Matrix Of Resistors Forms The Hot Hands Behind This Thermochromic Analog Clock

May 24, 2020 by Dan Maloney 20 Comments

If you’re going to ditch work, you might as well go big. A 1,024-pixel thermochromic analog clock is probably on the high side of what most people would try, but apparently [Daniel Valuch] really didn’t want to go to work that day.

The idea here is simple: heat up a resistor by putting some current through it, lay a bit of thermochromic film over it, and you’ve got one pixel. The next part was not so simple: expanding that single pixel to a 32 by 32 matrix.

To make each pixel square-ish, [Daniel] chose to pair up the 220-ohm SMD resistors for a whopping 2,048 components. Adding to the complexity was the choice to drive them with a 1,024-bit shift register made from discrete 74LVC1G175 flip flops. With the Arduino Nano and all the other support components, that’s over 3,000 devices with the potential to draw 50 amps, were someone to be foolish or unlucky enough to turn on every pixel at once. Luckily, [Daniel] chose to emulate an analog clock here; that led to additional problems, like dealing with cool-down lag in the thermochromic film when animating the hands, which had to be dealt with in software.

We’ve seen other thermochromic displays before, including recently with this temperature and humidity display. This one may not be the highest resolution display out there, but it’s big and bold and slightly dangerous, and that makes it a win in our book.

Thermochromic Display Tells You The Temperature Despite Your Current Mood

March 20, 2020 by Dan Maloney 8 Comments

Readers who survived the 1970s will no doubt remember the “mood ring” fad, where a liquid crystal mounted to a ring would magically reveal your current emotional state to all and sundry by changing color. This nifty thermochromic display is based on the same principle, and while it might not start a new craze, it’s still pretty mesmerizing to watch.

This isn’t [Moritz v. Sivers]’ first attempt at a thermochromic display. His earlier version was far more complicated, using separate copper plates clad with thermochromic film for each segment, with Peltier devices to cool and heat them individually. Version two is much simpler, using a printed circuit board with heating elements in the shape of seven-segment displays etched into it. The thermochromic film sits directly on the heater PCB; a control PCB below has the MCU and sensors on it. The display alternates between temperature and humidity, with the segments fading in an uneven and ghostly way that really makes this fun to watch. [Moritz] has made the build files available, and there’s a detailed Instructable as well.

We’re always on the lookout for alternate display modalities, especially when they look this cool. We’ve seen other thermochromic displays before, of course, and persistence of phosphorescence looks great, too.

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The Thermochromic Display You Didn’t Know You Needed

August 19, 2019 by Tom Nardi 8 Comments

We love unique ways of displaying data here at Hackaday, and this ingenious thermochromic display created by [Moritz v. Sivers] more than fits the bill. Using sheets of color changing liquid crystals and careful temperature control of the plates they’re mounted on, he’s built a giant seven-segment display that can colorfully (albeit somewhat slowly) show the current temperature and humidity.

The sheets of temperature sensitive liquid crystals are a bit like flattened out Mood Rings; they starts out black, but as heat is applied, their color cycles through vibrant reds, greens, and blues. The sheets are perhaps best known as the sort of vaguely scientific toys you might see in a museum gift shop, but here [Moritz] has put their unique properties to practical use.

To achieve the effect, he first cut each segment out of copper. The crystal sheets were applied to the segments, thanks to their handy self-stick backing, and the excess was carefully trimmed away. Each segment was then mounted to a TES1-12704 Peltier module by way of thermally conductive epoxy. TB6612FNG motor controllers and a bevy of Arduino Nano’s are used to control the Peltier modules, raising and lowering their temperature as necessary to get the desired effect.

You can see the final result in the video after the break. It’s easily one of the most attractive variations on the classic seven-segment display we’ve ever seen. In fact, we’d go as far as to say it could pass for an art installation. The idea of a device that shows the current temperature by heating itself up certainly has a thoughtful aspect to it.

This actually isn’t the first display we’ve seen that utilized this concept, though it’s by far the largest. Back in 2014 we featured a small flexible display that used nichrome wires to “print” digits on a sheet of liquid crystals.

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Results Of 3D-Printed Cylinder Head Testing Fail To Surprise

August 9, 2018 by Dan Maloney 68 Comments

It’s the suburbanista’s weekend nightmare: you’re almost done with the weekly chores, taking the last few passes with the lawn mower, when you hear a pop and bang. The cylinder head on your mower just blew, and you’re out of commission. Or are you? You’ve got a 3D printer – couldn’t it save the day?

