Peter wrote in about his experience with the Digi-Comp II:
I just wanted you and the entire Evil Mad Scientist team to know that the Digi-Comp II was a big success. I used it to explain digital computers to a group of second graders and fifth graders. In an age of iPads and smartphones, it’s surprisingly hard to demonstrate the beauty and magic of digital computer. The Digi-Comp II was perfect, looked great, and worked flawlessly. Thanks!
The folks at BoldPort have created PCBmodE, free open source software for designing printed circuit boards, but with an artistic perspective. Traditional EDA tools are designed from an engineering perspective, whereas PCBmodE treats the PCB as a creative palette. They aim to give you freedom to express your design with all the tools of the medium.
We wanted to create circuit boards that have curvey traces, meandering paths, and multiple soldermask layers, so we developed PCBmodE (say “PCB mode”), an open source Python software that unshackle us from the constraints imposed by traditional PCB design tools. We use the power of Inkscape — the leading open source vector graphics editor — to achieve any shape imaginable. Together with our powerful back-end tools, we can manufacturable beautifully functional boards.
They’ve posted about several of their example boards including pieceof (pictured above), a Raspberry Pi daughterboard called shimmy, and a tribute board dedicated to Bob Pease. This is a really neat approach to building circuit boards, and it looks like it has a lot of potential.
The conic sections are the four classic geometric curves that can occur at the intersection between a cone and a plane: the circle, ellipse, parabola, and hyperbola.
The scone is a classic single-serving quick bread that is often served with breakfast or tea.
And, at the intersection of the two, we present something entirely new, delightfully educational, and remarkably tasty: Sconic Sections.
In what follows, we’ll show you how to bake cone-shaped scones, to slice them into plane geometric curves, and to highlight those curves by selective application of toppings. We’ll also discuss some of the methods that didn’t work so well, as we refined our methods for making these.
Onwards, towards parabolic preserves and hyperbolic Nutella!
Continue reading Play with your food: How to Make Sconic Sections
When we recently wrote about looking at solder paste up close, we happened to mention that it has a shelf life— something that you might expect to be uncontroversial considering that there is an expiration date, printed right there on the jar.
But, our reader Trav commented
Very nice pics. What happens to solder paste when it expires? does it taste funny? Do the balls go flat?
I assume the paste rather gets runny and doesn’t hold the solder in place or it gets thick and won’t spread evenly.
I’ve heard of it expiring, but never knew how. I’ve had a tube of flux for 20 years now. When it gets too thick, I put in a couple drops of alcohol and it seems to work good as new.
We like the “balls go flat” theory! But seriously, we presume that they wouldn’t label paste with a short shelf life— typically 4-12 months, when kept refrigerated, depending on the type of paste —unless there were a reason (and hopefully, a good reason) to do so.
A blog post on the Indium Corporation web site offers a little insight. It turns out that the “activator” chemicals within the flux, which serve to clean oxides off of the surfaces that will be soldered, also interact with the microscopic solder balls, gradually scouring off their surface oxides. When the solder particles are clean enough, they can actually cold-weld together, resulting in increased effective grain size and viscosity. As Trav notes, adding a little alcohol can reduce the viscosity of flux, but we can see how increased grain size and other factors (such as having used up some of the activators) could affect performance in other ways.
But in any case, it sounds like there are a range of experiences out there, and we would like to open the question for discussion: What has your experience been with out-of-date solder paste? Has it worked just fine? And if not, what was the failure mode?
Separately, what about (flux-cored) solder wire?
Kester has this to say, in their policy about shelf life:
Flux cored solder wire has a limited shelf life determined by the alloy used in the wire. For alloys containing more than 70% lead, the shelf life is two years from date of manufacture. Other alloys have a shelf life of three years from date of manufacture.
So, our spool of lead-free solder pictured above, with date of manufacture 3/16/05 expired five years ago in 2008. Presumably one reason for a stated expiration date is that the flux becomes less active over time as it interacts with the solder metal.
But in our personal experience, this kind of solder seems to generally work just fine, even many years past its nominal shelf life.
Many others seem to have had a similar experience with solder wire.
When we wrote about assembling a vintage Heathkit, we mentioned that it came with solder. It actually came with two little packets of solder, specifically 60/40 rosin-core, cheerfully labeled “Made Expressly For Heathkit by Alpha Metals, Inc.”
