Grumpy is already using an Avalanche output stage and so i would like to look at building one also.
Reading from Spherics instructions on pulsing a bifilar coil the specs need to be as follows.
1kHz-3.5 MHz
Pulse minimum 150 Volts.
Must be able to drive a very low impedance coil.
I will use FMMT427 which is an Avalanche transistor capable 320V pulses and can run at over the required 3.5MHz, peak current is 60A
http://www.diodes.com/datasheets/FMMT415.pdf
Only 1 device is needed and with the voltage spec of this device i will chose to run it at between 200-250 volts.
The board will have an on board psu to supply the HV and allow TTL input to drive it.
preferably over 1kv - this agrees with that Italian device as well (Energia Celeste ?)
isolate the trigger or learn the hard way - LOL!
Pigeon steps G 300V first as it's easier to work with.
Here's the frist draft, need to round some of the component values, i decided to go for 300V first try.
Quote from: Grumpy on 2010.06.13, 13:50:06
isolate the trigger or learn the hard way - LOL!
Good advice thx G is this what blew your sig Gen
No, I always isolated the sig gens. I think it was either close proximity to pulsed coils or just age that took out my gens.
555 is running and adjustable. Looks real stable but has a slight overshoot at the rise of the pulse.
Pulse looks a little wide too, no that it matters, just wider than it needs to be. I'll probably differentiate anyway so it doesn't matter.
555 should have no trouble triggering the avalanche stack.
It will be a real kick in the ass of the nay-sayers to have an ou device running on a little 555 timer. I honestly think that SM used a multivibrator (they work with 100% feedback to the transistors) and he could easily crystal control this - pretty solid clock. He could have used hv transistors too, or placed them in series for higher voltage.
Hi G
thats great news with the 555, if a viable device was made using them we would be a laughing stock ;D
With your sig gens have you looked in to seeing if they have nov rams, as Ds found out it's the first thing to get corrupted, with my old scope it was constantly getting corrupted and i had to reset back to factory and a cal on it regularly.
Now over dinner i have been contemplating your specs for the output stage, maybe i should just go for it at 1200v
G you have made my life more complicated ;D
The good news is i am going to build a 1.2KV Psu that uses a 555 :D
Not my circuit
http://www.cosmicrays.org/muon-power-supply.php#captain
Edit
G you can alter the Mark/Space if you need to
http://en.wikibooks.org/w/index.php?title=Practical_Electronics/Astables/555#Design_equations_2
go higher than 1200v if you can as you need to drop at least 1000 volts to get cavitation
(I actually found an image of the cavitation oscillation in reference to the density - think I save it at work as I can't find it at home
cavitation is not the freeing of energy or anything like that it just moves the medium
remember you can tap into the stack at any point to see what is going on with a lower votlage ;D
for example, you ground the first trans and watch everything on the scope at a few hundred volts
thanks for the 555 tips. I am pretty sure that the unit I install in my car will have a more stable clock, but this is good for now.
555 straight to the av stack sucks - pulse is too wide
make the trigger shorter than the pulse
Keep in mind that you need a short sharp trigger pulse to the base of the transistor and that HV will be at the base when it fires. So, you can block with a diode or isolate the trigger with a transformer (can be 1:1 or an actual trigger transformer). Make sure your transformer can handle the HV and will not short through the core.
Methods to fire SCR's (thyristers) are suitable - hint hint...
You can differentiate your pulse to the transformer and clip off the neg spike (minimizes ringing and saturation issues) and then the trans former will differentiate again and you have to clip that neg off too - see attached for some good examples:
EDIT:
These are good to 1600v isolation: (just an example)
http://www.datasheetcatalog.org/datasheet/vishay/pt50.pdf
diodes - he he - 1N914 at 4ns recovery isn't fast enough
555 will drift like an SOB if R1 is 50 ohms - hot as hell to!
So, R1 (sets width) at 1k on 555, differentiate and restore dc with 1N914 to a trigger transformer of something like 1:35 ratio - decent pulse to av stack.
Getting noise from the overshoot on the output of the 555 - looking into that.
Ready to sweep with the 555 now.
for the trigger coil, I have a TC-21 and a TC-31:
http://www.qimeioe.com/en_product1.5.asp
These easily withstand the pulse voltage of 1500v and require no modification.
output pulse is low as little current is applied from the 555 or other controller but higher than a 1:1 would be
was hoping to have the sweep gen by now, but not here yet
Am i missing something if you look at this pdf they use 5v to trigger the stack
http://www.ccsenet.org/journal/index.php/apr/article/viewFile/3287/3601
OK i know this is not the config i need, but other documents dont seem to mention trigger problems either.
Have you tried a pull down resistor on the base to stop it floating.
Without a diagram to see your config i dont know really what you have their.
I need to drive my coil from the emitter though via a low ohm resistor i guess, i have not played with this yet, still trying to get the psu built.
Quote from: Peterae on 2010.06.17, 21:36:03
Am i missing something if you look at this pdf they use 5v to trigger the stack
http://www.ccsenet.org/journal/index.php/apr/article/viewFile/3287/3601
OK i know this is not the config i need, but other documents dont seem to mention trigger problems either.
Have you tried a pull down resistor on the base to stop it floating.
