Thermos temperature meter

We’re always a little surprised by how well a vacuum thermos works, but eventually the contents will cool down (or warm up depending on what’s in there). [Gamesh_] added a temperature meter to his thermos using an Arduino and a temperature sensor. The original post is in Portuguese but [Bruno] republished it in English.

The temperature sensor has been repurposed from a digital thermometer meant for taking your temperature. Holes for the LEDs making up the indicator bar were melted in the side of the plastic housing. When the hot liquid is poured out at about 0:45 into the video you can glimpse the Arduino hanging our on the other side of the pot and a power cord running off behind the laptop. It would be nice to see this migrated over to a less powerful chip and run from a small coin cell, but we like the concept.


  1. jeff-o says:

    Well heck – you can buy a battery-operated thermometer for less than 10 bucks that will do the trick. Carve out a space for it, run the cable, and you’re done!

  2. w0rdd says:


  3. Matt says:

    I’d like a mood ring looking output. Especially since a mood ring is a temperature sensor.

  4. dirk says:

    I don’t understand this concept outside the use of an open-topped carafe as seen in the video.

    In a proper ‘thermos’ unit, if you were to do anything that compromised either the seal of the screw-top lid or the internal bottle, you’d pretty much destroy the ability of the thermos to keep things warm.

    On reading the title I thought there might have been some novel wireless solution (coping with the fact that the internal module would be surrounded on nearly all sides with two layers of steel)

  5. dbro says:

    Why use an electric device when these exist? Can they be changed to indicate a wider range of temperatures?

  6. Kevin says:

    Why use a battery? Switch to a peltier module and have it power itself.

  7. nemo says:

    @kevin-because then you would bleed heat from the liquid inside the thermos, or heat up the liquid inside the thermos, and therefore remove the point of using a thermos in the first place.

  8. Lou Skunt says:

    You have to connect it to the computer or an external power supply? you suck…

  9. Pete says:

    This is all just very strange. I’m not sure what else to say.

  10. therian says:

    yey arduino is a fish tank sticker

  11. supershwa says:

    @dbro: Wouldn’t work – the exterior of the thermos would have a much lower temp than the core, so the strip thermometer couldn’t work properly.

    jeff-o is also right — just tear apart a $10 digital thermometer, and forget the LEDs and arduino (and laptop.) You could embed the LCD display into the thermos shell instead, and it would run off a coin cell…less power, less cost, and a dark digital LCD display instead of the bright color-coded meter (in my experience, the excessive use of LEDs can get pretty annoying to the user unless there’s a switch to disable them.)

  12. macegr says:

    The best way I can think to do this would be a non-contact IR thermometer installed in the lid of the thermos, or maybe pointing at the bottom of the bottle through a pair of un-silvered spots in the glass.

    Otherwise an RFID-style chip could be embedded inside the thermos and powered through induction when being read.

  13. Paul Potter says:

    It’s an interesting idea.

  14. Greg says:

    Similar, but not quite as complicated as an idea I had (but sadly don’t have the knowledge to make a reality).

    Add temperature sensing capability to an insulated container. Run info to a settable controller. Run back out to peltier or similar to adjust temp. This would be run off of a medium sized battery (LiPo R/C battery?). Set desired temp and the circuit would maintain it until the battery was dead.

    I have been dreaming of a solution like this for the cross country shipping of live coral specimens. I would think with a properly designed (read: efficient) circuit, a good battery and a well insulated package you could easily get a few days out of it keeping the specimen at 78 degrees. Anyone want to provide technical advice? :-)

  15. Renan says:

    É muito legal ver projetos publicados em portugues, especialmente do Brasil!

    It’s very nice to see projects publisheds in portuguese, specially from Brazil!

  16. mrgoogfan says:

    That aint no thermos. Cheap chineese thermoses cant keep nothing cool.

  17. martin says:

    The concept is great, but our friend would have done himself a favour if he had spent a few hours to embed the entire thing into the thermos. With an embeddable arduino, this would be still be expensive and overpowered, but far more impressive. Add a test button instead of permanent display and batteries should last for months.

  18. Drone says:

    Embed the temperature meter in the cap and have a plastic probe that sticks down into the thermos. Dump the arduino in favor of an ATtiny and LCD display with a supercap to hold a charge. Put solar cells on the cap. The ATtiny can double as a charge controller too.

  19. jeff-o says:

    @Greg: Peltier modules suck in a ton of power for what they do, I think they’re only 5-10% efficient. We’re talking a few amps, here. The battery pack would be huge, and you’d have to ship it by land because they won’t take big batteries on planes. It could probably be done, but it’s bordering on impractical.

  20. fartface says:

    Not a hack. It’s an experiment. plus the link has zero information.

    Honestly, it should not be listed here unless it has details on what was done.

  21. bored says:

    hey mom look what i can do with arduino.

  22. Gamesh_ says:

    I used the cable and not the battery to be able to read analog, but the arduino has a 9V battery just change the jumper.

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