Controller No 4 - Dual Fet Driver - Looking for Explosions in Wires

[BEP]

I was hoping with this controller to track down the explosions, but from the tests i need 80+ volts on my coil to get re triggering and my fet died straight away, shall i try limiting the current or do you not feel it was excess current that caused the failure.
If it was a large dv/dt that killed the fet maybe i should try a fet with a higher volts rating.

You have added more questions.
You call it re-triggering. Maybe it isn't. Re-triggering at the FET may just be a result not a cause. Is it really related to voltage, current or both?
If voltage then add a small capacitance across the FET. If current then place a small inductance between the coil and the FET. Either will change the frequency but will they make the FET live through a higher coil drive voltage?
I suspect it is a voltage issue destroying the gate junction. Here is where I would try Lindsay's suggestion.

Maybe to prove my theory with the white noise, i should build an amp and white noise generator and inject this into 1 coil of a bifilar and then inject sharp pulses in the other bifilat coil.

I have doubts creating spatial effects in a single coil will result in much, but who knows?

Do we know why the pulse appears with 1 pulse above 270khz but requires 1 pulse and then a delayed pulse below 270khz to get a sharp pulse.

I think the second pulse simulates a higher frequency on a longer wire. I use an external pulse to pinch current on another wire so it will 'fit better'<?>... long story. I think I told that one to you and .99 already.

Reestablish the test with these results and trim the wire. If the cutoff moves higher then you'll know the point is related to travel time through the wire. It won't be related to wavelength, perhaps pulse rise time instead? Is 270 the change point for other coil lengths? Is there anything else that can vary that 270 number? Ambient temperature? Something crazy like time-of-day?

Do i start trying to measure the power in the pulse verses power used to generate

Your results are differing from mine so I'm not sure you are at a point where it will be easy enough to measure accurately. You do have a lot of 'hash' going on. Maybe you can wrap your noisy coil in a secondary coil for measurements?

[Grumpy]

http://74.125.45.132/search?q=cache:k7xHbMIFUGkJ:hi.baidu.com/5281566/blog/item/5a32b78633884f3d66096ef9.html+lightning+gate+oxide+damage+MOSFET&cd=9&hl=en&ct=clnk&gl=us

(Scroll down to "Spurious oscillation", The "Miller" effect, and "Radiated interference with controller" )

Have you checked if the pulse produces a charging effect of any sort?  I.E. does it increase the voltage on a capacitor (precharge to 50v) with coiled wire leads, or increase the voltage of a battery.

In any event, the energy of the explosions appears to be released into the ambiant environment and lost - try to capture it.

[Peterae]

Thanks Guys
Not sure i have the resources to build Tube amps right now.

I will come up with some tests based on whats been suggested.

Cheers,
Peter

[Peterae]

I am making good headway now.

I wound a coil using thinner wire and longer more turns and tails, this has allowed me to use lower volts 50 ish.

I can now produce a popcorn noise from the coil, with a magnet close i can see the tails jumping slightly so this is interwind movement making this noise i think, it's not easy to maintain as everything around keeps crashing, PSU's and pic but i will try to get some footage soon.

A 1 loop shorted turn really increases the sharpness of the pulses

[Peterae]

This is getting very interesting

I am now getting the explosions consistently with this coil, and they appear at about 450kHz ish fundamental frequency.
I have one channel being driven by my pic and this is constantly reading garbage which would also mean the phase delay setting is random and constantly changing, i can see i need to build a white noise generator board now to plug in it's place.
Something really weird it appears i need to run the system for about 5 seconds before it appears, maybe the characteristics of the fet are changing to allow the effect

[darkspeed]

Something really weird it appears i need to run the system for about 5 seconds before it appears, maybe the characteristics of the fet are changing to allow the effect

Sounds like you may be plowing through a static charge on the surface of the conductors insulation...

If the  interwinding movement is faster than 340.29 m / s you will hear a crack like a tiny whip as the wire ( wires ) break the sound barrier ( helical rail gun )

You need a SA shot of what is on the wire and an SA shot of the audio through a mic

sounds good!

[Grumpy]

check for the good stuff - this only takes a few minutes:

Charge a 100V (or higher - ceramic if you have one) cap to 50V (24v or 35v should work too). Cut two separate pieces of wire around 8 feet long that has good insulation. Connect one wire to one terminal and the other wire to the other terminal - no circuit!. Curl the wires up into two rough cylinders, diameter unimportant. Place near your coil with the explosions. Now pulse the coil whilst measuring the voltage on the cap, and scoping the cap. On the scope, the stuff looks like a very short burst of sustained oscillation. Voltage on cap will steadily rise if you got the stuff.

Cut wire down to get best pulse definition.

[Peterae]

I will try G thanks when i get in tomorow.

Just uploading a video.

Yep got a SA shot in the vid

[Peterae]

OK Here's the Video.

