Rosemary Ainslie circuit demonstration on Saturday March 12th 2011

[cHeeseburger]

I think,
as long as the function generator is still used these
measurement problems persist and the circuit is not very useable.

So better all replicators try it with the 9 Volt battery first
and try to get it running in this oscillation mode
without any function generator.

And please use low or almost zero inductance shunts, if you measure
the current as what Hummbugger has posted is true, that the
inductance of the shunts can mess up your scope shots.

Stefan is correct here.  Rosemary has explained that she sees very large spikes in the shunt (reported by her to be +10V and -30V in amplitude) at the moments the function generator switches.  These come from the signal generator trying to suddenly change the voltage on the huge gate capacitance and are further hugely exaggerrated in amplitude by the fast-changing nature of the resulting current spike and the inductance of the shunt.  They are only present in the gate-current loop and are not present in the battery loop, as I explained.

I believe it is these spikes that she agrees are far more negative than positive which cause her scope average on the current trace to often show a small negative value (millivolts) which is then misinterpreted as battery charging current.  This only shows up in the scope-averaged current at the low-power operating level because the operating currents are very small, so these spikes throw off the average.  In the higher power mode of operation, these spikes still subtract from the measured average current, but that current is much larger in this mode so the overall average still always shows as a positive number.

To get a true measure of the actual battery current, either the function generator must be eliminated (as Stefan suggests) or the shunt must be moved out of the gate circuit loop and placed where it sees only battery currents.

In either case, the shunt must have an inductive reactance  that is far below the shunt resistance at 1.5MHz or the scope sampling and multiplying technique cannot be used due to large phase shifts in the apparent current versus the true current at any given sampling instant.  This is extremely difficult if not impossible to do, since even the length of a one inch straight wire will add 20nH to the shunt, causing many degrees of phase shift.  Even the very best "non-inductive" shunt resistors will exhibit several nanohenries of inductance and skew the phase at 1.5MHz significantly.

But all is not lost!  Even with a highly inductive shunt, as Rosemary is using, the true average current in the shunt is easy to obtain...without even using a scope that features averaging!

Recall my demonstration from an earlier post in this thread where I showed a 0-2A trapezoid wave and the effects on the voltage displayed that a large inductance would have.  The true average current in that setup was +1A and ramped evenly back and forth between zero and +2A, never going negative at all.  Yet the inductive voltage was well below zero half the time, whenever the true shunt current was down-ramping toward zero.  See the first picture, reproduced here for your convenience.

Now we take that same circuit, doing the same thing, with the same values (printed out for you on the second picture) and add two little simple  RC filters to average both traces.  Guess what!  Both traces now show the exact true average current of 1 Ampere positive (50mV on a 50m Ohm shunt resistance).  They are exactly superimposed.  So now we know the magnitude and direction of the actual DC equivalent average current flowing even though we have measured it across a highly (grossly in this case) inductive shunt resistor!

Humbugger

[Rosemary Ainslie]

Hello guys,

This thread is really going along well.  I've just been over the last points and delighted to acknowledge that I do not understand the significance of different caps and different shunts and on and on.  All exactly as it should be.  So.  I'll be leaving this thread to you guys.  I know it's in very capable hands with Neptune and Sprocket - and even Paul.  And I have much to do elsewhere.  I'll post here when I get more results. 

Just bear in mind the simple fact that - like the gold in 'them thar hills' there's energy in those spikes and even more in those oscillations.  But.  It releases heat - which is not the motive energy that you guys traditionally look for.  And Neptune, if it's taken a long, long time to get here - just think of our 'kick off' position all of 12 year ago now.  Then it was widely considered 'absurd' to try and return energy back to the source.  Paradigms are definitely shifting.

And Magzy - I'm hoping that you'll do us the favour of posting your results here on those tests.  They're BRILLIANT.  Every bit of evidence helps.  And such a clean way of showing it.

Nice thinking everyone.  Hopefully you'll all find that 'extra' in some kind of variant of this circuit.  And Stefan, many thanks for the input and - more to the point - for keeping this thread on topic.  I am not sure though that the inductance/impedance thing is that significant.  If you factor in for this - then the returns are even more extreme. 

I need to focus on getting my circuit up and ready for more demos.  And I need to focus on some much needed editing on my blog.  I'll certainly post here when I've got news and/or results.  I think I'll need a fortnight or so.

Kindest as ever,
Rosie

added

Just had a diagnosis.  2 of the MOSFETs blown.  Interestingly it's enough to block that oscillation.  Seems that they all need to work but still not sure if all 5 are required.  I'll let you know.  They're to be replaced - hopefully - by Monday.

[neptune]

Hi all . Mainly posting to keep this thread on the front page . Rosemary , sorry to hear your leaving us for a bit but the demo must take priority of course . If you can , let us know what will be different this time , apart from the audience . Maybe a non inductive shunt perhaps ? Regarding the dead mosfets , I would say it depends on their actual faults . If one or more went short circuit , it would no doubt kill everything . I personally think two would work , as this parasitic oscillation in parallel mostfets has been described  as a "push Pull" effect . One would think that more mosfets would be better for higher power circuits . I am sure we all wish you the best possible luck with the demo , and look forward to the results .

[nul-points]

added

Just had a diagnosis.  2 of the MOSFETs blown.  Interestingly it's enough to block that oscillation.

looks like that link was correct about possible damage to the MOSFETS

wonder if it's correct about the other 2 things i picked out from it, too?

  http://www.overunity.com/index.php?topic=10407.msg279486#msg279486

all the best
np


http://docsfreelunch.blogspot.com

[Rosemary Ainslie]

Hi all.  Just seen that Humbugger is still posting.  Please note that any attempt at 'averaging' is absolutely NOT acceptable measurement protocol.  I realise why it's so urgently advanced.  Also.  The non-inductive shunt has been tested and shows not the SLIGHTEST difference.  Also.  There is - indeed - a measurable 5 watts at the gate.  This RETURNS to the FG.  It does not COME from it. 

I think the most critical measurement, as has been rather obsessively poynted out - is the waveform at the terminal of the battery.  Early indications are that this is consistent with the measurements at the test point on the apparatus.  But to finalise this - I'll need to get that apparatus returned with the MOSFET's replaced.

Just  word of caution.  Please do NOT assume that Humbugger's opinions are anything more than that.  In fact it  is my opinion based on the inappropriate and anxious need to deny EVERYTHING related to this - not least of which is my own 'idiocy' as he refers to it on OUR.com - that he is rather anxious to kill all interest in this technology.  And I wonder at that need.  We may yet find that there's nothing in this experiment.  But NOTHING can be concluded from AVERAGING ANYTHING AT ALL.  Measurements of power is based on vi dt.  That's it.

Kindest regards,
Rosemary

Added.  While Humbugger continues to post - then I will definitely need to 'hang around'.  Pity.  I've got so much to do.  Anyway.  Hopefully I'll manage to diffuse some of his negativity.