Upcycle An Isolation Transformer

There are several reasons you should have an isolation transformer. They can prevent ground loops and also prevent a device under test from having a DC path to ground (or isolate an oscilloscope from DC ground, which can be dangerous in its own right, but that’s another discussion). [Tanner_tech] noticed that finding ballast transformers for sodium vapor street lights is getting easier as more street lights move to LED technology. What to do with these transformers? Build an isolation transformer, of course.

Of course, your dumpster transformer might be a little different than the one shown in the post (and the video, below). [Tanner] shows how to work out the leads you need. A little wood work and a PC power supply case finished the project.

Judging from the comments, some people take [Tanner’s] talk about safety as an implication that a transformer makes working on mains safe. It doesn’t. It makes it safer if you know what you are doing. Working with high voltage isn’t a place to learn by doing.

If you want some practical advice, [Jenny List] has a good read for you. You probably also ought to invest an hour in watching this video that has a lot of practical advice.

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Teardown a Classic : Tektronix P6042 Current Probe

[Paul Rako]’s teardown of his treasured P6042 current probe shows why Tektronix commands so much respect among the old hats of the electronics world.

Built in 1969, the P6042 is pretty sparse transistor-wise when compared a modern sensor. The user would clip the current probe, permanently attached to the case since the circuit was tuned for each one, over a wire and view the change in volts on an oscilloscope. When the voltage division on the oscilloscope was set properly the current in a circuit could be easily seen.

The teardown is of a working unit so it’s not completely disassembled, but it also sits as a nice guide on refurbishing your own P6043, if you manage to snag one from somewhere. Aside from capacitors and oxidized switch contacts there’s not much that can go wrong with this one.

As for how it compares, the linear power supply, analog circuit design, and general excellent engineering has the P6042 coming in with a cleaner signal than some newer models. Not bad for a relic! Do any of you have a favorite old bit of measurement kit?

Estimate Your English Vocabulary Using Python

We take our mother tongue for granted, a language we learn as young children without realizing the effort involved. It is only when as adults we try to pick up another language that we fully understand how much hard work surrounds each acquired word.

Depending on who you listen to, estimates vary as to the size of a typical native English speaker’s vocabulary. The ballpark figures seem to put most adults under 20 thousand words, while graduates achieve somewhere around 23 thousand words. It’s a subject [Alex Eames] became interested in after reading a BBC article on it, and he decided to write his own software to produce a personal estimate.

His Python script takes the Scrabble word list, and presents the user with a list of words, for each one of which they have to indicate their comprehension. After a hundred words have been presented it calculates an estimate of the size of the user’s vocabulary. [Alex] wrote it on and for the Raspberry Pi, but it should work quite happily on any platform with Python 3. It certainly had no problem with our Ubuntu-based PC.

There is plenty of opportunity for bragging over the size of one’s vocabulary with a script like this one, but it’s something of a statistical leveler in that if you are truthful in your responses it will almost certainly put you exactly where you might expect for your age or level of education. If you want to know the result this script returned for a Hackaday scribe, for example, the answer is 23554.

This subject is a slight departure into software from our usual hardware subject matter, but it’s one of those tests that becomes rather a consuming interest when performed competitively among a group of friends. How well will you fare?

Via [Recantha]

Homemade E-Drums Hit All The Right Notes

In our eyes, there isn’t a much higher calling for Arduinos than using them to make musical instruments. [victorh88] has elevated them to rock star status with his homemade electronic drum kit.

The kit uses an Arduino Mega because of the number of inputs [victorh88] included. It’s not quite Neil Peart-level, but it does have a kick drum, a pair of rack toms, a floor tom, a snare, a crash, a ride, and a hi-hat. With the exception of the hi-hat, all the pieces in the kit use a piezo element to detect the hit and play the appropriate sample based on [Evan Kale]’s code, which was built to turn a Rock Band controller into a MIDI drum kit. The hi-hat uses an LDR embedded in a flip-flop to properly mimic the range of an actual acoustic hi-hat. This is a good idea that we have seen before.

