How To Create Hermetically Sealed Electrical Connections

September 23, 2020 by Lewin Day 25 Comments

[Eric Strebel] is no stranger to pressure and vaccum tanks, regularly using them for all manner of resin casting jobs for his product design business. However, sometimes it becomes necessary to run equipment within a pressure tank, such as for rotomoulding or other similar jobs. In order to get power into a tank under pressure, [Eric] built a special plug with a hermetic seal to do the job. (Video, embedded below.)

The build starts with a large metal plug which screws into the pressure vessel, into which a square recess is machined. For the electrical passthrough, [Eric] selected GX-16 aviation connectors, in this case packing six conductors. The connectors are hooked up back-to-back through the hole in the metal tank plug, using bare copper wire. This is to avoid insulation on wires acting as a channel for gases to pass through. With the connectors wired up and an acrylic disc in place to stop overflow, the metal plug is filled with resin to create the hermetic seal.

Results are good, with the connectors functioning electrically and the resin acting as a perfect seal. There’s a small risk of short circuit with the exposed copper conductors, but [Eric] is exploring some easy solutions to avoid issues. We’ve seen his work before, too – like this great discussion on cardboard as a design tool. Video after the break.

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This DIY Drill Press Is Very Well Executed

September 22, 2020 by Bryan Cockfield 22 Comments

Plenty of projects we see here could easily be purchased in some form or other. Robot arms, home automation, drones, and even some software can all be had with a quick internet search, to be sure. But there’s no fun in simply buying something when it can be built instead. The same goes for tools as well, and this homemade drill press from [ericinventor] shows that it’s not only possible to build your own tools rather than buy them, but often it’s cheaper as well.

This mini drill press has every feature we could think of needing in a tool like this. It uses off-the-shelf components including the motor and linear bearing carriage (which was actually salvaged from the Z-axis of a CNC machine). The chassis was built from stock aluminum and bolted together, making sure to keep everything square so that the drill press is as precise as possible. The movement is controlled from a set of 3D printed gears which are turned by hand.

The drill press is capable of drilling holes in most materials, including metal, and although small it would be great for precision work. [ericinventor] notes that it’s not necessary to use a separate motor, and that it’s possible to use this build with a Dremel tool if one is already available to you. Either way, it’s a handy tool to have around the shop, and with only a few modifications it might be usable as a mill as well.

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Linkage Inferring Software Handwaves Away The Hard Stuff

September 22, 2020 by Sonya Vasquez 17 Comments

Jokes aside, manually designing linkages that move along specific paths is no easy task. Whether we’re doodling paper sketches or constraining lines in a CAD program, we still need to do the work of actually “imagining” the linkage design. If only there were some sort of tool that would do all that hard imagining work for us! Thankfully, we’re in luck! That’s exactly what researchers [Gen Nishida], [Adrien Bousseau2], and [Daniel G. Aliaga1] at Purdue have done. They’ve designed a software tool that lets us position important bodies in space in particular “key” frames, and then the software simply fills in the linkage for you!

To start the design process, the user inputs a few candidate locations that their solid bodies need to reach in the final linkage path. From here, these locations get fed to a particle filter. This particle filter seeds thousands of semi-random linkage configurations at small timesteps, selects some of the best-matching ones that most closely approximate the required body locations, removes the lesser-scoring results, re-creates a new set of possible joint configurations based on the best matching ones, and repeats until the tool converges on a linkage that respects our input key frames.

Like a brute force search, this solution takes lots and lots of samples to find a solution, but unlike a brute force search, trials iteratively improve, enabling the software to converge closer and closer to a final solution. Under the hood, the software needs to actually simulate these candidate linkage in order to grade them. It’s in this step that the team wrote in additional checks to remove impossible linkages like self-intersecting joints from this linkage “gene pool” before reseeding them. The result is a tool that does all that trial-and-error scratchwork for you–no brain cycles. For more details, have a peek at their (open access!) paper.

Design software that augments our mechanical design capabilities is a rare gem on these pages, and this one is no exception. If your curious to play with other useful linkages simulating tools, have a go at Linkage Designer. And if you’re in the mood for other tools that fill in the blanks, check out this machine learning algorithm that literally fills in footage between frames in a video feed.

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Upcycled Dryer Motor Makes Budget Disk Sander

September 21, 2020 by Al Williams 39 Comments

At the most basic level, most shop tools are just a motor with the right attachments. But the details are often far from simple. [DuctTapeMechanic] took a junker clothes dryer, yanked the electric motor from it, and converted it into a disk sander. The price was right at about $10. You can see it all after the break.

