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.

22 thoughts on “Thermos Temperature Meter

  1. 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)

  2. @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.)

  3. 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.

  4. 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? :-)

  5. 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.

  6. 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.

  7. @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.

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