Dennis Frost wrote:
>
> Hi all
>
> I am about to embark on a project to control the temperature of a small
> oven (About the size of a microwave oven).
>
> The temperature must be adjustable from room temp to 80 degree C and must
> be controlled to within a degree or two.
> There is a small fan in the oven that runs continuously.
> The heater element will be between 500W to 1000W
> I intend using a SMT160-30 (TO-92 housing) Smart temperature sensor that
> gives out a 4KHz duty-cycle modulated square wave.
> I want to use a triac to turn on x out of 100 cycles of the mains (220V
> 50Hz)
> I will use a PIC 16C84
>
> Getting the temperature into the PIC and the control out to the triac is
> easy it is the control software I need.
>
> If someone has some code to do this I would appreciate it.
> Otherwise any suggestions. Should I use PID or try Fuzzy Logic?
>
> Thanks
>         Dennis Frost
>
> Email: dennis.frost@pixie.co.za
> Pietermaritzburg, South Africa
Use a Dallas Temperature Controller DS1620.
This chip contains all you need for temperature control. A temperature
sensor, a A/D-Converter with a resolution of 0.5 deg. Celsius and two
programmable nonvolatile comparators. Two of the three outputs give an
alert below low-temp and above high-temp respectively. The third output
performs as a bang-bang controller (is this the right noun for that what
is called in german a "Zweipunktregler"/two point controller). So add a
power transistor or a relais.
All you have to add is a user interface.