Fun with Thermistors
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Fun with Thermistors

by EasternStarGeek on Fri May 11, 2012 10:43 am

Dear friends:

I have recently been experimenting with the waterproof Thermistor assembly for sale here at Adafruit, and was pleased with the results, so I decided to post the project to Github and make it available to all interested parties:

https://github.com/EasternStarGeek/Fun-with-Thermistors

My approach differs slightly in that I use a lookup table instead of the logarithmic formula given in the Adafruit tutorial. I didnt make any measurements, but it could very well run faster, since it doesn't depend on a lot of complex floating-point math. In any case, Lookup tables are useful sometimes, and my example not only shows how to do a lookup, but also how to interpolate between the two closest entries to the measured value.

You will also find a helper spreadsheet that was used to create the LUT used in the sketch, along with some interesting charts that show graphically, the relationship between temperature and thermistor resistance, as well as temperature versus ADC voltage.

This post could just as easily be called, "Fun with Github" because this was my first attempt at creating a public repository, and truthfully, my principle motivation was to practice Git Bash.

Have fun, and please let me know if you find any of this useful!
EasternStarGeek
 
Posts: 314
Joined: Mon Dec 13, 2010 12:39 pm
Location: Upper Eastern Tennessee

Re: Fun with Thermistors

by EasternStarGeek on Tue May 15, 2012 1:59 pm

New and Improved!

The Arduino sketch now includes a zero-wait Low Pass Filter for smoothing variations from reading to reading, as well as a function for dulling the resolution to 0.5 deg C, since that is approximately the useable limit of resolution with these kinds of sensors, plus, better comments all the way round.

Enjoy!
EasternStarGeek
 
Posts: 314
Joined: Mon Dec 13, 2010 12:39 pm
Location: Upper Eastern Tennessee