Gesture Recognition Using Ultrasound

April 5, 2014 by Will Sweatman 27 Comments

SAMSUNG

You’d be hard pressed to find a public restroom that wasn’t packed full of hands free technology these days. From the toilets to the sinks and paper towel dispensers, hands free tech is everywhere in modern public restrooms.

The idea is to cut down on the spread of germs. However, as we all know too well, this technology is not perfect. We’ve all gone from sink to sink in search of one that actually worked. Most of us have waved our hands wildly in the air to get a paper towel dispenser to dispense, creating new kung-fu moves in the process. IR simply has its limitations.

What if there was a better way? Check out [Ackerley] and [Lydia’s] work on gesture recognition using ultrasound. Such technology is cheap and could easily be implemented in countless applications where hands free control of our world is desired. Indeed, the free market has already been developing this technology for use in smart phones and tablets.

Where a video camera will use upwards of 1 watt of power to record video, an ultrasound device will use only micro watts. IR can still be used to detect gestures, as in this gesture based security lock, but lacks the resolution that can be obtained by ultrasound. So let us delve deep into the details of [Ackerley] and [Lydia’s] ultrasound version of a gesture recognizer, so that we might understand just how it all works, and you too can implement your own ultrasound gesture recognition system.

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Rebuilding A 50,000 Volt Power Supply

March 24, 2014 by Brian Benchoff 43 Comments

Spark

The theory behind building power supplies is relatively easy, but putting it into practice and building a multi-kilovolt supply is hard. A big transformer in air will simply spark to itself, turning what could be something very cool into something you just don’t want to be around. [glasslinger] over on YouTube is an expert at this sort of thing, as shown in his 50,000 Volt power supply build. That’s a 55 minute long video, and trust us: it’s worth every minute of your time.

[glasslinger] began his build by taking an old 15,000 Volt neon sign transformer and repurposing the coils and cores for his gigantic 50,000 volt transformer. There was a small problem with this little bit of recycling: the neon sign transformer was potted with tar that needed to be removed.

To de-pot the transformer, [glasslinger] made a small oven from a helium tank, melting all the goo out with an old school gasoline torch. From there, hours and hours of cleaning ensued.

The transformer cores were cleaned up and cut down, and a new primary wound. A small-scale test (shown above) using the old secondaries resulted in a proof of concept with some very large sparks. The next step was putting the entire transformer in a box and filling it with transformer oil.

The money shot for this build comes when [glasslinger] assembles his transformer, rectifier, and all the other electronics into a single, surprisingly compact unit and turns standard wall power into a 50,000 Volt spark. You can literally smell the ozone from the video.

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This Machine Sucks Balls

March 23, 2014 by Brian Benchoff 31 Comments

The best career choice anyone could ever make – aside from the richest astronaut to ever win the Super Bowl – is the designer of the kinetic art installations found in science centers that roll billiard balls along tracks, around loops, and through conveyors in a perpetual display of physics and mechanics. [Niklas Roy] isn’t quite at that level yet, but he has come up with a new twist on an old idea: a machine that literally sucks balls from a ball pit into transparent tubes, sending them whizzing around the installation space.

The installation consists of eighty meters of plastic tubing suspended in the staircase of Potocki Palace in Kraków. Electronically, the installation is extremely simple; a PIR sensor turns on a vacuum cleaner whenever someone is in the ball pit. This sucks balls up through a hose, around the space, and into a bin suspended over the pit. Pull a lever, and the balls stored in the bin are dispensed onto the person vacuuming up thousands of balls below.

Image source, with video below.

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Need To Reference The US Constitution Fast? How’s 6 Seconds Sound?

March 21, 2014 by James Hobson 34 Comments

CONSTI2GO-Thibault-Brevet-2

Well, unless you know exactly what you’re referencing it’s going to take you a lot longer, but this clever serial receipt printer hack will let you print the whole darn thing in just 6 seconds!

Commissioned by [Jeff Goldenson] for his LABRARY.bike (quite literally a pop-up library on a bike), it was actually shown off at SXSW Interactive — did anyone see it in person? The artist-hacker who created it is [Thibault Brevet], the guy who brought us the DRM chair that only works 8 times before it falls to pieces.

Anyway, this cool and rather suspicious looking tube with a serial cord hanging out contains an Arduino, a max232 chip and a small Li-Po battery. The Arduino communicates with the printer through the max232 chip by converting the TTL signal to RS-232. It has a single button on top, which when it is connected to the printer will send out the US Constitution over the serial interface via ESC/p language.

