Dead Simple Time-Domain Reflectometry With Just A Battery And An Oscilloscope

December 14, 2020 by 30 Comments

“Time-domain reflectometry” sure sounds like something that needs racks of expensive equipment to accomplish. In reality, TDR is just measuring the time between injecting a pulse into a cable and receiving its echo, either from the other end of the cable or from some fault or defect along the way. It’s a useful technique, and as [Allen Wolke (W2AEW)] shows us, it can be accomplished with little more than a battery, a resistor, and an oscilloscope. And a little math, of course.

There are, of course, dedicated time-domain reflectometers, but all of them are really just elaborations of the basic principles [W2AEW] demonstrates with his simple setup. The oscilloscope is set up with a tee connector on one channel; one side of the tee is connected to the cable under test, while the shield conductor of the other side is connected to the negative terminal of a 9V battery. A resistor connected to the center conductor is used to complete the circuit, which sends a brief pulse down the test cable. The scope is set up to capture the outgoing pulse as well as the return pulse, allowing the time between the two to be measured. Some simple math gives the length of the cable, the distance to a fault, or with a little rearrangement, the velocity factor of the cable.

The video below shows the simple method at work on coax and Cat 5e Ethernet cable. It even worked on a roll of zip cable, which was a little surprising. If this technique is too simple, you can always elaborate a bit and roll your own TDR tester. Googly eyes optional, of course, but recommended.

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Railroad Rail Transformed Into Blacksmith’s Anvil With The Simplest Of Tools

December 14, 2020 by 42 Comments

One of the biggest challenges facing the aspiring blacksmith is procuring the tools of the trade. And that means tackling the unenviable task of finding a decent anvil. Sure, one can buy an ASO — anvil-shaped object — at Harbor Freight, but a real anvil is much harder to come by. So perhaps the beginner smith’s first build should be this railroad rail to anvil conversion.

Repurposing sections of rail into anvils is hardly a new game, but [The Other Finnish Guy]’s build shows us just how little is needed in terms of specialized tooling to pull this off. Other than a file, the bulk of the work is done by angle grinders, which are used to cut off the curved crown of the rail section, cut the shape of the heel, and rough out the horn. Removing that much metal will not be a walk in the park, so patience — and a steady supply of cutting wheels and sanding discs — is surely required. But with time and skill, the anvil hidden inside the rail can be revealed and put to use.

We have questions about the final result, like its lack of a hardy hole and the fact that the face isn’t hardened. We wonder if some kind of induction heating could be used to solve the latter problem, or if perhaps a hardened plate could be welded into the top to make a composite anvil. Still, any anvil is better than no anvil. More on the anatomy and physiology of these tools can be had in [Jenny List]’s article on anvils, and her whole excellent series on blacksmithing is highly recommended. [Jenny]’s not the only smith we have on staff, though — [Bil Herd] has been known to smite a bit too.

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Pi Compute Module Is Love-child Of Raspberry And Arduino

December 14, 2020 by 27 Comments

The Raspberry Pi compute module is a powerful piece of hardware, especially for the price. With it, you get more IO than a normal Pi, plus the ability to design hardware around it that’s specifically tailored to your needs rather than simply to general-purpose consumers. However, this comes at the cost of needing a way to interface with it since the compute module doesn’t have the normal IO pins or ports, but [Timon] has come up with a handy development board for this module called the Piunora which solves a lot of these prototyping issues.

The development board expands the compute module to the familiar Arduino-like form factor, complete with IO headers, USB ports, and HDMI output. It doesn’t stop there, though. It has an M.2 connector, some built-in LEDs, a camera connector, and a few other features. It also opens up some other possibilities that would be difficult or impossible with a standard Pi 4, such as the ability to run the Pi as a USB gadget rather than as a host device which simplifies certain types of development, which is [Timon]’s intended function.

As a development board, this project has a lot of potential for the niche uses of the compute module when compared to the standard Raspberry Pi. For embedded applications it’s much easier to deploy, with the increased development costs as a tradeoff. If you’re still unsure what to do with the compute module 4, we have some reading for you. And Timon’s previous project is a great springboard.

China’s Moon Mission Was About More Than Rocks

December 14, 2020 by 67 Comments

If everything goes according to plan, China will soon become the third country behind the United States and the Soviet Union to successfully return a sample of lunar material. Their Chang’e 5 mission, which was designed to collect 2 kilograms (4.4 pounds) of soil and rock from the Moon’s surface, has so far gone off without a hitch. Assuming the returning spacecraft successfully renters the Earth’s atmosphere and lands safely on December 16th, China will officially be inducted into a very exclusive club of Moon explorers.

Of course, spaceflight is exceedingly difficult and atmospheric reentry is particularly challenging. Anything could happen in the next few days, so it would be premature to celebrate the Chang’e 5 mission as a complete success. But even if ground controllers lose contact with the vehicle on its return to Earth, or it burns up in the atmosphere, China will come away from this mission with a wealth of valuable experience that will guide its lunar program for years to come.

