In the comments to our recent article about Wimshurst machines, we saw that some hackers had never heard of them, reminding us that we all have different backgrounds and much to share. Well here’s one I’m guessing even fewer will have heard of. It’s never even shown up in a single Hackaday article, something that was also pointed out in a comment to that Wimshurst article. It is the Lord Kelvin’s Water Dropper aka Lord Kelvin’s Thunderstorm, invented in the 1860s by William Thomson, 1st Baron Kelvin, the same fellow for whom the Kelvin temperature scale is named. It’s a device that produces a high voltage and sparks from falling drops of water.
In a recent article, I lamented my distaste for carrying on the classic amateur radio conversation — calling CQ, having someone from far away or around the block call back, exchange call signs and signal reports and perhaps a few pleasantries. I think the idle chit-chat is a big turn-off to a lot of folks who would otherwise be interested in the World’s Greatest Hobby™, but thankfully there are plenty of ways for the mic-shy to get on the air. So as a public service I’d like to go over some of the many digital modes amateur radio offers as a way to avoid talking while still communicating.
Suppose you take a few measurements of a time-varying signal. Let’s say for concreteness that you have a microcontroller that reads some voltage 100 times per second. Collecting a bunch of data points together, you plot them out — this must surely have come from a sine wave at 35 Hz, you say. Just connect up the dots with a sine wave! It’s as plain as the nose on your face.
Sampling a 35 Hz wave at 100 Hz
35 Hz with -65 Hz
35 Hz with 135 Hz
And then some spoil-sport comes along and draws in a version of your sine wave at -65 Hz, and then another at 135 Hz. And then more at -165 Hz and 235 Hz or -265 Hz and 335 Hz. And then an arbitrary number of potential sine waves that fit the very same data, all spaced apart at positive and negative integer multiples of your 100 Hz sampling frequency. Soon, your very pretty picture is looking a bit more complicated than you’d bargained for, and you have no idea which of these frequencies generated your data. It seems hopeless! You go home in tears.
But then you realize that this phenomenon gives you super powers — the power to resolve frequencies that are significantly higher than your sampling frequency. Just as the 235 Hz wave leaves an apparent 35 Hz waveform in the data when sampled at 100 Hz, a 237 Hz signal will look like 37 Hz. You can tell them apart even though they’re well beyond your ability to sample that fast. You’re pulling in information from beyond the Nyquist limit!
This essential ambiguity in sampling — that all frequencies offset by an integer multiple of the sampling frequency produce the same data — is called “aliasing”. And understanding aliasing is the first step toward really understanding sampling, and that’s the first step into the big wide world of digital signal processing.
Whether aliasing corrupts your pristine data or provides you with super powers hinges on your understanding of the effect, and maybe some judicious pre-sampling filtering, so let’s get some knowledge.
If you need a high voltage, a voltage multiplier is one of the easiest ways to obtain it. A voltage multiplier is a specialized type of rectifier circuit that converts an AC voltage to a higher DC voltage. Invented by Heinrich Greinacher in 1919, they were used in the design of a particle accelerator that performed the first artificial nuclear disintegration, so you know they mean business.
Theoretically the output of the multiplier is an integer times the AC peak input voltage, and while they can work with any input voltage, the principal use for voltage multipliers is when very high voltages, in the order of tens of thousands or even millions of volts, are needed. They have the advantage of being relatively easy to build, and are cheaper than an equivalent high voltage transformer of the same output rating. If you need sparks for your mad science, perhaps a voltage multiplier can provide them for you.
Oh Nexus 5X, how could you? I found my beloved device was holding my files hostage having succumbed to the dreaded bootloop. But hey, we’re hackers, right? I’ve got this.
It was a long, quiet Friday afternoon when I noticed my Nexus 5X was asking to install yet another update. Usually I leave these things for a few days before eventually giving in, but at some point I must have accidentally clicked to accept the update. Later that day I found my phone mid-way through the update and figured I’d just wait it out. No dice — an hour later, my phone was off. Powering up led to it repeatedly falling back to the “Google” screen; the dreaded bootloop.
Stages of Grief
I kept my phone on me for the rest of the night’s jubilant activities, playing with it from time to time, but alas, nothing would make it budge. The problem was, my Nexus still had a full day’s video shoot locked away on its internal flash that I needed rather badly. I had to fix the phone, at least long enough to recover my files. This is the story of my attempt to debrick my Nexus 5X.
