[Diy_efi] Project/temperature ranges

[Bill Shaw]

I've recently been through a similar thing.  When sourcing parts for a 
project I was trying to use automotive grade components,  since this box 
is getting installed in vehicles.  The automotive grade of the 
microprocessors I used have about a 4 month lead time,  and this device 
needs to be in production now.  The factory rep suggested that I just 
use the commercial grade parts and don't worry about it.  He said the 
parts are all manufactured the same,  the higher grades are just 
screened for their temperature performance and the failure rate is very 
low. In a non-critical application like this the commercial stuff should 
be fine.

hth, ymmv,

Bill

Steven P. Donegan wrote:
> Well, the key things I see here are:
>
> 1) All automotive ECU's I've looked at have had Commercial grade
> components - and failure of these is very rare.
>
> 2) Most components I have selected (thus far) have Commercial and
> occaisionally Industrial temperature ranges - can I select different
> parts - perhaps. I have not found any which support Military grade - and
> my read through Digi-Key and Jameco don't show any Military grade parts
> (I haven't read both entire catalogs - but of what I have read - not a
> single part).
>
> 3) Least important to me is any additional cost - and from what I've
> seen thus far the difference between cost for Commercial to Industrial
> is fairly trivial.
>
> So, unless someone can point me to obtainable in qty 1 Mil spec parts I
> will use Industrial where available and Commercial where I must...
>
> On Tue, 2007-02-27 at 22:17 -0800, Dave Harvey wrote:
>   
>> I agree with Adam.  The cost of military-grade parts is small compared 
>> to the time and expense troubleshooting a thermal or design margin 
>> problem.   Unless you are GM, making electronics by the millions, a few 
>> extra bucks for parts is no big deal.  I work at the other end of the 
>> scale; designing electronics for space applications where we build a few 
>> (or one).  In that case, reliability and design margin are everything.  
>> I always use the best parts I can get because I've had some bad 
>> experiences when I didn't.  As a wise engineer once told me when I 
>> remarked on the extra size, weight and cost of additional design margin: 
>> "The only thing margin saves is your ass."
>>
>> -- Dave
>>
>> Adam Wade wrote:
>>     
>>> --- "Steven P. Donegan" <steve at donegan.org> wrote:
>>>
>>>   
>>>       
>>>> For the moment I am working more on function and
>>>> less on boundary conditions - ie I am working with
>>>> commercial temp range parts and 'reasonable' power
>>>> supply fluctuations. Once the system works in those
>>>> conditions I will indeed go to automotive/military
>>>> temperature range components and expect zero
>>>> goodness from vehicle power :-)
>>>>     
>>>>         
>>> I am probably late making the comment, but you
>>> probably stand a significant chance of having a bug
>>> crop up during development that will eventually be
>>> traced back to NOT having done something like spec'ing
>>> for wider limits in temp, noise tolerance and/or power
>>> supply issues.  If this happens, the time spent
>>> debugging in the testing the design phase will likely
>>> exceed the time (and effort) required to just spec out
>>> parts to handle much larger environmental limits than
>>> the basic "standard" you're using to get the thing off
>>> the ground.
>>>
>>> Of course, you might NOT run into a problem, and in
>>> that case, you'd end up spending only a little more
>>> time and effort to up-rate the design after basic
>>> development.  But to me, it doesn't seem like the
>>> initial effort would do anything but potentially speed
>>> up development, and could potentially save you some
>>> serious headaches...
>>>
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>>>
>>>