Without a diagram to see your config i dont know really what you have their.
I need to drive my coil from the emitter though via a low ohm resistor i guess, i have not played with this yet, still trying to get the psu built.
That is correct. Only a few volts to trigger and a trigger transformer is not required. I am having trouble getting a clean trigger and trying some different things. Playing with the differentiator components and all that. Think I need a decent cap across the output of the 555 as it doesn't like the trigger coil or the isolation transformer - rings or low output - hence I think I need a cap across it.
in your pdf link - I have not tried this method of triggering and just found this same file yesterday. Would be nice to not need the isolation! However, keep in mind that collector overvoltage switching results in a rise of about 2ns, but takes more current and exposes the trigger to full voltage.
here is an other stack triggered at the last transistor and not isolated - this config is for pos pulse
EDIT: wow! they triggered it with a 555 - LOL!!!
back to the bench!!!
OK
555 - differentiated - to base of 2N3906 with 12v supply = nice pulse across 50 ohms
Nice pulse to 1:1 transformer looks pretty good too
ready to pulse av stack with it
Well..
that sucked
tried one av trans at 240v - no 100 ohm resistor at the trigger - pop! shot to about 500v and grounded through the 555 circuit - not sure what fried yet - got a short and no oscillation
now, about that iso-trans thing...
Quote from: Grumpy on 2010.06.18, 04:55:00
Well..
that sucked
tried one av trans at 240v - no 100 ohm resistor at the trigger - pop! shot to about 500v and grounded through the 555 circuit - not sure what fried yet - got a short and no oscillation
now, about that iso-trans thing...
Sorry to hear that G, hopefully just the 555 has gone, i wonder if we were to use a 6v TVS or something to protect the driving stage, 555 are not so bad to blow but i am using my delay boards so will need to be sure all is ok and then maybe use a logic gate as a buffer, having said that just in case, i did order some isolation pulse transformers in my psu build component list.
https://www.rapidonline.com/netalogue/specs/88-2423.pdf
They are only good for 500v isolation, but that's all that supplier had so maybe next order from farnell i can get something better, i am still hoping to avoid using one, but i will need to experiment to see.
I have finished building 2 1.2KV switched psu's, so far they seem to work well, although in the circuit they published, the 555 was free running at 85kHz using his published values, the circuit specified 2kHz LOL so i changed the 330pF to 22nF and am running at about 2.6kHz and all tests well so far.
Still need to order the reservoir caps for the output stage but have loaded with 1.6kv 1Uf caps and the circuit seems to regulate and remain stable.
More load tests need to be done once i have the final caps.
I have used 12VA Transformer so i presume the max i would get at 1.2kv is about 10mA
I seem able to vary the voltage from 4 to 1200v using the pot which is great.
Looks good!
Is this based on your 1KVPSU104.jpg diag.?
Hi Ds Thx
Yes thats right, there is a link to the original design just above that diagram, it looks like theres a lot missing but it's all SM and each heatsink carries 2 fet's.
the difference is that i am using a 0-250vac / 6-0-6 transformer
and i am using 3 series 2M2 resistors instead of one 5M1
Not to size
sweet!
Cheers G
A lot of testing to do on it yet.
I am starting to think about the Avalanche stack now, and i am very worried about using the output drive from the emitter because of the chance of serious damage to the drive circuit even using a pulse transformer at such high voltages.
It looks to me as i am stuck with pulsing low if i understand this correctly it means i need to have one side of the output coil to +HT and then pulse the other end low with the stack, i guess from the coil perspective it doesn't matter?
EDIT which actually is what i am doing anyway but with lower voltage on my coils.
Quote from: Peterae on 2010.06.18, 20:22:51
Cheers G
A lot of testing to do on it yet.
I am starting to think about the Avalanche stack now, and i am very worried about using the output drive from the emitter because of the chance of serious damage to the drive circuit even using a pulse transformer at such high voltages.
It looks to me as i am stuck with pulsing low if i understand this correctly it means i need to have one side of the output coil to +HT and then pulse the other end low with the stack, i guess from the coil perspective it doesn't matter?
EDIT which actually is what i am doing anyway but with lower voltage on my coils.
been at the bench most of the day:
wasted a few hours with a 2N3906 that I thought was a 2N3904 - wtf?
my isolation transformer is now a tiny toroid (choke from radio shack) with 5 turns on it
circuit is a 555 to a half-shot multivibrator with the 2N3904 in it - no differentiator now - makes pulse shorter than 555 is capable of
almost there...
G is your stack setup for positive pulses, i cant see how it's possible without over rating the voltage on the bottom transistors.
Perhaps this:
.99
Quote from: Peterae on 2010.06.19, 15:12:05
G is your stack setup for positive pulses, i cant see how it's possible without over rating the voltage on the bottom transistors.
Positive pulses - every transistor sees the full 1.5kv - overvoltage is what avalanche is all about - it doesn't hurt them - but current does. Clunky, slow diodes and transistors work best.
