Thanks for the info - since I'm not sure about how to build an Opamp circuit, I found some thermosistors on digikey I think I can use. They are 1,000 ohms at 25C and 2300 ohm range at 175C. I think I can get decent control.... maybe I should say "sufficient" control?
I should be able to show temperature on a LCD display and control a relay both with that for a temperature controller. I'll work on that.
"IF" I knew which AVR chip had a 200x internal amplifier I "think" I could make a type J thermocouple work with that. I've got a couple feet (or 3ft?) of type J lying around.
Ken H>
--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
>
> No, amplify it with an opamp first.
>
> Some atmels come with up to x200 internal amplifier now, not sure if
> that would work.
>
> ST
>
> On Tue, Dec 29, 2009 at 1:06 AM, sailingto <sailingtoo@...> wrote:
> > Stefan, are you saying connecting a Type J (or K) Thermocouple direct to an analog input pin using a PIC12F683? What about a AVR chip such as a ATmega168 or similar? Perhaps using the internal 1.1 reference voltage? I wasn't sure the analog input would be sensitive enough to read the low mV of a thermocouple.
> >
> > Thanks for any input.
> >
> > Ken H>
>