Non Ohmic Constant Voltage Drop "Resistor"

Zener diode? ( over a limited current range.)

not sure but there are some very esoteric materials that exhibit a bit of constant voltage over a current range. I think one is what's used in the MOV protection devices. That's a passive device.

PS: to me, your subject line didn't match your question, almost didn't look at it. again, to me.

Battery ?>:-} ...Jim Thompson

slapping forehead, and yelling, now that's just embarrassing!

A battery might not be passive in the sense of a resistor or zener which never need charging.

I need to damp an oscillator down to zero current after one oscillation, critically damped. One oscillation is necessary for this to work. The voltage should damp down too, to a constant, maybe zero or at most a fraction of the maximum.

I may be able to use a conventional resister as well as or in place of the zener diode.

Bret Cahill

Try a regulator.. or maybe a zener diode..

Jamie

What kind of oscillator? If it's an LC, there is an optimum value resistor that, slapped across the tank, will kill the oscillation down to a very small voltage within one cycle time.

I make LC oscillators that start in nanoseconds and can be quenched in well under one cycle.

We had a thread in s.e.d. where I invented the fristor, the electrical equivalent to static friction. A fristor would kill an LC even faster than an ohmic resistor. I think.

The 'after one oscillation' indicates a holdoff time; the 'down to zero current' indicates clamping. The "critically damped" phrase seems out of place here.

Don't you want a timed capacitor grounding switch? Or, a timed open-the-inductor-so-no-current-flows switch?

The damping can start well before the end of the first oscillation.

It's OK if it's somewhat underdamped.

Too complicated. Cost down to pennies is an issue.

I just don't want much current after 2 - 3 cycles.

Bret Cahill

Millihertz? Hertz? Megahertz? Gigahertz?

w.

Any mechanical switch or relais can do that.

w.

Oh now that is interesting. (fristor) So I'm not sure how the analogy tran slates into electrical terms. But if you damp a mechanical oscillator with friction, such that it's "very hard"*, then you end up stopping the system in a state that still has some potential energy. (Unless you are lucky, o r smart.) Where the spring force is not enough to over come the frictional force. I'm not sure how that translates to the LC-fristor case. But mayb e it leaves some charge on the cap???

George H.

Without knowing more about your overall system, like whether it already includes a microprocessor, consider just generating the exact waveform you want. At 0.6 Hz you won't be taxing any uP system.

Best regards,

Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis

wow! I'm an analog guy, and *I* would be tempted to do this with a PIC-like chip! cheap, reliable, trouble free. and battery friendly. even the inards of an old Timex watch could do that. and those are cheap.

I know you know this, but still have to say it, an 'opposing' batery is the equivalent of static friction. So, yes, absolutely leaves energy in at some unknown state.

I did this once using an 'impulse' [think ball bat] The thing oscillates and just as it comes swinging near zero, whack it just right, like hitting it with a ball bat. It stops almost on zero. Or, probably better put, remove the energy from the system at the appropriate time.

The fristor is the equivalent to killing a mechanical resonator with sliding friction, not viscoscity. Note that the envelope decay is linear, not exponential.

It's not an exact analogy, because electronics can do cooler things than mechanics.

For a normalized LC (L=1, C=1) you want about 0.57 ohms across it to kill it fast.