Hi all
I want to build my own heater controller for a toaster oven using a triac or scr's.
It will be micro controlled as I want to implement the full reflow cycle of temperature ramp up, saturation, reflow, cool down.
I don't know the proper terminology for the two output methods I have so a quick description instead
The first is controlling the angle at which the thyristor fires, essentially chopping up the sine wave
Second is zero crossing activation for multiple cycles.
I can see two ways to control output in this second method. Choose a time period of say, several seconds and vary the on/off duty cycle (pseudo PWM) or simply just turn the heater elements on/off according to PID algorithm output.
I understand that changing methods is merely a change in software, but was curious if anybody had experience in which method (or others not described here) is the most accurate.
The other question I had is whether or not to employ burst triggering in the phase angle method.
I have used this successfully before in a design using 4 quadrant SCR's with RC snubbers driving an inductive load where current control was critical.
With the advent of high commutation, 3 quadrant SCR's and triacs and that a stray cycle here and there in a lagging system such as this, coupled with the fact that most heater elements would be mostly resistive, would it be over kill or should I consider CCT design re-use?