[IMSAI Guy] wants you to build a non-contact scope probe. The cost? Assuming you have a bit of wire and a regular scope probe, it won’t cost you anything. Why do you want such a thing? You can see what he does with it in the video below.
The probe is really just a coil with little slip-over coils that grab it. You can stick it on and remove it just as easily, so you don’t have to sacrifice the probe for normal use. It won’t give you high-accuracy readings, but if you want to sniff around a circuit without directly connecting to it, it will do the trick. If you are too lazy to make a coil, you can even clip a ground lead to the probe tip, although that won’t work quite as well.
Compared to through-hole construction, inspecting SMD construction is a whole other game. Things you thought were small before are almost invisible now, and making sure solder got where it’s supposed to go can be a real chore. Add some ball grid array (BGA) chips into the mix, where the solder joints are not visible by design, and inspection is more a leap of faith than objective proof of results.
How it works.
Unless, of course, you put the power of optics to work, as [Petteri Aimonen] does with this clever BGA inspection tool. It relies on a pair of tiny prisms to bounce light under one side of a BGA chip and back up the other. The prisms are made from thin sheets of acrylic; [Petteri] didn’t have any 1-mm acrylic sheet on hand, so he harvested material from a razor blade package. The edge of each piece was ground to a 45-degree angle and polished with successively finer grits until the surfaces were highly reflective. One prism was affixed to a small scrap of PCB with eleven SMD LEDs in a row, forming a light pipe that turns the light through 90 degrees. The light source is held along one edge of a BGA, shining light underneath to the other prism, bouncing light through the forest of solder balls and back toward the observer.
The results aren’t exactly crystal clear, which is understandable given the expedient nature of the materials and construction employed. But it’s certainly more than enough to see any gross problems lying below a BGA, like shorts or insufficiently melted solder. [Petteri] reports that flux can be a problem, too, as excess of the stuff can crystalize between pads under the BGA and obstruct the light. A little extra cleaning should help in such cases.
Haven’t tackled a BGA job yet? You might want to get up to speed on that.
We always can use more tools for FPGA debugging, and the Manta project by [Fischer Moseley] delivers without a shadow of a doubt. Manta lets you add a debug and data transfer channel between your computer and your FPGA, that you can easily access with helpfully included Python libraries.
With just a short configuration file as input, it gives you cores you add into your FPGA design, tapping the signals of interest as an FPGA-embedded logic analyzer, interacting with registers, and even letting you quickly transfer tons of data if you so desire.
Manta is easy to install, is developer-friendly, has been designed in Amaranth, and is fully open source as you would expect. At the moment, Manta supports both UART and Ethernet interfaces for data transfer. As for embedding the Manta cores into your project, they can be exported to both Amaranth and Verilog. You should check out the documentation website — it contains everything you might want to know to get started quick.
The Manta project has started out as our hacker’s MIT thesis, and we’re happy that we can cover it for you all. FPGA-embedded logic analyzers are a fascinating and much-needed tool, and we’ve had our own [Al Williams] tell you about his on-FPGA logic analysis journey!
Here’s a CH552G-based USB Blaster project from [nickchen] in case you needed more CH552G in your life, which you absolutely do. It gives you the expected IDC-10 header ready for JTAG, AS, and PS modes. What’s cool, it fits into the plastic shell of a typical USB Blaster, too!
The PCB is flexible enough, and has all the features you’d expect – a fully-featured side-mounted IDC-10 header, two LEDs, a button for CH552 programming mode, and even a UART header inside the case. There’s an option to add level shifter buffers, too – but you don’t have to populate them if you don’t want to do that for whatever reason! The Hackaday.io page outlines all the features you are getting, though you might have to ask your browser to translate from Chinese.
Sadly, there’s no firmware or PCB sources – just schematics, .hex, BOM, and Gerber .zip, so you can’t fix firmware bugs, or add the missing USB-C pulldowns. Nevertheless, it’s a cool project and having the PCB for it is lovely, because you never know when you might want to poke at a FPGA on a short notice. Which is to say, it’s yet another CH552 PCB you ought to put in your PCB fab’s shopping cart! This is not the only CH552G-based programming dongle that we’ve covered – here’s a recent Arduino programmer that does debugWire, and here’s like a dozen more different CH552G boards, programmers and otherwise.
Look around you. Chances are, there’s a BiC Cristal ballpoint pen among your odds and ends. Since 1950, it has far outsold the Rubik’s Cube and even the iPhone, and yet, it’s one of the most unsung and overlooked pieces of technology ever invented. And weirdly, it hasn’t had the honor of trademark erosion like Xerox or Kleenex. When you ‘flick a Bic’, you’re using a lighter.
