Testing the TK Tar Baby

[TinselKoala]

Is the 200 mA really a DC current ?
What about the AC component flowing while the oscillations are happening ?

If we would use just a 9 Volts battery with a pot and put on the oscillations,
then we would pronbly only have an AC current, right ?
Or will we have an AC current superimposed on a DC 200 mA current ?

Maybe TK can measure this and show it on a new video ?

Many thanks.

Regards, Stefan.

There appears to be a DC current. The "ac" can be measured wherever you hook a probe in the circuit. It's an RF oscillation that I can even hear on my FM radio.
I've posted a video showing the circuit with a 9v battery and pot.

[TinselKoala]

Just to clarify one point;

"bias" means a certain amount of pos. DC V_GS. This can be completely floating wrt the rest of the circuit.

So HOW you provide that bias, makes no difference whatsoever, it can be positive, negative, as long as V_GS is slightly positive, say about 5V.

I have simulated both cases, where the bias is applied to the Source and the Gate. In other words, I have proven what I wrote above.

Yes, and the behaviour of Tar Baby bears that out as well. That's why I said that the two of you are in violent agreement on this point, I think. The problem arises when you try to have that bias supply connected to the main battery. This is going to put one or the other of the bias supply rails at the circuit ground potential, in other words, no longer floating, unless some circuitry like the voltage inverter is used, I think.

I have still not been able to make consistent oscillations using a simple hookup to the main battery for bias. External supply: no problem as long as it's floating.

[picowatt]

I don't think we want 200mA of AC current flowing through our bias battery, that's why I isolated it.

With isolation, the battery supplies only a tiny DC current to slightly bias the MOSFET ON, and the AC path is provided capacitively, which bypasses the DC bias network.

.99,

I've re-read the above and I am now not quite sure what you are saying.

Regarding the method used to bias on Q2, AC current was not being discussed, other than its two paths.  From the RA first paper, much more than 200ma of AC current is indicated, but the present discussion was related to DC bias.

What is under question is if in the hypothetical situation I gave using a 200ma/Hr battery in series with a 50R at the Q2 source leg, and if the Q2 bias/quiescent DC current were 200ma, then the battery would last only around an hour, correct?   The question relates to whether or not the FG/555/battery in the source leg must provide 200ma to maintain Q2 biased on in the common gate configuration (or provide whatever the Q2 current is at DC).  If TK's 555 power supply is providing a supply current equal to or a bit more than the Q2 drain current, then the answer is yes, the FG/555/battery will have to be capable of supplying 200ma for the duration of any tests, hence any battery used as a bias supply must be sized accordingly.  I think TK's need for a heat sink on the 555 demonstrates this as well.  Again, bias current may not need to be as high as 200ma, I am only using that as an example.

PW

[TinselKoala]

TK,

I would decouple the wiper of the pot, or just use a 10K resistor from the first Bat+ to a cap and tie the other end of the cap to real ground (not the CSR, althogh you might want to try both ground points).  Then, to the junction of the resistor and cap, connect another resistor, 1Meg or so, and connect the other end of that high value resistor to the MOSFET gate.  You may have to add a bit of wire length between the end of the 1Meg and the gate to add some inductance to get the osc.  Possibly you will have to add some inductance (wire) in series with the 50R at the source as well.

PW

I think we are starting to lose the thread here. Whatever we do, I think it must terminate "as if" it were a dropin replacement for the FG in the NERD circuit. That means one terminal of it must connect to the point marked "FG +" and the other terminal must connect to "FG -" and if possible it must be capable of making both the negative-going drive which produces the oscillations without turning on Q1, AND it must also be able to make a positive drive voltage, turning Q1 on and _with enough negative_ to allow oscillations to occur. Please watch the video where I show this fine point using the function generator.
At least this is what I'm striving for, and I think this would be the fairest test for the circuit.

"The Gate" in your post is ambiguous at this point. The "FG+" connection goes to the Q1 gate and the Q2 sources. The "FG-" connection goes to the Q1 source and the Q2 gates.  Are you saying I should hook the 1M to the "FG+" connection, and nothing to the "FG-" connection? Perhaps a drawing would be helpful.
But... I still don't see the difference between that and what I've already tried, but I'll try it anyway as soon as my head clears a bit.

There is a lot going on and I find myself in a strange position. I feel like I am doing what the NERDs should have done, a long time ago, and I feel that I am not only testing but I am actually developing and designing circuitry for them. And yet... look at how I am treated. All of this, in spite of RA's allegations, is on my own dime and my own time, and my "controllers" don't even know about it.

At any rate: I have attained several of the primary goals. I have shown the basic 555 timer circuit that can run in place of the FG for the negative going pulse mode, and I know why it won't work for the positive going high-heat mode. I've developed a floating supply that can be used with the main battery and the 555 timer to operate in the low-heat mode. I've also shown that continuous oscillations can be made with the external battery.

I'm very sure that these same things will also work with the NERD device... so I expect them to begin their testing any day now.


Don't I?

[picowatt]

TK,

By "gate" I was referring to the gate of the four Q2's only, and all discussions using the positive voltage to the gate of Q2 have been with regard to Q1 being out of circuit.  Sorry, I thought we were just considering the osc portion of the circuit, I should have been more clear.   

You are right, of course, in that if the circuit deviates substantially from the NERD circuit, it will be argued that those modifications are responsible for any less than stellar observations during a run down test.

The only alternatives I can see would be to build an equivalent FG circuit running off an isolated DC to DC converter fed from the main batteries or use two batteries in series with their center taps tied to ground.  I would probably use low power opamps (for higher than the 555 rail voltage) configured as an astable and an output buffer with NPN/PNP emitter followers in the FB loop.  As stated, the supply could be a pair of batteries or an isolated DC-DC converter fed from the main batteries.  Though minimal, the added current draw on this circuit if operated from the main batteries would likely be questioned.  Even if the separate battery or batteries are used to operate the circuit, would that/those battery(s) going flat be considered proof of lack "over unity"?

If the "magic" happens during the osc phase, then I would focus only on Q2 as .99 has done in his burst osc as it should be possible to bias from the main batteries with very minimal current draw from those batteries using a similar circuit.

But, as you say, that is probably too different from the original circuit to be accepted.

As far as that goes, did not Rosemary say she already performed testing with this circuit using a 555 but was just having "stability" problems?  Possibly her circuit could be improved upon...

PW