Hello, my next arduino project i will be working on is a temperature sensitive mug. There will be a TMP36 sensor feeding the temperature of the mugs conents into the arduino. the arduino will then illuminate an LED bar-graph depending on the temperature. my question is: what is a good way to detect the temperature of the contents using a TMP36 without shorting the sensor out or having toxic effects on the beverage? basicly, how do i effectively and safely water-proof this sensor?
http://i.imgur.com/LMMoQ.png
Is the Arduino and LEDs a permanent addition to the mug, or do you want to move it from mug to mug?
If this is permanent, then bonding the sensor to the outside of the mug might some sense.
If not, I would pot the sensor and wire in something like medical grade epoxy or silicone. If this is just for you, then the local hobby store should have a good 60 minute cure epoxy that would work well. I would stay away from fast cure epoxies as they tend to be more dificult to flow around wires and get the bubbles out before your time expires. Gently heating the the epoxy makes it more liquid and will form fewer bubbles but will cure faster.
You can find medical grade materials from various suppliers.
Thanks for the tip! and no, the addition isnt permanant, ill be attaching all the ciruitry to a velcro strap for easy removal.
certainly you can go the epoxy coating route, it’s a fine a way to go. Personally, I think that appearance is important for food related applications and much prefer stainless steel. Something like this will look pretty professional though is going to cost more:
On a completely different approach, I would think about a termo-coaster. Basically, it looks like a coaster with a thermister that would contact the bottom of the cup. A little readout would display the temperature (or just an idiot light if you want to dumb down the interface). The delay in reporting the actual temperature can be minimized by using a predictive temperature algorithm. Especially when you pour hot liquid into a cold cup. Temperature rise will always follow a curve that allows you to determine the eventual measurement before it is reached. Wouldn’t work for insulated mugs, though.
Just recently someone sent Dave Jones of EEVBLOG.com a coaster kit just like this. The details I thik are in one of the last 1-4 mailbag videos.