of slugs, a considerably non-trivial problem since there are few AI models that are already trained for slugs.

So far, [Tegwyn] has acquired 5,712 images of slugs in their natural environment – no mean feat as they only come out at night, they blend into their background, and their slimy surface makes for challenging reflections. The video below shows moderate success of the trained model using a static image of a slug; it also gives a glimpse at the hardware used, which includes an Nvidia Jetson TX2. [Tegwyn] plans to capture even more images to refine the model and boost it up from the 50 to 60% confidence level to something that will allow for the remediation phase of the project, which apparently involves lasers. Although he’s willing to entertain other methods of disposal; perhaps a salt-shooting turret gun?

This isn’t the first garden-tending project [Tegwyn] has tackled. You may recall The Weedinator, his 2018 Hackaday Prize entry. This slug buster is one of his entries for the 2019 Hackaday Prize, which was just announced. We’re looking forward to seeing the onslaught of cool new projects everyone will be coming up with.

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Hiding Messages In Magnets

April 4, 2019 by 12 Comments

Magnets have always been fun, particularly since the super-powerful neodymium type became readily available. You can stack them up, pull them apart, or, if you really want, use them for something practical. Now [Adric] has shown us a new use for them entirely – by writing hidden messages on them.

It’s a remarkably simple hack, but ingenious all the same. [Adric] was pretty sure that the Quelab hackerspace laser wasn’t powerful enough to cut or etch a nickel-plated neodymium magnet. However, they suspected it would have just enough power to heat localised parts of the magnet above the Curie temperature, where the magnetic properties of the material break down.

Thus, the laser cutter was set up to run a few passes over some neodymium magnets. By placing a magnetic viewing film over the magnet, it’s possible to make the etched pattern visible. There was also some incidental visible marking of the magnet surface, which [Adric] thinks is due to the tape applied to the magnet before the laser processing.

For those of you operating spy rings in deep cover, you’ve now got a new way to send them secret messages. Just be sure to check in with the local postal service as to their policies regarding giant magnets in the post. Then you can contemplate whether you have the ability to sense magnetic fields.