In fact, one could argue that was always the real goal of the mission. While there’s plenty of scientific knowledge and not an inconsequential amount of national pride to be gained from bringing a few pounds of Moon rocks back to Earth, it’s no secret that China has greater aspirations when it comes to our nearest celestial neighbor. Starting with the launch of the Chang’e 1 in 2007, the Chinese Lunar Exploration Program has progressed through several operational phases, each more technically challenging than the last. Chang’e 5 represents the third phase of the plan, with only the establishment of robotic research station to go before the country says they’ll proceed with a crewed landing in the 2030s.

Which helps explain why, even for a sample return from the Moon, Chang’e 5 is such an extremely complex mission. A close look at the hardware and techniques involved shows a mission profile considerably more difficult than was strictly necessary. The logical conclusion is that China intentionally took the long way around so they could use it as a dry run for the more challenging missions that still lay ahead.

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Join Us For The “Holiday With Hackaday And Tindie” Meet-Up

December 14, 2020 by 4 Comments

It’s a ritual in workplaces around the world this time of any other year but 2020: the office holiday party. Too much food, perhaps too much alcohol, and garish sweaters that you wouldn’t be caught dead in on any other occasion. Things are, of course, a tad different this year, which is why we’re putting our community’s party online with the Holiday with Hackaday and Tindie meet-up on Tuesday, December 15 at noon Pacific time!

Why should you come to this hangout? Because why not! This is going to be a loose, informal meet-up that will give us all a chance to get to know one another. We’ve got an amazing community here, and just putting faces to names can be really valuable. You’ll be able to connect with old friends and perhaps make new ones. It’s your chance to reach out and find someone to collaborate with, or perhaps just find an answer to a thorny problem you’ve been stuck on. Be sure to bring your latest projects to show off, and maybe even consider giving everyone a virtual tour of your shop. Ugly sweaters are optional, of course, and we don’t judge.

The Holiday with Hackaday and Tindie meet-up is being held on Remo. Those of you who joined the Friday night Bring-a-Hack session at Remoticon this year will no doubt remember the platform, which we got a lot of good feedback on. You’ll want to check browser compatibility ahead of time and reserve your spot, so head over to Remo and make it so. If you need help with timezone conversions, we’ve got you covered on that too.

We’re looking forward to seeing everyone at the Holiday with Hackaday and Tindie meet-up!

Save Your Original Xbox From A Corrosive Death

December 14, 2020 by 21 Comments

Fans of retro computers from the 8-bit and 16-bit eras will be well aware of the green death that eats these machines from the inside out. A common cause is leaking electrolytic capacitors, with RTC batteries being an even more vicious scourge when it comes to corrosion that destroys motherboards. Of course, time rolls on, and new generations of machines are now prone to this risk. [MattKC] has explored the issue on Microsoft’s original Xbox, built from 2001 to 2009.

Despite looking okay from above, the capacitor inside the Xbox had already started leaking underneath. Leaving this in the console would inevitably cause major damage.

The original Xbox does include a real-time clock, however, it doesn’t rely on a battery. Due to the RTC hardware being included in the bigger NVIDA MCPX X3 sound chip, the current draw on standby was too high to use a standard coin cell as a backup battery. Instead, a fancy high-value capacitor was used, allowing the clock to be maintained for a few hours away from AC power. The problem is that these capacitors were made during the Capacitor Plague in the early 2000s. Over time they leak and deposit corrosive material on the motherboard, which can easily kill the Xbox.

The solution? Removing the capacitor and cleaning off any goop that may have already been left on the board. The fastidious can replace the part, though the Xbox will work just fine without the capacitor in place; you’ll just have to reset the clock every time you unplug the console. [MattKC] also points out that this is a good time to inspect other caps on the board for harmful leakage.

We’ve seen [MattKC] dive into consoles before, burning his own PS1 modchip from sourcecode found online. Video after the break.

Edit: As noted by [Doge Microsystems], this scourage only effects pre-1.6 Xboxes; later models don’t suffer the same problem, and shouldn’t be modified in this way.

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Peeking Inside A VW Gearbox Reveals Die Casting Truths

December 14, 2020 by 70 Comments

Recently, I was offered a 1997 Volkswagen Golf for the low, low price of free — assuming I could haul it away, as it suffered from a thoroughly borked automatic transmission. Being incapable of saying no to such an opportunity, I set about trailering the poor convertible home and immediately tore into the mechanicals to see what was wrong.

Alas, I have thus far failed to resurrect the beast from Wolfsburg, but while I was wrist deep in transmission fluid, I spotted something that caught my eye. Come along for a look at the nitty-gritty of transmission manufacturing!

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