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Author Topic: Testing the TK Tar Baby  (Read 1998476 times)

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #255 on: April 09, 2012, 10:25:58 PM »
TK,

That variable oscillator I designed around the TC4426 doesn't have a very wide range of frequency or duty cycle adjustment. It's just enough to play with things a bit and provide an adequate drive to the MOSFET. Feel free to use your FG or 555 there instead if you do build this.
I just took another look at your schematic and it looks like I might be able to build an oscillator around the 4426 driver chip (excellent choice btw, makes a killer H-bridge SSTC driver with its complement 4427.)
I don't have any on hand at the moment but I do have some Intersil mosfet H-bridge driver chips all on one chip, 16 pin DIP IIRC. But I'm about to go to the store so if I'm lucky I'll pick up some of the 4426s. Perhaps using the 555 to clock the 4426 might work to give the wide range and still drive the mosfet "properly".

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #256 on: April 10, 2012, 03:35:22 AM »
Tar Baby likes the 10R in series with the 555 pin 3 output-- thanks PW---. And my inductance meter finally arrived.

Revision B:


TinselKoala

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Re: Testing the TK Tar Baby
« Reply #257 on: April 10, 2012, 06:43:02 PM »
Can anyone tell me what are these "Phase Shifts" that suddenly have appeared in Rosemary's imaginings...er.... data? Is she talking about Paper2Fig8 below?

If she is talking about the phase relationship between the current (voltage drop) in the CVR , and the "battery" trace (or more useful for power readings, the common drain trace) oscillations at that frequency, my demonstration of that is being uploaded now.

And of course there is a "phase shift" in these signals... it's AC at RF frequencies, and besides... current and voltage are expected to be out of phase, or rather at a basic 180 degrees difference,  plus or minus , right?

picowatt

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Re: Testing the TK Tar Baby
« Reply #258 on: April 10, 2012, 09:28:06 PM »
Tar Baby likes the 10R in series with the 555 pin 3 output-- thanks PW---. And my inductance meter finally arrived.

Revision B:

TK,

Did you take the time to measure the drain current versus temp before and after the 10R?  Just curious, that, to me, would at least be a bit of "fun". 

.99,

I am not sure why the switching circuit and switched mosfet in the source leg is required at all.  Why not just put a 50R in the source leg instead of the switched mosfet and let it run?  The 50R would emulate RA's FG out and you an set the bias current by adjusting the applied gate voltage.  Alternately, of course, the gate voltage could be fixed and Rsource adjusted to set Ibias.

PW

fuzzytomcat

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Re: Testing the TK Tar Baby
« Reply #259 on: April 10, 2012, 09:50:10 PM »
Hi Tk,

Here is another 555 timer circuit that was hidden in plain sight on the internet .... with a 5% to 95% duty cycle .... don't tell everyone where it is.  :-X

Cheers,
Fuzzy
 ;)

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #260 on: April 10, 2012, 09:58:48 PM »
@PW: no, not yet, the batteries I'm using are just about ready for Dim Bulb 2 and other circuit features are not yet stable enough for me to want to put in the sustained attention that a good time-temp-current profile will take. Besides, looking at the recent posts from RA, I think she's decompensating and getting further and further removed from reality and I'm feeling discouraged a bit.

Now... if I had a nice, paper chart recorder and a mile of chart paper, I could just sleep through the whole thing.

But I did purchase two more batteries, so now I have a matched set of 6 ea. 12 V nominal, 5 A-H sealed lead-acid batteries, so if voltage is the key, I can supply it, and if good randomised Dim Bulb repeats are necessary I can handle that too. I'm setting up right now to see if intercell lead inductance and another battery or two will bring my osc freqs down to the 1.5 MHz range.

picowatt

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Re: Testing the TK Tar Baby
« Reply #261 on: April 10, 2012, 10:10:22 PM »
TK,

All I can say is, well, "geeeeesh..".  I now have a much greater understanding of certain "frustrations" I have noted in "other" threads. 

I am beginning to wonder how a few IRFPG50's would perform as a class A electrostatic driver amp amp.  It is beginning to sound like a better use for them.

I just wish they were not so slow, i.e., large Ciss.

PW 



TinselKoala

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Re: Testing the TK Tar Baby
« Reply #262 on: April 10, 2012, 10:14:28 PM »
More data: with fewer than 30 Volts in the main supply, the oscillations (at least using the 555 timer) become less and less strong and more and more "picky" in terms of the 555 input power range needed to produce them, until they become difficult indeed to find at below 29 volts indicated in-circuit. Of course at less than 10 volts indicated each, these batteries could be considered completely flat.

