A Homebrew AC Upgrade For The Fluke 8840A

October 20, 2022 by Lewin Day 11 Comments

[William Dudley] picked up a Fluke 8840A bench multimeter at an auction, but was sad to find out that it was reading resistances inaccurately. It was also missing the optional board to enable AC measurements. Desiring to use the otherwise lovely meter, he set about repairing and upgrading the device.

Thankfully, the 8840A was from a time when Fluke used to openly publish schematics in its manuals. Thus, combined with taking a look at some photos online, it was straightforward for [William] to recreate the original AC “Option 09” board to enable the desired functionality. As is usually the way, his efforts didn’t work first time, but after some bodge wires were installed, all was well. [William] reports the measurements are “reasonable, maybe even sufficient” with no calibration undertaken.

Repairing the resistance issue was easy. It turned out to be corrosion on the selector switches, revealed when high-resistance measurements were accurate, but low-resistance measurements weren’t. A bit of flick-flacker with some contact cleaner sprayed into the switches got things working again nicely.

It’s nice to see old hardware restored to full functionality, particularly when it’s as attractive and well-built as an old Fluke meter. Bringing back old tools from the dead? You know we wanna hear about it!

Rubber Stamping Your Way To Custom PCBs

October 19, 2022 by Lewin Day 24 Comments

Many of us now outsource PCB production to board houses overseas, which offer high-quality boards with increasingly impressive turnaround times. You might still brew up your own PCB, though, and a reader found this great old hack from [William Hare] that might be worth a look.

Forget toner transfer or marker pens — this build is all about speed. [William] decided to use a rubber stamp to quickly transfer ink to a copper board that can then be etched to produce a PCB. It’s simple and straightforward enough. We’ve used the same technique for silkscreen and pad art, but never as an etch resist.

The trick is to make several rubber stamps with different circuit elements, though. The genius part is that you can then assemble a PCB by simply stamping down the various circuit components you need. The boards will still need to be drilled if you’re working with through-hole parts, but tipster [Shri] notes that the technique is super useful for producing single-sided surface mount boards.

We’ve seen some other unique methods to producing PCBs at home, such as using a 3D printer to help out. If you’ve got your own innovative homebrew PCB hacks, be sure to drop us a line!

Thanks [Shri Hari Ram] for the tip!

A digital caliper connected to a tablet computer

Custom Interface Adds USB And Wi-Fi To Digital Calipers

October 17, 2022 by Robin Kearey 26 Comments

Although old-school machinists typically prefer the mechanical vernier scale on their trusty calipers, many users nowadays buy calipers with a digital readout. These models often come with additional features like differential measurements, or a “hold” function for those situations where you have to maneuver the instrument somewhere deep inside a machine. Another useful feature is a data link that lets you log your measurements on a computer directly instead of manually entering all the values.

The VINCA-branded caliper that [Liba2k] bought has such a data link feature, which requires a USB adapter that’s sold separately. There is a micro-USB connector on the tool itself, but instead of implementing a USB interface, this is used to carry a proprietary serial protocol — a design decision that ought to be classified as a felony if you ask us. Rather than buying the official USB adapter, [Liba2k] decoded the protocol and built his own interface called VINCA Reader that can connect through either USB or Wi-Fi.

The serial format turned out to be a simple serial bus that clocks out 24 bits at a time. In order to adapt its 1.2 V signal level to the 3.3 V used by an ESP32, [Liba2k] designed a simple level shifter circuit using a handful of discrete components. The ESP can communicate with the computer through its Wi-Fi interface, for which [Liba2k] wrote a spreadsheet-like application; alternatively, an ordinary USB cable can be connected to emulate a keyboard for use with any other software.

With its added Wi-Fi feature, the VINCA Reader is actually more complete than the official USB adapter, and will probably be cheaper as well. The serial interface appears to be common to all caliper manufacturers, although many went for a more sensible connector than micro-USB. An automated readout system is particularly handy if you have to make thousands of similar measurements.

A 3D Printed Ratchet That Can Really Take The Torque

October 15, 2022 by Donald Papp 5 Comments

Printed tools aren’t exactly known for their durability, but [Gladius] shows us that with some thoughtful design, it’s possible to print a ratcheting wrench that can handle surprising amounts of torque.

Look closely, and you can see that the parts are almost entirely made up of perimeters (click to enlarge).

