>-----Original Message-----
>From: Zipwize@AOL.COM [mailto:Zipwize@AOL.COM]
>Sent: 22 April 2004 15:49
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [PIC]: UL Approval of products with PIC's
>
>
>Hi All,
>
>I have done some minor controls of products that have been UL,
>CSA, CCC approved and CE Marked. The controls did not include
>safety shutdown circuits. I was wondering how difficult it
>would be to have the safety shutdown controls on the PIC and
>get it approved by the agencies. The product would be a
>welding power supply. The safety circuit cuts the bias supply
>and opens a contactor relay. The shutdown is caused by
>excessive output voltage, or over temperature. I save some
>cost by putting this in code instead of analog comparators.
>
>Any shared experiences are appreciated.
>
>Fred


To be honest "CPU", "welding" and "safety critical" is not the best
combination you could wish for.  Welding generaly causes huge amount of EMI,
and a PIC is going to be far more vulnerable to failure than a robust analog
cricuit in this situation.

Regards

Mike




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