Rosemary Ainslie circuit demonstration on Saturday March 12th 2011

[i_ron]

Actually,

Rose's haphazard use of her loaned function generators is immaterial to the facts.

It is common sense that we should not be driving a high current output INTO our function generators. Perhaps there are those not familiar with how MOSFETs or transistor circuits work in general, and they do not see the MOSFET Source as a high current output, but I assure you, it can be, and in this case it is.

Why is the original circuit (see below) shown with the CSR (current-sensing resistor) located in the MOSFET Source leg? Note also that the function generator is connected to the MOSFET Gate only, not the MOSFET Source.

.99

Just out of curiosity I connected up a FET, driving a load and applied first 9.5 volts positive to the gate and then 9.5 volts negative to the gate though a DMM set on the lowest scale, 2 mA and noticed that there is no measurable current flowing into or out of the gate.

In the sketch below it matters not that the FG ground lead is connected to B or D, except for a matter of .25 ohms.

Ron

PS:"Note also that the function generator is connected to the MOSFET Gate only, not the MOSFET Source."  With statements like this can you not see the glorious humor of my 5/6 battery parody?  LOL

[poynt99]

Just out of curiosity I connected up a FET, driving a load and applied first 9.5 volts positive to the gate and then 9.5 volts negative to the gate though a DMM set on the lowest scale, 2 mA and noticed that there is no measurable current flowing into or out of the gate.

Correct.

In the sketch below it matters not that the FG ground lead is connected to B or D, except for a matter of .25 ohms.

Ron

Depends.

It can matter if the FG is at a high frequency, OR if the circuit is self-oscillating (such as the case with Rose's actual circuit) when the CSR has even a tiny bit of inductance associated with it, which of course is not shown on that particular diagram.

.99

[nul-points]

[...]
noticed that there is no measurable current flowing into or out of the gate.
[...]

good on ya, Ron, for trying out some tests with actual components!

throughout the mountain of posts relating to the RA circuit(s), i don't think there's been any issue with the single MOSFET example as far as the drive conditions are concerned

the possible issue with the FG o/p, here, is down to the build 'mistake'/ 'happy accident' which meant that the gate of the 1st device (Q1) got connected to the load via the Sources of Q2-Q5 whenever there was a suitably positive voltage on the Gates of Q2-Q5

because of the original placement of Rshunt (CSR), this suitably positive voltage could occur when the FG o/p (& therefore Q1 Gate) was negative

the negative FG o/p would then be connected via its total Q1 Gate drive impedance, to the load (receiving current i/p as a result)

this 'unintended' system connectivity appears to be largely, if not completely, responsible for these particular oscillations of the MOSFETS, thus the FG o/p could be subjected to a repetitive injection of current at a frequency of several MHz

in addition to the potential issue for the FG o/p - a side-effect of this Q2-Q5 switching of current cycles from load to Q1 Gate - with the original placing of Rshunt - is that any such 'unplanned' switched current path effectively by-passes Rshunt

the data collected on Rshunt would therefore *not* represent the total current flow across the battery stack (because there is now a switched parallel path across Q1 Gate-Drain)

the original Rshunt data can not therefore be used as intended in order to calculate the total energy draw from/to the battery


i hope that i've presented a fair and accurate summation of the situation with the system - as tested on March 12th - and relating to the issue with the FG o/p using the schematic as at that test

suggestions have been made from all concerned, and are possibly being followed up, as to how to avoid the issues i've just tried to summarize


right - back in the box for me

cheers all
np


http://docsfreelunch.blogspot.com


[edited to remove superfluous 'from']

[i_ron]

good on ya, Ron, for trying out some tests with actual components!

snip
i hope that i've presented a fair and accurate summation of the situation with the system - as tested on March 12th - and relating to the issue with the FG o/p using the schematic as at that test

suggestions have been made from from all concerned, and are possibly being followed up, as to how to avoid the issues i've just tried to summarize


right - back in the box for me

cheers all
np


http://docsfreelunch.blogspot.com

NP,

Yes, I agree to a certain point but no real numbers have come out of this.

But as .99 chose this particular sketch to illustrate his argument, I was more or less confining my rebuttal to this sketch... meaning that the FG as source  or sink hypothesis is not applicable here, likewise the placement of Rshunt.

Ron

[Rosemary Ainslie]

Golly. I think I'm in.  Slow register though.  And I still can't see any pictures.  And no 'reply' quote buttons But there's a reply at the top of the page that I can use. 

Guys - not sure if this is going to 'take' but I see that Poynty is still going on and on about that schematic.  Here's what I think.  I think that you should try whatever you want.  And it is ABSOLUTE nonsense that there's any significant current going into the FG.  I will give you proof of this when I get easier access to my computers.

I saw your comments there Bill.  I'll try it out.  But I can't get this done before Thursday. Please ask Harti to answer my email.  I need to know who's removing my posts.  I think it may just be my own view though.  Is that even possible?

Groundloop I can't see the schematics that I assume you've added.  I wonder if I can impose on you to email this to me.  My other computer is absolutely OFF LIMITS.  I don't think I would be able to stand having that one corrupted.  It holds my email.  But I can also be reached on rosemaryainslie@gmail.com - which is here on this 'corrupted' version.  So.  Groundloop - if it's not too much of an imposition I'd be very glad to have a look.  Sorry I didn't get around to that sketch.  I've been up to my ears all day.  I solemnly promise to do this tomorrow.  Not that it'll help - but I'm sure you'll see where I'm going.

Kindest regards
Rosie