Rosemary Ainslie circuit demonstration on Saturday March 12th 2011

[Rosemary Ainslie]

...All the scope traces I've seen her present show an input (battery) voltage with over a hundred volts of AC at over 1MHz on it.  That can't be right.

Well then.  It seems then that cHeeseburger knows that they're wrong.  To the best of my knowledge there is nothing unfolded in these waveforms that are not in line with previous replications.  I distinctly recall the evidence of AC waveforms - in one form or another - on every single test either on own circuit or on replications.

There must be some large inductances or long wires being used in the battery circuit.

Indeed.  There are.  They need to span a large bank of batteries. 

No decent battery would have such a high impedance on its own as to allow such a large AC voltage swing.  She says her batteries are brand new and very high quality types.

Here cHeesburger is wrong.  I have never claimed that the batteries are high quality types.  I've simply shown the battery brand.  And they most certainly ARE NOT brand new.  They've had a known shelf life for 9 months prior to their use and they've been used rather extensively for the last 5 months.

Second, she recently showed her latest circuit and parts values.  I noticed that the shunt being used to measure the battery current flow is made up of several quite long ceramic wirewound resistors.  She states the combined inductance as being 130nH or something like that and 0.25 Ohms combined parallel resistance.  With an oscillation frequency of over 1MHz, the inductance is the predominating part of the shunt impedance (by a huge margin) and the shunt impedance will be adding a large phase shift and showing much larger voltages across it than a pure 0.25 Ohm resistor would.

Here cHeesburger makes his first valid point.  Indeed.  There is no question that there is inductance.  Add that in.  And IF that inductance and impedance is responsible for that wild oscillation and any consequent phase shift - then I would strongly recommend that they be retained for ALL applications.  It's highly exploitable.  Whatever is finally determined to cause that osciallation needs to be factored IN not OUT.  Self-evidently it results in a waveform that PERFECTLY reinforces itself.  And that means that in those wildly swinging oscillations - which persist and would probably persist as long as the gate voltage is negative - also relies on those properties of the shunt.  If, however, the oscillation resulted in a 'cancelling out' that it all decayed into a sad little flat ringing trace - then indeed - there would be no value to that oscillation.   

So, when the wildly oscillating AC "battery voltage" is multiplied (sample by sample) within her oscilloscope math by the phase-skewed voltage across her inductive shunt, the results will be totally unrelated to the actual DC-equivalent average power.

Here cHeesburger's logic becomes hard to follow.  That 'phase-skewed voltage' persists over time.  And it seems that it would persist as long as a negative charge is applied at the gate.  There is no question that it adds to the system.  Indeed.  If you also factored in the increase to the Ohmage of the shunt - then it would add even more to the system than is currently being shown.   

Measurements made on this deeply-flawed basis could quite easily show a negative (reflected) power being returned to the battery when such was not actually the case at all.  Or they could easily show zero (or close to zero) power being drawn when, in reality, significant power was being drawn out of the battery.

Nothing is 'deeply flawed' here other than cHeesburger's conclusions.  I think what we've shown - conclusively - is that it is possible to generate two opposing cycles of current that perfectly reinforce each other with a zero discharge of energy during that oscillation.  What is also proved is that this results in a sustained dissipation of heat at the resistor element.  Much desired.

I would suggest that a simple low-pass filter be applied on both the shunt voltage measurement and the battery voltage measurement in order to find the actual DC equivalent input power.  This will eliminate the false readings associated with the phase shifts and inductive parasitics in the circuitry and reveal quickly the actual DC net power flow either out of or into the battery.

I would suggest that cHeesburger is determined to deny us the benefit from those circuit components including the wiring.  I'm reasonably satisfied that if we, indeed, eliminated the inductance on the circuit - including the wiring - then we would, also, indeed, lose all that advantage.

This has been suggested to Rosemary many times by many folks on several forums but, so far, she refuses to do it and has ignored all such advice.  Adding fifty cents worth of R and C to form a simple first-order low-pass filter and then just measuring the results with a DMM is all that is needed.

While I persist in ignoring cHeesburger's advices I could do nothing to stop him from doing his own tests.  Perhaps he should take the trouble - before commenting so freely.  And I'm somewhat disinclined to follow his advices when they're evidentially aimed at negating the very advantages that the circuit requires. 

It's much easier than trying to change the batteries to smaller ones or run using a capacitor or DC power supply.  It could be done in five minutes at almost no cost and would give results that are far more ACCURATE AND TRUSTWORTHY than doing math on 8-bit scope traces which are wildly swinging around with huge imposed AC voltages far beyond what would appear across any decent battery or a pure resistive shunt.

Here cHeeseburger is indulging in a standard of comment that really does NOT deserve and answer.

This technique has been used for decades and is well-known to any engineer who has tried to make accurate DC-equivalent power measurements on circuits that have pulsed or high frequency AC current draw.  Multiplying phase-skewed values derived across inductive shunts and batteries hooked up with long wires and no bypass capacitors has no chance of ever yielding accurate DC-equivalent power numbers.

From where I sit it seems that cHeesburger wants to retain the status quo and deny the rights to explore this waveform.  I'm sure he's free to do so.

P.S.  Hooking two or more MOSFETS directly in parallel is well known to cause parasitic oscillations that are, in fact, difficult to get rid of when they are unwanted.  Rosemary is using a function generator and has liberally applied DC offset voltages to the pulse output and tweaked that offset to enhance the oscillations, so using a 555 timer circuit will probably not work the same way at all.  Anyone desiring to replicate should forget all about the earlier Rosemary Ainslie COP 17 schematics and use the latest circuit shown in her blog report.  Don't forget to use at least ten feet of wire to hook up the batteries!  And NEVER add any bypass caps ANYWHERE!  Oh...and use a long twisted pair of small-guage wires to run from the signal generator to the MOSFET gates.  That extra inductance and impedance mismatch can get a solid oscillation going even with a single MOSFET.