This particular wrench is inspired by NASA’s 3D printed ratcheting wrench, and also from an early 1900s design. It sports a 1/2 inch square socket into which modern adapters can be fitted, allowing those steel parts to do their job while the wrench itself delivers the muscle.

[Gladius] found that the strongest results came from slicing parts — especially the handle — so that they come out consisting almost entirely of perimeters, with virtually no traditional infill. Want to know more? There’s a discussion on reddit where [Gladius] goes into added detail about measurements and performance.

Over the years, we’ve seen our share of powerful prints. For example, what the Crimson Axlef*cker can do looks downright intimidating. Speaking of printing things that move, we want to remind you about this handy tip for easily and reliably joining motor shafts to printed parts by (mis)using jaw couplings.

Organizational Inspiration From The Discount Tool Company

October 15, 2022 by Bryan Cockfield 13 Comments

When in need of any tool to get a job done quickly, or only for a small number of times, it’s great to have a local “discount tool” company locally for some working, yet often low-quality solution to whatever problem might arise. While there are some gems, most of these tools won’t last through heavy, sustained use like their more expensive counterparts will. On the other hand, there are other things to be had at these discount shops, such as inspiration for tackling a storage problem.

This particular storage system comes from Harbor Freight, and uses a set linked crosshairs, the center of which is hollowed out. A set of movable compartments sits on top with feet that can interlock inside the crosshairs. This allows much more efficient use of space within the toolboxes, but [Alan] wanted it to be useful for more that that. He designed and implemented the Storage Case Base Template (SCBT) which allows for a container of any size to be fitted with a similar crosshair network.

With this non-proprietary system implemented and printed, the original goal of reducing the clutter in [Alan]’s workspace was accomplished. The 3D printing files can be modified easily for any space, and are available both on Thingiverse and Printables. For some other ways of packing a lot into a small space, we featured this tiny workshop a while back that’s packed with storage hacks.

How To Achieve Knurling On A Flat Surface

October 15, 2022 by Lewin Day 20 Comments

Knurling is a popular way to finish handles of tools and other hardware, with a pattern of crossed lines rolled into metal to provide better grip and an attractive finish. It’s most commonly done on a lathe to round stock, but it can also be achieved on flat surfaces if you have the right tool. Of course, you can make one yourself.

The build is simple, and is based around by creating a special carrier out of a solid piece of steel. It’s a long bar has a space milled out to hold two wheels in the middle. A pair of off-the-shelf knurling wheels are then installed in the bar, with socket head bolts serving as axles.

With the tooling complete, it’s then a simple matter of installing the carrier bar in a lathe and running it back and forth over a flat workpiece. The workpiece is rolled back and forth to allow the wheels to do their work, while also being shifted horizontally to allow the entire flat surface to be worked over.

A nice knurled finish really can elevate the form and function of any tool or other piece of metal craftsmanship. We’ve explored how to create your own knurled knobs before, too.

Continue reading “How To Achieve Knurling On A Flat Surface” →

The dosing spoon shown, with many round openings for medication pellets to go into

Medicine Dosing Spoon Discontinued, Made 3D Printable Instead

October 14, 2022 by Arya Voronova 45 Comments

[Gregor Herz] caught wind of a problem that neuropediatric clinics in Germany have been facing recently. Orfiril, a seizure-preventing medication used in those clinics for treating children, is normally prescribed to adults, and the usual dosages are too high for kids. Orfiril comes in regular pill-shaped capsules, each capsule containing a bunch of small medication-soaked pellets, and you only need a certain amount of these pellets if you want to achieve a lower dose.

It used to be that you could get a special spoon helping you to get a proper dosage — but sadly, the original supplier has quit making these. So, our hacker designed a 3D printable model instead.

[Gregor] tells us that a lot of clinics in Germany are facing this exact issue right now, so sharing this model may mean that more hospitals can work around the supply issue. Provided a friendly hobbyist has food-grade 3D printing conditions available, anyway. He tells about some suitable filaments models you can buy, as well as research on food-grade printing requirements — a topic we’ve talked about in detail, and just this month have seen someone revisit with reassuring results. Are you interested in printing some of these? If so, there might be a clinic nearby that’d be thankful.

We’ve seen a surge of 3D printing for medical uses two years ago, back when supply chain issues had doctors face PPE shortages, and some critical parts for equipment were in short supply. Before that, we’d sometimes see medical purpose 3D printing done in dire circumstances, when no other choices were available. Now 3D printing of medical devices is more accepted, and we can’t wait for more research and hacking on this front!