Color changing coaster has a built-in drink detector

[Robert] put together his own illuminated coasters that know when they hold a drink. They look fantastic, thanks to professionally produced PCBs and a layered, laser-cut acrylic case. They’re much like the pagers given to restaurant-goes who are waiting for tables, but this version is much fancier (and doesn’t include the vibrating/paging feature).

The RGB-LED board is a previous project which was developed using eight surface mount RGB LED modules around a circular board. It uses an ATmega168 paired with an MBI5168 constant-current LED sink driver. The coaster enclosure gave him room for a few more items, like the pair of AA batteries which work in conjunction with a boost converter to power the device. It also houses an IR reflectance sensor which is used to detect the presence of a drink on the coaster. This is important since an on-occupied coaster looks like it would be blindingly bright if there wasn’t a glass to diffuse the intensity of the LEDs.

He mentions that incandescent light bulbs mess with the IR reflectance sensor. But there must be some way to account for ambient conditions with the code, right?


  1. atomsoft says:

    Clear isnt a good look really. A milky white would have made this 100% awesome! but since its not that color i still give this 90% thumbs up!

  2. Hirudinea says:

    Hey it’s Dr. Theopolis, nice to see him working again.

  3. rtspitz says:

    I guess the IR sensor wouldn’t like the milky acrylic very much though.

  4. NewCommentor1283 says:

    i too think this needs frosted(heavily sanded) plastic

    and the cup’s LEDs could be seperate from out-facing LEDs or ect

    combine this with the “video loading” pattern and … volia! drunk confusion.

    … “so umm, so i have to finish this drink for the cupholder to finish loading? WTF?!?!
    im DRINKING BANDWIDTH?!?!?!?!!?”


    or no, put a WEIGHT SENSOR and display LIQUID REMAINING!!! red is getting low! oh no!


  5. M4CGYV3R says:

    The rather limited manual of a commercial version with linking features:

  6. echodelta says:

    Tiny shouldered screws holding plastic, crack! Good looking till then. Cool colours only with cold drinks, hot etc. Senses when ice gets low, or cold coffee.

  7. Galane says:

    Now what it needs to do is detect what type of liquid is in the glass and change color accordingly.

  8. Scott says:

    I wanted to do something like this for a beer pong table but with a capacitance sensor. Changing the color value as beer was poured into the cup for a nice even fill for each cup. Instead i just put a light under the cups with frosted lexan because i hadnt completed any circuit projects at that time.

    Using a capacitance sensor here would be cool every time you pick up your drink for a sip you would have a different color value when you put your drink back on the coaster.

    • Dan says:

      I built that. (My youtube video: ) The capacitive version (Mark II) was a senior design project.

      It never worked quite as well as I wanted. To make it look good, you needed space between the LEDs and the cup, but to make it work good, you needed the sensors to be as close as possible.

      Also, any water on the table top will trigger the sensor. (Duh!)

      The IR version hated ambient light, even with the modulated sensor. I suspect it was because of the diffuser.

  9. DiRWiN says:

    Should Induction Charge Battery with Coaster Holder

  10. Jim says:

    I love the clear look. With a frosted top you wouldn’t be able to see the innards and it wouldn’t light the drink quite as well.

  11. Josh says:

    “This is important since an on-occupied coaster looks like it would be blindingly bright if there wasn’t a glass to diffuse the intensity of the LEDs.”

    Reminds me of Hackaday’s website when my eyes bleed every time I come here. It’s like 1997 or some shit over here, guys. Love the content, though. Killer site for years now otherwise.

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