Display Cup prototype

So I had this idea. What if you took one of those flexible e-ink displays and wrapped it around a coffee mug so you could have a programmable cup?

It's actually been harder to do that I thought. Mainly because I haven't found a decent cup to use. I attempted to fabricate one from acrylic sheet that I wrapped around a cylinder, at a size that would allow one of those "I am not a paper cup" coffee cups to be inserted within it. This didn't work out so well given that I didn't have the best tools on hand.

Then I remembered how my kids made custom mugs years ago, using these cups that have a clear outside with a cup insert. I had a hard time finding them though, but finally located one at Hobby Lobby. Unfortunately, they are really flimsy (but also really cheap.. less than a dollar). But it worked for a prototype.

The electronics are pretty simple. I used a Lolin ESP32 lite, because it has a built in battery charger, Bluetooth LE, and enough memory to store lots of images. It's probably overkill on the processing and memory needs, but it was convenient to use.

Attached to this is a Waveshare 2.13" flexible e-ink display with its driver "hat". I have not be able to find anybody selling any other size of flexible display. This one is easy to find on ebay and ali-express.

Finally, I got a little 150Mah Lipo battery with JST connector.

Luckily, the space at the bottom of the cup under the insert was just big enough to fit all this in there when arranged just right. I taped it all down to a thin round of cardboard.

 Once assembled and tested with real coffee I discovered that the display doesn't particularly like to be warmed to the temperature of coffee, and begins to fade! Also coffee doesn't stay warm long. So I improvised some insulation by taking a styrofoam cup and cutting off the bottom and then wrapping it around the cup insert. This helped a great deal.

Again the cup is really low quality and only barely usable as a novelty, but, it's pretty cool having a cup with a display that changes while you are using it! The battery lasts a few hours on a charge with the display changing every 30 seconds and putting the ESP32 into deep sleep.

I am working on a more practical version using a double wall insulated ceramic or metal cup, and going back to fabricating my own acrylic outside holder.