A Ridiculous Way To Light An LED: Candle-power

March 30, 2016 by Jenny List 31 Comments

If you have ever entertained yourself by reading comprehensive electronic-theory textbooks you’ll have seen references to technologies that sound really interesting but which you will rarely hold in your hand. They may be dead-ends that have been superseded by more recent innovations, or they may be technologies that have found uses but in other fields from those in which they originally showed promise. What if you could take these crazy parts and actually build something?

[Fedetft] has an interesting project that combines two of those intriguing textbook references, he’s created a thermopile that lights an LED through an inverter whose oscillator is a tunnel diode. Dig out the textbook.

If you’ve used a thermocouple thermometer or a semiconductor thermoelectric generator then you’ll have encountered the thermoelectric effect. Perhaps you’ve even operated a Peltier cooling element in this mode. When a circuit is made with two junctions between different types of conductor with a temperature difference between the two junctions, a current will flow in the circuit which is dependent on both the scale of the temperature difference and the properties of the conductors.

A thermopile is a collection of these thermoelectric junction circuits between metal conductors, arranged in series to increase the voltage. [Fedetft]’s thermopile uses chromel and alumel wires taken from a K-type thermocouple. He’s made six sets of junctions, and supported them with small pieces of mica sheet. Using the heat from a candle he found he could generate about 200mV with it, at about 3.7mW.

Such a tiny source of electricity would be of little use to light an LED directly, so he needed to build an inverter. And that’s where the tunnel diode comes in. Tunnel diodes have a negative-resistance region that can be used to amplify and oscillate at extremely high frequencies in extremely simple circuits, yet they’re not exactly a device you’d encounter very often in 2016. [Fedetft] has a Russian tunnel diode, and he’s used it with a toroidal transformer in an inverter circuit he found in an RCA tunnel diode manual from 1963. It’s a two-component Joule Thief. The RCA manual is a good read in itself for those curious about tunnel diodes.

The resulting circuit produces a 15kHz oscillation with 4.5v peaks, and has just enough power to light an LED.

While it might seem pointless to barely light an LED from a brightly lit candle, the important part of [Fedetft]’s project is to gain some understanding of two of those technological backwaters from the textbooks. And we applaud that.

It’s the mark of a truly esoteric technology that it features rarely on Hackaday, and neither of these two disappoint. We’ve only mentioned tunnel diode in passing when looking at diodes in general, and we’ve tended to use “thermopile” in another sense to refer to thermal imaging cameras.

Blinky LED Bike Bag

March 13, 2016 by Richard Baguley 20 Comments

Bicycle riders can never be too visible: the more visible you are, the less chance there is someone will hit you. That’s the idea behind the Arduibag, a neat open-source project from [Michaël D’Auria] and [Stéphane De Graeve]. The project combines a joystick that mounts on the handlebars with a dot matrix LED display in a backpack. By moving the joystick, the user can indicate things such as that they are turning, stopping, say thank you or show a hazard triangle to warn of an accident.

The whole project is built from simple components, such as an Adafruit LED matrix and a Bluno (an Arduino-compatible board with built-in Bluetooth 4.0) combined with a big battery that drives the LED matrix. This connects to the joystick, which is in a 3D printed case that clips onto the handlebars for easy use. It looks like a fairly simple build, with the larger components being mounted on a board that fits into the backpack and holds everything in place. You then add a clear plastic cover to part of the backpack over the LED matrix, and you are ready to hit the road, hopefully without actually hitting the road.

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Banish Dangerous Shadows Under Kitchen Cabinets

March 10, 2016 by Gerrit Coetzee 30 Comments

[nebulous] has a lot of problems with his kitchen cabinets. Aside from a noted lack of micro-controllers, he was especially suspicious of the dark spaces under them. Anything could be hiding there.

The core of the project is a $10 Arduino-compatible esp8266 board from digistump. The board is powered by the five volt regulator of an L298N motor driver module hooked to a power-supply. All this controls a set-of LED strips adhered to the underside of the cabinets with the traditionally bad adhesive strips with which they come standard. We can predict an hour spent bent awkwardly cursing at them, a hot-glue gun in one hand, in [nebulous]’s future. The whole set-up is housed in a SparkFun cardboard box above the microwave. You can barely tell it’s not a commercial product.