By triggering the top one, each subsequent transistor sees a higher voltage and you get a "snap the whip" effect.
yeah i could see that, for some reason i was trying to work out how on earth you trigger from the bottom of the chain, i couldn't get my head around it as the base would have had loads of volts on it potentially, until Poynt pointed me to the article again you posted with the trigger on the top trany, antway looks like e don't need positive pulses so i will go with the easier negative pulse and just drive with a couple of inverters as buffers and stick maybe a couple of TVS or Zener protection diodes across the inverters to stop any mishap going back to my Digital mono chips.
Cheers, guys my head is feeling clearer now ;D
EDIT do you still use the coax on the larger chain or do you just go with caps?
Caps are easy to swap out for quick tuning but need coax for square shape. The fall sucks with caps.
No isolation? - you have been warned...
if the pulse goes through the TVS rather than the coil...oops
you can optocouple too
back in the saddle again...
So here's the first draft.
Looks great!
some ideas:
run a stack for each bifilar and you can delay the trigger
if rise is too slow then change to triggering the first transistor
an avalanche diode can also be used to sharpen the output pulse
10cm coax may be a bit short and you may not rise to full voltage
Cheers G
Yeah i will be building 2 of these, one for each coil of the bifilar, i can then do nS phase delays exactly the same way i have so far but using much higher voltage pulses.
But if the required delay was known i guess i could just use another bit of coax, and then avoid any logic controll for a finished unit.
Plenty to try yet, trim values and coax length ect.
Could always stick 4 or 5 saturable inductors in series with the output if i need to sharpen things up, but i am hoping i wont need to do this.
We will see where it goes anyway, first i must get one working correctly.
Good news sounds like you sorted yours now and are up and running ;D
blew the crap out of it
(need a ballast resistor)
i=C (dv/dt)
i=100pf (1200/100nS)
i=1.2A
i=100pf (1200/10nS)
i=12A
i=500pf (1200/20nS)
i=30A
I can manage 60A for 20nS so if i go for 30A for safety i need a cap-coax value of about 500pF
Hope i have this right.
Thanks - pulsing up to 500v now
I need to adjust the bandwidth of the 555 down (it is about 180kHz to over 1MHz now), but other than that I am ready to go to 1500v with the little chip that could - LOL! At 500v pulse amplitude, I measure only a few volts across the coil - which is very good. It rings down a little after the peak and longer delay increases the ringing a little. Pretty happy with it so far.
For my ballast resitor I used R=V/I and for 1 ma R is 1.5 meg so I used a 1.2 and there is no change in the output voltage when pulsing.
OK Plan C ;D
I am going to use a 10 cap output filter stage, and i will use link jumpers to enable each stage so it should give me pulse currents 6amps @ 20nS per stage allowing me to vary up to the 60A max value of the Zetex transistor.
Quote from: Peterae on 2010.06.23, 10:58:04
OK Plan C ;D
I am going to use a 10 cap output filter stage, and i will use link jumpers to enable each stage so it should give me pulse currents 6amps @ 20nS per stage allowing me to vary up to the 60A max value of the Zetex transistor.
Try to hold it down to 10ma or less. You do not need, want, or desire current in the pulse. You cannot look at this from conventional transmission line theory as it does not apply. You are pushing nature, and nature is pushing back - hard!
resistors ok
caps suck - will try them in series or start rolling new ones or making a cap array
tried a 1uf 1kv cap at 1kv and this is not enough capacitance to keep voltage up
ballast resistor adjusted down to 10k to keep voltage at about 1430v
one step forward and two steps back...
Quoteone step forward and two steps back...
Isn't that always the case ::)
The cap arrived for my psu's, i have used 10uF 450V with 3 in series for the positive cycle rectification and 3 in the negative side.
The regulation is fantastic @ 500V, i loaded with a 60K resistor and the voltage remained 500V exactly very little ripple, thats just over 8ma and 4.1 Watts being drawn.
Very happy so far
Need to try regulation at a 1000V next
EDIT ok tested higher volts, it looses regulation above 700V when i try to draw 4 watts, so i guess i need to try something other than 2kHz drive frequency to find a sweet spot these transformers like to work at, 2 kHz seems too low anyway i would have thought it should be operating much higher than this, maybe the 2kHz was a typo on the circuit diagram and that explains why the component values on the 555 were for operating at a higher frequency.
I am going to try the value that was originally published on their diagram and retry
One thing I miss about a freg gen is you can just change the freq anytime you want. Still waiting for delivery of my new one. You can adjust a 555 circuit but it has a set range and you have to change components to change the range. Low freqs can be good when testing as can a single shot switch - hint hint.
I have an article somewhere of a comparison of two circuits using PFL's: one was twice as efficient as the other and our normal av stack is the 50% efficient form. I used the more efficient circuit with 10kv and it gave excellent results. I had the explosions with two series gaps and three PFL's though. I am going to try this with an av stack today - just for kicks - pun intended.
See attached.
put caps in series and I'm at 1460v - supply won't go higher but used to go over 1500v - not sure what happened to it, might be the resistor that adjust the output
EDIT: oops had it wired wrong - caps stop at about 750v and won't take more even in series - must be why they are "surplus"
Working up a spreadsheet now to see what I can get to capacitance-wise with the caps I have left. All of my other hv caps are low capacitance, .01uf at best.
you could build an MMC.
