Unconnected part LTSpice seems to need (weird ...)

But all I have and take is white pills, calcium & magnesium supplement. Would those work?

:-)

What if the cracks last more than four hours?

Whoa, there--it isn't so cut and dried. LTSpice has built-in heuristics to prune stuff like that before it runs, but they aren't perfect.

It's a reasonable question why it should work at all, though, and why it silently generates wrong answers without complaining.

ISTM it's a minor bug in the heuristics.

Cheers

Phil Hobbs

Then she's going to have to finish by herself.

Joerg expounded in news: snipped-for-privacy@mid.individual.net:

That only works for Morpheus.

Warren

I prefer when software tells me before or after it prunes something.

Forrest Gump would have said "It's like a box of chocolates, you never know what you gonna get" :-)

Some sims will go from running in seconds to running in hours, with minor changes.

I used to run a DOS sim, called ECA, that didn't use the Spice core. It was cool, ran very fast on a 486. It would announce, but cruise right through, warnings of singularities, divide by zero, all that stuff. It just kept going.

John

Interesting, I also grew up with good old ECA224 but that was when the

I find this sim behavior odd. It seems only naturaly that, in a "what-if" scenario, an engineer disconnects just one leg of a part. After all, that's how we also do it in real life. SPICE is not supposed to "partially smoosh that" and then not tell anyone.

A lint-equivalent for SPICE netlists would be useful. But since most people seem to use SPICE by poking things until the sim looks nice, it's an experimental science anyway. ;)

Cheers

Phil Hobbs

Mikey is fond of hanging "gmin" on unconnected nodes. I would suspect there's a setting to turn that off, then you get "floating node" errors until you find them all ;-) ...Jim Thompson

I'd certainly prefer floating node error messages over guestimating what LTSpice might hang onto a node that is unconnected in the schematic.

Looking a bit further (I don't use LTspice as my current production tool) it happens that:

• a default 10^-12 gmin option is permanently set. No way to defeat it, apprat from, maybe, setting it to zero.
• look at the log file. The unconnected node is detected.

-- Thanks, Fred.

Thanks, this would explain a lot. That's what Jim suspected, he beat you by 14 minutes :-)

Well, if it can't be turned off I guess I'll have to learn to live with that stuff. No complaints because LTSpice is free and generally doesn't crash. Other SPICEs cost an arm amnd a leg and crash a lot.

In PSpice each component's pins can be defined as connect with gmin or report error. So maybe it's a component issue? ...Jim Thompson

In LTSpice click Tools/Control Panel. Click the Spice tab. Change Gmin as you wish in the upper right box.

John S

Could be dicey. If I set it to zero other things my go kablouie because it's then universal.

The VALUE of gmin isn't the problem, it's that unconnected pins are being connected to ground (most likely) via gmin. I basically only use LTspice as a viwer and to run netlists, so I don't know the ins-and-outs of configuring pins. Make sure your symbols don't default to connecting thru gmin, rather than balking. ...Jim Thompson

topologycheck Num. 1 Set to zero to skip check for floating nodes, loops of voltage sources, and non-physical transformer winding topology Make sure it's set to "1" ...Jim Thompson

Also...

"Mark unconnected pins: Draw a small square at each unconnected pin to flag it as unconnected."

...Jim Thompson