Re: gEDA-user: merge multi symbol components

[Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx>]

John P. Doty wrote:
> Joerg wrote:
>> Totally OT here, quick question since you seem to be quite the expert on 
>> this:  Do you know some sort of main distributor or clearing house for 
>> space-rated parts? Or is the only way to just piece it all together like 
>> usual, via individual quotes from companies such as Solitron?
>>
>>   
> 
> I don't know of any shortcuts. If you have a customer who insists on 
> "space qualified" parts, you need to talk to them. Everybody has their 
> own rules. If you're dealing with somebody with a lot of rules, you'll 
> need a parts specialist to deal with them. This is more like lawyering 
> than engineering.
> 

Yes, that's what it looks like to me.


>  From an engineering perspective, "space qualified" is almost 
> meaningless, since "space" is neither an environment nor an application, 
> but a wide range of them. If the part that best fits your requirements 
> is in stock at Digi-Key, use that. I've flown a lot of these with great 
> success. "Space qualified" parts tend to fragile, obsolete junk that 
> behaves unpredictably in actual applications. But they've been blessed 
> by the priesthood.
> 

That's what I have seen a lot, older parts from obsolete parts dealers. 
Don't want to rely on that because when the pot is empty the meal is 
going to be over.


> Regardless:
> 
> Understand the mission.
> Understand the environment.
> Understand the physics of the interaction of the environment with the 
> technology.
> Understand the requirements.
> 

Agree. I understand the concerns about rad-hard and common failure 
mechanisms. Understanding the mission will hopefully be achieved after 
the next meeting. Where I'll have a whole lot of questions ;-)


> In depth, not in the shallow, sloppy way that too many "designers" think 
> adequate. There are no cribsheets, and "space qualified" is no guarantee 
> of anything, except maybe on paper. God is in the details.
> 

God is in heaven, much farther than this craft can go but still near 
enough for me ;-)


> Don't torque your parts selection around to solve issues better 
> addressed at the system level. Not every part needs to be immune to 
> radiation-induced upset, for example.
> 

That's what I am planning to do. Keep it as simple as possible, 
prototype with Digikey parts and then take a hard look to see which ones 
could be critical. Then I'll sit down with the customer. But it might be 
a back-to-the-wall situation because they in turn will be bound by 
agreements. Of course, there always comes a point where it's "either we 
modify a requirement or we can't do it".

Thanks for the insight, John, I appreciate that.

-- 
Regards, Joerg

http://www.analogconsultants.com/



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