Temperature Controller for Oven

[anele]

I want to build a Fuzzy Oven and a controller for my final design project at University. I have encounted some problems the first being how to automatically vary the current flowing through the heat element in order to control the temperature of the oven.

First I tried using a digital resistor connected in series with the element. I would then vary the resistance of the total circuit in order to control the current. The resistor just ended up burning up due to initial high current I believe.

My next idea was to build a 0 - 10 A current source but cant find any schematics for this online.

The circuit voltage supply is 220 V (ac) and the resistance of the heat element is 30 ohms (rated for 1500 W), meaning the current flowing through the element is 7.38 A when nothing else is connected.

Can someone point me in the right direction to be able to control the temp of the element without using on/off control.

 

[Minder]

For a electronic version of a oven controller there is the Picmicro AN958, even comes with code!
There is also Fairchild AN-3006 for non-micro version.
M.

 

[Alec_t]

An element like that would be controlled by switching it on and off with a variable duty-cycle. Considering the element's high thermal inertia, the switching could be done either by phase angle control or by whole cycle counting.

 

[anele]

I am quite new to electronics so this might be a dumb question. I have decided to the Picmicro AN958 circuit for control.
does it matter what diode and transister I use for this circuit?

 

[anele]

For a electronic version of a oven controller there is the Picmicro AN958, even comes with code!
There is also Fairchild AN-3006 for non-micro version.
M.

I am quite new to electronics so this might be a dumb question. I have decided to the Picmicro AN958 circuit for control.
does it matter what diode and transister I use for this circuit?

 

[Minder]

The transistor is not critical, if referring to D2 then a 1n4005/7 would work..
M.