--- In
Homebrew_PCBs@yahoogroups.com, "John Craddock"
<John.Craddock@...> wrote:
>
> Hi Philip,
> Yes, I read the article and have been doing some research of
thermocouple interfacing. My problem with the max6675 is that Maxim
lists the price at US$3.88 in 1K quantities. By the time I get a single
unit to OZ it costs me A$ 10 times that amount whereas cold junction
compensation with an LM335 costs me A$2.72 plus an instrumentation op
amp at about A$4.00 plus using a micro with ADC channels gives me the
digitising for free (no SPI programming). BTW the AD595 (Analog Devices
equivalent to the max6675) would cost me $35.98 as well. Sooo, I am
heading down the LM335 track with an 18F series PIC (unless I can find a
lower price on the 6675 or the 595. BTW, using glass covered @K@ type
thermocouple wire welded at the hot junction end with a blow torch is a
pretty cheap way of getting reasonable thermocouples. Some of the code
in the elector article is useful as it is written in C and therefore
reasonable portable.
> Regards
> John C
> \\
Try www.futurlec.com.au <
http://www.futurlec.com.au> for the 6675, i
think its about $8
>
> > -----Original Message-----
> > From: Philip Mac Cabe [mailto:Philip@...]
> > Sent: 23 August 2006 18:43
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: [Homebrew_PCBs] Re: How not to control ovens - was - The
list
> > is huge! Really huge!
> >
> >
> > Has anyone actually read the recent (January) Elektor article on the
> > SMD oven? It uses a K-type thermocouple talking to a MAX6675.
> >
> > The program in the AT8952 calibrates autmagically and then
> > compensates
> > for over and undershoot. Has an LCD display etc etc etc.
> >
> > The CPU is available from Elektor ready programmed for about
> > £12. The
> > code is available for free download from their site.
> >
> > I'm not in favour of totally slavishly following published
> > designs but
> > in this case all of the hard work has been done leaving the usual
> > personal customisation.
> >
> > Before someone asks, I don't have shares in Elektor and I do think
> > that lots of their designs are way overcomplex.
> >
> > Here in Ireland, local supply of components is always a problem but
> > between Mouser in the US and RS and Maplin locally we can usually
get
> > what we need.
> >
> > Elephants was deliberate ;-)
> >
> > Regards,
> >
> > Philip
> >
> >
> >
> >
> > Be sure to visit the group home and check for new Links,
> > Files, and Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> >
> > If Files or Photos are running short of space, post them here:
> > http://groups.yahoo.com/group/Homebrew_PCBs_Archives/
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
>
Regards
Ian
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