Testing the TK Tar Baby

[MileHigh]

TK:

There is a test that you can do to confirm this.  This would have to be verified on the bench because the signals will probably be quite low level and some tweaking may be required.

Start off by making a small rectangular wire loop, say 3 cm x 2 cm and 25 turns.  You can use very fine wire.   You then place this alongside the main wire so that you can sense the current flow.  This test may run better with a small ferrite bead placed through the main wire and through the rectangular loop but I am not sure.  That would perhaps give you a stronger signal but the losses and possible bandwidth issues in the ferrite bead may cause some problems.

You connect the output from the rectangular loop to your scope probe.  The EMF produced by this loop will be the first derivative of the current flow.  That will give us some very important information.

Let's imagine two simplified cases.

In first case imagine there is a pulse of current that starts at zero, rises to +1 amp, then is steady at +1 amp for a while, then it starts to decrease, passes through zero, continues to -1 amp, stays at -1 amp for a very short time, the rises back to zero.  In other words, this is a simplified description of what we apparently see through the CVR right now.

In the first case we should see the following output from the current sensing loop:  a positive pulse, then zero volts, then a negative pulse followed by a positive pulse, then zero volts.

In second case imagine there is a pulse of current that starts at zero, rises to +1 amp, then is steady at +1 amp for a while, then drops to zero.  In other words, this is a simplified description of what I believe is actually happening - there is no reversal of the current.

In the second case we should see the following output from the current sensing loop:  a positive pulse, then zero volts, then a negative pulse, then zero volts.

You can see the difference between the two is that in the first case there is an extra positive pulse output from the current sensing loop at the end of the pulse cycle.

If the current really is reversing then you would have to see the second positive pulse.  If there is no second positive pulse then you have proof that the current is in fact not reversing.

MileHigh

[verpies]

TK:

I think that I have finally figured out the explanation for the apparent negative current flow as indicated by the CVR.  This has been bugging me for some time and for all I know Poynt already explained it a long time ago indirectly.  For a while I thought that the current was actually reversing and I was trying to explain that.  Now the answer seems so simple.

Certainly, assuming that you and others concur, this spells DOOM for Rosemary's claim, not that I ever doubted that her claim was doomed before.

It all goes back to our good old friend the wire inductance.  When the MOSFET is switching off, the energy stored in the inductance in the wire (including the CVR) between the MOSFET source and the battery negative terminal has to discharge.  During this discharge you have one end of the wire anchored to the ground potential of the battery and the end of the wire at the MOSFET source is "the end of the EMF whip."  Relative to the battery ground terminal, and working "backwards" or counterclockwise through the wire, the potential increasingly drops as you move along the wire, and is at maximum negative potential at the MOSFET source.  The energy stored in the wire is dissipated in the MOSFET itself.

So, what appears to be "negative current" is really just the "EMF whip" dropping in potential as the wire inductance discharges.  The "far" side of the CVR (relative to the battery negative terminal) is simply along for the ride and that shows up as negative potential on the scope trace.  So this negative EMF due to the wire inductance discharging appears to be reverse current through the CVR but in fact it's not the case.

Does this make sense to you?

So this means that the current never reverses in direction and there is never any energy being returned to the battery.  It's all a fake-out.

In the next posting I will discuss a test to confirm this.

MileHigh

But the inductance of the wire is very small.  It would matter only at very high frequencies. 
What are they precisely in this device?

[MileHigh]

Verpies:

The frequencies are very high, they are from the trailing edge of a square wave in a sense.

TK:

I got my inspiration from a clip by Itsu.  He has a totally unrelated MOSFET switching circuit with trailing-edge negative spikes on his CVR waveform.

http://www.youtube.com/watch?v=eZWa-NSQWBc&feature=plcp

The waveform from 5:00 into the clip is shown below.  It's the same thing for his circuit; there is no reason for the current to apparently reverse direction but we clearly see the negative CVR voltage on his scope.

MileHigh

[Groundloop]

TK:

I think that I have finally figured out the explanation for the apparent negative current flow as indicated by the CVR.  This has been bugging me for some time and for all I know Poynt already explained it a long time ago indirectly.  For a while I thought that the current was actually reversing and I was trying to explain that.  Now the answer seems so simple.

Certainly, assuming that you and others concur, this spells DOOM for Rosemary's claim, not that I ever doubted that her claim was doomed before.

It all goes back to our good old friend the wire inductance.  When the MOSFET is switching off, the energy stored in the inductance in the wire (including the CVR) between the MOSFET source and the battery negative terminal has to discharge.  During this discharge you have one end of the wire anchored to the ground potential of the battery and the end of the wire at the MOSFET source is "the end of the EMF whip."  Relative to the battery ground terminal, and working "backwards" or counterclockwise through the wire, the potential increasingly drops as you move along the wire, and is at maximum negative potential at the MOSFET source.  The energy stored in the wire is dissipated in the MOSFET itself.

So, what appears to be "negative current" is really just the "EMF whip" dropping in potential as the wire inductance discharges.  The "far" side of the CVR (relative to the battery negative terminal) is simply along for the ride and that shows up as negative potential on the scope trace.  So this negative EMF due to the wire inductance discharging appears to be reverse current through the CVR but in fact it's not the case.

Does this make sense to you?

So this means that the current never reverses in direction and there is never any energy being returned to the battery.  It's all a fake-out.

In the next posting I will discuss a test to confirm this.

MileHigh

The negative current comes from the inductive part connected to the Drain of the MOSFET. When the MOSFET turns off and the charged
inductance changes polarity then there is a path through the internal MOSFET body diode through the diode and through the CSR
and to the negative terminal of the battery. The inductance in the CSR is probably so small that it does not matter anyway.

GL.

[MileHigh]

Groundloop:

I disagree with you and in addition I barely understand what you are saying.  Your description is inadequate.  If you want to try again with a longer and clearer description that would be nice, possibly with a diagram.  I believe that English is not your first language and I can understand how that can make it a bit harder.

I am convinced that the current never reverses direction at all, and the whole time Rosemary and the NERD team have been chasing after an illusion.

MileHigh