Celebrating The Infinity Of Pi Day With Thermochromic Foil

Thermal printer with a loop of thermochromic foil inserted in it, printing digits of Pi on the loop.The digits gradually disappear from the foil as it exits the printer.

It might take you some time to understand what’s happening in the video that Hackaday alum [Moritz Sivers] shared with us. This is [Moritz]’s contribution for this year’s Pi Day – a machine that shows digits of Pi in a (technically, not quite) infinite loop, and shows us a neat trick we wouldn’t have thought of.

The two main elements of this machine are a looped piece of thermochromic foil and a thermal printer. As digits are marked on the foil by the printer’s heating element, they’re visible for a few seconds until the foil disappears from the view, only to be eventually looped back and thermally embossed anew. The “Pi digits calculation” part is offloaded to Google’s pi.delivery service, a π-as-a-Service endpoint that will stream up to 50 trillion first digits of Pi in case you ever need them – an ESP8266 dutifully fetches the digits and sends them off to the thermal printer.

This machine could print the digits until something breaks or the trillions of digits available run out, and is an appropriate tribute to the infinite nature of Pi, a number we all have no choice but to fundamentally respect. A few days ago, we’ve shown a similar Pi Day tribute, albeit a more self-sufficient one – an Arduino calculating and printing digits of Pi on a character display! We could’ve been celebrating this day for millennia, if Archimedes could just count a little better.

8 thoughts on “Celebrating The Infinity Of Pi Day With Thermochromic Foil

    1. @vib said: “Could not find a source for thermochromic film. I wonder where [Moritz Sivers] / {Moritz} found it.”

      * 3 Packs Liquid Crystal Sheet 6 x 6 Inch Heat Sensitive Sheet Temperature Sensitive Liquid Crystal Sheet 6 Color Changing Heat Sensitive Board, 24 to 34 Celsius Degree Transition for Science Experiment $19.99


      * Thermochromic Sheets & Films

      Thermochromic material can be used to monitor hot spots on circuit boards or advertising. They are available in various size formats. 6″ x 6″, 12 x 12″ or 12″ x 18″ and can be cut to fit your application. Additionally we can supply 54″ Wide x “tell us how long”. Sheets come With or Without Adhesive. Lexan material is dull and will not show finger prints. Polyvinyl is shinny or VInyl Flex ( TLCSEN455 & TLCSEN456 ) is available in B lack or Blue and has one specific temperature 25°C ~ 30°C


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