Steve, Sorry to tread on your toes! If you read my post carefully you will note an alternative suggestion that concurs with your original point. I consider that the following parts of the post supports the context of the suggestion of the EZ-bake group.
Regards
John C
> -----Original Message-----
> From: Steve [mailto:alienrelics@...]
> Sent: 25 August 2006 08:29
> To: Homebrew_PCBs@yahoogroups.com
> Subject: [Homebrew_PCBs] Re: How to DO thermocouple interfacing
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "John Craddock"
> <John.Craddock@...> wrote:
> >
> > Or maybe: -
> > http://groups.yahoo.com/group/E-Z_Bake/
> >
> > This thread is related to Stefan's toaster oven mods to be able to
> > bake direct inkjet pcbs; and perhaps to double as a reflow oven
> > (my objective).
>
> Yes, but it is squarely into electronic design now. We've been over
> this before, if you try and say that anything remotely related to
> making PCBs is on topic, soon we're discussing brake linings and
> baseball scores because you might drive your car to pick up hydrogen
> peroxide and listen to the game on the way.
>
> There have already been past discussions and links to PID and such on
> the Electronics_101 list. Absolutely integral to a project
> such as this.
>
> > BTW, I bought the MAX6675 (A$8.64), much happier now,
> > thanks to help from members of this list. BTW2 a diode
> > compensator requires a isothermal block at the cold junction;
> > the MAX6675 gets away without this.
>
> I just ordered a couple of samples of both the MAX6675 and DS2761.
> Although the DS2761 is a LiIon battery monitor IC, Maxim has an app
> note on how to use it as a thermocouple chip. The thermocouple
> connects to the battery voltage monitor input, and the chip's built-in
> temp monitors cold junction temp. However, an external computer must
> do all the processing.
>
> No, the MAX6675 does -not- remove the need for some kind of isothermal
> block. The thermocouple wires -must- be soldered/connected right at
> the IC, or the connections will be at a different temp than the sensor
> inside the IC.
>
> Having a silicon diode in intimate physical contact with the
> thermocouple to PCB connections is not difficult.
>
> Steve Greenfield
>
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