This Pogo Pin Test Fixture Keep Your SMDs From Taking Flight

December 5, 2023 by Dan Maloney 12 Comments

There’s no denying how useful surface mount technology is, and how enabling the ability to make really small circuits has become. It comes at a price, though; most of us probably know what it’s like for the slightest wrong move to send a part the size of a grain of sand into another dimension.

To help make testing these parts a little easier, [IMSAI Guy] has come up with this clever little SMD test fixture. It’s designed to hook up to another custom board, which in turn connects to a wonderful old Hewlett-Packard 4275A LCR meter. The jig is based on two pogo pins mounted directly across from each other on a scrap of single-clad PCB. The spring-loaded contacts, which short together when not in use, are pulled apart to load an SMD part, like the 1-μH inductors shown in the video below. The pins hold the component firmly and make good electrical contact, allowing hands-free testing without the risk of an errant touch of the test probes sending it flying.

While the test fixture works well for larger SMDs, we could see this being a bit fussy for smaller parts. That would be easy enough to fix with perhaps some 3D-printed arms that retract the pogo pins symmetrically, holding them open until the part is loaded. A centering fixture might help too, as would a clear shield to contain any parts that get the urge to go for a ride. But, for the tactical application [IMSAI Guy] has in mind, this sure seems like enough.

Just getting into surface mount? If so, you might want to check out this handy guide to the often cryptic markings used on SMD parts.

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LED Tester Also Calculates Resistor For Target Voltage

December 2, 2023 by Donald Papp 12 Comments

[mircemk] built a slick-looking LED tester with a couple handy functions built in. Not only can one select a target current to put through an LED, but by providing a target voltage, the system will automatically calculate the necessary series resistor. If for example the LED is destined for 14 V, this device will not only show how the LED looks at the chosen current, but will calculate the required resistor to get the same results on a 14 V system.

The buttons on the left control the target current and the voltage of the destination system. Once an LED is connected it will light up and the display indicates the LED’s forward voltage, the LED current, and the calculated series resistor value to obtain the same result at the selected target voltage. It’s a handy way to empirically dial in LED brightness values without needing to actually set up any particular test environment.

On the inside there’s little more than a handful of passive components, an Arduino, an LCD display, and a few buttons. This kind of tool reminds us of the highly clever component testers that hit the hobbyist scene years ago, showing what kind of advanced tricks a modern microcontroller is capable of with the right programming. (Here’s a look at how those work, if you’re interested in some deeper details.)

[mircemk] demonstrates his tool in the video, embedded below. We particularly like the attention he paid to the enclosure, giving it a very functional layout. It goes to show that when designing something, it’s never too early to consider enclosure and UI layout.

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Arbitrary Wave Generator For The Raspberry Pi Pico

November 29, 2023 by Lewin Day 6 Comments

Once upon a time, if you wanted to generate some waveforms, you needed to buy an expensive off-the-shelf function generator or whip up a big pile of analog electronics. Not so today, when you can grab a fast microcontroller off the shelf and have it squirt out whatever fancy waves you might desire. That’s just what [rgco] did to build this nifty arbitrary wave generator.

The build improves on prior work by [rgco] with the Arduino Uno, with which they built a device that could output at 381 kilosamples per second, with each sample update taking 42 instruction cycles. Thanks to the Pi Pico’s faster clock speed and certain performance optimizations, they were able to up that to a mighty 125 megasamples per second, using the DMA and PIO subsystems to output a new sample every single clock cycle.

The result is a cheap function generator you can build with a Pi Pico and a handful of resistors, which will probably cost you the grand total of $12. It readily outperforms, at least in regards of speed, devices based on the AD9833 function generator chip, which only runs at 25 megasamples. Plus, that chip can only output sines, triangles, and squares!

Even a passable function generator can be a useful tool to have in the workshop, as we’ve seen before. Video after the break.

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Come For The PCB Holder, Stay For The Tour Of FreeCAD

November 26, 2023 by Donald Papp 10 Comments

PCB holders are great tools. Not only is the PCB Solder Fren from [PistonPin] a nice DIY design, it offers some insight into the parts design process with FreeCAD.

This design nicely demonstrates FreeCAD’s workflow for designing parts.

The PCB holder uses 3D-printed parts, M5 hardware, a length of 2020 aluminum extrusion, and one spring to create a handy and adjustable design that accommodates a variety of PCB sizes and shapes. If the ends of the extrusion are threaded, the end caps can be screwed in. Otherwise, a little glue ought to do the trick.