If this bench test of plastic cylinder heads is any indication, it’s possible – just as long as you’ve only got 40 seconds of mowing left to do. [Project Farm] has been running all sorts of tests on different materials as field-expedient cylinder heads for small gasoline engines, using everything from JB Weld epoxy to a slab of walnut. For this test, two chunky heads were printed, one from ABS, of the thermochromic variety apparently, the other in PLA. The test went pretty much as expected for something made of thermoplastic exposed to burning gasoline at high pressure, although ABS was the clear winner with two 40-second runs. The PLA only lasted half as long before the spark plug threads melted and the plug blew out. A gasket printed from flexible filament was also tested, with predictably awful results.

As bad as all this was, it still shows that 3D-printed parts are surprisingly tough. Each part was able to perform decently under a compression test, showing that they can stand up to pressure as long as there’s no heat. If nothing else, it was a learning experience. And as an aside, the cylinder heads were printed by [Terry] from the RedNeckCanadians YouTube channel. That video is worth a watch, if just for a few tips on making a 3D-printed copy of an object. Continue reading “Results Of 3D-Printed Cylinder Head Testing Fail To Surprise” →

HairIO: An Interactive Extension Of The Self

March 29, 2018 by Kristina Panos 19 Comments

Most of what we see on the wearable tech front is built around traditional textiles, like adding turn signals to a jacket for safer bike riding, or wiring up a scarf with RGB LEDs and a color sensor to make it match any outfit. Although we’ve seen the odd light-up hair accessory here and there, we’ve never seen anything quite like these Bluetooth-enabled, shape-shifting, touch-sensing hair extensions created by UC Berkeley students [Sarah], [Molly], and [Christine].

HairIO is based on the idea that hair is an important part of self-expression, and that it can be a natural platform for sandboxing wearable interactivity. Each hair extension is braided up with nitinol wire, which holds one shape at room temperature and changes to a different shape when heated. The idea is that you could walk around with a straight braid that curls up when you get a text, or lifts up to guide the way when a friend sends directions. You could even use the braid to wrap up your hair in a bun for work, and then literally let it down at 5:00 by sending a signal to straighten out the braid. There’s a slick video after the break that demonstrates the possibilities.

HairIO is controlled with an Arduino Nano and a custom PCB that combines the Nano, a Bluetooth module, and BJTs that drive the braid. Each braid circuit also has a thermistor to keep the heat under control. The team also adapted the swept-frequency capacitive sensing of Disney’s Touché project to make HairIO extensions respond to complex touches. Our favorite part has to be that they chalked some of the artificial tresses with thermochromic pigment powder so they change color with heat. Makes us wish we still had our Hypercolor t-shirt.

Nitinol wire is nifty stuff. You can use it to retract the landing gear on an RC plane, or make a marker dance to Duke Nukem.

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DIY Curved Display Makes Use Of Cool Thermochromic Properties

January 24, 2014 by James Hobson 18 Comments

flexible screen

[Marin Davide] was on a mission. A mission to build his own curved display screen, using an Arduino, nichrome wire, and thermochromic liquid crystal ink.

The prototype he’s designed uses a sheet of plastic coated in thermochromic ink, curved on an MDF frame. This particular thermochromic ink turns bright blue when heated to around 27°C.

To display digits, he’s created tiny segments of the 7-segment display by wrapping the nichrome wire around pieces of cardboard, which then have been glued to the back of the display. Each of these is controlled separately from his Arduino Mega. He muses that you could also make a rudimentary dot matrix display with this — it would be interesting to see what kind of resolution you could obtain!

To see more photos check out the original DesignNews post linked above. We’re not sure why the bulk of the details are only available in this PDF. If we’re just missing a direct link to the original project page let us know in the comments and we’ll update the post.

Interested in more thermochromic black magic? How about these awesome temperature sensitive photos? Or what about a digital clock face, illuminated by heating resistors?

Thermochromic Imaging

December 19, 2013 by James Hobson 10 Comments

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[clarii_d] is currently finishing up her thesis project on thermochromic pigment to silkscreen receipts. The idea behind it is that when a receipt is touched, part of it fades revealing a hidden message.

As you can guess, thermochromic paint is a type of substance that changes color when introduced to heat — or in this case, fades altogether. Remember when mood rings were all the rage? Same thing.

In her project she is using silkscreening to transfer text onto the back of receipt paper using regular ink. Once dried, she silkscreens an image over top of the message, this time using a thermochromic pigment. The result is a slightly obscured image, but after holding it for a few seconds, it disappears and only the text remains.

Color-changing anything is a bit gimmicky, but we think [clarii_d’s] project is a pretty cool and unique application of it. A few years ago we shared another interesting project utilizing thermochromism; a color-changing clock face that utilized the heat given off by resistors!