Powerful Crossbow Is Almost Entirely 3D Printed

January 12, 2016 by 21 Comments

As it turns out, it’s not feasible to print an entire crossbow yet. But [Dan]’s crossbow build does a good job of leveraging what a 3D printer is good at. Most of the printed parts reside in the crossbow’s trigger group, and the diagrams in the write-up clearly show how the trigger, sear and safety all interact. Particularly nice is the automatic nature of the safety, which is engaged by drawing back the string. We also like the printed spring that keeps the quarrel in place on the bridle, and the Picatinny rail for mounting a scope. Non-printed parts include the aluminum tubes used in the stocks, and the bow itself, a composite design with fiberglass rods inside PVC pipe. The video below shows the crossbow in action, and it looks pretty powerful.

Actually, we’ll partially retract our earlier dismissal of entirely 3D-printed crossbows, but [Dan]’s version is a lot more practical and useful than this model. And for a more traditional crossbow design, check out this entirely hand-made crossbow.

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LUX Searches In The Deep For Dark Matter

January 12, 2016 by 38 Comments

The Homestake Mine started yielding gold in 1876. If you had asked George Hearst, the operator at the time, if the mine would someday yield the secrets of the universe I bet he would have laughed you out of the room. But sure enough, by 1960 a laboratory deep in the mine started doing just that. Many experiments have been conducted there in the five and a half decades since. The Large Underground Xenon (LUX) experiment is one of them, and has been running is what is now called the Sanford Underground Research Facility (SURF) for about four years. LUX’s first round of data was collected in 2013, with the experiment and the rest of the data slated to conclude in 2016. The method, hardware, and results wrapped up in LUX are utterly fascinating.

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Hacking Chipped 3D Printer Filament On The Da Vinci Printer

January 12, 2016 by 64 Comments

XYZ Printing has been selling 3D printers for years now with one very special feature not found in more mainstream printers. They’re using a chipped filament cartridge with a small chip inside each of their proprietary filament cartridges, meaning you can only use their filament. It’s the Gillette and ink jet model – sell the printer cheap, and make their money back on filament cartridges.

Last week at CES, XYZ Printing introduced their cheapest printer yet. It’s called the da Vinci Mini, a printer with a 15x15x15 cm build volume that costs only $269. Needless to say, a lot of these will be sold. A lot of people will also be disappointed with chipped filament cartridges in the coming months, so here’s how you defeat the latest version of chipped filament.

A little bit of research showed [WB6CQA] the latest versions of XYZ Printing’s filament uses an NFC chip. Just like the earlier EEPROM version, the latest spools of filament just store a value in memory without any encryption. [WB6CQA] pulled a board from the printer, connected it up to a logic analyzer, and checked out the data sheet for the NFC chip, giving him access to the data on the filament chip.

After running a few prints and comparing the data before and after, [WB6CQA] found a few values that changed. These values could be written back to their previous values, effectively resetting the chip in the filament and allowing third party filament to be used in this printer. It’s a kludge, but it works. More effort will be needed to remove the need to capture data with logic analyzers, but we’re well on our way to chipless filament on da Vinci printers.

String Racing Robots Are Here !

January 12, 2016 by 24 Comments

This could be the start of a new thing. [HarpDude] showed off his String Car Racers over on the Adafruit forum. It’s like a small model cable car on caffeine. String up enough of them and go head to head racing with others.

A motor with a small pulley runs over a length of string stretched between 2 posts. Below the pulley, acting as a counterweight balance, is the rest of the racer. A Trinket board, motor driver, 9V battery and a pair of long lever micro switches to detect end of travel. The switches also help reverse the motor. A piece of galvanized wire acts as a guide preventing the String Car from jumping off the string. And discovering the benefits of a micro-controller design, as against discrete TTL/CMOS, old timer [HarpDude] added two operational modes via software. “Pong”, where the String Car keeps going back and forth over the string until it stops of (battery) exhaustion. The other mode is “Boomerang” – a single return trip back and forth.

We are guessing the next upgrade would be to add some kind of radio on the car (ESP8266 perhaps) and build an app to control the String Car. That’s when gaming could become fun as it opens up possibilities. One way to improve performance would be to add two “idler” pulleys in line with the main drive pulley, and then snake the string through the three of them. Now you know what to do with all of those old motors you’ve scavenged from tape drives, CD drives and printers. Let the Games begin!

Thanks [Mike Stone] for tipping us off on this.

Using Over 3000A To Rapidly Charge An IPhone

January 11, 2016 by 63 Comments

Earlier this week I had the pleasure of doing something very stupid with another YouTuber. We wanted to see what would happen if you push over 3000A through an iPhone. The result? Fire. You get fire.

To perform this experiment we prepared a few different setups for maximum electrocution. The first was with the tried and true technique of re-wrapping a transformer to put out low volts at high current — essentially, a DIY spot welder. Now while most of those use a little transformer taken out of a microwave, I happened to have an industrial transformer about four times the size. Once re-wrapped to become a step-down transformer, it can produce approximately 1000A @ 1V … Or if you plug it into a 240V outlet, upwards of 2000A @ 2V — all depending on the resistance of whatever you’re putting in-between the contacts.

During the actual test we read about 1400A going through the iPhone with an ammeter. Which puts an iPhone 6 at a resistance of about 0.0014 ohms.

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A CNC Build Log From The Not So Distant Past

January 11, 2016 by 3 Comments

2007 wasn’t that long ago, but [Adam Ziegler’s] build log is, nevertheless, a pleasant romp through a not so distant past. From beginning to the end of the build, we enjoyed reading [Adam]’s progress and struggles as he worked through the build. Sometimes it’s hard to see the very normal daily work that goes into a project when it’s all polished up at the end.

He designed the mechanics himself, but after some less-successful attempts, decided to just buy the electronics. The machine is a well executed MDF gantry mill with conduit rails and 6000-series ball bearings on angle stock. It’s a good example of what you can do with cheap materials and careful planning.

[Adam] ran a few jobs on the machine, some of which he took on before it was even built (which he doesn’t recommend doing). After his adventure with this gateway machine, he’s put it up for sale and is purportedly working on a new model. The standard pattern of CNC addiction is a live alive and well.

If you’re looking to get into CNC machining on the cheap, we’ve seen similar affordable builds for your inspiration.

Learning And Failing At Digital Electronics

January 11, 2016 by 36 Comments

[spencerhamblin] is starting his explorations into digital electronics the hard way: reproducing a “simple” IC’s functionality by wiring up a board full of discrete transistors. In this case, the end product is a binary-to-seven-segment decoder built from scratch.

In engineering circles, this circuit is better known as a 7447 BCD to seven-segment decoder/driver, but just using a single chip has little pedagogical value. Building a simple circuit with 39 transistors, 31 resistors, and a handful of diodes is a good introduction to digital electronics, and after two attempts, [spencerhamblin] knocked it out of the park.

The build began with a piece of copper clad board, a bunch of cheap FETs from fleabay, and an incorrect schematic. While the first version of the project looked fantastic with Manhattan-style construction, and jumper wires everywhere, the schematic was fundamentally flawed and [spencer] got a little confused when converting the circuit to a common anode display.

Version two used a more standardized construction. This circuit was plotted in DipTrace, and the resulting PCB was sent off to OSHPark. The build was cleaner, but in capturing the schematic, [spencer] reversed the footprint of the seven segment display. That was easy enough to fix with a few short wires, and after a little bit of work [spencer] had a device that would convert binary to a seven segment display.