Hotend Becomes The Z Probe With A Kinematic Coupling

November 13, 2018 by 5 Comments

3D Printer tool changers are bedazzling to watch, but even failed attempts at tool changers can yield something marvelous. Such is the case for [Raymond] who transformed a tool changer attempt into a perfectly capable z-level probe that uses the hotend itself as a limit switch.

The secret sauce behind this mechanism: a kinematic coupling. This coupling takes two planar surfaces and perfectly constrains them relative to each other by mating them together at exactly 6 points of contact. The result is that repeatedly separating and joining the two surfaces will always land them in the same spot within a few microns. To transform these surfaces into a switch, we need only run a small current between the points of contact. That was easy since there were all-metal balls and pins making the connection. Both surfaces are held together with magnets with the upper surface holding the hotend. To trip the limit switch, the printer simply lowers the z-height until the hotend “probes” the bed, defeating the magnets and breaking the current. Presto! No switches or P.I.N.D.A. probes. Just good old fashioned electricity and steel pins.

With so much focus on pricey probes and repeatable switches, it’s great to see some good old-fashioned geometry guiding the precision behind this printer’s sensing. It’s also heartwarming hear that the whole project was actually inspired by another coupling-equipped 3D printer that landed here a few years ago! Finally, if you’re curious to see some other folks getting some more mileage out of kinematic couplings, have a look at this homebrew CNC touch probe.

Mechanisms: Lead Screws And Ball Screws

November 13, 2018 by 52 Comments

Translating rotary motion to linear motion is a basic part of mechatronic design. Take a look at the nearest 3D-printer or CNC router — at least the Cartesian variety — and you’ll see some mechanism that converts the rotation of the the motor shafts into the smooth linear motion needed for each axis.

Hobby-grade machines are as likely as not to use pulleys and timing belts to achieve this translation, and that generally meets the needs of the machine. But in some machines, the stretchiness of a belt won’t cut it, and the designer may turn to some variety of screw drive to do the job.

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Alice Evans: Brucellosis, Or Why We Pasteurize Milk

November 13, 2018 by 51 Comments

It’s easy to forget how much illness and death was caused by our food and drink just one hundred years ago. Our modern food systems, backed by sound research and decent regulation, have elevated food safety to the point where outbreaks of illness are big news. If you get sick from a burger, or a nice tall glass of milk, it’s no longer a mystery what happened. Instead we ask why, and “who screwed up?”

In the early 20th century though, many food-borne illnesses were still a mystery, and microbiology was a scientific endeavor that was just getting started. Alice Catherine Evans was an unlikely figure to make a dent in this world at the time, but through her research at the United States Department of Agriculture’s (USDA), and later at the Hygienic Laboratory (now the National Institute of Health) she had a huge impact on the field of bacteriology, the dairy industry, and consumer safety. Continue reading “Alice Evans: Brucellosis, Or Why We Pasteurize Milk” →

Unique Flat-Screen Display Put To Use In CRT Game Boy

November 13, 2018 by 30 Comments

The cathode-ray tube ruled the display world from the earliest days of TV until only comparatively recently, when flat-screen technology began to take over. CRTs just kept getting bigger over that time until they reached a limit beyond which the tubes got just too bulky to be practical.

But there was action at the low end of the CRT market, too. Tiny CRTs popped up in all sorts of products, from camcorders to the famous Sony Watchman. One nifty CRT from this group, a flat(tish) tube from a video intercom system, ended up in [bitluni]’s lab, where he’s in the process of turning it into a retro Game Boy clone with a CRT display. The display, which once showed the video from a door-mounted camera, was a gift from a viewer. Date codes on the display show it’s a surprisingly recent device; were monochrome TFT displays that hard to come by in 2007? Regardless, it’s a neat design, with the electron gun shooting upward toward a curved phosphor screen. With a little Google-assisted reverse engineering, [Bitluni] was able to track done the video connections needed to use his retro game console, which uses an ESP32 that outputs composite video. He harvested the intercom speaker for game audio, added a temporary Nintendo gamepad, and soon he was playing Tetris in glorious monochrome on the flat screen.

The video below is only the first in a series where the prototype will be stuffed into one nice tidy package. It certainly still needs some tweaking, but it’s off to a great start. We can’t wait to see the finished product.