I have better luck with MMC's than i do with the big expensive pulse caps
Cornell-Dubillier 942C20P15K-F are my favorite.. last forever!
got some old electrolytics - which I dispise - probably will short the second I hook them up
EDIT: yep, they suck
will try with less capacitance and more ballast to limit the current - if I can get at least 1200v I'll keep on - if not I'll put the driver on a board and make that permanent while I wait for some new caps
pulsing at 1200v to 1350v depending on the frequency - got more caps but need to hook them up - only .005uf now but have .05uf to add
not sure if I am getting full avalanche, but I looks like it is - scope is 300mhz and probe is 250mhz - might be too slow
also not really sure of pulse amplitude do to slow scope
Need to play around with trigger and delay line
so far, everything seems a little wierd with this setup:
trigger voltage effects amplitude of pulse on scope (not sure about real amplitude) and also effect max voltage for stack
trigger rings after the isolation transformer and this ringing is also in the output right after the initial pulse - would like to filter this out and get a clean trigger
difference between 1x and 10x probe setting is only like 2x or 3x on the scope - which makes me think that the pulse is just too damn fast
also notice that pulse on scope appears twice as high when first connected than a few minutes later - kinda like when caps leak more and more when overvolted
removed ballast resistor as it is like almost no current is there
quadrupled cap across supply and very little difference from low value cap - I think that the cap across the su pply is active when the stack is self-triggering as the voltage at the cap is all over the place
long square triggers show spike at beginning and then small square same as trigger but higher
will start to check for effects tomorrow
G the pulse maybe too fast dv/dt but if you are using a x1 probe i would have thought you maybe cooking your scope front end, the max my scope allows on x1 is 80V and on x10 800V much above this can do some damage (So it says in the manual), really need x100 probes for this sort of thing.
Ive just realized to get a higher voltage output all i need do is wind the power supply up.
I have been running at 12v and i can get 1200V but under load it's more like 650V for a 4watt load but i can goto 16V with the 555 and 36 with the LM339 so really i need to put a regulator in for the 555 and i would then be driving the center tapped 6-0-6 transformer with up to 36-0-36 instead of a max of 16-0-16 at the moment before damaging the 555, i just have to watch i dont exceed the 5.6A rating of the FET's which using 12 volts is only 10-50mA without a load and goes up to a maximum of 1Amp right now under load.
I am quiet impressed so far with this psu design, it should be interesting to see how it performs when i have the Avalanche board up and running, which is not that far off now.
I have attached a circuit of the finished PSU and the prototype of the Avalanche board.
The Avalanche board has a 9 stage Cap-Inductor pulse shaping circuit which is link jumper selectable from 1 to all 9 stages.
Quote from: Peterae on 2010.06.26, 10:32:08
G the pulse maybe too fast dv/dt but if you are using a x1 probe i would have thought you maybe cooking your scope front end, the max my scope allows on x1 is 80V and on x10 800V much above this can do some damage (So it says in the manual), really need x100 probes for this sort of thing.
I know, but what can you do? 10x probe is more than a used scope and some are low freq. (I have a good article on making your own.) Even with 100X, my 300MHz scope is too slow.
will check battery and cap effects next - give the scope a break...LOL!
So far, 1500v sucks and 10kv is the only way to ride - LOL!
Negative test for rise on a battery - so far - this was with a string of 12 AA batteries to a coil wrapped outside the coil being pulsed.
Haven't tried a cap yet...
I'll keep messing with this some more and compare notes when Peter's unit is running.
I need to see what really going on:
Article: Basics of HV Probe Design
I managed to pick up 2 x100 scope probes some time ago G so i should be ok, if they are fast enough to catch the pulse.
Over 1kv is not so easy, all my meters only goto 1kv, i cant even find one that goes over that, even if i could i guess the price would be high, although it is possible to buy HV meter leads with a converter built in, probably just similar to your design pdf.
So i will need to rely on my scope with the x100 probes to monitor the volts.
I am not sure how keen i am on going to high, this stuff is getting dangerous,need to think first then touch or not as is the case with a lot of this circuitry.
10KV i want to spin my coils field not make the earth spin faster ::)
With 10kv - you can feel something happening - there is no doubt about it
plus you are sure to meet the requirements and that is more voltage more effect
My trigger signal really sucks and is not always adequate - I'll pull 28v off the supply to 1.5kv supply and see if I can boost the trigger - base triggering kinda sucks as the trigger signal will effect the output shape and it takes more current - either that or go to collector triggering.
increased the current to the trigger and it look really good now - 500ma setting at 15v on the supply - but still only a couple of volts after the isolation ransformer but ringing is greatly reduced and output look pretty clean from the stack
It does not appear that my delay line (10 feet of coax) is charging correctly so will take a look at this now
If this pulser ends up blowing up as the fet stage did when i get the crackles, maybe the next solution is to develop a saturable inductor stage which if i remember correctly is what Spheric suggested in the first place.
Still working to getting the board done, and still have parts to order so i am being a bit slow right now, i have 2 smmt417 in the lab so i will give a 600v pulser a go while more arrive ,this should give me a feel for it.
Lots to do yet
I am going to need to buy 10 x 100pf caps for each stage, is there any preference of the type, are the blue 3kv ceramics ok for this or do they need to be more exotic?