It's not very good, i am using a normal camera which has video function oin it and is normally pretty good but the sound is crap.

You need to wack your volume up to hear the crackling where as it's quiet loud in reality.
Maybe tomorow i can try and capture the sound using my laptop and an external mike, and try a SA plot from it.

The Spectrum video shot show dark blue bursts this is when the crackles occur you will also see it go flat line, thats where i flick the switch on the psu to reset it because it keeps crashing into Constant Current mode, you will see the SA go flat line and take a few seconds to re start the Crackle burst, even though the psu reset is instant the crackles take a short time to restart up.
The best crackling sound can be heard right towards the end of the video when i move right up close to the coil.

If I remember corectly the SA band is 0-50Mhz i think you can just see that in the video.

The coil is flat and rectangular, seems to be a better setup for the explosions.

[Peterae]

Crackles1 picture = Crackle happening
Crackles2 picture = without crackle
Crackles3 picture = Crackle Happening

[Grumpy]

Plug your ears with your fingers - is the sound still loud?  (seriously)

[darkspeed]

Focus man focus!  

What kind of wire? what is the breakdown voltage of the insulation?  Sounds like arc over from the vid..

[Peterae]

It's automatic and consistently out of focus  

the best cam i have is built into my laptop but since i got a laptop based scope i cant use it DOH

but i could do a screen dump on it which should be perfect if thats needed

Shall i try getting a sound sample tomorow with a mike, and record it as a wav, i think theres some free software somewhere never used it yet though

[darkspeed]

How does it look in the dark? like no light at all... give your eyes a while to adjust and look for flashes

[Peterae]

I dont think it's electrostatic i can place my finger over it and it makes little difference as long as i dont deform the coil, it's always light when i'm at work LOL so it could be hard to get it dark

I think i need to try capturing the effect using a detector, i will try G's suggestion first

must try digging my compass out as well

[Peterae]

Do the SA shots mean anything to anyone?

Dont forget the tug in the valve that SM mentioned is a mechanical tug or alignment with the earths mag field, no plasma there

[darkspeed]

This may sound stupid but stand the board up where the coil is in earths plane.. any better results?

Can you do a clearer screen capture of no effect / effect ?

I would really like to compare the two!!!

[Peterae]

Yeah indeed i can do will be tomorow now.

[darkspeed]

Do the SA shots mean anything to anyone?

Yes they do!

They mean you need to SA above 50mhz or you need a much longer wire to bring the pulse down in frequency

Your many thin lines in your NON EVENT photo show two freq that are not harmonics of each other + intermodulations so the amplitude is not exactly additive

Your fewer thick lines in your EVENT photo show that the frequencies are much closer to being harmonics of each other and the products are closer as well so the amplitude is additive

This is the same thing i am getting with two freq that are just a few hz apart.

[darkspeed]

In the background there is a green pulse on a black background... what freq is the pulse ringing at?  ( frequency of the ringdown )

[Grumpy]

there is structure (order) to the crackles per the SA shot

Where was the SA probe located ?

[BEP]

there is structure (order) to the crackles per the SA shot

Where was the SA probe located ?

Agreed. There are two or more entrained signals. Sonic? Coil length vs. coil diameter? modulating the 450 carrier?

[Grumpy]

what is the spacing between the groups when the crackles are occuring?  (can't see - blurry picture)

EDIT:

OK looked again and it looks like the peaks are about 3mHz apart

what is the resonant freq of your coil?  I am wonder ing if you may be seeing the excitation of the coil itself

[darkspeed]

G - is correct it very well may be resonant rise at a very high frequency due to the short length of coil wire

looks like the board is 4" x .5" and the coil is about .75" ?  

so the coil would be 10" dia x .75"

28awg?

so say maybe 50 turns

1570" of wire

1180Uh self inductance and 26.40Pf self capacatance

so 900khz natural resonant frequency ??

that was just a wild guess... but  it fits nicely with the 450khz results  

[Peterae]

Thanks for all your help Guys i cant do this without you 

I will attempt to answer all the above question during the day as i do tests ect.

My PSU seems to randomly switch to constant current mode during some of the EM bursts and it stops working because i had the Current in that mode turned to zero, so i thought i could save myself some trouble by winding up the current, bearing in mind it's only a 1A PSU, as soon as i did a FET blew, this time it was the non delayed FET, this is interesting because it means there was enough energy in the system to blow that FET, previously i had seen the delayed FET blew only it has blow slightly different to the last one.

G-S 1.5 K Ohm
G-D 1.510 K Ohm
D-S 3.5 Ohms

The Former dimensions are
81mm x 6 mm and i have used 4 layers of 1.5 mm card
Turns = 32
So total coil wire length = 5.568 meters or 219.212 Inches

L = 41.25uH @ 10 kHz
Q = 1.8508
R = 1.4006 Ohms
Z = 2.9464 Ohms

Driven Frequency where Explosions were heard was 378.79 kHz

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