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Author Topic: Controller No5 With Protection - Looking for Explosions  (Read 104193 times)

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It's not as complicated as it may seem...
I was thinking a long time and I could not think of a good reason for this MOSFET to become turned on with the gate shorted to source.

Is it turning on? Might that opposite pulse on the undriven MOSFET and 1k resistor be what's expected if one considers the bifilar coil to be an open-ended transmission line?
   

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It's not as complicated as it may seem...
In 2009 when Peter and I worked on these experiments, the following is some background and suggestions based on the path I followed and results I achieved shortly afterward.

As the test setup consisted of two switches and two coils (in a bifilar configuration), and we found the "pulse" only occurred on the delayed coil, it was hypothesized that we may be able to eliminate one coil. That became the second test configuration, and basically where the collaborative experiments ended as far as I remember.

From here I began working to developing the simulated effect with some success. One key factor was that I surmised the connecting wiring between the coil and DC supply could/should be replaced with a transmission line, aka coax cable. This improved and solidified my results a great deal. In discussing the improvement with Wavewatcher/BEP, he suggested I replace even the coil with a length of coax, and this proved to be a fruitful modification. In fact, best performance was achieved when the two halves of TX line were of the same length. At this point it appeared to me to be a new and novel form of Blumlein/step-recovery-diode hybrid  Pulser. The diode is very important, and the pulses are NOT produced without it. Some diodes work better than others, so I recommend trying a few types.

I found that the second, delayed MOSFET can also be dispensed with, as one MOSFET can do the job. It turned out that once the coax length, DC supply voltage and drive pulse period are "tuned" just right, a 50% duty input pulse will drive the circuit into a form of resonance where the pulses are 5 to 10 times the amplitude of the DC supply voltage, depending on the resulting output pulse width and gate drive period. In theory this circuit might achieve extremely high voltage/narrow pulses from ordinary supply voltages. One might consider this circuit a "tuned voltage compression device", where it converts a regular 50% pulsed DC input, to a proportional v x t pulsed output; the smaller that "t" is, the higher "v" is, so that the input and output v x t is always equal. At any rate, you can see one scope shot here showing the circuit hitting a "resonant" point where the output voltage is multiplied and time-diminished by about the same factor. The attached pics are using a 20V supply voltage.

- sim01 is the two MOSFET setup, with single red and violet gate pulses, and resulting delayed MOSFET drain pulse.

- sim03 is hitting "resonance" with continuous gate drive.

- 2-TX Line Schematic was my final configuration and starting point timing values.
   

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Thanks Poynt for looking into this, but the 1K resistor setup was done later to see what would happen (nothing weird)
when using a 1K instead of the shorted MOSFET.

So the strangeness we see is at the posts roughly between post #412 and 415.

It looks to me in posts 412 and 414 screenshots there is evidence of the shorted MOSFET to turn on looking
at the drain voltage and drain current signals.

Anyway,   nice idea to have the bifilar coil replaced by certain lengths of coax.
The pulses i see without the 50 Ohm protection resistor at the PS are already huge and fast in the bifilar coil
setup, so i can only imagine what they look like with a coax cable and the proper (DSR?)Diode.


Itsu   
   

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In 2009 when Peter and I worked on these experiments, the following is some background and suggestions based on the path I followed and results I achieved shortly afterward.

As the test setup consisted of two switches and two coils (in a bifilar configuration), and we found the "pulse" only occurred on the delayed coil, it was hypothesized that we may be able to eliminate one coil. That became the second test configuration, and basically where the collaborative experiments ended as far as I remember.

From here I began working to developing the simulated effect with some success. One key factor was that I surmised the connecting wiring between the coil and DC supply could/should be replaced with a transmission line, aka coax cable. This improved and solidified my results a great deal. In discussing the improvement with Wavewatcher/BEP, he suggested I replace even the coil with a length of coax, and this proved to be a fruitful modification. In fact, best performance was achieved when the two halves of TX line were of the same length. At this point it appeared to me to be a new and novel form of Blumlein/step-recovery-diode hybrid  Pulser. The diode is very important, and the pulses are NOT produced without it. Some diodes work better than others, so I recommend trying a few types.

I found that the second, delayed MOSFET can also be dispensed with, as one MOSFET can do the job. It turned out that once the coax length, DC supply voltage and drive pulse period are "tuned" just right, a 50% duty input pulse will drive the circuit into a form of resonance where the pulses are 5 to 10 times the amplitude of the DC supply voltage, depending on the resulting output pulse width and gate drive period. In theory this circuit might achieve extremely high voltage/narrow pulses from ordinary supply voltages. One might consider this circuit a "tuned voltage compression device", where it converts a regular 50% pulsed DC input, to a proportional v x t pulsed output; the smaller that "t" is, the higher "v" is, so that the input and output v x t is always equal. At any rate, you can see one scope shot here showing the circuit hitting a "resonant" point where the output voltage is multiplied and time-diminished by about the same factor. The attached pics are using a 20V supply voltage.

- sim01 is the two MOSFET setup, with single red and violet gate pulses, and resulting delayed MOSFET drain pulse.

- sim03 is hitting "resonance" with continuous gate drive.

- 2-TX Line Schematic was my final configuration and starting point timing values.

Hi Poynt

Looking at your circuit, from a layman's point of view, I would say your two pieces of coax are acting as inductors and capacitors all in one. The mosfet switches on and charges the two inductors in series, the mosfet switches off and there is a discharge through the diode to the junction of the two coaxial wires, from this point on the inductive capacitance of the second coax goes into oscillation, being fed by the capacitive charge of the first coax to keep up the voltage.

It is parametric, you changed the inductance  and capacitance with the diode connection, the diode supplied "DC" to the Parallel LC of the second coax cable which then went into oscillation. what is interesting is the "level" of oscillation, not the usual drop to zero.

Regards

Mike


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   
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