[victorh88] made all the drums and pads out of MDF with four layers of pet screen sandwiched in between. In theory, this kit should be able to take anything he can throw at it, including YYZ. The crash and ride cymbals are MDF with a layer of EVA foam on top. This serves two purposes: it absorbs the shock from the sticks and mutes the sound of wood against wood. After that, it was just a matter of attaching everything to a standard e-drum frame using the existing interfaces. Watch [victorh88] beat a tattoo after the break.

If you hate Arduinos but are still reading for some reason, here’s a kit made with a Pi.

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Finding A Use For Surplus Filament Spools

If you’re a heavy user of a 3D printer, or a welder, you’ll know the problem of empty spools. You’ve used up all the filament or the welding wire, and you’re left with a substantial plastic spool. It’s got to be useful for something, you think, and thus it’s Too Good To Throw Away. Before you know it you have a huge pile of the things all looking for a use that you know one day you’ll find.

If you follow the example of [Chuck Hellebuyck], you could use them as wheels for a small go-kart (YouTube link). He 3D-printed some hub adapters for the spools to use skate bearings, mounted them of threaded axles to a classic wooden go-kart frame, and set off downhill wearing his stock-car racing helmet.

Of course, [Chuck]’s go-kart is a bit of fun, but it’s probably fair to say that 3D printer spools are not the ideal wheel. Those rims aren’t particularly durable, and with no tires he’s in for a bumpy ride. Perhaps a tire could be found to fit and a tube placed within it, but that would start to sound expensive against those cheap off-the-shelf wheelbarrow items.

But the project does raise the interesting question: what exactly do you do with your empty spools? There have to be some awesome uses for them, so please share yours in the comments. Meanwhile follow Chuck’s go-kart adventures in the video below the break.

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Hackaday Prize Entry: A 3D Printed Prosthetic Foot

For the last few years of the Hackaday Prize, there have been more than a few prosthetic devices presented. Almost without exception, the target for these projects are prosthetic hands. That’s a laudable goal, but mechanically, at least, feet are much more interesting. A human foot must sustain more than the weight of the human it’s attached to, and when it comes to making this out of plastic and metal, that means some crazy mechanics.

This Hackaday Prize entry is a complete reversal of all the prosthetic limbs we’ve seen before. It’s a prosthetic foot, and in the tradition of easily made and easily modified prosthetic arms, this prosthetic foot is mostly 3D printed.

A foot will take a lot more abuse and weight than a hand, and because of this 3D printing all the parts might not seem like the best idea. Exotic filaments exist, though, and the team behind this project does have access to a few pieces of test equipment in a materials engineering lab. With the right geometry, everything seems to support the load required.

There are some relatively new twists to this 3D printed prosthetic foot, including electronic control, a micro-hydraulic power plant, and sensors to measure and adjust the user’s gait. It’s all very cool, and deserves a lot more engineering than even the most complicated 3D printed prosthetic hand.

Weather Ticker Shows How Easy It Can Be

[Petru] seems to have designed his weather ticker project with beginners in mind. Leveraging the inexorable forces of both the Raspberry Pi and cheap online auction house modules, it’s nearly the Hackaday equivalent of painting by numbers. But not everyone is a Picasso, and encouraging beginners to get their feet wet by painting happy little trees is a good cause.

Behind the simplicity is actually a clever architecture. An installation script makes installing the right Raspbian distro simple, and installs a few scripts that automatically update the user code from a GitHub repository. To change the code running on the machine, you can upload a new version to GitHub and press the reset button. (We would also want a way to push up code changes locally, for speed reasons.) Something like this is a great idea for a permanent Pi-based IoT device.

But as a first project, the hope is that something like this will encourage folks who find code too abstract, but who are nonetheless drawn by the allure of blinking lights, to play around with code. And unsurprisingly, this has already been entered in our Enlightened Raspberry Pi Contest which focuses on the simple-yet-impressive stuff you can do with a tiny computer and some electronics.