As you might imagine, having the motor is only half the battle. You also need a way to mount the thing securely and a way to affix the sanding disk. While this doesn’t pose the same challenges as, say, a drill press, it does take some thought. The motor in the donor dryer didn’t have threads on the shaft, so a bolt and some welding time took care of that. We suspect that’s tricky because you need the shaft and the bolt to be concentric and level.

Once you have a threaded shaft, the rest of the build is anti-climatic. A little carpentry and a little electrical. We would probably cover up the electrical connections a bit more. It seems like you’d want to know which way the motor spins so you could use a reverse thread, if necessary. From the video, we think the motor he has was spinning the right way, but we don’t know if that’s always true.

There’s something satisfying about building your own tools. If you work on smaller things, we’ve seen a miniature sander that might be handy to have around. If you want to go the other way, try finding an old floor polisher instead of a dryer.

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A Budget Testing Rig For Low-Volume Production

September 20, 2020 by Lewin Day 2 Comments

It’s not unheard of for those who tinker in the land of electronics to suddenly find themselves with a project on their hands and potential customers clamoring at the door. Of course, the road to shipping a product is a long one, and requires a unique set of skills quite distinct from those required to build the initial prototype. In developing a product for Airsoft use, [bald greg] realized that a testing rig would be key to ensuring their hundreds of units left the building in working condition.

When shipping units in the hundreds rather than thousands, keeping overheads low is key to maintain a sustainable profit margin on each unit sold. Thus, [bald greg] built a rig that would allow for effective testing of devices rather than breaking the bank. The rig also handles programming, saving the cost of purchasing pre-programmed microcontrollers from the manufacturer. A Raspberry Pi runs the show, using its GPIO pins to program boards and saving test results and serial numbers for later reference. A bed of nails fixture is used to connect to each individual board. Additionally, to test each board as realistically as possible, hardware mimicking a real Airsoft electric pistol is used to properly load the hardware.

[bald greg]’s work is a great example of approaching QC on a budget, and we suspect he’ll sleep soundly knowing the boards in the mail are going to work first time. We’ve seen others take similar approaches, too. If you’re working on your own production testing rig, be sure to let us know!

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E-Textile Tools Get The Multimeter Hookup

September 19, 2020 by Kristina Panos No comments

[Irene Posch] has done some incredible work with knitted, crocheted, and fabric circuits — check out the crocheted ALUs and embroidered computer for starters. Now, it seems [Irene] is building up a how-to catalog of e-textile tools that can be easily connected to a multimeter.

So far, this toolbox includes a seam ripper and a crochet hook. The concept is similar for both — print out a handle and connect the tool to a banana jack that can then be connected to a multimeter. The crochet hook is simple: just print out the handle, jam the hook in one end, and stick a mini banana jack in the other end. They’re designed to butt up against each other and make a connection without wires.

Building the ripper takes a bit more effort. There’s another printed handle involved, but you must first free the seam ripper from its stock plastic handle and solder a wire to it. Then twist the other end of the wire around a banana jack and and put that in the other end of the handle.

It’s great to see a little bit insight into the troubleshooting tools of e-textiles, especially because they are all-around fiddly. It all starts with a circuit, so why not do your prototyping with a thread-friendly breadboard?

Rolex Becomes World’s Most Expensive ESD Strap

September 19, 2020 by Lewin Day 26 Comments

Anti-static ESD straps are de rigueur in lab settings for those working with sensitive electronics. They’re a simple protective device, and one that generally doesn’t warrant a second thought. However, [Daniel Bogdanoff] figured they could stand to be a little more fashionable, and set to work on a fancier design.

The first step was to take a look at a regular ESD strap. Typically, they consist of a band that fastens around the wearer’s wrist, with a metal stud for connecting to the earthing lead. The earthing lead contains a high resistance to limit the discharge current to avoid ugly high-energy shorts when wearing the strap.

The metal stud is attached to a replacement link on the ROLEX’s strap, making the modification neat, tidy, and reversible.

With a good understanding of the basics, [Daniel] set about modifying a CASIO calculator watch for practice. After soldering a metal stud to the watch case failed, a second attempt with conductive epoxy worked great. The watch could be connected to the earthing strap, and an ESD tester confirmed the device was doing its job.

But unfortunately, permanently modifying the borrowed ROLEX wasn’t an option. Instead, [Daniel] limited his work to a single replacement link which could be inserted into the watch band. Hooked up to an earthing strap, the luxury watch also passed a basic ESD test successfully.

[Daniel] notes that while this is a fun experiment, using properly rated safety equipment is best. Additionally, he points out that the ROLEX is likely to do worse than the CASIO for the simple fact that a metal-banded watch is more likely to cause shorts when working on electronics. Of course, if a watch isn’t your thing, consider a ring instead. Video after the break.

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