Sprucing Up A Bell & Howell Model 34 Oscilloscope

July 4, 2019 by Tom Nardi 20 Comments

We’ll admit it, in an era when you can get a four channel digital storage oscilloscope with protocol decoding for a few hundred bucks, it can be hard not to see the appeal of analog CRT scopes from decades past. Sure they’re heavy, harder to use, and less capable, but they just look so cool. Who could say no to having one of these classic pieces of gear on their bench?

[Cody Nybo] certainly couldn’t. Despite the fact that he already has a digital scope, he couldn’t pass up the chance to add a Bell & Howell Schools Model 34 from circa 1973 to his collection. It needed a bit of TLC before it could be brought back into service, but now it’s all fixed up and ready to put in some work. Not bad for a piece of gear with nearly a half-century on the clock.

The restoration of the Model 34 was aided by the fact that [Cody] got the original manual and schematics for the scope in the deal, which he was kind enough to scan and upload for the rest of the class to enjoy. Those of you who have worked on older electronics can already guess where the scope needed the most love: all the capacitors needed to be swapped out for fresh ones. He also found a few resistors that were out of spec, and the occasional bad solder joint here and there.

Even if you’re not looking to repair your own middle-aged oscilloscope, his pictures of the inside of Model 34 are fascinating. The scope was sold as a kit, so the construction is surprisingly simple and almost entirely point-to-point. Of course, there’s something of a trade-off at work: [Cody] says it won’t display much more than 2.5 MHz before things start getting wonky. But then again, that’s a more than reasonable frequency ceiling for audio work and most hobbyist projects.

Oscilloscopes have come a long way since the days when they had to draw out their readings on a piece of paper. While newer devices have all but buried the classic analog scope, a beauty like this would still have a place of honor in our lab.

Hacked Calipers Make Automated Measurements A Breeze

July 4, 2019 by Dan Maloney 22 Comments

Now, digital calipers with wired interfaces to capture the current reading are nothing new. But the good ones are expensive, and really, where’s the fun in plugging a $75 cable into a computer? So when [Max Holliday] was asked to trick out some calipers for automating data capture, he had to get creative.

[Max] found that cheap Harbor Freight digital calipers have the telltale door that covers a serial connector, making them a perfect target for hacking. A little Internet sleuthing revealed the pinout for the connector as well as some details on the serial protocol used by most digital calipers: 24-bit packets is six four-bit words. [Max] used his SAM32, a neat open-source board with both a SAMD51 and an ESP32 that can run CircuitPython. An inverting buffer interfaces the serial lines to the board, which is just the right size to mount on the back of the caliper head. It’s hard to tell how [Max] is triggering readings, but the SAM32 is mounted as a USB device and sends keystrokes directly to a spreadsheet – yes, with the ESP32 it could have been wireless, but his client specifically requested a wired setup. Taking multiple readings is easy now that the user never has to swap calipers for a pen.

Cheap calipers like these are pretty hackable – you can add Bluetooth, turn them into DROs for a milling machine, or even make them talk.

Spice With A Sound Card

July 3, 2019 by Al Williams 11 Comments

In years gone by, trying out a new circuit probably would have meant heating up a soldering iron. Solderless breadboards have made that even easier and computer simulation is easier still, but there’s something not quite as satisfying about building a circuit virtually. [Thedeuluiz] has a way to get some of the best of both worlds with the RTSpice project.

The idea is simple in concept, although not as simple in execution. The program does a Spice-like simulation of a circuit and can accept input and produce output from a PC’s sound card. Obviously, that means you can’t simulate RF circuits — at least not at the input and the output. It also means the simulation has to run lightning fast to keep up with the sound card sample rate. According to the author, it works best with modest circuits but exactly how big you can go will depend on your hardware.

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Hands-On: GreatFET Is An Embedded Tool That Does It All

July 2, 2019 by Mike Szczys 43 Comments

There’s a new embedded hacking tool on the scene that gives you an interactive Python interface for a speedy chip on a board with oodles of GPIO, the ability to masquerade as different USB devices, and a legacy of tricks up its sleeve. This is the GreatFET, the successor to the much loved GoodFET.

I first heard this board was close to launch almost a year ago and asked for an early look. When shipping began at the end of April, they sent me one. Let’s dig in for a hands-on review of the GreatFET from Great Scott Gadgets.

