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WBA Consulting
08-29-2010, 03:54 AM
I have been trying to organize my garage which includes clearing out my project boxes. This means digging through about 7 years worth of "project potential" and creating a more focused project stock.
With that said, I have some overstock thermistors left over from a 2006 project. I started posting some on eBay, but figured I should post some here as well. Free shipping for forum users, so if you are in the U.S., $10 gets you 10 of these via priority mail. Just shoot me a PM if interested.


Thermistors are potted into a vinyl cap and have 48" long leads of 24AWG zipwire (I have some grey and some white). Wire can be cut to length and the cap can be used to mount using a ziptie and ziptie mount. Thermistors are high precision and designed for long life by being potted inside a protective vinyl cap. Accuracy from 10-43C is +/- 0.2C. Temperature curve data is here (http://www.ussensor.com/rt%20charts/PT103J2.htm). Here's a link to my eBay seller page (http://shop.ebay.com/uxorious/m.html), too.


Using thermistors with Parallax products:
RCDecay with the Propeller (PE Kit book, pg 122, section 7)
RCTime activities with the Stamp (WAM book, pg 139, chapter 5)
or search the forums for thermistor, RC Time, or RC Decay

Loopy Byteloose
08-29-2010, 05:14 PM
Hello,
They look very useful. Your Ebay listing appear to have 10 of them for 99 cents - very reasonable.

What comes to mind is that they would be very useful with battery chargers to shut off whenever the battery gets too hot. I've had several gel cells overheat and one lithium cell in DIY projects. And of course, I charge NiCads that I am convinced are dying prematurely due to excess heating during charge cycles.

But being in Taiwan, I wonder if it is worth the bother to send 10 here.

logan996
09-02-2010, 08:48 PM
What are these used for again? (still a newbie :D )

WBA Consulting
09-03-2010, 05:39 AM
Thermistors are temperature driven variable resistors. These are of a 10k@25c type, so that means at 25 degrees C (77 degrees F), these resistors measure 10k ohms. By using RCTime or RC Decay setups with the Stamp/Propeller, you can determine temperature with enough accuracy for things like controlling ventilation fans in an attic. Utilizing proper lookup tables or going as far as doing the full mathematical equations (Steinhart-Hart equation), you can get very accurate temperature readings so you can display actual temperatures.

http://en.wikipedia.org/wiki/Thermistor

Duane Degn
09-21-2010, 01:28 PM
Andrew,

Do know what kind of temperatures these can tolerate?

Could they be used directly in boiling water?

I'll probably want 10 no matter the range, but it would be nice to know how careful I need to be with them.

Duane

WBA Consulting
09-21-2010, 04:01 PM
The specs are in the second image on my first post, however I noticed that the GIF format doesn't view well. I created another screenshot and cut out all of the data that cannot be shared. The pertinent data is intact. The thermistors can be used from -40 to +85 degrees Celsius. The thermistor used can tolerate up to 150C so I believe the +85 rating comes from the potting material used. If the boiling water turns black, then it's the potting that is the limiting factor.

Duane Degn
09-21-2010, 05:19 PM
Thanks for the update. (Was that second image there a few hours ago?)

I'll let you know how my thermister tea turns out.

Duane

WBA Consulting
09-21-2010, 05:33 PM
Yes, it was, but since it is an oddball GIF, it does not show well. I re-captured and saved as a JPG to make it cleaner.