Hacking Old Ethernet Gear

December 6, 2015 by Al Williams 22 Comments

Have you ever wanted a pocket-sized device that could tell you if a network jack was live or not? [TanzerGuy] did and he hacked a piece of old networking gear to do the job.

Today when you think of Ethernet, you probably think of CAT-5 cable or something similar. But it hasn’t always been like that. In the early days of Ethernet networking, an Ethernet cable was a big piece of coax. A media attachment unit (MAU) clamped to the cable and then connected to an attachment unit interface (AUI) that resided in the actual network card. Later standards used thinner coax that attached to the card using a Tee connector, but even these are rare today.

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A Teensy Logic Analyzer For A 6502

December 4, 2015 by Brian Benchoff 11 Comments

[John] has an interesting, if old piece of tech sitting on his workbench. It’s an Ohio Scientific C3-8P computer from the late 70s by way of a few garages, basements, and attics. As with most tech of this vintage, there are some problems, and [John] found debugging a little frustrating without the ability to trace and watch the programs. He needed a logic analyzer, and found one in an unlikely piece of hardware. [John] built one using a Teensy microcontroller, and further refinement of this project could turn it into a full in-system emulator.

The old Ohio Scientific computer [John] is trying to bring back from the dead is based on the 6502 CPU. That’s sixteen address lines to monitor, eight data lines, and four control lines. These were wired directly to a Teensy 3.1.

Reading and controlling all the signals from a 6502 is a task that falls to Linux. A command line program controls the Teensy and is capable of reading memory, setting trigger addresses, dumping the entire address space to a file, or just recording the last 5,000 clock cycles. This kind of tech existed back in the late 70s and early 80s. It also cost a fortune. Now, with a $20 Teensy and probably another $30 in ribbon cables and test clips, anyone can build a logic analyser for a very old computer system.

Videos below.

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Nuts About Volts

December 3, 2015 by Nava Whiteford 30 Comments

Among multimeters one instrument stands far and above the rest. An object desired for its accuracy, resolution and shear engineering beauty. I speak of course of the HP 3458A. That’s right, not Keysight, not even Agilent (though of course it goes by those brands too). The 3458A was released in 1989, when HP was still… well… HP. An elegant meter from a more civilized age. As the HP Journal documents, the 3458A was a significant engineering feat and has remained in production (and largely unchallenged) for the last 26 years.

But what, you might ask, makes the 3458A such a significant and desirable instrument? It’s all in the digits. The 3458A is one of the few 8.5 digit multimeters available. It is therefore sensitive to microvolt deflections on 10 volt measurements. It is this ability to distinguished tiny changes on large signals that sets high precision multimeters apart. Imagine weighing an elephant and being able to count the number of flies that land on its back by the change in weight. The 3458A accomplishes a similar feat.

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Matthias Builds A Belt Sander

December 1, 2015 by Brian Benchoff 26 Comments

[Matthias Wandel] is the preeminent YouTube woodworker, with dozens of machines constructed from wooden gears, amazing machines that produce perfect mortise and tenons, and home-built table saws and jointers. Actually building something instead of buying it is a hallmark of [Matthias]’ channel, and he’s at it again, building his own woodworking machines. This time it’s a 1″ wide belt sander. Of course anyone can go out and simply buy one of these sanders for under $100, but what’s the point in that when you can build one out of plywood and a motor you picked out of the trash?

The design of this belt sander – just like the commercial version he’s improving upon – uses three wheels to guide the 42″ long strip of sandpaper around its course. [Matthias] is using rollerblade wheels for the front wheels. Rollerblade wheels aren’t the best shape for bearings, this can be fixed by using a table saw as a lathe. Yes, [Matthias] lathes with a table saw. He’s just that good.

The rest of the frame was carefully constructed out of plywood and powered by a 1/3 horsepower furnace fan motor pulled from the trash. There are a few interesting features that make this belt sander exceptionally useful: a rounded platen behind the belt makes sanding interior corners very easy, and is something that isn’t usually found on commercial belt sanders.

You can check out [Matthias]’ video below.

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Easy Power Supply Mod Takes Control

November 30, 2015 by Kevin Dady 30 Comments

Inexpensive bench top power supplies are great for the home hobbyist, featuring wide voltage range and current limiting for a low price. What’s not to love? The controls; most have a single-turn pot that is typically very fidgety, especially at low voltage.

The solution is to replace the factory pots with nice wire-wound 10 turn units in order to gain 10x the precision. Of course nothing is ever drop in, the new pots didn’t fit the old holes, but that is nothing a few moments with a drill can’t fix. Also the original knobs no longer fit, but that’s just an opportunity for a knob upgrade.

The end result is still a power supply with fidgety controls, but instead of holding your breath, tippy tapping knobs to get within 100mV of your target, you can dial right in to within 10mV of your target. That makes life much easier, especially on low voltage projects that may not have power regulation quite yet.

Join us after the break for a video with all the info.

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The Grid Dip Meter: Forgotten Instrument

November 30, 2015 by Al Williams 74 Comments

It used to be a major rite of passage for a hardware hacker to acquire an oscilloscope. Until recently, new instruments were rarely in normal people’s budgets, so you probably made do with a used scope. Now, there are lots of inexpensive options, especially if you include low-end PC scopes and “scope meters.” Digital meters are also now inexpensive (often free at some major stores), along with signal generators, frequency counters, and even logic analyzers.

But there is one piece of test equipment you don’t see as often as you used to and its a shame, because it is a very versatile piece of kit. Admittedly, if you aren’t doing wireless work, it might not be high on your wish list, but if you do anything with RF, it is not only a versatile tool, but a good value, too. What’s it called? That depends. Historically, they went by the name “Grid Dip Oscillator” or GDO. Sometimes you’d hear it called a “Grid Dip Meter” instead. However, modern versions don’t have tubes (and, thus, no grid) so sometimes you hear them now called dip meters or maybe just dippers.

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Automated Picasso Coming To A Ceiling Near You

November 29, 2015 by Sonya Vasquez 3 Comments

It’s not a day too late to switch your career from engineering to art or vice-versa! While some of us tend far towards one end or the other, some like [Chris] show us just how cool it is to walk the line… er, ceiling in this case. [Chris] took a cue from his fiancée’s latest mural project to create an automated painting jig he calls ARTbOT.

Spraying the ceiling with ARTbOT sounds like fun, but it’s a dream [Chris] needed to realize with only his spare time and small budget. Constraints aside, he’s pulled it off elegantly with a cluster of extruded aluminum tubing, a few paint sprayers, and a LabView-driven Fet triggered by encoder ticks on the drop wheel. To pain the image, it’s first binarized and scaled to accommodate ARTbOT’s 8-inch pixel size. ARTbOT then gets a boost from a scissor-lift where it can then track it’s linear position with the drop wheel to spray the pixel-pattern correctly.

[Chris] pulled this rig together to help his fiancée and her art company tackle huge canvases, in this case, large freeway underpasses. With preliminary studio tests running smoothly with ARTbOT proudly printing its name, we can’t wait to see the final piece. In the meantime, have a look at this edgy handheld alternative. Watch out mural artists! There’s an 8-bit contender in the ring these days.

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