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Temperature regulator (how do i measure temp with pic)

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osiris

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temperature regulator pic

Hi, im working on a circuit to regulate the temperature of a mains heating element. Im planning to use a triac driven by a pic16f84. Does anyone know how i can measure a temperature in the range of 0-350 deg centigrade with a pic? i only need to be acurate to a few degrees, and need a relatively cheap solution.
 

flatulent

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measure temp

With the high end of your range above semiconductor limits, you will be limited to either a metal resistor device whose resistance changes with temperature or with a thermocouple. The latter will require a cold junction compensation IC.
 

pool_77

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ad595+pic

For low cost solution use Nickel (Ni) resistor. It has nearly the same parameters as a platinum resistor (Pt100). The nelinear characteristic is described by a polynom (of seventh order). You can make linearization by operational netvork or e.g. by table in CPU....
For higher tepm you must use Pt rezistor or termocouple.
For compensation of cold junction of termocouple and linearization you can use special IC (if i remember from AD).


regards,
pool_77
 

Sobakava

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temperature regulator with thermocouple

AD594 for J type
AD595 for K type thermocouples...
you can get 10mV/Celcius easly.
 

FoxyRick

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ad595 with pic

Another option is the MAX6675 from Maxim:

Works with a standard type-K thermocouple
Performs cold-junction compensation
0 to 1024 Celcius readings
8-pin SO package
3-wire/SPI interface
12-bit, 0.25 Celcius resolution
+/- 3 Celcius accuracy
Samples available from Maxim
See: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3149

I have a few samples to try in my home-made reflow oven when I get around to finishing it. Looks nice and easy to use.

Best wishes,
FoxyRick.
 

batdin

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measure temperature use pic

If you use 16F84,you need to make the hysteresis and the thresholding externally.This means some more components.Actually the PIC will be of no use at all.
Instead you can use PIC with ADC and make the thing in the right way.
This way you can easily use a look-up table to measure the exact temperature.
This is just my opinion though.
 

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