It’s probably hard to imagine writing with a feather and a bottle of ink, but that’s what writing was limited to for hundreds of years. When fountain pens first came along, they were revolutionary, albeit expensive and leaky. In 1900, the world literacy rate stood around 20%, and exorbitantly-priced, unreliable utensils weren’t helping.
In 1888, American inventor John Loud created the first ballpoint pen. It worked well on leather and wood and the like, but absolutely shredded paper, making it almost useless.
One problem was that while the ball worked better than a nib, it had to be an absolutely perfect fit, or ink would either get stuck or leak out everywhere. Then along came László Bíró, who turned instead to the ink to solve the problems of the ballpoint.
One of the most basic tools for tinkering with electronics is a multimeter. Today, even a cheap meter has capabilities that would have been either very expensive or unobtainable back in the 1970s. Still, even then, a meter was the most affordable way to do various tasks around the shop. Is this cable open? Are these two wires shorted? What’s the value of this resistor? Is the circuit getting power? Is the line voltage dropping? You can answer all those questions — and many more — with a basic meter. But there’s one thing that hasn’t changed much over the years: probes. That’s a shame because there are a lot of useful options.
The probes that came with your meter probably have much in common with the probes a 1970-era meter had. Yeah, the banana plugs probably have a little plastic cover, and the plastic itself might be a little different. Parts are small these days, so the tips might be a little finer than older probes. But if you sent your probes back in time, few people would notice them.
The Blinders Syndrome
One problem is that those probes are usually good enough. We’ve all clipped an alligator clip to a test probe. I’ve even fashioned super pointy probes out of syringes. Years ago, I bought an expensive kit with many attachments I rarely use, like little hooks and spade lugs. Then, I happened to go down the wrong aisle at Harbor Freight.
Back probes ready for action.
In the automotive section, I noticed a tidy plastic box labeled “22 pc. back probe kit.” I’d never heard the term “back probe,” but it was clearly some sort of wire. It turns out the kit has a bunch of very fine needles on banana jacks and some patch cables to connect them to your meter.
They are “back probes” because you can jam them in the back of connectors next to the wire. There are five colors of needles, and each color set has three items: a straight needle, a bent needle, and a 90-degree bend needle.
I’d never heard of this, and that started me down the rabbit hole of looking at what other exotic probes were out there. If you search the usual sources for “back probe,” you’ll see plenty of variations. There are also tons of inexpensive probe kits with many useful tips for different situations. Like everything, the price was much lower than I had paid for the rarely used kit I bought years ago. The only thing I really use out of that kit are the test hook clips and you can buy those now for a few bucks that just push over your probes.
Choices
Wire-piercing probe works best for larger wires.
You could probably use the needles to stick through insulation, too. But if that’s your goal, they make piercing clip test probes specifically for that purpose. A little plastic holder has a hook for your wire and a needle that threads in to penetrate the wire.
These alligator clips fit over most probes.
I also picked up some little alligator clips that slide over standard 2mm probe tips. These are very handy and prevent you from having to clip a lead to your probe so you can clip the other end to the circuit. However, if you look for a “test lead kit,” you’ll find many options for about $20. One kit had interchangeable probe tips, alligator clips, spades, SMD tweezers, and tiny hooks for IC legs. The alligator clips on the one I bought are the newer style that has a solid insulating body — not the cheap rubbery covers. They feel better and are easier to handle, too.
Breadboarding
Some of the accessories in the test probe kit.
Of course, you can make your own solderless breadboard jumpers, and you’ve probably seen that you can buy jumpers of various kinds. But if you search, you can even find test probes with breadboard wire ends. The other end will terminate in a test hook or alligator clips. You can also get them with banana plugs on the end to plug right into your meter. You can usually find versions with the male pin for a breadboard or a female receptacle for connecting to pins.
There’s no doubt that cheap digital calipers are useful, especially when designing 3D-printed parts. Unfortunately, cheap digital calipers are also cheap, and tend to burn through batteries quickly. Sure, you can remove the battery when you’re done using them, but that’s for suckers — winners turn to solar power to keep their calipers always at the ready.
[Johan]’s solar upgrade begins with, unsurprisingly, a solar cell, one that just fits on the back of his digital calipers. Like most of these cheap calipers, this one is powered by a single 1.5 V LR44 button cell, while the polycrystalline solar cell is rated for 5 V, so [Johan] used a red LED as a crude voltage regulator. He also added a stack of fourteen 100 μF SMD capacitors soldered together in parallel. The 1206 devices form a 1,400 μF block that’s smaller than the original button cell so that everything fits in the vacated battery compartment. It’s pretty slick.
