LZ: TI-85 Thermometer

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LZ: TI-85 Thermometer

Today I successfully interfaced a Temperature Senser with an I2C bus to the 
TI-85 using Per Finander's I2C bus routines.  As of now, I have the stuff 
on a breadboard, but I plan to put it into the calc eventually.  The chip 
itself is a surface mount chip that is .5mm by .5mm including the 8 pins. 
 The only other components needed are a capacitor (for power, right now I 
am using a 100uF one, but I'm going to experiment with smaller ones to save 
space) and two tiny diodes.  Being the first thing I interfaced to the 
calc, I was surprised that it worked on my first try, both hardware and 
software.  The chip has a resolution of .5 degrees Celcius and an accuracy 
of +-3 degrees.  It's working temperature is -55 to 125 degrees Celcius.


If you would like to do this, you can order a sample chip for FREE from 
National Semiconductor (www.national.com).   You first have to register (it 
costs nothing, all you do is type in some info) and then you can order up 
to five per week.  They're meant for companies that plan to buy quantities 
of them every year, but oh well.  If you can't find the site from their 
home page, try searching for I2C and temperature on YAHOO.  If anyone is 
interested in seeing my schematics (mostly taken from Per Finanders 
schematics), I'll send them to you or post them to the list.  Also, if you 
want I can post my software for it.  If you have any questions, just ask. 
 And, to give you an idea of how simple it is to make, I got the chip from 
Fed Ex at about noon and I finished the same day.  That included etching a 
PC Board to hold the chip, and writing the program.


Ed Plese, Jr.
(eplese@lnd.com)