Restarting with a full battery pack at 38.4 volts open-circuit, the oscs return in full force and controllability.

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #263 on: April 10, 2012, 10:52:48 PM »
TK,

All I can say is, well, "geeeeesh..".  I now have a much greater understanding of certain "frustrations" I have noted in "other" threads. 

I am beginning to wonder how a few IRFPG50's would perform as a class A electrostatic driver amp amp.  It is beginning to sound like a better use for them.

I just wish they were not so slow, i.e., large Ciss.

PW
Frustration isn't the half of it. It was the same three years ago on Naked Scientists only not so much with builders. The threads there are still archived. And it was the same two years ago with the Energetic Forum (panacea u.) And it was the same last year here and on .99's forum. And it's the same now.

Yeah, you really have to pump them power hexfets to wake them up. In my next SSTC I'll use these, and discharge a tantalum cap into the gates via a phase transformer. That'll kick start those puppies, I'll bet.

Something like this but more better.
http://www.youtube.com/watch?v=HQfR-wsDoBI

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #264 on: April 10, 2012, 11:04:40 PM »
This shot is more typical of the scope shots RA usually tries to show. She's been doing this kind of stuff for years. The few other shots in the papers are the only really informative shots she's ever posted, as far as I can tell. Usually they are a mess of false triggering, aliasing, and continuous combs all across the screen, like this silly, improperly triggered, useless for anything shot here. I swear, if misuse of an oscilloscope is a crime, these people are the Moriartys of South Africa.

Paper 1, Figure 8:



TinselKoala

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Re: Testing the TK Tar Baby
« Reply #265 on: April 10, 2012, 11:10:19 PM »
Hi Tk,

Here is another 555 timer circuit that was hidden in plain sight on the internet .... with a 5% to 95% duty cycle .... don't tell everyone where it is.  :-X

Cheers,
Fuzzy
 ;)

Heh... thanks, Fuzzy.

I just happen to have a copy of Forrest Mims' "Engineer's Mini-Notebook" volume on the 555.... lots of top secret information in there !

And I made a great score yesterday at the used bookstore: a copy of the third SAMS edition of the book "IC Op-Amp Cookbook" by Walter Jung. A classic reference and in excellent shape. Seven chapters of application circuits of common op-amps.
 8)

MileHigh

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Re: Testing the TK Tar Baby
« Reply #266 on: April 10, 2012, 11:16:55 PM »
You are a Seventies nerd if you had a copy of Don Lancaster's CMOS Cookbook.

I recall all of the National Semi. 'blue' books.  I think there was one dedicated to op-amp application notes.  They were really good too.  Adders, subtractors, integrators, differentiatiors, low-pass filters, band-pass filters, high-pass filters, comparitors, oscillators, quadrature oscillators.... Wet dream material!   ;D :P

picowatt

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Re: Testing the TK Tar Baby
« Reply #267 on: April 10, 2012, 11:34:02 PM »
MH,

Hey, be kind, the pages may be yellowing, but all those books still reside on a shelf here!

And MH, don't you dare start giving up on analog scopes, I won't permit it.  It happened to audio, it is not going to happen to my bench!!!!  An 8-10 bit digital can't hold a candle to a good analog.  I still use old analogs with cursors and love them.  I only use digital here for hi res FFT's so my PC scopes are all 16 bit.  I routinely need to see out to a few meg at THD's of close to (or even below) -100dB (yes, that is .001% and I have the generators to do so as well!).  I  suppose I could live with a 12 bit digital scope for most things, but at that res and at any real bandwidth, they are very pricey.  I have used 8 bit DSO's and even some LeCroy's, and hated dealing with 8 bit, particularly for non-repetitive signals and if looking at/for noise.

PW


picowatt

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Re: Testing the TK Tar Baby
« Reply #268 on: April 10, 2012, 11:44:43 PM »
MH,

As well I have maintained my full set of "blue books".  I have an entire library of now defunct data books that for some reason I just can't bear to send to recycle.  Can we say Intersil, for example?  At some point I'll decide the space they take up is better spent otherwise.  Everything today is a PDF from a mfg web site, and actually, quite a bit handier.

TK, apologies for the off topic..

PW

TinselKoala

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Re: Testing the TK Tar Baby
« Reply #269 on: April 11, 2012, 12:40:43 AM »
How can this be off topic? I have my CMOS and TTL cookbooks at the other undisclosed location....
and my sophomore EE textbook "Circuits Devices and Systems" by Ralph Smith close at hand on the shelf over there.
And here's a couple of little toys that I often sometimes use: