3D Printer Guardian Watches for Worst-case Failures

Some devices have one job to do, but that job can have many facets. To [jmcservv], an example of this is the job of protecting against worst-case failures in a 3D printer, and it led him to develop the 3D Printer Watchdog Guardian. When it comes to fire, secondary protection is the name of the game because it’s one thing to detect thermal runaway and turn off a heater, but what if that isn’t enough? The MOSFET controlling the heater could have failed closed and can no longer be turned off in a normal sense. In such cases, some kind of backup is needed. Of course, a protection system should also notify an operator of any serious problem, but what’s the best way to do that? These are the kinds of issues that [jmcservv] is working to address with his watchdog, which not only keeps a careful eye on any heating elements in the system, but can take a variety of actions as a result.

Some outcomes (like fire) are bad enough that it’s worth the extra work and cost of additional protection, and that’s the thinking that has led [jmcservv] to submit his watchdog system for The Hackaday Prize.

Robotic Muscles from Fishing Line and Nichrome

Did you know that under the right conditions, nylon can be used as a type of artificial muscle? We certainly didn’t until we came across [Brandon T. Wood]’s Material Linear-Actuator for Robotics entry for the 2018 Hackaday Prize.

When [Brandon] first learned about Nylon Linear Material Actuators (NLMAs), he became determined to find a repeatable and practical method of making and experimenting with them. This is how it works: hyper-wound coils of nylon, when heated, will contract along their length while expanding in width. Upon cooling, they return to their original shape.

[Brandon] has been busy mainly with the kind of work that is important but not very flashy: finding accessible methods to reliably create strands of artificial nylon muscles cheaply and reliably. His current method uses a jig to wind nylon fishing line until it coils upon itself tightly, then twist a length of nichrome wire around the outside to act as a heater. Using this method, the coils can be electrically controlled. [Brandon] is currently experimenting with creating bundles of individual nylon coils to act all together as one big muscle, because while one wire isn’t particularly strong, a bundle could be quite another story. It’s definitely unusual and is doing a lot of work to turn a known phenomenon into something hackable, which makes it lovely to see in this year’s Hackaday Prize.

N64 Emulated in VR Makes Hyrule go 3D

The Nintendo 64 had some groundbreaking and popular 3D games, and [Avaer Kazmer] felt it was only right to tamper with things just enough to trick an emulator into playing Ocarina of Time in VR, complete with stereoscopic 3D. The result is more than just running an emulator on a simulated screen in virtual reality; the software correctly renders a slightly different perspective of the world of Hyrule to each eye in order to really make the 3D pop in a way the original never could, and make it playable with VR controllers in the process. The VR emulator solution is called Emukit and works best with Exokit, a JavaScript web browser for AR and VR environments for which [Avaer] is a developer.

It turns out that there were a few challenges to work around and a few new problems to solve, not least of which was mapping VR controllers to control an N64 game in a sensible way. One thing that wasn’t avoidable is that the N64’s rendered world may now pop in 3D, but it still springs forth from a rectangular stage. The N64, after all, is still only rendering a world in a TV-screen-sized portion; anything outside that rectangular window doesn’t really exist, and there’s no way around it as long an emulated N64 is running the show. Still, the result is impressive, and a video demo is embedded below where you can see the effect for yourself.

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Ultra-Low Power, Energy Harvesting Battery Charger

This half-inch square ultra-low power energy harvesting LiPo cell charger by [Kris Winer] uses a low voltage solar panel to top up a small lithium-polymer cell, which together can be used as the sole power source for projects. It’s handy enough that [Kris] uses them for his own projects and offers them for sale to fellow hackers. It’s also his entry into the Power Harvesting Challenge of the Hackaday Prize.

The board is essentially a breakout board for the Texas Instrument BQ25504, configured to charge and maintain a single lithium-polymer cell. The BQ25504 is an integrated part that takes care of most of the heavy lifting and has nifty features like battery health monitoring and undervoltage protection. [Kris] has been using the board along with a small 2.2 Volt solar panel and a 150 mAh LiPo cell to power another project of his: the SensorTile environmental data logger.

It’s a practical and useful way to test things; he says that an average of 6 hours of direct sunlight daily is just enough to keep the 1.8 mA SensorTile running indefinitely. These are small amounts of power, to be sure, but it’s free and self-sustaining which is just what a remote sensing unit needs.

Worn Train Rails Get Judged by Laser

[Calango] is a railway technician, and for a school final project created the Rail Wear Surveillance Trolley (RWST) which is a delightfully designed device made mainly from PVC conduit with one job: travel down a segment of train track while shining a green laser onto the rail, and capture camera images. The trolley holds both the laser and the camera at just the right angles for the camera to capture a profile of the rail’s curved surface. The images are sent via Bluetooth to a smartphone for later analysis. Rail wear can be judged by checking how well the profile of the rail conforms to the ideal profile of an unworn segment. The trolley is manually pushed by an operator, but [Calango] says that ideally, it would be self-propelled and able to inspect a length of the track then return on its own.

The project was made on a tight budget, which led to some clever solutions like using a rotary encoder attached to a wheel as a makeshift distance sensor. If things get desperate enough, it’s even possible to roll your own rotary encoder with a 3D printer and two microswitches.

RGB Sensor’s New Job: Cryptocurrency Trade Advisor

[XenonJohn] dabbles in cryptocurrency trading, and when he saw an opportunity to buy an RGB color sensor, his immediate thought — which he admitted to us would probably not be the immediate thought of most normal people — was that he could point it to his laptop screen and have it analyze the ratio of green (buy) orders to red (sell) orders being made for crypto trading. In theory, if at a given moment there are more people looking to buy than there are people looking to sell, the value of a commodity could be expected to go up slightly in the short-term. The reverse is true if a lot of sell orders coming in relative to buy orders. Having this information and possibly acting on it could be useful, but then again it might not. Either way, as far as out-of-left-field project ideas go, promoting an RGB color sensor to Cryptocurrency Trading Advisor is a pretty good one.

Since the RGB sensor only sees what is directly in front of it, [XenonJohn] assembled a sort of simple light guide. By enclosing the area of the screen that contains orders in foil-lined cardboard, the sensor can get a general approximation of the amount of red (sell orders) versus green (buy orders). The data gets read by an Arduino which does a simple analysis and sends alerts when a threshold is crossed. He dubbed it the Crypto-Eye, and a video demo is embedded below.

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A Peek Into a Weed-Eating Robot’s Test Fixtures

When it comes to production, fast is good! But right the first time is better. Anything that helps prevent rework down the line is worth investing in. Some of the best tools to catch problems are good test fixtures. The folks at Tertill (a solar-powered robot for killing weeds that kickstarted last year) took the time to share two brief videos of DIY test fixtures they use to test components before assembly.

The videos are short, but they demonstrate all the things that make a good test: on the motor tester there are no connectors or wires to fiddle with, the test starts automatically, and there is clear feedback via prominent LEDs. The UI board tester also starts automatically and has unambiguous LED feedback, and sports a custom board holder with a recess just the right shape for the PCB. Once the board is in, the sled is pushed like a drawer to make contact with the test hardware and begin the test. The perfectly formed recesses in both units serve another function as well; they act as a go/no-go test for the physical shape of the components and contacts being tested.

Both videos are embedded below; and while there isn’t much detail on the actual test hardware, we do spy a Raspberry Pi and at least two Adafruit logos among other hacker-familiar elements like laser-cut acrylic, 3D printed plastic, pogo pins, and a PVC junction box.

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