The Thermochromic Display You Didn’t Know You Needed

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.

8 thoughts on “The Thermochromic Display You Didn’t Know You Needed

  1. These things are super cool and fascinate me since childhood but I don’t remember many applications for them.

    – Medical thermometers. They wouldn’t tell the exact temperature, but fine for quick screening OK/NOT OK.
    – beer bottles that would indicate that they need cooling and frying pans that indicate that they’re hot enough
    – silly batteries with charge gauge
    – … ?

    Re: this project, I’d be tempted to add some airflow from the front side of it.

    1. Medical thermometers – yeah, if you can convince everyone to stick them to forehead. Otherwise an IR thermometer is THE solution – two seconds per patient and can even be used on sleeping patients without disturbing them.

      – beer bottles – yeah. frying pans – nope, too hot for liquid crystals, but already done by tefal with thermochromic paints.

      – batteries with charge gauge – that’s exactly how it’s done, but again with thermochromic paint (like in thos temperature cups), not liquid crystals.

      Also airflow is not required, they have peltiers under each segment (can cool and heat).

      1. Those thermometers were from 30 years ago, IR thermometers weren’t really commonplace back then, if they existed at all. I was a kid and we were very happy to stick a piece of real magic to our foreheads.

        I thought airflow because the liquid crystals in the video seem to dissipate the heat slowly, even though they’re being actively cooled from the back side.

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