AVR-Chat

In MCUs DS18S20 is a much better solution than LM35 since it gets rid 
of the inaccuracies assiciated with ADC (though it is slightly 
expensive).
Resolution upto 0.0625 DegC can be obtained.
It comes calibrated and the output is digitized - no further 
calibration is required.
it comes in TO-92 package (the popular small transistor pack) which is 
very handy to integrate into a probe or similar application (ofcourse 
LM35 also comes in TO92).
NTC may turn out to be a headache on linearization (calibration).
If you are not worried about the precise reading, you can go for a 
thermistor(NTC/PTC)without linearization - but you need a current 
source to convert the resistance to a voltage and again the nuances 
associated with ADC.
The preference shall be DS18S20, LM35 & Thermistor in that order.

Instead of pot, you can use three buttons - UP, DOWN & ENTER if you 
have a means to display the setting - like LCD, 7 seg LED or Terminal.
If you are going for a blind controller then Pot is the solution.

A combination of DS18S20 and buttons will allow you to use AVRs 
without ADC like 2313

Compilers like FASTAVR, CODEVISION, BASCOM etc provide sample code for 
DS18S20, PWM, ADC etc.
Only you have to adopt codebits from different examples.
It just depends on your compiler

--- In AVR-Chat@yahoogroups.com, "Steven Chang-Lin Yu" <stevenyu@p...> 
wrote:
> There is also some other digital signal temperature sensor from 
maximum,
> national…etc.  Most of them are either 1wire or 2wire protocol
> 
>  
> 
> __________________________________________________________________
> Steven Chang-Lin Yu
> QUT EESE Student, Computer Technician
> ICQ#: 66369374
> 
> 
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> __________________________________________________________________
> 
> -----Original Message-----
> From: jay marante [mailto:jaythesis@y...] 
> Sent: Tuesday, 2 December 2003 3:24 PM
> To: AVR-Chat@yahoogroups.com
> Subject: Re: [AVR-Chat] Temperature Sensor Ideas
> 
>  
> 
> It depends on what kind of output youre looking for
> (voltage, current, resistance). Theres also LM135,
> LM235, and LM335. There output is proportional to
> either celcium, farenheit or kelvin. Ive used LM35
> before but only for analog signals.
> --- adiy@a... <adiy@a...> wrote:
> > Hi,
> > 
> > Anybody have some ideas for sensing temperature and
> controlling fans 
> > depending on temperature? I am thinking about using
> PWM to control fan 
> > speed and multiple triggers to request fan action,
> amongst them feedback 
> > from a temperature sensor.
> > 
> > For sensors I am thinking of using a NTC thermistor,
> DS1820 or LM35. To 
> > set the threshold levels I could use a potentiometer
> attached to an ADC 
> > channel or binary coded jumpers/switches. 
> > 
> > Anything I missed? Anybody knows of app notes or
> projects I could peak at 
> > to get some ideas to get started? I suspect this
> will be my first hands-on 
> > AVR project.
> > 
> > Adi