Seeing as (1) the kit and solder date back nearly 40 years, (2) Alpha Metals also uses the three-year figure for shelf life, and (3) we already had a fresh, open spool of Alpha Metals 60/40 rosin-core solder in the lab, we opted to use the fresh spool and save the vintage solder packets for a rainy day. Were we wrong to do so? Certainly, some of our readers thought so:
Solder shelf life? Are you sure about that? Solder paste has a shelf life but I’ve never heard of a shelf life for a real coil of 60/40 rosin core solder. I’ve used some pretty old stuff myself, a quick Google search for solder shelf life found me a discussion where a guy is talking about using solder from the 60s with no problem on the first click!
So what has your experience been? Have you used “old” solder, and if so, how well did it work?
You may already be familiar with Super Awesome Sylvia, who has been working hard with us on the WaterColorBot toward our planned launch in July. Sylvia was just featured in the June 24 issue of People Magazine. Way to go, Sylvia!
Previously: White House Science Fair Roundup
Here in the San Francisco Bay area, we’ve been watching the progress of the replacement of the east span of the Bay Bridge, which connects San Francisco to Oakland via Yerba Buena Island.
The California Department of Transportation has been doing an incredible job of sharing the progress with the public since construction began in 2002. The latest set of drool-worthy engineering photos is up on the Bay Bridge Info site, giving a peek deep inside the project.
The media archive chronicles the project since its start in video and pictures, so you can delve even deeper. You can also follow @BayBridgeInfo on twitter for updates. The new bridge is nearing completion, and is scheduled to open Labor Day weekend this year.
MakerBot is running a birdhouse design challenge, and the first prize is an Eggbot! The challenge runs through July 16, and the designs will be judged on functionality, printability and creativity. There are already quite a few entries on thingiverse, including the Death Star Birdhouse by plainolddave below.
Good news if you’re still working on— or haven’t yet started —your proposal for this year’s Open Hardware Summit: The call for papers has been extended, so you’ve got another week to fine tune your talk, poster, or demo proposal.
Submissions are now due by JUNE 28, 2013.
The Open Hardware Summit is the world’s first comprehensive conference on open hardware; a venue to discuss and draw attention to the rapidly growing Open Source Hardware movement. This year’s summit takes place on September 6 at MIT.
Previously: The 2013 Open Hardware Summit: Call for Papers,
The 2013 Open Hardware Summit: Tickets Now Available
Photo credit: Open Hardware Summit on Flickr.
Peter T. recently stopped by our shop with his Peggy 2LE and showed us his incredibly cool hack. He had noticed that the 0.1″ pin spacing for a standard through-hole LED is just about perfect to accommodate LEDs in a 1206 surface mount package.
Once he had finished populating all the LED locations, he brought it by again. He used an alignment jig he had made to keep everything in straight rows while soldering.
The surface mount LEDs look great on the grid designed for T-1 3/4!
We plugged it in so we could see his pretty orange LEDs in action. Thanks to Peter for bringing it by and letting us take pictures!
Courtesy of the United States Navy comes this incredible introduction to analog mechanical computers.
The context for this is that massive, mechanical computers were used aboard US Navy ships ranging from destroyers to battleships, from about 1944-1969, as part of the “Fire Control” system. This type of computer would take up to 25 continuously changing input variables in order to calculate the proper bearing and elevation for heavy caliber guns aboard the ship. This calculation— to ensure that a projectile will land at the place where the target is going to be —is marvelously complex, taking into account variables such as wind speed and direction, relative velocity of the ship and target, and parallax between the different guns on the ship. What’s truly remarkable is that it was all done with mechanical mechanisms such as gear differentials, cams, and mechanical integrators.
This two-part training film, from 1953, introduces the basic mechanisms that made these computers work:
The video embedded above (41:53 total length) contains both films, one after the other. (And, the YouTube link is here.)
Basic Mechanisms in Fire Control Computers, Part 1 discusses shafts, gears, cams, and differentials. Note that the first couple of minutes are not so much about the mechanisms, but more of an explanation— to the servicemen —of why they needed to learn about them.
Basic Mechanisms in Fire Control Computers, Part 2 discusses component solvers, integrators, and multipliers
If you enjoy these training films, you may also want to read through the little book entitled Ordnance Pamphlet 1140: Basic Fire Control Mechanisms, available here in PDF format, which covers much of the same ground.
