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From: "k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz>
Newsgroups: sci.electronics.design
Subject: Re: pcb-mount air flow sensor
Date: Tue, 31 Jul 2012 22:27:08 -0400
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On Tue, 31 Jul 2012 18:54:13 -0700, John Larkin
<jlar...@highlandtechnology.com> wrote:

>On Wed, 01 Aug 2012 01:18:37 GMT, n...@puntnl.niks (Nico Coesel)
>wrote:
>
>>John Larkin <jlar...@highlandtechnology.com> wrote:
>>
>>>On Tue, 31 Jul 2012 22:20:49 GMT, n...@puntnl.niks (Nico Coesel)
>>>wrote:
>>>
>>>>John Larkin <jlar...@highlandtechnology.com> wrote:
>>>>
>>>>>On Tue, 31 Jul 2012 10:52:21 -0700, Fred Abse
>>>>><excretatau...@invalid.invalid> wrote:
>>>>>
>>>>>>On Tue, 31 Jul 2012 10:22:53 -0700, John Larkin wrote:
>>>>>>
>>>>>>> 
>>>>>>> 
>>>>>>> Anybody know of a good one?
>>>>>>> 
>>>>>>> I guess we could make our own. I was thinking about maybe using two LM71
>>>>>>> temperature sensors, one mounted on a copper pour with a resistor heater.
>>>>>>> We don't need a lot of accuracy... this would be mostly a fan fail sensor.
>>>>>>
>>>>>>Fans with stall sensing are pretty common, these days. Why not use those?
>>>>>
>>>>>This will be on a couple of PCI Express crate controllers that plug
>>>>>into VME or VXI crates. We thought it would be cool if we reported
>>>>>crate power supply voltages, power supply noise, air temperature, and
>>>>>air flow. We don't have access to the fans.
>>>>
>>>>I'd leave it out if it ain't required. If it ain't there it cannot
>>>>break down and the customer can't complain or ask difficult questions
>>>>about it.
>>>
>>>But the customer can specify "The crate controller shall include..."
>>>and disqualify our competition. And some potential customers may
>>>think these features are cool, or even useful.
>>
>>True. But only if you can keep track of budget (time & money). I've
>>seen too many projects going way over budget because people had no
>>clue how much work was involved.
>
>With uPs and FPGAs and cheap parts, featuritis is a serious problem,
>deciding what goodies to include, knowing when to quit. If the uP has
>an ADC, why not add a mux and digitize all the power supplies? Then
>why not compute noise? That's about where we are, trying to add
>sensible features that don't overload the engineering time.

Don't forget testing time.  If it's there, it has to be tested.
<...>