a question about resistors in an arc experiment

And JFs circuit doesn't work.

John

That explanation doesn't hold water. If the difference was the language, explain Verilog? While VHDL is based on ADA, Verilog is quite 'C' like.

Then, of course, there is System-C, which is supposed to make hardware designers out of script kiddies. :-(

I'm with you on assembler (though not 68K) and VHDL. ;-)

Phil is sort of the backround music, a kind of profane Muzak.

John

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That depends on which sort of negative resistor you are talking about. There are two types. Both obey Ohms law but they are very different creatures. Both can be used to cancel out the real resistance in an RLC tuned circuit.

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Yes gulp! I've even met one of the guys who wrote some of the code. No thanks I'll drive.

How much code space does the micro have? That will tell you when you will be done. :)

Nah, that's only the start of the fun.

That reminds me of a tale about a number of University Computer Science professors being asked whether they'd be willing to travel in an aircraft whose flight software had been written by their students.

All except one said "No way".

When the stand out was challenged on his reasoning he said "It's because I'm quite sure it won't get off the ground in the first place."

Sylvia.

--- You're probably miffed because Phil knocked you off as a troll and you're trying to undo his commentary with a single 'slyish' denigration but, regardless of his outrageous style, Phil participates in civil debate when it's not nonsensical and he is, as far as I'm concerned, a very welcome, very valuable technical contributor to these groups.

These groups _are_ bastions of civilized debate, but that doesn't mean some of us won't cut you off at the knees if you're a smartass and you make a mistake you won't own up to.

So far, for some reason unknown to me, you seem to have taken an adversarial stance with regard to posts that I've made about negative resistances.

In particular, you've chosen to show disdain for my work without even extending the courtesy of examining it which is, at best, foolish.

If you want to fight, go for it, but expect no quarter just because you're female.

JF

I'm about to conclude that Sylvia is just a female rendition of AlwaysWrong... either obstinate to the point of ignorance or a troll.

If she continues to exhibit a closed mind I'll write her off.

...Jim Thompson

A lot of our VME modules (say, half of our production) goes into test stands for FADECS, "full authority" jet engine control computers. They test the hell out of them, simulating all the sensors and actuators, normal and failed, running scripts that take days to execute, and generate feet of paper reports. If they change a tiny bit of code, they run it all again. That's cool, because they can never take down a test stand, so we're always supplying new modules.

"Full Authority" means no mechanical or hydraulic backups. Code fails, plane falls.

John

John L & Sylvia... sounds like a '60's rock group ;-)

...Jim Thompson

If you "can't be bothered" why are you persisting in this thread?

Too ignorant, yet too obstinate to listen to your peers?

...Jim Thompson

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Well, to me a proper negative resistor is one that has zero current when shorted. Its I vs E curve is just the same as a real resistor of the same absolute value, but the current sign is flipped. It obeys Ohm's law in all quadrants, in all situations.

The nice thing about this resistor is that you can plug its negative value into all the classic equations... series and paralleled resistors, voltage dividers, capacitor rc exponentials, rlc resonators, whatever... and the equations still describe what you'll simulate or measure, small-signal or large.

This is also what LT Spice will do if you assign a negative value to a resistor.

What's the mathematical definition of the other type?

John

"Sylvia and John" sounds better. But I am about as un-musical as Horatio Hornblower.

But don't you agree about JFs circuit? If it is a negative resistor, it violates conservation of energy.

John

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One type does:

I =3D V/R

the other does

V =3D I * R

in both cases without doing math on the situation. In one case, the voltage serves as the input and in the other the current does.

This circuit: R GND ---!!---))))---/\\/\\--- GND

wants the second type to make an oscillator. With the first type. The small disturbance will send the thing rocketing to the rails.

A parallel resonant system needs the first type.

Reeling? What strange ideas you harbor.

Both the LTC opamp model, and LT Spice, are working fine in your simulation. The opamp output is railed low, there's no negative resistance, current is flowing OUT of V3, Conservation of Energy is not being violated, the whole mess looks about like a 1K regular resistor (plus the opamp Icc), and you were probably reading the current direction backwards.

Build one, use a 12 volt battery for V3, and see if it charges the battery.

John