Learn Functional Reactive Programming On Your Arduino

May 25, 2016 by Elliot Williams 49 Comments

Everyone loves learning a new programming language, right? Well, even if you don’t like it, you should do it anyway, because thinking about problems from different perspectives is great for the imagination.

Juniper is a functional reactive programming language for the Arduino platform. What that means is that you’ll be writing your code using anonymous functions, map/fold operations, recursion, and signals. It’s like taking the event-driven style that you should be programming in one step further; you write a=b+3 and when b changes, the compiler takes care of changing a automatically for you. (That’s the “reactive” part.)

If you’re used to the first-do-this-then-do-that style of Arduino (and most C/C++) programming, this is going to be mind expanding. But we do notice that a lot of microcontroller code looks for changes in the environment, and then acts (more or less asynchronously) on that data. At that level of abstraction, something like Juniper looks like a good fit.

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Black Line Follower: A Modern Bristlebot

May 25, 2016 by Elliot Williams 5 Comments

It’s been a while since we’ve seen much action on the bristlebot front, which is too bad. So we’re happy to see [Extreme Electronics]’s take on the classic introductory “robot”: the Black Line Follower. The beauty of these things is their simplicity, so we’ll just point you to his build instructions and leave the rest to you.

The original bristlebot is a fantastic introduction to electronics, because it’s simple enough that you can cobble one together in no time. A battery, a pager motor, and a toothbrush head are all you need. But it goes where it wants, rather than where you want it to go.

Adding steering is as simple as tying two bristlebots together and firing one motor at a time to execute a turn. The Black Line Follower is of this style.

Of course, any good idea can be taken to extremes, as in this giant weight-shifting bristlebot, or this super-tiny IR-controlled bristlebot.

But that was more than five years ago now. What happened to the mighty engines of bristlebot creativity? Has the b-bot seen its finest hour? Or are we just waiting for the next generation to wiggle up to the plate?

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Secret Listening To Elevator Music

May 24, 2016 by Elliot Williams 24 Comments

While we don’t think this qualifies as a “fail”, it’s certainly not a triumph. But that’s what happens when you notice something funny and start to investigate: if you’re lucky, it ends with “Eureka!”, but most of the time it’s just “oh”. Still, it’s good to record the “ohs”.

Gökberk [gkbrk] Yaltıraklı was staying in a hotel long enough that he got bored and started snooping around the network, like you do. Breaking out Wireshark, he noticed a lot of UDP traffic on a nonstandard port, so he thought he’d have a look.

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Identify Your Devices By Their Unintentional Radiation

May 22, 2016 by Elliot Williams 46 Comments

RFID was supposed to revolutionize asset tracking, replacing the barcode everywhere. Or at least that was the prediction once tags got under five cents apiece. They still cost seven to fifteen cents, even in bulk, and the barcode is still sitting pretty. [Chouchang (Jack) Yang] and [Alanson Sample] of Disney Research hope to change that.

Instead of tagging every electronic device, they use whatever electromagnetic emissions the device currently produces when it’s powered up. What’s surprising is not that they can tell an iPhone from a toy lightsaber, but that they can tell the toy lightsabers apart. But apparently there’s enough manufacturing and tolerance differences from piece to piece that they appear unique most of the time.

The paper (PDF) goes through the details and procedure. The coolest bit? The sensor they use is an RTL-SDR unit with the radio-mixer front end removed and replaced with a simple transformer. This lets them feed baseband (tuning from 0 to 28.8 MHz) straight into the ~~DAC~~ ADC and on to the computer which does the heavy math. Sawing off the frontend of a TV tuner is a hack, for those of you out there with empty bingo cards.

If you like statistics, you’ll want to read the paper for details about how they exactly do the classification of objects, but the overview is that they first start by figuring out what type of device they’re “hearing” and then focusing on which particular one it is. The measure that they use ends up being essentially a normalized correlation.

While we’re not sure how well this will scale to thousands of devices, they get remarkably good results (around 95%) for picking one device out of five. The method won’t be robust to overclocking or underclocking of the device’s CPU, so we’re concerned about temperature and battery-voltage effects. But it’s a novel idea, and one that’s ripe for the hacker-rebuild. And for the price of an RTL-SDR, and with no additional per-tag outlay as with an RFID system, it’s pretty neat.

