Goldilocks Beverage Coaster Tells You When It’s Just Right

If you ask us, morning is the only excuse we need for a hot caffeinated beverage — weather be damned. Wherever [gokux] is, they may be experiencing actual winter this year, given that they are out there getting cozy with a hot cup of what-have-you. But how do they know it’s at the right temperature for drinking? Enter the temperature-monitoring smart coaster.

At the heart of this build is a GY-906 infrared temperature sensor, which senses the warmth (or lack thereof) and displays the degrees on a small OLED screen thanks to a Seeed Xiao SAMD21. To make things simple, there is also an ideogram that corresponds to the current temperature — snowflake for too cold, danger sign for too hot, and thumbs up for that just-right range. Although this coaster is mostly 3D-printed, the mug sits on a slotted piece of aluminium that is removable for easy cleaning. This would be a good-looking and useful addition to any desk.

This is isn’t the first temperature-indicating beverage coaster we’ve seen. The most recent one ultimately used a probe, which is likely about as accurate (and messy) as you can get with these things.

16 thoughts on “Goldilocks Beverage Coaster Tells You When It’s Just Right

  1. This is nicely made, but I wonder if it’s the right solution to the problem. You’ll also want to keep your drink as long as possible at that “ideal” temperature. This coaster won’t help you with that.
    I’d probably go for a “smart cup cover”. It opens the lid when it’s too hot and closes it when the ideal temperature is about the be reached. That would also make it easier to measure the temperature of the vapor or the liquid instead of measuring the temperature of the cup.
    You could also make a “sipping hole”, allowing you to drink without removing the cover. In that case, food-grade/safe materials would have to be used.
    This technology could be integrated in thermos bottles as well. Someone must have thought about this already? e.g. For medicine use, making sure the cold chain has not been broken.

    1. >> e.g. For medicine use, making sure the cold chain has not been broken.
      When shipping temperature-sensitive products a telltale is generally used to record the temperature during the entire journey. If the recording shows the temperature went too high or too low at any point, the item or shipment is discarded. Usually the recording is done at the conveyance (truck/container/boxcar/etc.) level. I believe you can also get liquid-crystal indicators (think “mood ring”) that you can affix to individual packages, which will permanently change appearance if the temperature either rises above or falls below a given level at any point after it is activated.

      1. I was thinking the same about the “mood ring”. There are those temperature indicating strips with adhesive backing for aquariums that have been around for a long time. I’m sure someone at some point has slapped one onto the side of their coffee mug.

    2. Yeah, that’s a huge industry right there.

      The simplest ones are like the water indicator in electronics, they turn red if a set temperature is exceeded. Dunno how they work, one was basically a thermometer that dyed the window bit if the liquid reached there.

      You’ve got tags for too hot, too cold, both, timed ones (eg for food with a shelf life once out of the fridge), etc etc. Some are even resetable, which is nice because some of them ain’t cheap.

      Then there are shock tags (like in hard drives), tilt tags, EMP tags, light tags and so on.

      1. The water indicators do indeed work like a thermometer. The bulb is filled with a clear liquid with the tube containing a dye solution. Between them sits an immiscible liquid in the high end ones and an air bubble in the cheaper ones. If the temperature drops low enough, the fall in the level of the tube causes the dye solution to reach the bulb and mix with the main body of clear liquid.

    3. For desk surfing I had the problem of my standard favourite coffee mug going cold as distracted by typing etc.
      I started looking into heated plates etc.
      Then I went to an industry show and came away with a free “insulated” aluminium mug with lid and small drinking hole.
      Coffee at the keyboard now switched to this mug and stays at acceptable temperature for at least an hour.
      Also works for tea.
      I end to over think things too.

    4. I love my vacuum-insulated cup and it keeps my beverage in the sweet spot for a long time, but I _prefer_ to drink out of a classic ceramic mug with a grip that fits my hand well. I’ve tried using those warmer plates, but they really do nothing unless your mug has a completely flat bottom, and literally none do – they’re all rimmed and somewhat concave for durability.

      There’s just something so nice about a well-made and well-fitting mug. Pity they can’t hold heat worth a darn.

  2. I seem to remember hearing about a cup with a large copper heatsink – rapidly reducing liquid temps and then providing a large reservoir of energy to maintain it at ideal-ish temps.

    People who desire scalding coffee are masochists and have negatively impacted life for the rest of us

      1. They phrase things in such a way that it makes me think they are using generic paraffin wax like the other similar products, but they don’t want to admit it.
        Palm wax would perform similarly, and beeswax could allow a slightly higher starting temperature but worse actual storage and regulation of heat. (
        Beeswax is a mix of things, and I believe some beeswaxes would perform differently from others. Maybe someone might know whether it’s possible to separate only those parts which solidify at the higher temperature.

        1. The ratio of wax to coffee isn’t good enough.

          Been tried, several times. Sort of works, if you don’t mind carrying something the size of a liter insulated travel mug that holds a cup.