I think that's about right.  It seems that cHeeseburger has indeed found the recipe.

Rosemary

[Rosemary Ainslie]

And with reference to this post.
I'll comment here because some of these points are good.  Some not so good.

I believe the evidence points to the idea that Rosemary has chosen option B a long time ago.  To expect that any thinking person would accept her claims without even a statement from her regarding her measured input power seems just nuts to me.

Input and output are measured across the shunt.  The input is that voltage above ground the output is that voltage below ground.  It is the difference that we highlight.  And in as much the there is more out than in - then one may conclude that there is a zero loss to the battery.  This is evident in the scope traces and the spreadsheet analysis confirms the indications that are shown in the math trace.  That much is reported. 

What she and everyone else seems to have blindly overlooked is that the measurement of input power is plagued with the exact same complications of inductance-based phase shifts and power factor complexities that were deemed too difficult to overcome on the output side.  There is no difference!

'blindly overlooked'.  Strong words here by cHeesburger. Golly. In point of fact these have NEVER been overlooked.  But it intrigues me that he needs to claim this.

Yet, thosands of forum posts and blogs and hundreds of thousands of words and arduous special arrangements to borrow fancy oscilloscopes and try to lern to use them and bitter heated arguments have since ensued all regarding the correct measurement of the inpuit power.  To date, no numbers have emerged!

IF indeed, cHeesburger had been following all this then he has failed - rather sadly - in understanding the actual argument.  To the best of my knowledge there have been no 'bitter arguments' about the correct measurments to apply.  And no person on our team required any special training to get their heads around those DSO's.  I wonder if cHeesburger is trying to put a slant on things - and to what end? 

All I am suggesting is that simple techniques that in no way alter the circuit operation, i.e. using a simple RC low-pass filter on the battery voltage and current shunt voltage will give the exact same advantage that using the thermal integratiion method of obtaining equivalent DC power provides in the output measurement.  Even better, there is no need for a "control" or comparison test at the input side as must be done on the output side.

Here he is, emphatically, wrong.  Any filters applied will most certainly block that required resonance.

The only reason to use an oscilloscope in this whole exercise is to "tune and tweak" the circuit for whatever characteristics Rosemary thinks are best.  Once that is done, the scope should be turned off and forgotten.

cHeesburger is clearly NOT aware of the fact that the value of those DSO's is in their bandwidth capabilities.  Else the measurements would be ENTIRELY suspect. 

Measure the average DC-equivalent input voltage and current using a good DMM and the RC filter.  Multiply.  End of story!

I trust that cHeeseburger realises that there is nothing holding him back from applying his own tests here.  Then I'm sure he's free to apply whatever measuring technique he chooses.  Whether or not one relies on his methods of measurement would need to be determined by our experts.  Thus far it is experts who have guided us in our measurement protocols. 

Rosemary

[Rosemary Ainslie]

Guys, may I remind you all.  That oscillation - that thing that is always factored out of switching circuits - it's usable.  The proof is in this.  We can set the duty cycle that it switches once ever 2.7 minutes.  Then for about three minutes we get a sustained oscillation.  During that period there is no evident loss of heat from the element.  There is also no measured loss of energy from the supply.  On the contrary.  The battery voltage is seen to climb.  Interestingly it only climbs to its previous high.  Then it stays there.

Yet.  If we disconnect the circuit for a period of three minutes there's a dramatic cooling evident at the resistor.  Why do the implications of this not grab you?  There is no error in the measurements.  Unless from here on we must ignore measurements. 

That's what I was rather hoping you'd all consider.  We've been throwing away an advantage in switching circuits at our cost.  And if we persist in applying 'standard' age old tried and tested techniques then we will NEVER find out new things.  More to the point.  We are now doing so at our peril.  It is a truth that this technology may yet confront any need to expand nuclear programs - at LEAST.  Surely that's a good thing?  This technology is scalable and it hardly needs modification to apply it to our household hot water requirements.  That takes up a HUGE amount of energy.  And there's no noise.  Previous switches had noise and it was really problematic.

Rosemary

[MrMag]

Rosemary,

I have got to give you a lot of credit. You are a very patient person. Most would of stopped posting by now. I haven't followed your posts or blogs but I do pop in once in a while to see whats going on. It seems like you are always being asked the same questions. In the other forum by hambugger and over here by cheeseburger and others. You must be doing a lot of cut and paste.

Keep up the good work and I wish you success in your circuit.

[neptune]

First of all , many thanks to nul-points and FatBird for their excellent replies to my questions . It is all much clearer now . This circuit is , in essence , a very simple circuit , but as allways the devil is in the detail . I feel that Rosemary has made some very valid points regarding measurements . The thing that convinces me of the reality of the phenomenon , is the 2.7 seconds of oscillation between pulses . We all have our own ideas on this , and I urge everyone to keep cool . You cant really argue with Rosemary when she says that everyone is free to choose their own power supply , including caps , and make their own measurements . Sadly , failing eyesight prevents me participating , but I follow all points of view with interest .At this stage the problem is that few people have test equipment of high enough quality to replicate this .I have just noticed something else . Cheeseburger says that Rosemary has applied "voltage offset" to the output of the function generator she is using .Does that mean moving the zero line so that the off puses become negative? If it does, then that is how the gate becomes negative