Thanks [Static] for the tip! Via Engadget.

3D Print It Or Fix It?

May 22, 2016 by Elliot Williams 20 Comments

[Tim Trzepacz] is working on a pretty cool MIDI controller project over on Hackaday.io. It involves, naturally, a bunch of knobs and buttons. And it’s one of these nice arcade-style buttons that broke when he slammed on his car brakes and it went flying.

He tried gluing the plastic bits back together, but we all know how that works — temporarily. Next, he thought that maybe he could 3D-print a model of the arcade button’s housing. Besides being a lot of work, [Tim] didn’t have a reliable printer on hand. But he did have filament and a soldering iron.

The rest of the story is a slightly ugly mess, but it looks like it’ll work. (And it’s on the inside of the case, after all.) A working part is a good part.

The irony here is that the original choice of 3 mm ABS filament as a printing material is that it’s cheap and available because it’s commonly used in plastic welding. And there are more elegant ways to melt the plastic than with a soldering iron. And more ways to get it melted than direct heating, like ultrasonic welding and friction welding, for instance.

But we still like to see the occasional quickly hacked together effort, at least one per day. What’s your craziest plastic welding success or failure?

Beautiful Kegerator, Built The Hard Way

May 19, 2016 by Elliot Williams 11 Comments

[Luke] brews his own beer. And like all beer brewers, he discovered that the worst part of homebrewing is cleaning out all the bottles. Time for a kegging system! And that means, time for a kegerator to keep the brew cold.

Normal kegerators are just a few holes drilled in an appropriate refrigerator. Most fridges have a step in the back where the compressor lives, which makes kegs an awkward fit, so [Luke] decided to build his own refrigerator.

He used beautiful wood and plenty of insulation. He failed, though, because he succumbed to the lure of the Peltier cooler. If there’s one problem with Peltier projects, it’s building first and looking up the specs second. They never have enough cool-juice. To quote [Luke]:

“… a comment I had seen somewhere on the Internet began to sink in: all projects involving peltier devices ultimately end in disappointment.“

(Bolding and italics from the original.) But at least he learned about defrosting, and he had a nice wood-paneled fridge-box in the basement.

Rather than give up, he found a suitable donor fridge, ripped out its guts, and transplanted them into his homemade box. A beautiful tap head sitting on top completes the look. And of course, there’s an ESP8266 inside logging the temperature and controlling the compressor, with all the data pushed out over WiFi. Try doing that with your ~~Faraday Cage~~ metal fridge!

We’ve seen kegerator builds before. Some of our favorites include this one that has a motorized retracting tap tower, and one that’s built into the walls of the house.

Electromagnetic Field’s Badge Hanging In The Balance

May 18, 2016 by Elliot Williams 5 Comments

Making conference badges is a tough job. Unless you’re sitting on a gold mine, you have to contact a whole bunch of sponsors for help, work the parts that you can get into a coherent design, and do it all on the quick for a large audience. The EMF team is this close to getting it done, but they need some sponsorship for the assembly. If you know anyone, help them out! If they can’t line something up in the next two weeks, they’ll have to pull the plug on the badge entirely.

Electromagnetic Field is a summer-camp hacker convention / festival that takes place in England and is now in its third iteration. As with other big cons, the badge is a good part of the fun.

The 2016 EMF badge looks to be amazing. It’s powered by an ST STM32L4 low-power micro, a color LCD screen, a TI CC3100 WiFi radio module onboard, and a ridiculous number of other features including a gyro and magnetometer, and a giant battery. It’s also a testbed for the brand-new MicroPython, which aims to bring everyone’s favorite scripting language to embedded processors. In fact, they’ve largely built the MicroPython WiFi drivers for the badge.

If they can’t get a sponsor, all is not lost because everything is open source. We’ll all reap the benefits of their hard work. But that’s not the point. The point is that hundreds of hackers will be standing around in a field outside of London without the most audacious badge that we’ve seen designed dangling from their necks.
If you know anyone who can help, get in touch?

Thanks [schneider] for the tip!