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Re: Group Design

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On 08/08/2020 01:37, Chris wrote:
> On 08/07/20 14:57, Phil Hobbs wrote:
> 
>> I know it isn't what the cool kids do, but that doesn't make it
>> unreliable or cause it to fail safety inspections AFAICT. Medical may be
>> different, but it would pass UL with no issues. What regulations nwould
>> you expect it to fall foul of?
>>
>> Cheers
>>
>> Phil Hobbs
>>
> 
> It's not the regulations, as afaics approvals are more concerned with
> *process*, how the design decisons were made and why. Would not
> necessarily catch design errors that resulted in a regulator running
> near it's design limit, though avionics or mil temperature cycle
> testing might  cause a failure because of lack of margin for a device.
> 
> Whatever you might think, it's well known that high temperatures and
> cycling shortens the life of electronics and no, I don't have
> references,but it's all on the web. Some prefer to skimp every penny,
> others prefer conservative design rules. It's the difference between
> consumer electronics and pro kit. may look like the same parts, but
> the design tradeoffs are different. Engineering design is always an
> approximation and compromise: performance, cost, reliability, pick any
> two...
> 
> Chris
> 

I think it's fair to say that this 70 C case with poor thermal contact 
with the board is an indicator of bad design - bad schematic design 
(using a linear regulator rather than a switch mode), and bad layout 
design (poor cooling).  And poor design in such an obvious case suggests 
poor design overall - which is not going to go well for any kind of 
safety requirements or regulations where the design process is considered.

It is also correct to say that the reliability of a system is a function 
of the reliability of all the parts, and that high temperatures and 
temperature cycling shorten lifetimes and increase the rate of failures. 
  But you can't say how significant this particular part would be 
without a lot more information about the rest of the system.  As Phil 
says, a part rated for 125 C is not going to see much increased failure 
risk at 70 C compared to 50 C.  But if it sits next to a part that is 
rated to 85 C and the final system is mounted in a closed box and used 
in the Qatar summer, perhaps it will have a relevant effect.

All in all, this looks like a rush job put together by people with no 
experience with high reliability or safety-related systems.  That's the 
general problem, rather than one particular hot regulator.

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Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-07 18:46 -0700
  Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-07 19:02 -0700
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-07 20:36 -0700
      Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-07-08 09:31 +0200
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 07:08 -0700
  Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 14:13 +0200
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 07:19 -0700
      Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 18:57 +0200
        Re: Group Design Theo <theom+news@chiark.greenend.org.uk> - 2020-07-08 18:28 +0100
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 11:12 -0700
          Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 23:34 +0200
            Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 15:20 -0700
              Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-08 23:00 -0700
              Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-10 10:09 +0200
              Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-07 00:01 +0100
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 17:37 -0700
                Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-08-07 03:06 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 21:50 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 19:12 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 22:27 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 19:36 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 23:39 -0400
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-07 12:30 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 09:57 -0400
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-08 00:37 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 20:29 -0400
                Re: Group Design upsidedown@downunder.com - 2020-08-08 08:59 +0300
                Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-08-10 15:43 +0200
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-10 09:18 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 07:12 -0700
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-08 00:00 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 20:30 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 17:57 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 17:56 -0700
                Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-08-07 18:10 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 19:43 -0700
                Re: Group Design Dimiter_Popoff <dp@tgi-sci.com> - 2020-08-07 20:42 +0300
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 13:48 -0700
      Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-08 14:11 -0700
      Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-07-09 04:25 -0400
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 11:37 -0700
          Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-09 11:54 -0700
          Re: Group Design Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-07-09 20:02 +0100
          Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-07-09 15:31 -0400
            Re: Group Design lasselangwadtchristensen@gmail.com - 2020-07-09 15:36 -0700
              Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 18:36 -0700
                Re: Group Design Clifford Heath <no.spam@please.net> - 2020-07-10 16:17 +1000
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 23:36 -0700
                Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-10 10:22 +0200
      Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-07-09 14:40 +0200
  Re: Group Design John Speth <johnspeth@yahoo.com> - 2020-07-09 07:59 -0700
  Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 18:33 -0700
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 19:01 -0700
      Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 22:32 -0700
      Re: Group Design George Neuner <gneuner2@comcast.net> - 2020-07-10 17:36 -0400
        Re: Group Design Ed Prochak <edprochak@gmail.com> - 2020-07-14 11:09 -0700
          Re: Group Design George Neuner <gneuner2@comcast.net> - 2020-07-16 00:26 -0400
  Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 22:48 -0700
    Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 23:53 -0700
      Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-10 01:15 -0700
        Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-10 02:22 -0700

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