An ever-present challenge in electronic circuit design is selecting suitable components that not only perform their intended task but also will survive under foreseeable operating conditions. A big part of that process is making sure that your components will stay within their safe operating limits in terms of current, voltage, and power. Of those three, the "power" portion is often the most difficult (for both newcomers and experts) because the safe operating area can depend so strongly on the particulars of the situation.

In what follows, we'll introduce some of the basic concepts of power dissipation in electronic components, with an eye towards understanding how to select components for simple circuits with power limitations in mind.

From the forums:

Guy Albertelli wrote in with an unexpected use of his Alpha Clock Five kit: a turn signal machine for the back of his Xtracycle-- complete with a "SORRY" button and a random-scrolling-message mode (that isn't shown in the video). There's even a clock mode with an improvised "second hand."

One might argue that the scrolling messages could be a little simpler, but that's really missing the point: this is an awfully clever application for a bright and self-contained alphanumeric LED display.

Guy's video is embedded above. (YouTube link).

A mermaid's purse is the iconic protective egg case of certain oviparous (egg laying) sharks and skates.

Here's another version, made of crepes, perfect for protecting your eggs at breakfast time.

Capitalism Works For Me! True/False is a beautiful interactive art piece by Steve Lambert designed to spark conversation around a difficult subject. It was made after a successful kickstarter campaign and is now touring the country.

From the project description:

Start a conversation about capitalism and friends edge away slowly, and strangers even faster. This is what art is for. This is what art does well. It creates a space where new ideas and perspectives can be explored. A space unlike any other.

Our very own 12" seven segment displays were used for showing the vote tallies as viewers interact with the piece.

After being first displayed in Cleveland, it is currently on its way to Boston for the 2012 deCordova Biennial which opens January 22. You can check up on its progress and destinations through kickstarter updates or Steve's site.

Zener diodes are a special type of semiconductor diode-- devices that allow current to flow in one direction only --that also allow current to flow in the opposite direction, but only when exposed to enough voltage. And while that sounds a bit esoteric, they're actually among the handiest components ever to cross an engineer's bench, providing great solutions to a number of common needs in circuit design.

In what follows, we'll show you how (and when) to use a Zener, for applications including simple reference voltages, clamping signals to specific voltage ranges, and easing the load on a voltage regulator.

The San Francisco Chronicle ran a profile of us yesterday.

"In recent times, they have helped create an accepted definition of open source hardware, participated in the annual Open Source Hardware Summit in New York, and are in the exploratory stages of building a foundation to support open source hardware."

You can read the rest of the (front page!) article here.

Recently we have seen some fantastic DIY examples of CNC image carving with traditional halftones and alternative versions with regions generated with reaction-diffusion equations. More impressively, all of this is now possible with freely available, homegrown software released by the people behind those projects (Here and here.)

Seeing these examples reminded us of another "classic" method of making halftones: ASCII art. In what follows, we walk through the process of using making CNC halftones for engraving or carving from both vintage and automatically generated ASCII art.

One of the finest cocktails that we have ever come across is the cucumber martini, a cocktail which-- correctly executed --can be a bracingly refreshing blast of intense cucumber flavor, highlighting what is perhaps an under-appreciated member of the melon family.

Unfortunately, cucumber martinis often fail to live up to their potential, ending up as watery infusions that might be mistaken for scented mineral water. And that's an injustice.

To set the record straight, here is how to make your own thoroughly-awesome cucumber martini. To go one step further, we present three distinct variations: the Sweet Vodka Cucumber Martini, the gin-based Savory Cucumber Martini, and the non-alcoholic Cucumber Fizzy.

Here's some easy to make festive holiday candy that doesn't taste anything like candy-canes, fruitcake, gingerbread or eggnog.

What's cooler than itty bitty alphanumeric LED displays? Freaking huge ultrabright alphanumeric LED displays, that's what!

And so today we're releasing a new kit, the Alpha Clock Five, an open-source, hacker-friendly alarm clock kit, based around an block of five ultrabright red 2.3" character height alphanumeric displays:

So, how big are these things?

For scale, here's one of the displays next to a Diavolino board:

These displays are great in many ways-- they're extremely bright for one --but the downside is that they are actually a bit tricky to drive. The 10 "big" segments each have two LED elements in series, twice in parallel, while the smaller segments have two LED elements in series, but not in parallel, and the decimal points each have a single LED element. To drive each LED element at (for example) 25 mA and 2 V requires 4V, 50 mA to be provided to ten segments, 4V 25 mA to the six short segments, and 2 V at 25 mA to each decimal point. And, it's a fair number of signals to manage as well.

To solve the problem, we designed a multiplexed driver board, with two LED driver chips at different current set points. A 16-bit constant-current LED driver is preset at 50 mA and drives the ten large segments, while a separate 8-bit constant-current LED is preset at 25 mA and drives the short segments and the decimal place. The multiplexing is in analogy with an LED matrix, where each alphanumeric character comprises one row of our matrix-- which just happens to have 54 LED elements inside. One row is switched on at a time by one of five transistors. We used high-current, low-saturation-voltage PNP transistors, type 2STX2220-- the low saturation voltage means that you *can* use these to switch a useful 4 V load, even when running at 5 V.

The circuit board is 9.430 X 2.736" in size, and extra stiff at 0.094" thick in order to support those heavy LED displays in their sockets. An ATmega644A microcontroller runs the show, and is preloaded with a bootloader so that you can program it like a Sanguino board, through a version of the Arduino IDE with added extensions. There's also a magnetic buzzer so that it can be a full-on alarm clock, and a spot for a Chronodot module, for good timekeeping and battery backup.

Here's what the front of the "brick" looks like, with the five displays socketed next to one another. There are four right-angle tactile button switches hanging off of the top edge, so that you can adjust the time, alarm time, brightness, and so forth. If you hold the two rightmost buttons for a couple of seconds, it brings you to the options menu, where you can (for example) switch between 12 and 24 hour modes:

The circuit board, laden with alphanumeric displays, sits inside an acrylic case:

The front side of the case is deep red transparent acrylic (#2423 red transparent, should that come in handy), and serves to increase the contrast of the displays. The back of the case is gray transparent acrylic, and the top and bottom are black. The top surface has engraved labels for the four buttons, and four button keys cut into the acrylic. The thin beam flexes easily, contacting the right-angle switch below, when the circuit board is there.

The back of the case is transparent so that you can see the circuit board. There's also a white LED "night light" on the circuit board that can be enabled or disabled with the top buttons, and the sides are open to provide easy access to the TTL serial interface.

Obviously there's a lot that could be done by hooking up a nice 5-character alphanumeric data display device to your computer.

On top of everything else, Alpha Clock Five is also a full-fledged alarm clock, right down to the snooze mode--- although the word "SNOOZE" didn't quite fit on the display (it says "SNOOZ," if you must know).

Perhaps the biggest challenge for making it "bedroom compatible" was that it needed to not just be able to be extremely bright, it also has to be able to go crazy dim-- which it can do, with fourteen levels of adjustable brightness.

And it has some fantastic features as an alarm clock-- for example multiple alarm tones and digits that are big enough to see even if you normally wear glasses.

And with a bit of code, it can be so much more. Soon, yours might say spell out "TRACY WAKE THE HECK UP" or use a couple of its spare I/O lines-- and only make you coffee if you actually manage to get up on time.

Alpha Clock Five is available now at Evil Mad Science.