What the Flux: How Does Solder Work Anyway?

I’ve been soldering for a long time, and I take pride in my abilities. I won’t say that I’m the best solder-slinger around, but I’m pretty good at this essential shop skill — at least for through-hole and “traditional” soldering; I haven’t had much practice at SMD stuff yet. I’m confident that I could make a good, strong, stable joint that’s both electrically and mechanically sound in just about any kind of wire or conductor.

But like some many of us, I learned soldering as a practical skill; put solder and iron together, observe results, repeat the stuff that works and avoid the stuff that doesn’t. Seems like adding a little inside information might help me improve my skills, so I set about learning what’s going on mechanically and chemically inside a solder joint.

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An Open Source Lead Tester

If you’ve ever needed an example of colossal failure of government actors, you need only to look at Flint, Michigan’s water crisis. After the city of Flint changed water supplies from Detroit to the Flint river, city officials failed to add the correct corrosion inhibitors. This meant that lead dissolved into the water, thousands of children were exposed to lead in drinking water, a government coverup ensued, [Erin Brockovich] showed up, the foreman of the Flint water plant was found dead, and the City Hall office containing the water records was broken into.

Perhaps inspired by Flint, [Matthew] is working on an Open Source Lead Tester for his entry into the 2016 Hackaday Prize.

[Matthew]’s lead tester doesn’t test the water directly. Instead, it uses a photodiode and RGB LED to look at the color of a lead test strip. These results are recorded, and with a bit of a software backend, an entire city can be mapped for lead contamination in a few days with just a few of these devices.

One problem [Matthew] has run into is the fact the Pi does not have analog to digital conversion, making reading a photodiode a little harder than just plugging a single part into a pin header and watching an analog value rise and fall. That really shouldn’t be a problem – ADCs are cheap, especially if you only need a single channel of analog input with low resolution. [Matthew] is also looking into using the Pi webcam for measuring the lead test strip. There are a lot of decisions to make, but any functional device that comes out of this project will be very useful in normal, functioning governments. And hopefully in Flint, Michigan too.

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Retrotechtacular: Submarine Cable Splicing is Serious Business

Really. As this wonderfully narrated talkie picture from 1939 will attest, keeping even one drop of water from penetrating undersea cables is of the utmost importance.

How do they do it? Many, many layers of protection, including several of jute wrapping. The video centers on splicing a new cable to an existing one in the San Francisco Bay to bring the wonder of telephony to a man-made island created for the Golden Gate International Expo.

The narrator makes these men out to be heroes, and when you see how much lead they came into contact with, you’ll understand what he means. Each of the 1,056 individually insulated wires must be spliced by hand. After that comes a boiling out process in which petrolatum is poured over the splice to remove all moisture. Then, a lead sleeve is pulled over the connections. Molten lead is poured over the sleeve and smoothed out by hand.

At this point, the splice is tested. The sleeve is punctured and nitrogen gas is pumped in at 20psi.  Then comes the most important step: the entire sleeve is painted with soap suds.  Any gas that escapes will make telltale bubbles.

Once they are satisfied with the integrity of the sheath, they wrap the whole thing in what appears to be lead cables and pound them into submission. Surely that would be enough, don’t you think?  Nope.  They weld the cables all around and then apply two coats of tar-treated jute wrapping, which retards saltwater corrosion considerably.

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Hackaday Links: Sunday, May 12th, 2013


[Johnathan Crawford] isn’t bashful about tearing the insides of his truck apart. He’s built his own remote starter using a Raspberry Pi.

We vaguely remember hearing about a startup that planned to deliver tacos using quadcopters instead of people. We assume that company was a bust but here’s the concept in action at the 2013 RoboGames [thanks Don].

On the topic of food: pizza and joysticks… do they go together? Perhaps. Here’s a joystick made out of an empty pizza box (note the remains of grease stains inside).

[Jonathan] brings to our attention the problem of running out of fingers to press all the buttons on your Monome at just the right moment. No worries, just add some solenoids to act as extra fingers.

Apparently some Samsung cameras (NX20, NX210 and NX1000) can use their USB port as a shutter release. The trick is finding the right resistor values for the ID pin [thanks Janne].

Plagued with a tablet dock that wasn’t weighty enough to prevent the device from tipping over [John] filled base with lead to keep the thing upright.

[Helmut’s] bathroom had no windows. He faked one using an Arduino and an RGB led.

And finally, as a reward for all the readers that made it to the bottom of the article, here’s a gem of a project. [Charlie] was inspired by the recent logic combo lock post to send in his own plans for a lock he made years ago. Unfortunately he can’t find the pictures from the build but the theory behind it is quite engaging.

Gravity bike

This bicycle has no pedals and really nothing that resembles a seat. It’s not so much a way to get around as it’s a way to get down. Down from the mountain, and down low to the pavement. This is a gravity bike built by the guys at S.I.N. Cycles.

The frame is a long triangle which stretches the wheel base to make room for the rider. After getting the layout just right and welding the frame together they added the rather unorthodox building step of pouring molten lead into the hollow frame tube. This bike is used to descend a mountain road with the force of gravity, so the extra weight will help pull it just a bit faster. There’s one thing you’ll want to make sure is working before you climb aboard — the single front brake which you’ll need when coming into the curves. Check out some ride footage on this thing in the video after the break.

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Making a cold heat soldering iron


Cold Heat soldering irons are pretty cool. They heat up in seconds and cool down just as quickly. [photozz] shows us how we can make one from stuff we probably have sitting around right now. Cold Heat soldering irons work off of resistance, the tip material heats very quickly when electricity is passed through the two halves. Upon assessing what he had lying around, [photozz] realized that graphite would work much the same way.  He modified a regular soldering iron with a new two piece graphite tip, and powered it with an old pc power supply. The end result is quite nice, though it still needs some kind of temperature control.  You may recall seeing other electrical uses for graphite, such as making quick and dirty light.

How-To: Go green with lead free solder

We covered many of [Jason Rollette]’s personal projects in the past and are happy to welcome him as our newest Hack-A-Day contributor.

The electronics industry has shifted to lead free compliance, but most hobbyists haven’t even considered the personal impact of using lead. Today’s How-To will cover what it takes to switch from tin/lead solder to completely lead free. Our previous posts Introduction to soldering and the follow-up still apply to lead free. You may have never considered switching to lead free before, but we hope to help you make an informed decision.

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