This may sound like a strange idea but is there anyway to choke the output from your fet just above the freq. required for crackles and then have another path for the energy that is killing your fet to travel like a calibrated spark gap ( surge arrestor ) that has a voltage slightly higher than what you are working with.
Quote from: Peterae on 2010.06.27, 21:36:20
If this pulser ends up blowing up as the fet stage did when i get the crackles, maybe the next solution is to develop a saturable inductor stage which if i remember correctly is what Spheric suggested in the first place.
If you need scans of it.. I have the only known complete unedited original copy of " Magnetic Amplifiers - A rising star in naval electronics "
Cheers for the offfer Ds, not really ready to put any time on this yet, but it maybe the next project after this one, i will give you a shout when i'm ready cheers.
Quote from: Peterae on 2010.06.27, 21:36:20
If this pulser ends up blowing up as the fet stage did when i get the crackles, maybe the next solution is to develop a saturable inductor stage which if i remember correctly is what Spheric suggested in the first place.
Still working to getting the board done, and still have parts to order so i am being a bit slow right now, i have 2 smmt417 in the lab so i will give a 600v pulser a go while more arrive ,this should give me a feel for it.
Lots to do yet
I am going to need to buy 10 x 100pf caps for each stage, is there any preference of the type, are the blue 3kv ceramics ok for this or do they need to be more exotic?
I use 2kv blue ones : 56pf across each transistor - they form a divider as well
I don't think I have enough current to drive a coil with this high of an inductance and still achieve avalanche at the stack. Even with a 10 ohm load a single transistor at 200v is only providing a spike of about 50v. You may need to match the load of the coil with a resistor after all.
Looking for another supply...hmm...do I dare use a MOT?
I have hv transformers. What is the best way to make them variable?
Quote from: darkspeed on 2010.06.27, 21:53:00
If you need scans of it.. I have the only known complete unedited original copy of " Magnetic Amplifiers - A rising star in naval electronics "
Sorry, I just gotta bite on this one ;D
No ya don't. The only marks mine has in it are my hand penciled notes from the class. The edited version went to the regulars but it wasn't identified as 'edited' or with an incremented edition number. What does it say about means for eliminating switching leakage for MAs in switch-mode?
( nope - wasn't in the Navy. Also took training from other branches at the demand of uncle Sam).
Quote from: Grumpy on 2010.06.28, 00:21:22
I have hv transformers. What is the best way to make them variable?
this is fairly cheap...
use a variac on the 120v side of the mot
you can use smaller caps for what you are doing
This just uses computer buss capacitors
The power resistor limits the current draw from the MOT on an empty cap bank - go big Watt if you can
and if you want to tune it down to 1200v you can put a stop on your variac as a high limit or a power resistor in series
This is basically what i did with 811 driver
http://www.overunityresearch.com/index.php?topic=211.msg2558#msg2558
OR...
If you find that you need a super quiet dc and the MOT is too noisy - try one of these - http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370189794492
Quote from: WaveWatcher on 2010.06.28, 01:07:03
Sorry, I just gotta bite on this one ;D
No ya don't. The only marks mine has in it are my hand penciled notes from the class. The edited version went to the regulars but it wasn't identified as 'edited' or with an incremented edition number. What does it say about means for eliminating switching leakage for MAs in switch-mode?
( nope - wasn't in the Navy. Also took training from other branches at the demand of uncle Sam).
Ok i stand corrected 2 ;D
I guess this means we are two of the biggest geeks ???
Edit>>
Oh! On your 2500V PS schematic, above... you got away without balancing resistors across the caps? For me, that is like (doing you know what) into the wind. I had a whole bank go off like a string of firecrackers.
Quote from: darkspeed on 2010.06.27, 21:53:00
If you need scans of it.. I have the only known complete unedited original copy of " Magnetic Amplifiers - A rising star in naval electronics "
What are the differences with the edited version? I don't seem to have either version...could you pass it along?
Thanks,
.99
ETA: Is this the same as "
Magnetic Amplifiers - Another Lost Technology"? That one I do have. It appears to be a re-packaging of the original material from 1951. This one was re-issued in 2000. http://www.powells.com/biblio/7-9780970961853-1
I think that one is missing about a hundred pages. The one I have in my attic is about an inch thick. The photos of the German documents, in German, of course, aren't in the unedited edited one.
The only text I found interesting was the method of controlling the V2 guidance. '51? I thought it was '47.
I don't think the magnetic bridge rectifier is in the latest, EMDevices found a document from the 1880's describing that and shared it.
Magnetic switching, not spoke of commonly but used in inductive reactive load banks (added to resistive load so test can be ran somewhere beside unity P.F.).
Nothing in the book will make OU.
I want the one from the Army that details the same functions using dielectric amplifiers. It had the same big red letters ink stamped on the cover - back in the '70's. Never got to read it. Didn't have the 'Need to Know' :(
Quote from: WaveWatcher on 2010.06.28, 02:30:36
I guess this means we are two of the biggest geeks ???
Edit>>
Oh! On your 2500V PS schematic, above... you got away without balancing resistors across the caps? For me, that is like (doing you know what) into the wind. I had a whole bank go off like a string of firecrackers.