Did we mention how fast it is?

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Good Vibrations: Giving The HC-SR04 A Brain Transplant

March 17, 2014 by Adam Fabio 23 Comments

[Emil] got his hands on a dozen HC-SR04 ultrasonic sensors, but wasn’t too happy with their performance. Rather than give up, he reverse engineered the sensor and built an improved version. Hackers, Makers, and robotics enthusiasts have had easy access to standard sonar platforms since the early 1980’s, when Polaroid began selling their 6500 sonar modules. A number of companies have released sonar boards since then, notably The Parallax Ping))) module. The HC-SR04 appeared on the market a few years back as a low-cost alternative of the Ping.

[Emil] found that the HC-SR04 would work reliably on hard surfaces as far as 4 meters away from the sensor. However, he got a lot of bad data back when using soft sided targets, or when no target was present at all. [Emil] reverse engineered the schematic of the HC-SR04 and found some interesting design decisions. A Max232 RS-232 converter chip is used for its ~~+-12V~~ +-10V charge pumps. The charge pumps are connected to create ~~24V~~ 20V at the ultrasonic transmitter. A mask programmed microcontroller manages the entire unit, commanding the ultrasonic transmitter to send 40Khz pulses, and listening for returns on the receive side of the system. [Emil] believes the micro is running in polled mode, due to the fact that it sometimes misses pulses. Even worse, the micro runs on an unmarked 27MHz crystal which had quite a bit of drift.

[Emil] solved these problems by creating his own PCB with an ATtiny24 and a 12MHz crystal. He increased the pin count from 4 to 6, allowing the ATtiny to be programmed in circuit, as well as opening the door to I2C and SPI operation. To build the boards up, [Emil] first solders his micro and crystal. He then uses a hot air gun to move all the components from the HC-SR04 board to his own. The new boards are still being tested, but [Emil] has posted his PCB and BOM data. He’s also promised to post his AVR code when it is available.

Measuring Poop For A Better Sanitation Service

March 14, 2014 by James Hobson 17 Comments

poop

Hacking can make a huge difference in peoples’ lives. So when the Nottingham Hackerspace was challenged with optimizing Ugandan Toilets, they hopped on-board.

Back in January of this year [Nicola Greene] approached the hackerspace with this real-life design problem. She represents Water for People, with support from a UK-based Engineers Without Borders organization. Water for People is involved with improving access to sanitation in Uganda and many other third world countries — to make sure everyone has access to a safe and usable toilet. The cool thing with Water for People is they don’t just want to build an infrastructure for the people and run away, they want to bring together local entrepreneurs and the community to establish a system that will actually last.

So, what is the problem anyway? Well, since Uganda doesn’t have quite the same network of sanitation businesses as we might, it’s important for the new infrastructure to know a few things — in particular, how much do we poop? This question was summarized into a basic goal for the Nottingham Hackerspace:

To develop a low-cost (<$200) monitoring device to give an approximation of what volume of liquids — and in an ideal world, solids, is entering the latrine.

Before you click through, think about how you would solve this?

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Face Tanner PCB UV Lamp Is So Bright, You Gotta Wear Shades

March 6, 2014 by Kristina Panos 11 Comments

There may be nothing new under the sun when it comes to etching PCBs with UV light, but [Heliosoph] has brought finer control to a used face tanner he bought that now exposes his boards in ~50 seconds.

The original system allowed for exposure times from 1-99 minutes to be programmed in 1-minute increments. [Heliosoph] though it would be perfect as-is, but the lamp is so powerful that even one minute of exposure was too much. He hoped to find TTL when he opened the thing and was pleasantly surprised to discover a COP410L microcontroller and an MM5484 display driver. Unfortunately, the COP410L’s clock range is too small and he didn’t want to overclock it.

[Heliosoph] built a new board based on the ATMega328P with a salvaged 16×2 LCD, which he was able to easily integrate using the library that ships with the Arduino IDE. He then replaced the BT136 triac lamp switch with a solid state relay, conveniently isolating the electronics from mains power. He re-purposed the unit’s push buttons using the M2tklib, which supports a plethora of common menu functions.

If you need some help with the whole UV PCB etching process, you can’t go wrong with this tutorial from [CNLohr].