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Automatic Cut-Off Saw Takes The Tedium Out Of A Twenty-Minute Job

June 29, 2019 by Dan Maloney 26 Comments

For [Turbo Conquering Mega Eagle], the question was simple: Do I spend 20 minutes slaving away in front of a bandsaw to cut a bunch of short brass rods into even shorter pieces of brass rod? Or do I spend days designing and building an automatic cutoff saw to do the same job? The answer is obvious.

It’s only at the end of the video below that [TCME] reveals the need for these brass bits: they’re for riveting together the handles of knives he makes and sells. That makes the effort that went into his “Auto Mega Cut-O-Matic” a little easier to swallow, although we still think he ran afoul of this relevant XKCD. The saw is built out of scraps and odd bits using angle iron as a base and an electric die grinder to spin a cut-off wheel. A small gear motor feeds the brass rod down a guide tube until it hits a microswitch stop, which starts the cut cycle. Another motor swivels the saw to make the cut then moves it out of the way so the stock can advance. The impressive thing is that the only control mechanism is a series of microswitches, cams, levers, and springs – no Arduino needed. Heck, there’s not even a 555, which we find a refreshing change.

Yes, it’s overkill, but he had fun and made something pretty ingenious. [Turbo Conquering Mega Eagle] always has something interesting going on in the shop, and we couldn’t help but notice him using his aluminum-melting tea kettle to make some parts for this build.

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Stopping A Bench Grinder Quickly

June 26, 2019 by Brian Benchoff 56 Comments

In every workshop ever, there’s a power tool that goes unnoticed. It’s the bench grinder. It’s useful when you need it, and completely invisible when you don’t. We take the bench grinder for granted, in part because we keep it over there with that box of oily rags, and partly because it’s so unassuming.

But you can really mess your hands up on a bench grinder. Words like ‘degloving’ are thrown around, and that doesn’t involve actual gloves. For his Hackaday Prize entry, [Scott] is adding safety to the ubiquitous bench grinder. It’s called the Grinder Minder, and it aims to make the humble bench grinder a lot safer.

There are a few goals to the Grinder Minder, most importantly is DC injection braking. This stops the grinder from spinning, and if you’ve ever turned off a bench grinder and waited for it to spin down, you know there’s either a lot of energy in a grinder wheel. Grinder Minder also adds accidental restart protection and an actual ANSI-compliant emergency stop. All of this is designed so that’s it’s a direct drop-in electronics package for a standard off-the-shelf grinder.

The early prototypes for the Grinder Minder have the requisite MOSFETs and gigantic wire-wound resistors , but the team has recently hit an impasse. The current market research tells them the best way forward is designing a product for bigger, more powerful tools that use three-phase power. The team is currently researching what this means for their project, and we’re looking forward to seeing where that research lands them.

Laser Cutting Wooden Pogo Pin Test Jigs

June 25, 2019 by Tom Nardi 10 Comments

Now as far as problems go, selling so many products on Tindie that you need to come up with a faster way to test them is a pretty good one to have. But it’s still a problem that needs solving. For [Eric Gunnerson] the solution involved finding a quick and easy way to produce wooden pogo test jigs on his laser cutter, and we have a feeling he’s not the only one who’ll benefit from it.

The first step was exporting the PCB design from KiCad into an SVG, which [Eric] then brought into Inkscape for editing. He deleted all of the traces that he wasn’t interested in, leaving behind just the ones he wanted to ultimately tap into with the pogo pins. He then used the Circle tool to put a 0.85 mm red dot in the center of each pad.

You’re probably wondering where those specific parameters came from. The color is easy enough to explain: his GlowForge laser cutter allows him to select by color, so [Eric] can easily tell the machine to cut out anything that’s red. As for the size, he did a test run on a scrap of wood and found that 0.85 mm was the perfect dimensions to hold onto a pogo pin with friction.

[Eric] ran off three identical pieces of birch plywood, plus one spacer. The pogo pins are inserted into the first piece, the wires get soldered around the back, and finally secured with the spacer. The whole thing is then capped off with the two remaining pieces, and wrapped up in tape to keep it together.

Whether you 3D print one of your own design or even modify a popular development board to do your bidding, the test jig is invaluable when you make the leap to small scale production.