Good point - the diag. is not a complete build diag. its missing and rf filter , fuse on the 120v side, balance / bleed resistors , and a hf choke on the output side to kill anything coming back.
And it would be quite spectacular if it unloaded :o
OK
MOT's are readily available and this puts it in the hands of more people.
Dumping 1500v to a high impedance load of say 250uh takes a few ma.
I had hoped to avoid the variac and go with some sort of oscillator for the MOT primary using MOSFET's or transistors.
You all know where this is going, so lay it on me.
Like a pwm driving a mot?
The mot can really suck up the amps.
I have never seen that done
you will need to limit the current - or even put another mot in line with the 120v side with its secondary shorted to act as a magnetic ballast to the main mot..
You could try a (pwm) dimmer for a low voltage lighting magnetic transformer - those are good for about 6-10 A - must specifically say for magnetic transformer!
Like this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180493912689
here is the mfg page for the above unit:
http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?item=22329§ion=13608
or
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230492024291
Sounds like you ultimately need a 500w 1500v inverter circuit
Quote from: WaveWatcher on 2010.06.28, 03:33:46
I think that one is missing about a hundred pages. The one I have in my attic is about an inch thick.
Apparently the bibliography was over 40% of the original document, and was removed in this issue. It can be purchased as well. These may be the missing pages to which you are referring.
.99
Quote from: darkspeed on 2010.06.28, 05:53:50
Sounds like you ultimately need a 500w 1500v inverter circuit
500W ? Ouch!
Quote from: poynt99 on 2010.06.28, 12:15:00
Apparently the bibliography was over 40% of the original document, and was removed in this issue. It can be purchased as well. These may be the missing pages to which you are referring.
.99
Probably. The first part read more like a history with some short stories inserted. Right now, my attic is probably about 130 deg. F. I'll wait till it cools down and dig for the book.
@WW
That's the problem with attics. Either too hot or too cold and when it is just right, you don't feel like go'in up, so you say "ahhhh, maybe next year". lol
Yea. I had a computer monitor go on the fritz a couple of years ago. I knew I had a monitor in the attic.
After an hour of digging I found it. It was a 10" Hercules amber monochrome NIB >:( I didn't have anything to test it on.... Bah!
Well it looks pretty enough ;D
but will it work.
Still a little to do yet.
Looking spiffy, Peter!
I'll be back up and running sometime today at about 2kv (give or take)
I'm using this driver circuit with an IRF510 (saving my 840's) and running it through a 12v transformer flipped around to get 120 out to a MOT - thus it will be adjustable and current-limited and much lower current than normal which was to high anyway. Will run it off my adj power supply. You can run other transformers off it as well and even flybacks.
That looks really great.
At the risk of sounding really stupid (won't be the first time). Would this Avalanche circuit do about the same thing as a post I made some time ago about an idea I have concerning a Voltage Grabber Circuit animation I made located here;
http://purco.qc.ca/ftp/Wattsups%27%20stuff/voltage-grabber-circuit-VGC/wattsup-VGC1a.gif
Basically it would use several stages, charging small capacitors one by one, then putting them in series to discharge them all into a larger capacitor, then doing it again and discharging into another larger capacitor, etc.
Sorry if maybe this is off topic.
Looks perdy Peter. ;)
Hope it works as desired.
.99
Thats looks great!
I like the quick connect pins for the incendiary devices ;D
Cheers Guys
ds ;D
Wattsup
Each stage forms part of a pulse shaping circuit and has charged capacitors which release their energy in a controlled fashion thus in theory giving me a 1-9 stage pulse width and energy controlled pulse, hopefully more controlled than a piece of coax, but this is new ground for my poor digital brain so it's a steep learning curve for me and it may not work as intended yet.
Ok I must have missed it - what is the goal voltage / amperage / speed ?
Impulse current maximun is 60A pulse settable in 9 stages from about 12 amps per stage.
Can use up to 5 smmt417's in a string each is capable of over 300volts each so max pulse voltage is 1500V-1800V
Pulse width if my guesstimate is right should be between 40-120nS again settable.
What are you using for a power supply?
The power unit was documented earlier in this thread, you need to realize i realtively slow charge a string 0f 100pf caps and inductors, and when the avalanche transistor fires it dumps the energy into the coil at short high impulse amperage.
http://www.overunityresearch.com/index.php?topic=307.msg3878#msg3878
http://www.overunityresearch.com/index.php?topic=307.msg4025#msg4025
(http://www.overunityresearch.com/index.php?action=dlattach;topic=307.0;attach=1847)
Peterae,
Just an observation of that fine looking layout...
Every time you pulse a coil it will induce a reverse current in the coils before and after it - maybe in the other run, as well.
To minimize this, you can only have 6 stages, unless you're going to fire in a sequence that allows each previous coil to aid the next fired?
As usual, very interesting designs!
The whole point of the cap/inductor chain is to spread out the discharged energy over a longer period of time to form a square pulse of longer duration, just like G uses a length of coax to control his pulse.
I think the coils as they are should aid each other hopefully, but i maybe wrong.
If they don't, you could try having a decreasing pulse width for each newly fired coil. The idea there is for each previously fired coil to 'make way' for the next coil in the firing sequence. You should see maximum voltage output this way. Should be the same result as a saturated core pulse former.
