DIY Spot Welder Doesn’t Look Like It Will Immediately Kill You

April 24, 2016 by Gerrit Coetzee 30 Comments

We love hacks that involve mains voltage, but most of the time, for safety’s sake, we secretly hope for that one macabre commenter that details every imaginable way the questionable design choices will result in death. This spot welder may still be dangerous, but it looks like they took some precautions to make it non-lethal, and that counts for a lot.

After their extremely questionable high speed belt sander, this one is, refreshingly, extremely well done. It starts of as a dead standard microwave spot welder build: take apart microwave, try not to die from large capacitor, remove coil, modify coil, and hook up.

After that, it gets to some nice heavy metal music fabrication. Aside from a slightly shocking number of fresh OSHA reportable hand injuries (wear gloves!) the build goes together well. A lot of planning obviously went into it, from the actively cooled transformer to what appears to be a resettable timer circuit for the weld duration, not to mention the way that it just fit together so well at the end. There were some neat ideas as far as home mechanics go that we’ll be using in some of our projects.

In the end, the proof is in the spot-weld. The timer is set, pedal gets pressed down, and when tested, the sheet metal breaks instead of the weld. Video after the break.

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Magical Blinky Capacitive Sensing Tweezers

April 23, 2016 by Brian Benchoff 10 Comments

Electronic tweezers – the kind that can test the voltage between two contacts, the resistance of an SMD resistor, or the capacitance of a circuit – are very cool and very useful if somewhat expensive. We’ve seen commercial versions of these smart tweezers, hacks to make them more useful, and homebrew versions that still work very well. All of these versions are pretty large, as far as tweezers go. [kodera2t]’s version of electronic tweezers submitted for this year’s Hackaday Prize goes in the other direction: it’s the smallest set of electronic tweezers that’s still useful.

[kodera]’s electronic sensing tweezers only measure capacitors, and for good reason: chip caps usually don’t have values printed on them. These tweezers don’t print out the value of a cap on a display, either. Instead, these tweezers just flash an LED if the value of the cap is above 0.1uF. It’s simple, but surprisingly useful for most soldering jobs.

The circuit for this pair of magical tweezers is about as simple as if can get, with all the smarts contained in a very small ATtiny10. The PCB [kodera] designed is smaller than the coin cell battery, and with the help of some copper tape and possibly an insulator, this device can be mounted to any pair of tweezers. It’s a simple tool, yes, but that’s the beauty of it, and makes for a great entry into the Hackaday Prize

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Casting A Lathe Out Of Concrete

April 20, 2016 by Brian Benchoff 75 Comments

Look up ‘concrete lathe’ and you’ll quickly find yourself reading the works of [David Gingery]. His series of books on building a machine shop from scrap begin with a charcoal foundry, and quickly move to creating a metal lathe out of concrete. Before [Gingery]’s lathe, around the time of World War I, many factories created gigantic machine tools out of concrete. It’s an old idea, but you’ll be hard pressed to find anyone with a shop featuring concrete machine tools. Cheap lathes are plentiful on Craigslist, after all.

Building a metal lathe from concrete is more of a challenge. This challenge was recently taken up by [Curt Filipowski] in a five part YouTube series that resulted in a real, working lathe made out of concrete, scrap, and a lot of bolts.

The concrete lathe begins with a form, and for this [Curt] cut out all the parts on a CNC router. Creating the form isn’t quite as simple as you would think – the concrete form included several bolts that would alow [Curt] to bolt bearings, ways made out of gas pipe, and angle iron. This form was filled with concrete in [Curt]’s kitchen, and after a nice long cure, the lathe was moved up to the upstairs shop. That’s a five hundred pound block moved up a flight of stairs by a single person.

The rest of the build deals with the cast concrete carriage which rides along the polished gas pipe ways, a tool post holder milled out of a block of aluminum, and finally making some chips. While it’s not the most practical lathe – the carriage moves along the ways by turning a wheel underneath the tailstock – it does demonstrate a concrete lathe is possible.

