Easy answer,   Go buy a new oven.  ;-)

Grant

Dr Skip wrote:
> I'm having a creative thought blockage to what should be an easy EE problem....
>
> I have an kitchen oven (with range top) that is electronically controlled and 
> 20 years old. It consists of a control board with the only real chip on it 
> looking like it's the display controller, not a general micro. It has the 
> thermocouple input, 3v and 23v AC inputs and 4 outputs to control a relay board 
> for 2 elements, a fan, and a door lock (self clean).
>
> Early on the unit was flaky, often quiting with odd codes. Kicking it would 
> help... Turned out a row of solder joints were cracked on the connector of the 
> relay board. After resoldering, all has been fine for years. Seems it gets hot 
> in there. ;) Until yesterday. The error code during use implied a bad 
> controller board once, but that was just once. Even cold, it now says the 
> thermocouple is out of range. It isn't, I tested. Wiring is fine too.
>
> I'm also getting some flickering segments on the display. It is probably the 
> controller, although nothing seems visibly awry. No board schematics, and it's 
> several boards mounted in a sandwich with almost all discretes.
>
> Before one thinks I'm looking for a repairman, I've always thought of 
> re-designing the controller, since it has a separate relay board and low 
> voltage control to it. I haven't had a chance to study the extras, like cycling 
> during self cleaning, etc. Unfortunately, now it HAS to be done and time is 
> important.
>
> So the question: given I've got a good thermocouple, but without knowing its 
> temperature curve, and that I can get at controlling the elements, what would 
> be the quickest, simplest, most creative way one could control oven temp with 
> these resources? My PIC skills are not fast enough, and the time pressure has 
> blunted my creativity. I'm hoping I'm overlooking a simple analog design that 
> will allow me to control the elements to temperature using the current 
> thermocouple or another component (to 550F approx or better). Time is urgent it 
> seems (a hungry family), so parts count and availability are important.
>
> Any ideas?
>
> TIA, Skip
>
>
>
>   

-- 
Kind Regards
Grant Brown

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