Cannons firing cannons ;)
Sorry Peterae - i didnt see that - so your doing this as a one shot.
If you had a lot of hv in reserve capacity how fast could you cycle the output stage?
Quote from: darkspeed on 2010.07.01, 23:07:20
Sorry Peterae - i didnt see that - so your doing this as a one shot.
If you had a lot of hv in reserve capacity how fast could you cycle the output stage?
It depends on the resistor chain and how much juice the psu can throw into the cap bank.
I wont know for sure until i fire this up, but it will also be a function of how many stages i am using at the time.
I abandoned the MOT idea for now - too inefficient
4kv supply is up and running, but low on time until tomorrow
Boom!
big flash in my 0-60vdc 0-6A supply and then my 4kv supply lit on fire - arc and sparks everywhere - my kid standing right there "Wow Dad! That's cool!
Variable supply is toasted. It's a Lambda LK 345A FM - probably worth fixing.
Looks like just the transformer in the 4kv supply is dead - variable supply was set at 2v and went supernova.
I was just starting to get the arcs to insulated objects when it went. Have an avalanche transistor stack of 20 2N5551's.
One step forward, two steps back...but it was starting to work.
Wow.. sorry G....
Have you ever built a Terry Filter? Maybe a consideration? Do you have an overshoot gap to dump anything that is way over what you expect in voltage?
just the way it goes in the tall grass...ROFLMAO!!!!
Dam Sorry to hear that G
Was this using the circuit i built with the 555 and the LM339 and 510 fets to drive the transformer.
Was using a 4kv neon supply (little one) running off my variable bench power supply.
I found that outlet is not grounded. Anyway, something in the supply blew - saw a flash - voltage on supply pegged the meter (lost regulation) and smoked the transistor in the 4kv supply.
I have a couple of other supplies but they are 500ma and 300ma and I need 1A - Soooo - I pulled out an old PC pwr supply an it has one leg that is 12vdc at 1A - perfect.
Got to fix that outlet first though.
Hate to lose that supply, but I was getting the polarization current and that shows that it was working. Also was able to arc after the oil so was getting some good voltage through the coil.
The 1000v limit happens to also be the minimum for detecting the polarization current and I recommend as high a voltage as you can get. Took 20 2N5551'a to handle the 4kv.
Hey - quick question - the capacitors (.01uF 20kv ceramic - 4 of them) on the output of the 4kv supply were really "squeeling" and I am wondering "why"?
If it s squeeling it is most likley punched through
When you unloaded your supply - big volts - big amps - many turns - the pulse on the output side may have been 40kv 50kv?
can you run your supply from a battery?
Quote from: darkspeed on 2010.07.04, 17:34:27
If it s squeeling it is most likley punched through
When you unloaded your supply - big volts - big amps - many turns - the pulse on the output side may have been 40kv 50kv?
can you run your supply from a battery?
I thought one of them may be leaking, but they are rated at 20kv and I was only using 4kv and only about 15 or 20mA I was running off my supply at 12v and 1A. The caps are after a full bridge rectifier too. Funny...
(I have a big hand-rolled .005uF "Ganga Mon!" cap with about 10 layers of poly in it that I bet won't squeal.)
Just back from the Shack and will replace the 2055 tranny in the 4kv supply and see if that is all that smoked..fingers crossed...got a 12v transformer too and regulator to build 12v 1A supply.
Your squealing could have been from coronal discharge outside the caps. If it squeals again (with a slow ramp up of volts), turn the lights off and let your eyes adjust. You should be able to see it.
they only squeal when pulsing the load
Is this from low impedance pulse into high impedance load?
EDIT:
replaced transistor (was a 3055 not 2055) and pulled a new wire from electrical panel to fix outlet.
Now, where was I?
EDIT:
pulsing again at 3.5kv ...
I'm ready to start testing now with 2 stages of Transistors @ 600v
First thing there's no way i am going to scope my coil because both sides are @ 600V and i dont fancy the earth lead of my scope sitting at this higher voltage(Scope is connected to usb of my laptop also), to start i will use my bifilar pancake coil, i can scope the 2nd bifilar coil which will give isolation and hopefully show me whats happening.
I use a resistive divider and other means of detection.
My probes are x100 so have the divider built in but because both sides of my coil sit at 600V i dont want to connect my probe earth to it.
Anyway seems i have trouble, the 2 transistors drain my psu and shut it down.
When i measure the base+emitter(which are shorted) to the collector of that transistor on a diode meter i get a reading of 0.3 which a normal diode would give me 0.66, on ohms i get about 730 Ohms, well there's no way i could poke 600volts on the collector and hope it stays up, so what did i miss.
Well i guess it's obvious that the transistors died, maybe 600volts was too much for only 2 transistors in the chain, anyway looks like i'm going to be joining G, i have ordered a pack of 50 2n5551 transistors as these smt417 transistors are too expensive to burn.
Quote from: Peterae on 2010.07.08, 14:07:36
My probes are x100 so have the divider built in but because both sides of my coil sit at 600V i dont want to connect my probe earth to it.
Anyway seems i have trouble, the 2 transistors drain my psu and shut it down.