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Low-energy ESP8266-based Board Sleeps Like A Log Until Triggered

November 13, 2018 by 32 Comments

Given the popularity of hacking and repurposing Amazon Dash buttons, there appears to be a real need amongst tinkerers for a simple “do something interesting on the internet when a button is pressed” device. If you have this need but don’t feel like fighting to bend a Dash device to your will, take a look at [Kevin Darrah]’s trigBoard instead.

The trigBoard is a battery-powered, ESP8266-based board that includes some clever circuitry to help it barely sip power (less than one microamp!) while waiting to be triggered by a digital input. This input could be a magnetic reed switch, push button, or similar, and you can configure the board for either normally open or normally closed switches.

The clever hardware bits that allow for such low power consumption are explained in [Kevin]’s YouTube video, which we’ve also embedded after the break. To summarize: the EPS8266 spends most of it’s time completely unpowered. A Texas Instruments TPL5111 power timer chip burns 35 nanoamps and wakes the ESP8266 up every hour to check on the battery. This chip also has a manual wake pin, and it’s this pin – along with more power-saving circuitry – that’s used to trigger actions based on the external input.

Apparently the microcontroller can somehow distinguish between being woken up for a battery check versus a button press, so you needn’t worry about accidentally sending yourself an alert every hour. The default firmware is set up to use Pushbullet to send notifications, but of course you could do anything an EPS8266 is capable of. The code is available on the project’s wiki page.

The board also includes a standard micro-JST connector for a LiPo battery, and can charge said battery through a micro-USB port. The trigBoard’s full schematic is on the wiki, and pre-built devices are available on Tindie.

[Kevin]’s hardware walkthrough video is embedded after the break.

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Internet-connected Advent calendar

Advent Calendar Tracks The Days Until Christmas

November 12, 2018 by 2 Comments

Internet-connected Advent calendarWhat’s a hacker to do when Halloween’s over and a new source of ideas is needed for more hacks? Make something for Christmas of course. That’s what [Dario Breitenstein] did when he made his Advent calendar both as a decoration and to help instill some Christmas spirit.

Designed in SketchUp, it’s a WS2812 LED strip mounted in a clean looking walnut enclosure. The light diffuses through 3D-printed PETG lids with vinyl over them to outline the days. Naturally, it had to be Internet-connected and so an ESP8266 based WEMOS D1 mini board fetches the date and time from an NTP server. Sundays light up in red and Christmas Eve in purple.

This appears to be just the thing hackers like [vk2zay] could use for inspiration during their sort-of-annual Advent Calendar of Circuits wherein a different circuit is made each day leading up to Christmas.

Hacked Heating Instruments For The DIY Biology Lab

November 12, 2018 by 4 Comments

[Justin] from The Thought Emporium takes on a common molecular biology problem with these homebrew heating instruments for the DIY biology lab.

The action at the molecular biology bench boils down to a few simple tasks: suck stuff, spit stuff, cool stuff, and heat stuff. Pipettes take care of the sucking and spitting, while ice buckets and refrigerators do the cooling. The heating, however, can be problematic; vessels of various sizes need to be accommodated at different, carefully controlled temperatures. It’s not uncommon to see dozens of different incubators, heat blocks, heat plates, and even walk-in environmental chambers in the typical lab, all acquired and maintained at great cost. It’s enough to discourage any would-be biohacker from starting a lab.

[Justin] knew It doesn’t need to be that way, though. So he tackled two common devices:  the incubator and the heating block. The build used as many off-the-shelf components as possible, keeping costs down. The incubator is dead simple: an insulated plastic picnic cooler with a thermostatically controlled reptile heating pad. That proves to be more than serviceable up to 40°, at the high end of what most yeast and bacterial cultures require.

The heat block, used to heat small plastic reaction vessels called Eppendorf tubes, was a little more complicated to construct. Scrap heat sinks yielded aluminum stock, which despite going through a bit of a machinist’s nightmare on the drill press came out surprisingly nice. Heat for the block is provided by a commercial Peltier module and controller; it looks good up to 42°, a common temperature for heat-shocking yeast and tricking them into taking up foreign DNA.

We’re impressed with how cheaply [Justin] was able to throw together these instruments, and we’re looking forward to seeing how he utilizes them. He’s already biohacked himself, so seeing what happens to yeast and bacteria in his DIY lab should be interesting.

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