[sdiy] Breadboards

[Scott Gravenhorst]

harrybissell <harrybissell at prodigy.net> wrote:
>Scott Gravenhorst wrote:
>
>> I do not use simulation software principally because in is _NOT_ physical
>> electronics and it's quirks can be vexing, even with the best and most
>> expensive simulators.  Yes, they can work, but no, not always and when
>> they don't it can be frustrating to understand why.  I will even
>> speculate that it's possible for a simulator to give a result indicating
>> a design works when it will not in a physical circuit due to limitations
>> in component simulation parameters (models).  While this may be rare, it
>> can happen.
>
>wha ?...     RARE ???

Well, now I know (c;

>Its not rare at all. Its very common (of course if you don't USE simulation you
>
>wouldn't know HOW common...)

Ah.

>First of all... a LOT of models (especially the 'defaut' models that simulate
>quickly)
>do not look for obvious dumb mistakes.  Try feeding a 741 opamp a +/-100V
>supply and it will probably allow you almost 200Vpk-pk output... minus the
>maybe
>1.5V off the rail.  Hope you didn't try that.  My simulator was happy to go to
>KV
>on the supply pins.

That's actually humorous  (c:

>Transistors are prefectly matched. So you can design (say...) a discrete OTA
>and
>the performance will be fantastic.  The trannies will all be at the same
>temperature
>as well...even if one is conducting uA's and another A's...
>
>I'm not as rabid as Bob Pease (who hates SPICE totally)... but Scott is right
>here.
>Unless you verify the results in the real world, you will get hurt !
>
>I don't quite agree about the SBB having 'real world' physics problems. Its not
>that
>the SBB has capacitance, or contact resistance...  but that these are not
>always
>the same every time.  You can't (like the simulations) count on them.

Right, but if you constrain the use of an SBB to things it _can_ do and stay
away from things it can't, I think it serves a proper place in an electronics
laboratory.  I am always very aware that there can be problems introduced,
however, I think that most DC to 20KHz, low power cicruits can be adequately
"proof of concept" tested - on a good quality, unabused SBB.  And only the
actual finished, chassis installed with PCBs project is a prototype.  And the
fact remains that every problem with an SBB is a physical electronic component,
even if it varies in performance.  These things don't scare me away, but they
have modified my behavior.  As a result, I've been more than pleased with SBB
results, they've shown me where my designs are wrong, helped me correct them,
and either proved or disproved a concept.


>Many folks hate IC sockets... then why put every component in a socket ???
>
>OK. Its quick and easy, and it might work.  As long as you're not doing rocket
>science... enjoy enjoy...  :^P

Oh, I have and I will...  (c;

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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