Want a little more insight into what making a part like this involves? [Jo Hinchliffe] at FreeCAD reached out to [PistonPin] for more detail and has a blog post explaining the workflow and steps involved in this part. As a bonus, STEP files and the FreeCAD project file are all included!

Not only is FreeCAD simple to use, but it’s also flexible enough to accommodate custom, niche extensions like a Rocketry workbench, so be sure to give it a look for your open-source CAD needs.

CNC Plus Microscope Plus Game Controller Equals Awesome

November 20, 2023 by Richard Baguley 4 Comments

What do you get if you strap a microscope onto a CNC and throw in a gaming controller? The answer, according to Reddit user [AskewedBox] is something kind of awesome: you get a microscope that can be controlled with the game controller for easier tracking of tiny creepy-crawlies.

[ASkewedBox] set up this interesting combination of devices, attaching their Adonostar AD246S microscope to the stage of a no-brand 1610 CNC bought off Amazon, then connected the CNC to a computer running Universal G-Code Sender. This great open source program takes the input from an Xbox game controller and uses it to jog the CNC.

With a bit of tweaking, the game controller can now move the microscope, so it can be used to track microbes and other small creatures as they wander around on the slide mounted below the microscope eating each other. The movement of this is surprisingly smooth: the small CNC and a well-mounted microscope means that there seems to be very little wobble or backlash as the microscope moves.

[Askewedbox] hasn’t finished yet, though: in the latest update, he adds a polarizing lens to the setup and mentions that he wants to add focus control to the system, which is controlled by a remote that comes with the microscope.

There are plenty of other things that could be added beyond that, though, such as auto pan and stitch for larger photos, auto focus stacking and perhaps even auto tracking using OpenCV to track the hideous tiny creatures that live in the microscopic realm. What would you do to make this even cooler?

Miniature Hydraulic Jack Is A Scale Marvel

November 19, 2023 by Julian Scheffers 6 Comments

Most hydraulic jacks are big tools that can lift upwards of 1000 kg but [Maker B]’s is quite a bit smaller than average.

The world’s smallest hydraulic jack is a tiny hand-machined model made out of tiny pieces of iron, brass and copper. But here’s the kicker: It’s a real hydraulic jack with real hydraulic fluid! At 1/5th scale, it obviously isn’t as strong as a full-size jack, but it can still easily lift an impressive 24 soda cans! Switching between the lathe and mill, [Maker B] shows how all the parts of the jack are made from stock metal in detail, and even explains in simple terms how a hydraulic jack works in this masterpiece of a video.

Over the years, we’ve seen plenty of tiny objects cranked out from stock pieces of metal — often bolts. But the fact that the end result here is a working tool, puts it into a decidedly less common niche. Of course, given what we’ve seen from [Maker B] in the past, it’s hardly a surprise.
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A 3D Printed Grinder For Printed Lens Blanks

November 16, 2023 by Dan Maloney 20 Comments

When one thinks of applications for 3D printing, optical components don’t seem to be a good fit. With the possible exception of Fresnel lenses, FDM printing doesn’t seem up to the job of getting the smooth surfaces and precision dimensions needed to focus light. Resin printing might be a little closer to the mark, but there’s still a long way to go between a printed blank and a finished lens.

That gap is what [Fraens] aims to fill with this homebrew lens grinding machine. It uses the same basic methods used to grind and polish lenses for centuries, only with printed components and lens blanks. The machine itself consists of a motorized chuck for holding the lens blank, plus an articulated arm to hold the polishing tool. The tool arm has an eccentric drive that wobbles the polishing tool back and forth across the blank while it rotates in the chuck. Lens grinding requires a lot of water and abrasive, so a large bowl is provided to catch the swarf and keep the work area clean.

Lens blanks are printed to approximately their finished dimensions using clear resin in an SLA printer. [Fraens] spent a lot of time optimizing the printing geometry to minimize the number of print layers required. He found that a 30° angle between the lens and the resin pool worked best, resulting in the clearest blanks. To polish the rough blanks, a lapping tool is made from polymer modeling clay; after baking it dry, the tool can hold a variety of pads and polishing compounds. From there it’s just a matter of running the blank through a range of abrasives to get the desired final surface.

Are the lenses fantastic? Well, they’re probably not going to make it into fine optical equipment, but they’re a lot better than you might expect. Of course, there’s plenty of room for improvement; better resins might result in clearer blanks, and perhaps degassing the uncured resin under vacuum might help with bubbles. Skipping the printed blanks and going with CNC-machined acrylic might be worth a try, too.

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