We’re not certain if we like a future where even our cabinetry has an IP address. However, this is a good weekend project that could make all our cabinetry brighter, safer, and more connected.

Faking A Hollow State Device

March 6, 2016 by Al Williams 30 Comments

There’s been a resurgence of interest in vacuum tubes. Even if you do think audio sounds better through a tube, you have to admit the care and feeding of filaments and plate voltages isn’t trivial. [Ed Nisley] decided to sidestep all that and just build an objet d’art that looks like a tube.

A burned out halogen bulb stands in for the tube, and a ceramic base holds the bulb. It also conceals–what else–an Arduino. The Arduino drives a knock-off Neopixel LED hidden in a faux plate cap. The result is a glass envelope bathed in a cold blue and purple glow that changes under software control.

We’d really like to see this kind of tube inside some rebuilt piece of tube gear. Or maybe Korg should offer LED lighting options for their recent tube in a chip form factor. If you really want to be a top-tier tube hacker, you can always try your hand at repair.

Polyhedrone

March 4, 2016 by Jenny List 6 Comments

[Brainsmoke] had a simple plan. Make a quadcopter with lots of addressable LEDs.

Not just a normal quadcopter with ugly festoons of LED tape though. [Brainsmoke] wanted to put his LEDs in a ball. Thus was born the polyhedrone, the idea of a flying deltoidal hexecontahedron covered as you might expect with all those addressable LEDs.

A Catalan solid makes a good choice for the homebrew polyhedron builder because its faces are all identical. Thus if you are making PCBs to carry LEDs, for example, you need only create a single PCB design to use on all faces. A bit of work in KiCAD, and a single face design with interlocking edges was ready. The boards were tested, a wiring layout was worked out, and the polyhedron was assembled.

But [Brainsmoke] didn’t stop there. He produced a flight case for the polyhedron, in the form of a larger polyhedron from what looks like lasercut thin ply.

Having a finished polyhedron, the next thing was to hook up a Raspberry Pi and write some software. First in Python, then in Go.

The results are simply stunning. If the mathematics and construction of a polyhedron were not enough to make this project worth a second look, then the gallery of images should be enough. You’ll notice that this is ostensibly a quadcopter project, yet no mention of flying has been made on this page. That’s because this is still a work in progress at Tech Inc Amsterdam, and there is more to come. But it honestly doesn’t matter if this project never moves a millimeter off the ground, as far as we are concerned [Brainsmoke] has created a superbly built thing of beauty in its own right, and we like that.

As you might expect, this is just the latest of many projects featured here that have involved addressable LEDs or quadcopters. Of note among them is this LED polyhedron that cleverly closes in all its bits, and this LED-equipped quadcopter that generates very pleasing patterns with a hi-res cross of pixels.

Building An Interactive LED Lamp To Annoy Yourself

March 1, 2016 by Gerrit Coetzee 12 Comments

[Norwegian Creations] makes things as a business model. Tired of the mundane lamp above their heads, they decided to put their skills to use. The basic idea was simple, plot out a cool 3D function, put some RGB LEDs behind it, make it an awesome mathematical rainbow light display, hang it right above their desks, and then ignore it for their monitors while they worked.

The brains of the project is a Raspberry Pi B+, WS2812 LED strips, and a Fadecandy controller from Adafruit. They 3D printed hexagonal towers out of clear plastic and labeled each carefully. Then they attached the strips to the board, glued on the hexagons, and covered the remaining surface in cotton balls to give it a cloud-like appearance.

The lamp normally plays patterns or maintains a steady light. As the day turns to night it reflects the world outside. However, if someone likes their Facebook page the light has a little one robot strobe party, which we imagine can get annoying over time. Video after the break.

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Musical Shades

February 17, 2016 by Al Williams 17 Comments

There are only so many blinking light patterns you can create with a microcontroller before you get bored. [Garrett] apparently felt that way and decided to build a music-driven LED display on some LED shades. The system has three main elements: a microphone, a preamp, and a 7-band spectrum analyzer chip. You can see the results in the video below.

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