When i measure the base+emitter(which are shorted) to the collector of that transistor on a diode meter i get a reading of 0.3 which a normal diode would give me 0.66, on ohms i get about 730 Ohms, well there's no way i could poke 600volts on the collector and hope it stays up, so what did i miss.
They blow when you have to much current and those only need something like 100uA to avalanche. 600v doesn't matter as it can take thousands of volts if the current is kept low.
Quote from: Peterae on 2010.07.08, 14:53:32
Well i guess it's obvious that the transistors died, maybe 600volts was too much for only 2 transistors in the chain, anyway looks like i'm going to be joining G, i have ordered a pack of 50 2N5551 transistors as these smt417 transistors are too expensive to burn.
2N5551's require 2mA to avalanche.
Something i dont understand with the FMMT417 Vcbo is 320V but the Vceo is only 100V, now if i have 300 volts between my base and collector that should be ok but the emitter is also connected to the base on each stage bar the first and therefore surely i am going over the Vceo by 200V ::)
OUCH i also didn't realize you have to watch the base current that much.
http://www.diodes.com/datasheets/FMMT415.pdf
Quote from: Peterae on 2010.07.08, 15:56:48
Something i dont understand with the FMMT417 Vcbo is 320V but the Vceo is only 100V, now if i have 300 volts between my base and collector that should be ok but the emitter is also connected to the base on each stage bar the first and therefore surely i am going over the Vceo by 200V ::)
OUCH i also didn't realize you have to watch the base current that much.
http://www.diodes.com/datasheets/FMMT415.pdf
avalanche is determined by the Vcbo: see attached
OK G i was getting confused.
Also, notice that the avalanche voltage depends on several things. (look at the charts)
I decided to start a fresh with the Avalanche Pulser after i determined that the efficiency of a Saturable pulse shaper was only a few % efficient.
Using the details in this doc posted by Grumpy
http://icecube.wisc.edu/~kitamura/NK/Flasher_Board/Useful/research/RSI00308.pdf
I built the transistor tester circuit Figure 1.
but used my digital mono and a hex inverter to drive the stage.
Here's a proto test of the stage, in the final pcb i will build the marx device with plug in 900v modules
The circuit should allow me to evaluate the performance of the bag of 2N5551 transistors i bought from china.
I am still testing things right now, here's 2 pulse shots,
One with a base capacitor of 10nF and one without
The one without was a lower voltage Peak but enabled me to drive it with a shorter pulse
The one with had a higher peak switched voltage.
Hopefully when i switch away from standard caps to a enamel wire wound cap i should get a more square pulse.
A couple of pictures of a 3 2N5551 transistor stack, 300pf cap,340K feed resistor. 47 Ohm load resistor, supply was 900V
Green Trace is across 47R load resistor
Yellow trace is on collector of the top transistor
I am almost in business
I tried my cap idea by winding enamelled wire axially along a length of wire to form a capacitor, although my cap meter measured 100pf i could not get it to work properly so have given up on the cap idea for now.
This means i need to buy some 200pf caps :(
Anyway i have etched 7 Marx modules , 2 driver boards and 2 output boards, i already built sometime ago the 2 900V switched psu's
At the moment i have used 100pf caps and with a 47R resistor load the Marx boards do not work(The pulse doesnt get bigger with more modules GULP), as a temporary test i loaded with a 680K resistor and this verified they do work, once i get the caps i can try a coil.
A photo of the finished boards some still need making up
3 Scope shots of the pulse across a 680K load resistor (Yellow Trace) with 1,2 and 3 modules stacked as you can see each Marx module does indeed add to the final output pulse amplitude.
Good stuff Peter!
You're becoming quite the "marxman" ;)
What's next in your "sights"?
.99
QuoteYou're becoming quite the "marxman"
;D Thanks Darren
Well once i have 2 of these working i will try nS phase shifting the 2 pulses connected to a coil, but primarily i want to use the 2 channels for injecting pulses into a closed toroidal ring and see what sort of effects i can see.
Here's the circuit, incredibly easy to build and i am yet to find a failed transistor and have tested over 20 of the 2n5551 from the 50 i ordered from china.
I tested my 2N5551's for avalanche point and at Zener breakdown and found that any that were noisy at Zener had higher resistance at avalanche (as evidenced by lower pulse), so I put those aside. May not really matter though.
Hi G
I have not seen much variation in Avalanche pulse size really so far, i did initially run some tests looking for the avalanche voltage and this did seem to vary quiet a bit.
I still do not know how a low impedance coil will affect the pulse loading yet, but with a resistor even a 1K starts loading up a 3 stage setup.
When i upgrade to 200pf caps hopefully i will be able to pump twice the impulse energy and increase the loaded peak amplitude.
Here's 2 pictures, 1 with a 1K and another with a 50K load using 3 modules stages.
Looks like i am getting a fall rate of about 18nS for the 1K load @ 740V pulse
and for 50K the pulse is about 1100V
Grumpy,
The .PDF in posted Reply #14 has no "root" or it's invalid. I get a blank black screen for an output of the .PDF
--Lee
Looks like it was one of those files that got damaged about a year ago, It will need to be re uploaded by Grumpy if he still has it.
Okay, thanks. He might have another file, or not?, that has a circuit which does something similar to the original? In any event, I like to see it.
--Lee