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Building A Taller Drillpress

April 16, 2016 by Elliot Williams 23 Comments

[BF38] bought a mid-range miniature drill-press, and discovered that it was just too short for some of his applications. “No problem,” he thought, “I’ll just measure the column and swap it out for a longer one.” It sounds foolproof on paper.

He discovered, after having bought a new 48.3 mm steel column, that the original was 48 mm exactly in diameter. He’d have to make it fit. But how do you bore out a 48 mm diameter hole, keeping it perfectly round, and only increase the diameter by 0.3 mm? A file is out because you’d never get it round. A lathe is out because [BF38] doesn’t have a lathe.

[BF38] ended up making a DIY honing head, which is a gadget that presses (in this case) two pieces of sandpaper evenly against the sides of the hole to be widened. The head in question is a little bit rough — it was made as a learning project, but it looks like it served the purpose admirably.

One SMT Breakout To Rule Them All

April 16, 2016 by Elliot Williams 33 Comments

You need to use surface-mount technology (SMT) parts in your design. But you also need to prototype. How to fit those little buggers into your breadboard?

[Simon] came up with a general-purpose SMT-to-breadboard solution. Now, there are already myriad adapter boards for the many-pin devices: SSOP-to-DIP adapters and so on. But what do you do when you just need to work that tiny SOT223 voltage regulator into a breadboarded circuit?

[Simon]’s solution fills that gap with one breadboardable design to handle all of your small-pin-count part needs. It accommodates SOT223, SOT323, and SOT23 three-pin parts like transistors or voltage regulators, and also has pads for all of the common two-terminal parts like resistors and capacitors from 0402 on up to 1206. You could build up a full voltage regulator circuit on one of these things. He’s even included some whitespace on the back for your notes.

SMT parts aren’t even the future any more. And with the right procedure, they’re not hard to hand-assemble. So the next time you have some extra space in a PCB order, toss in a couple of [Simon]’s breakouts and you’ll be ready for your next breadboarding session.

Measuring Parts Badly For Accurate Reverse Engineering

April 15, 2016 by Gerrit Coetzee 107 Comments

Previous headquarters of Useful Thing Inc. They made the best widget you could buy in the 80s.

Like most hackers, I’ve run into a part that looks like it might do what I want, but the only documentation came from a company so thoroughly defunct their corporate office is now a nail salon and a Subway.

So, as any hacker who’s wandered through a discount store with a spare twenty, at one point I bought a Chinese caliper. Sure it measures wrong when the battery is low, the temperature has changed, if I’ve held it in my hand too long, the moon is out, etc. but it was only twenty dollars. Either way, how do I get accurate measurements out of it? Well, half-wizardry and telling yourself educated lies.

There are two golden rules to getting accurate measurements by telling lies. It may be obvious to some, but it took me quite a bit of suffering to arrive at them.

Engineers are lazy. So lazy. Most things are going to be even numbers, common fractions, and if possible standard sizes. If sheets and screws come in 2 and 3mm then you bet you’re going to see a lot of 2mm and 3mm features. Also, even though the metric world is supposedly pure, you’re still going to see more 0.25 (1/4) mm measurements than you are .333333 (1/3) mm measurements. Because some small fractions are easier to think about than decimals.
Your eyes lie. If it matters, measure it to be sure.

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Poor Man’s Time Domain Reflectometer

April 15, 2016 by Al Williams 25 Comments

A time domain reflectometer, or TDR, is an essential piece of test gear when working on long cables. The idea is simple: send a pulse down the cable and listen for the reflection from the far end. The catch is that pesky universal constant, the speed of light.

The reason the speed of light is an issue is that, in a traditional system, the pulse needs to be complete before the reflection. Also, time is resolution, so a 1 GHz sampling rate provides a resolution of about 10 centimeters. [Krampmeier] has a different design. He sends variable length pulses and measures the overlap between the outgoing and reflected pulses. The approach allows a much simpler design compared to the traditional method.

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