Homebrew PCBs

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


> -----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
> 
> 
> 
>  
> 
> 
> 
>