Improved Thermochromic Clock Uses PCB Heaters For Better Contrast

January 4, 2022 by Dave Rowntree 11 Comments

We love timepiece projects round these parts, so here we are with another unusual 7-segment clock design. Hackaday’s own [Moritz Sivers] wasn’t completely satisfied with his last thermochromic clock, so has gone away and built another one, solved a few of the issues, and this time designed it to be wall mounted. The original design had a single heater PCB using discrete resistors as heating elements. This meant that the heat from active elements spread out to adjacent areas, reducing the contrast and little making it a bit hard to read, but it did look really cool nonetheless.

This new version dispenses with the resistors, using individual segment-shaped PCBs with heater traces, which gives the segment a more even heat and limited bleeding of heat into neighbouring inactive air-gapped segments. Control is via the same Wemos D1 Mini ESP8266 module, driving a chain of 74HC595 shift registers and a pile of dual NMOS transistors. A DS18B20 thermometer allows the firmware to adjust for ambient temperature, giving more consistency to the colour change effect. All this is wrapped up in an aluminium frame, and the results look pretty nice if you ask us.

Both PCB designs and the Arduino firmware can be found on the project GitHub, so reproducing this should be straightforward enough for those so inclined, just make sure your power supply can handle at least 3 amps, as these heaters sure are power hungry!

Got a perfectly good clock, but desperately need a thermochromic temperature/humidity display? [Moritz] has you covered. And if this digital clock is just too simple, how about a mad 1024-element analog thermochromic clock instead?

Continue reading “Improved Thermochromic Clock Uses PCB Heaters For Better Contrast” →

3D Printing Liquid Crystal

August 22, 2021 by Al Williams 7 Comments

If you think at all about liquid crystals, you probably think of display technology. However, researchers have worked out a way to use an ink-jet-like process to 3D print iridescent colors using a liquid crystal elastomer. The process can mimic iridescent coloring found in nature and may have applications in things as diverse as antitheft tags, art objects, or materials with very special optical properties.

For example, one item created by the team is an arrow that only appears totally green when viewed from a certain angle. The optical properties depend on the thickness of the material which, being crystalline, self-organizes. Controlling the speed of deposition changes the thickness of the material which allows the printer to tune its optical properties.

The ink doesn’t sound too exotic to create, although the chemicals in it are an alphabet soup of unpronounceable organic compounds. At least they appeared available if you know where to shop for exotic chemicals.

The iridescent coloring is common in nature, so art objects like butterfly wings are natural with this method. While inkjet printers aren’t common in the hacker community, they aren’t that hard to create, so this seems like it would be repeatable in a garage lab.

Liquid crystals have all kinds of interesting properties and we wonder if this material would help you print those sorts of things. If you want to experiment, we have seen a few hacked inkjet printers.

Thanks [jscotta] for the tip.

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.

Continue reading “Thermochromic Display Tells You The Temperature Despite Your Current Mood” →

Monochrome CRT And Liquid Crystal Shutter Team Up For Color Video

October 1, 2019 by Dan Maloney 21 Comments

If you were tasked with designing a color video monitor, it’s pretty clear how you’d go about it. But what if you’d been asked to do so 20 years ago? Would it have been a cut and dried from an engineering standpoint? Apparently not, as this hybrid LCD-CRT video monitor demonstrates.

We’d honestly never heard of this particular design, dubbed “LCCS”, or liquid crystal color shutter, until [Technology Connections]’ partial teardown of the JVC monitor and explanation of its operation. The idea is simple and hearkens back to the earliest days of color TV in the United States, when broadcasters were busy trying to bring color to a monochrome world in a way that would maximize profits. One scheme involved rotating a color wheel in front of the black-and-white CRT and synchronizing the two, which is essentially what’s happening in the LCCS system. The liquid crystal panel cycles between red, blue, and green tints in time with the CRT’s images behind it, creating a full-color picture. “But wait!” you cry. “Surely there were small color CRTs back in the year 2000!” Of course there were, but they kind of sucked. Just look at the comparison of a color CRT and the LCCS in the video below and you’ll see why this system carved out a niche in the pro video market, especially for video assist monitors in the days before digital cinematography. A similar system was used by Tektronix for color oscilloscopes, too.

As usual, [Technology Connections] has managed to dig up an interesting bit of the technological fossil record and present it in a fascinating way. From video on vinyl to 1980s copy protection to the innards of a toaster, we enjoy the look under the hood of forgotten tech.

Continue reading “Monochrome CRT And Liquid Crystal Shutter Team Up For Color Video” →

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.

Continue reading “The Thermochromic Display You Didn’t Know You Needed” →

How To Make A Custom LCD From Scratch

June 17, 2016 by Donald Papp 16 Comments

If you have ever wondered what it took to make your own custom graphic LCD from scratch, this video from [Applied Science] is worth a watch. It’s concise and to the point, while still telling you what you need to know should you be interested in rolling your own. There is also a related video which goes into much more detail about experimenting with LCD technology.

[Applied Science] used microscope slides and parts purchased online to make an LCD that displays a custom graphic when activated. The only step that home experimenters might have trouble following is coating the glass slides with a clear conductive layer, which in the video is done via a process called sputtering to deposit a thin film. You don’t need to do this yourself, though. Pre-coated glass is readily available online. (Search for Indium-Tin Oxide or ‘ITO’ coated glass.)

The LCD consists of a layer of liquid crystal suspended between two layers of conductive glass. An electrical field is used to change the orientation of crystals in the suspension, which modulate the light passing through them. Polarizing filters result in a sharp contrast and therefore a visible image. To show a particular shape, some of the conductive coating is removed from one of the layers in the shape of the desired image. The process [Applied Science] uses to do this is nearly identical to etching a custom PCB. Continue reading “How To Make A Custom LCD From Scratch” →

Crafting A Liquid Crystal Display

December 2, 2013 by Brian Benchoff 17 Comments

Throughout the 1960s, the management at RCA thought LCD ~~displays~~ were too difficult to commercialize and sent their engineers and researchers involved in LCDs off into the hinterlands. After watching [Ben Krasnow]’s efforts to build a liquid crystal display, we can easily see why the suits thought what they did. It’s an amazing engineering feat.

Before building his own version of an LCD (seen above in action), he goes through the mechanics of how LCDs operate. Light enters the display, goes through a polarizer, and is twisted by a liquid crystal material. The first successful LCDs used two types of liquid crystals – chiral and nematic. By combining these two types of molecules in the right proportion, the display can ‘twist’ the polarized light exactly 90 degrees so it is blocked by the second piece of polarizing film in the display.

Besides getting the right crystals and engineering processes, another major hurdle for the development of LCDs ~~displays~~ is transparent electrically conductive traces. [Ben], along with every other LCD manufacturer, uses a thin layer of indium tin oxide, or ITO. By embedding these clear electrodes in the display, segments can be built up, like the seven segment displays of a calculator or a bunch of tiny dots as found in a TV or computer monitor.

In the end, [Ben] was able to build an extremely simple single-segment LCD ~~display~~ out of a pair of microscope slides. It does modulate light, just barely. With a lot of work it could be made in to a calculator type display but for now it’s an awesome demonstration of how LCDs actually work. Continue reading “Crafting A Liquid Crystal Display” →