          The problem is the market. People serious about coffee consume enough, it’s hot enough. People who drink translucent coffee just don’t care. Cold coffee/sugar/milk/nutsweat drink people are also ‘hard no’s.

          1. Grabbing some random figures for the wax and running with them without checking their accuracy. Paraffin wax has over half the specific heat, ranging widely so let’s guess 2.5J/g-K, about 210J/g latent, and something like eight or nine-tenths the density. If your phase transition is around 60C, suppose the most wax you’ll bother using is enough to bring recently-brewed 90C coffee/tea down to that temperature before running out of wax to melt. That’s around 125 joules per gram for the coffee modeled as water with the 30 degree difference.

            Just on latent heat you’re going to have 0.6g of wax per gram of water. But the wax also needed to be heated up by nearly 40 degrees or so from ambient, so about 100J/g of wax actually went into that instead – or at the previous mass ratio about 60 J per gram of water, so it needs to be recalculated. 0.4g of wax can absorb 124 joules by heating the wax 40 degrees and then melting it, so there’s approximately your gram of water’s heat. So 0.4g/g plus a thin steel wall is maybe 0.5mL/mL of wax vs water, so 1/3 of the total volume goes to wax in that case, not 3/4 of it. (You said a liter insulated, so if the insulation is in common and external to the liter, it can be ignored)

            It’s not nothing, but having looked at various double-walled containers, the volume spent on the vacuum has varied a fair amount. One in front of me seems to use at least 1/5 of the total volume on vacuum, but I’ve seen both better and worse. They have to make sure the tolerances are good enough, especially when someone dents the thing potentially.

          2. By your own analysis. That’s 100J/g of heat in the wax and 25J/g or heat in the wax’s phase transition.

            Only the phase transition heat is useful. The rest might as well be in the mug.

            IMHO you’d want to use lower melting point wax, my quick search shows the lower range is 46 C. Kind of cold, but still ‘warm enough for gulping’. Use more wax, get better heat return ratio. But makes wax/coffee ratio worse.

            Even if they could engineer special wax with high phase transition energy, the basic problem remains. Cold coffee is not an issue to people that like coffee. Even if you wanted to cut my mug volume by 10% the answer would be no.

          3. No, that’s not what my analysis says. Maybe I was unclear; the 100 joules is per gram of WAX. At 0.4g of wax per gram of water and the temperatures I mentioned, there’s 40 joules going into heating the wax and 84-ish going into melting it. So two-thirds of the energy initially absorbed is available for keeping the drink warm later on with that particular wax before the temperature should drop further, and once it does it’ll of course still have the thermal mass and the vacuum flask insulation. I can agree that a lower melting wax would be nice, but I didn’t have data on what properties are available so ran it for waxes such as gulf wax.

            Also, you keep trying to say that people who don’t like to burn themselves or who care what temperature it is must not actually like coffee. I think that’s a bad take. The average person surely likes coffee some average amount. Then someone who likes coffee enough to say they like it probably drinks more of it than the first guy, and maybe that second guy wants quantity. But someone who likes coffee more than the second guy is almost certain to have preferences, specific things about the taste of coffee that he likes more than other drinks. Somebody who likes coffee enough to spend effort on getting the flavor just the way they want it is probably going to be more focused on quality than just quantity, and is likely to have opinions on the temperature too. Maybe they prefer specialty beans fresh from the roaster and they grind them right before brewing using whatever special brewing method they feel like. And at the extremes of the spectrum would probably be someone who goes and buys coffee directly from a farmer and has better equipment than a coffee shop at home.

    1. I have even heard of triple-layer thermoses with wax, which stores enough heat that it can help the temperature quickly drop before stabilizing at a more drinkable amount. The wax isn’t very dense or conductive, but at least it’s non-toxic and decent for the mass. I think I worked out that one of the liquid metal alloys could work too, with higher conductivity so you wouldn’t necessarily need to use three layers. You could put it in a puck at the bottom, or some sealed balls like the opposite of ice cubes. But it’d be heavy, expensive, and wouldn’t have as sharp of a phase change, so still not great.

  3. seems to be a lot of these but i simply don’t understand it. i start sipping nervously, and it burns me. and then i keep sipping until it doesn’t burn me, and then i can gulp as i will. and then it’s gone. or alternatively, some kids / chore thing drags me off and i don’t get back to it until it’s cold. :( i don’t know where technology can fit into that.

    otoh my brewing…for tea, i have got an 0.1 gram-precision digital scale, a meat thermometer stuck into a drilled hole in the side of my kettle, and a timer for steeping. and i often run into the problem of paying insufficient attention, then i need to add cold water to the kettle. i would actually get excited about a good immersion heater kettle with a temperature knob. maybe not excited enough to go shopping and read the reviews about early failure modes though :)

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.