Poetic SSIDs

June 6, 2016 by Elliot Williams 34 Comments

Artists see the same world that the rest of us do. They just see it from a little bit off to the left. Where you see picking an ESSID for your router as being a hassle, or an opportunity to insult your neighbors, [Dmitry], alias [::vtol::] sees a poetry-delivery mechanism.

Based on ESP8266 units, each “poet” has a battery and a switch. Turn it on and it changes its SSID once every ten seconds, feeding everyone who’s listening the next line of a poem. You can’t connect to the network, but you can occasionally hit refresh on your WiFi scanner and read along.

Since they’re so cheap to build, [::vtol::] sees them almost as if they were poetry-throwies. You could easily afford to leave a few around the city, guerilla-style, broadcasting your (slow) message one SSID at a time. We love the video clips (inlined below) of him riding the subway with the device on.

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Hackaday Prize Entry: Dave Thomas’ Desert Dryer

June 5, 2016 by Elliot Williams 34 Comments

It seemed utter madness — people living in hot desert climates paying to heat air. At least it seemed that way to [David Thomas] before he modified his tumble dryer to take advantage of Arizona’s arid environment.

Hanging the wash out to dry is a time-honored solution, and should be a no-brainer in the desert. But hanging the wash takes a lot of human effort, your laundry comes back stiff, and if there’s a risk of dust storms ruining your laundry, we can see why people run the dryer indoors. But there’s no reason to waste further energy heating up your air-conditioned interior air when hot air is plentiful just a few meters away.

[David]’s modification includes removing the gas heating components of the dryer and adding an in-line filter. He explains it all in a series of videos, which at least for his model, leave no screw unturned. It’s not an expensive modification either, consisting mostly of rigid dryer hose and copious amounts of aluminum duct tape. He mentions the small fire that resulted from failing to remove the gas igniter, so consider yourself warned. The intake filter and box were originally intended for a house air-conditioning system, and required only minimal modifications.

This is a great build, being both cheap and easy to implement as well as being environmentally friendly without requiring a drastic change to [David]’s lifestyle. It makes us wish we had a similar endless supply of hot air.

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In Soviet Russia, DIY Laser Rangefinder Scan YOU!!

June 5, 2016 by Elliot Williams 40 Comments

Yakov Smirnoff used to say, “In America, you can always find a party. In Soviet Russia, Party finds YOU!!” Only here, it’s a laser rangefinder.

In this project (automatic translation), [iliasam] makes his own scanning laser rangefinder, like the ones that we’ve seen in fancy vacuum cleaners. But he does it from scratch.

While this sort of thing is easy if you have a webcam and a ton of processing power to throw at it, [iliasam] takes the hard way out — measuring the parallax of the reflected spot through a lens on a linear image sensor (which renders as “photodetector line” in translated Russian).

Linear image sensors are a lot like the elements in your CMOS digital camera, with the exception that the elements are arranged in a line instead of a plane, and they’re a lot easier to interface with a microcontroller. Hold a data line high to take an exposure, and then clock out the (analog) voltage values that correspond to the amount of light that hit each cell in the line array. While [iliasam] paid an estimated $18 for his, we’ve found them much cheaper on eBay. And there’s usually a linear sensor, often RGB and complete with driver circuitry, in a scanner if you take one apart. This could be done for just a few bucks if you were thrifty.

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Learning ARM Without Dev Board

June 5, 2016 by Elliot Williams 25 Comments

There’s a tremendous amount of value in using pre-built, known-good development environments. It saves you hours of potential headaches when things aren’t working. Is the bug in the hardware or the software? If you bought a dev kit, you can be pretty sure it’s your software. But sometimes using a dev kit also feels like there’s a black box in the system. [Kevin] wanted to peer inside the black box, so he ordered a tray of cheap STM32F103 chips on eBay, and did the rest himself.

“The rest” isn’t all that much, but figuring that out is half the battle. [Kevin] soldered the TQFP chip onto a breakout board, added some decoupling capacitors, and connected four pins up to a dirt-cheap ST-Link programmer clone. The rest of the article describes the toolchain he used to compile for and program the chip. The end result is, natch, a blinking LED.

If you’re a bit experienced with microcontrollers and want to dive head-first into an ARM chip, [Kevin]’s writeup is just the ticket. In a single (long) blog post, he walks you through all the steps. If this is your first rodeo, you might be tempted to cheese out and buy a pre-built board on eBay (search “STM32F103” and you’ll find many options to choose from) and we don’t think that’s a bad idea either. Still, there’s just something to be said for the confidence that you’ll have once you’ve built the whole system from scratch.

Real-Time FPGA Finger Detection

June 4, 2016 by Elliot Williams 12 Comments

The student projects that come out of [Bruce Land]’s microcontroller- and FPGA-programming classes feature here a lot, simple because some of them are amazing, but also because each project is a building-block for another. And we hope they will be for you.

This time around, [Junyin Chen] and [Ziqi Yang] created a five-in-a-row video game that is controlled by a pointing finger. A camera, pointed at the screen, films the player’s hand and passes the VGA data to an FPGA. And that’s where things get interesting.

An algorithm in the FPGA detects skin color and, after a few opening and closing operations, comes up with a pretty good outline of the hand. The fingertip localization is pretty clever. They sum up the number of detected pixels in the X- and Y-axis, and since a point finger is long and thin, locate the tip because it’s going to have a maximum value in one axis and a minimum along the other. Sweet (although the player has to wear long sleeves to make it work perfectly).

How does the camera not pick up the game going on in the background? They use a black-and-white game field that the skin-color detection simply ignores. And the game itself runs in a Nios embedded processor in the FPGA. There’s a lot more detail on the project page, and of course there’s a demo video below.

We love to follow along with Prof. Land‘s classes. His video series is invaluable, and the course projects have been an inspiration.

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Flying Balls Of Molten Aluminum!

June 3, 2016 by Elliot Williams 47 Comments

We’re replacing “holy moley” in our vocabulary. Levitating globs of molten aluminum are that much more amazing. It’s not that we couldn’t believe it would work — we understand the physics after the fact. It’s just that we never would have thought to build an induction forge that can simultaneously melt and levitate a chunk of aluminum. (Video embedded below.)

[imsmoother] has had plans for 3 kW and 10 kW induction heaters online since at least 2011, and we’re wondering how we haven’t covered it before. Anyway, in the video, he’s using the smaller of the two to melt a chunk of aluminum. Continue reading “Flying Balls Of Molten Aluminum!” →

Minimal MQTT: Power And Privacy

June 2, 2016 by Elliot Williams 43 Comments

In this installment of Minimal MQTT, I’m going to cover two loose ends: one on the sensor node side, and one on the MQTT server side. Specifically, I’ll tackle the NodeMCU’s sleep mode to reduce power and step you through bridging MQTT servers to get your data securely out of your home server and into “the cloud”, which is really just other people’s servers.

If you’re just stepping into this series now, you should really check out the other three posts, where I set up a server, then build up some sensor nodes, and then flesh-out a few ways to control everything from your phone or the web. That’s the coolest material, anyway. This last installment just refines what we’ve built on. Let’s go!

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