In this kind of application it is often acceptable to work without
cold junction compensation. (Room temperature variations would be
inside acceptable temperature error). That way you could avoid the
costly AD595.
Another alternative would be to use a thermistor instead, one suitable
for this temperature could be found in every laser printer at the
fuser roller.
ST
On Sat, Dec 26, 2009 at 6:34 PM, rdheiliger <rdheiliger@...> wrote:
> I have modified my PIC based temperature control to use a K thermocouple instead of a LM34. I used an AD595 chip to linearize K thermocouples to 10 mV/∗C. This is a simple circuit using a PIC12F683 for analog input and a PWM output to a digital panel meter for display of temperature and set point. Two switches are use to set the temperature. Normaly the temperature is displayed. When either the increment or decrement switch is pressed the unit displays the set point and allows it to be changed. A relay with on/off control keeps the overshoot to less than 8 degrees C.
>
> I changed to thermocouple input when i needed temperatures in the 160 ∗C + range.
>
> The AD595 and K thermocouple can be obtained from Spark Fun Electronics. Tho not cheap.
>
> RD
>
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>