Destructive Testing On SPICE

One of the dorkier simulators would put little animated flames over the symbols of parts that dissipated too much power.

But that's a gimmick. It's hard for Spice to understand your intent, application, heatsinking, and duty cycles.

LT Spice will generate an "efficiency report" which lists power dissipation of various components.

John

It would have to be set up with inputs for current, wattage or voltage limits. Usually in reliability you have one distribution curve for strength and another for expected loading over the lifetime of a structure.

Another much more daunting but related undertaking would be to take the electronics / mechanics analogy much further, i.e., determining the electronic analogues to Coriolis forces, angular momentum, moment of inertia in beam bending, etc.

The principle difference is few care if someone burns up a chip but just about everyone cares if an RC building or prestressed concrete overpass comes down. Even that difference fades in power production.

A serious attempt at such a project would probably yield a lot of valuable insights and innovations long before it was completed.

Instead of using SPICE for simple mechanical impedance problems a generalized application could be used for either.

A single click would convert mechanical to electronic and vice versa..

Bret Cahill

Those of us who are electronics design engineers don't work by analogy. We use real facts and hard numbers.

There are accepted ways to calculate MTBF of electronic systems, and accepted ways to stress and test actual working hardware. A good EE can design electronics that has multiples longer MTBF than the MIL-HDBK-217 or Bellcore calculations suggest. A bad designer will often come in much, much worse.

None of that last part makes sense to me.

John

Late at night, by candle light, Bret Cahill penned this immortal opus:

That's what analog computers were made for. Convert the mechanical values into their electrical equivalents (analogues), set up the circuitry, let it run and plot the outputs. The operational amplifiers did the mathematics (operations). Nowadays digital computers do it faster with more accuracy.

- YD.

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Remove HAT if replying by mail.

This isn't about a solution to a specific problem.

It's a fishing expedition for new ideas.

The goal here would be new methods and new devices.

You draw a low pass fliter on the program, say a capacitor to ground, and the mechanical equivalent, say a spring and damper, is automatically drawn up as well.

A couple issues may complicate things:

A lot of the analogues probably wouldn't "map" one to one and anyone using it would need to know which analogue to specify.

The hardest part would be formalizing the math for all those messy mechanical situations that are "merely omitted" from many engineering programs. The WTC "pancaked" down because the architect didn't think joints were glamorous enough for his time.

Some researchers at MIT took a better look at the joints _after_ 9/11.

Bret Cahill

Different analogy. The goal here isn't just calculating but new devices and methods of dealing with older problems.

Bret Cahill

The "Work Bench" Program? I seem to remember my kid using that in school and it would generate some nice effects if you made a mistake in the circuit that would otherwise destroy something..

Jamie

You can use Spice to simulate relatively simple mechanical and thermal systems, but real-world mechanical systems have complex geometries that need finite-element methods, and thermal systems involve diffusion, neither of which Spice is especially good at.

Spice can model simple thermal systems with the equivalents...

1 farad = 1 gram of aluminum

1 amp = 1 watt of heat flow

1 ohm = 1 degree C per watt

1 volt = 1 degree C

1 second = 1 second

which is good to 5% maybe.

Worse sims are electromagnetics, where Maxwell's equations have to be solved in space and time. The worst are chaotic nonlinear things, like weather.

John

Only in power generation -- megawatts -- does the destruction of anything in a circuit amount to a hill of beans.

You can fry computer chips all day long and never attract more attention than Al Gore in a dust devil.

Bret Cahill

The best way is to write your own macros. For instance I have a macro that checks MOS for hot electron SOA issues. ...Jim Thompson

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Spice is like a sports car... Performance only as good as the person behind the wheel.