Many credit the invention of the incandescent light bulb with Edison or Swan but its development actually took place over two centuries and by the time Edison and Swan got involved, the tech was down to the details. Those details, however, meant the difference between a laboratory curiosity that lasted minutes before burning out, and something that could be sold to consumers and last for months. Here then is the story of how the incandescent light bulb was invented.
This is Hackaday’s global engineering initiative that encourages people to direct their skill and energy to make the world a better place. We call it the Hackaday Prize, but it’s far more than that. Join a community of talented people who enrich their own lives by seeking out new challenges and new technologies, then pioneers a way to combine them to Build Something that Matters. Show us your build by starting a Hackaday.io project page and enter today!
You Have Every Reason to Get Involved
The Hackaday Prize truly has something for everyone. Making the world a better place doesn’t end with a grand prize for a single build. Just by talking about your ideas and sharing your excitement you become the inspiration for this and every successive generation of problem solvers. But yes, there are prizes — a lot of prizes — and they’re spectacular.
We have over $250,000 in cash going out to hundreds of entries this year. The Grand Prize of $50,000 is joined once again this year by the Best Product Prize of $30,000. Four other entries will place second through fifth and receive $20k, $15k, $10k, and $5k respectively.
But the breadth of entries is too great to stop at that. We’ll select 120 projects as finalists and award each $1000. You can even get in on Seed Funding starting right away. We’re saving those details for the end of this announcement.
How Do I Build Something that Matters?
Whoa, all this talk of prizes, but you want to know what kind of hardware will be a hit for the Hackaday Prize? Here’s what you need to know: you can enter your project at any time from now until October 16th. But the exact time that you enter matters.
Your best bet is to get started right away. The first challenge of the Hackaday Prize is: Design Your Concept. Every great build starts with a plan and this is the time to show us what you got. The key is to consider if the project benefits society in some way. Show us how, document your build plan, and you can be one of the first twenty finalists to receive $1k cash and move on to compete for the big prizes.
We’ll have four more challenges that focus on different types of entries. You only need to enter one challenge, but you may choose to enter (and win) as many of the five challenges as you wish. We’ll be looking for connected devices that don’t suck Internet of Useful Things during the IuT ! IoT challenge. After that, it’s on to all things mobile with the Wheels, Wings, and Walkers challenge. Assistive Technology challenges you to make the world a better place for the physically or mentally challenged and aging or sick people of the world. And finally, a Hackaday favorite closes the challenge rounds with Anything Goes — as long as it clearly benefits society. Each of these five challenges will yield twenty finalists who receive $1000. That’s $100k!
The Return of Best Product
Two years ago we tried something new by adding the Best Product Prize to the mix and it was an enormous hit. We’re happy to be able to bring it back again this year.
There is a difficult path from a working prototype to a product ready for its audience. As hardware development is unlocked for an ever wider engineering community, we want to see the path made wider so that the journey becomes easier. Best Product is designed to do just that.
Any Hackaday Prize entry may also choose to compete and be named the Best Product (receiving much deserved recognition as well as the addition $30k prize). You need to submit your entry no later than July 24th, which includes full documentation of the project as well as a bill of materials used in the build. We’ll select twenty finalists (sending $1k to each) who will then need to deliver three working beta test units for the final judging round of the Best Product.
How Can We Pick the Top Entries?
One amazing part of the Hackaday Prize family are the world-renowned experts who donate their time and talent as Judges. They are just as eager as everyone else to see all of this creative energy focused on solving the problems facing our civilization.
When realized to their full potential, design concepts should knock the socks off of anyone who reads through them. Because of this we have one more thing in store for you during the first challenge which starts right now.
Entries with the most likes at the end of the first round will split $4,000. Each time someone on Hackaday.io “likes” your project it will move a bit higher on the leaderboard found on the Hackaday Prize page. The top projects will receive $1 for each like, with a max of $200 per entry so that at least twenty will win (but likely many more).
This seed funding is a little push to help offset the cost of building prototypes. But it really comes down to your decision to make the time and to make a difference. Enter your project in the Hackaday Prize now.
We have over $250,000 in cash going out to hundreds of entries this year. The Grand Prize of $50,000 is joined once again this year by the Best Product Prize of $30,000. Four other entries will place second through fifth and receive $20k, $15k, $10k, and $5k respectively.
Your best bet is to get started right away. The first challenge of the Hackaday Prize is: Design Your Concept. Every great build starts with a plan and this is the time to show us what you got. The key is to consider if the project benefits society in some way. Show us how, document your build plan, and you can be one of the first twenty finalists to receive $1k cash and move on to compete for the big prizes.
