[NewCandle] Parasitic Cap Charging

[John Winterflood]

Keith Nagel wrote:
> Hi John + Ron,
>
> While I can't now go to Ron's website to see the circuit again, I gather
> from the email that he's got some kind of colpitts oscillator going on. 
>
> http://en.wikipedia.org/wiki/Colpitts_oscillator
>   
Ron's website went down also before I could study his circuit but I 
based my comments on the circuit on this guy's blog page 
http://creatorguy.com/ click near the bottom of the page where it says 
"MicroSECSchematic".  If you redraw it in a more standard arrangement 
you will see that it is not a Colpitts, and indeed the only connection 
between the output (collector) and input (base) would seem to be the 
collector to base (or miller) capacitance.  This is of the wrong 
polarity of course to help oscillation.  But now I am starting to think 
that it might be the load inductor (L2 in the above schematic) and neon 
on the output that is the real key to the circuits operation.  Maybe the 
periodic negative-resistance breakdown of the neon is sucking current 
through L2, reverse biasing the collector-base junction (ie forward 
biasing the C-B diode junction) and sucking pulses of current from the 
base tank circuit through this path!
> This oscillator indeed has a negative resistance characteristic, and
> fills the claim of a circuit with such using only one BJT.  
My claim was that I couldn't think of a way to make a (OK!) 
*differential* negative resistance which works down to DC using a single 
BJT.  With two
BJTs of course it is easy.
> Not too quibble over nomenclature, but what you (John)
> are describing is a negative differential
> resistance. A true negative resistance is one in which energy is
> inserted into the circuit through the "resistance".
Yes I appreciate the difference.  One can also make a very good (near 
perfect) negative resistance with an op-amp wired appropriately (see 
diagram at http://www.answers.com/topic/negative-resistance-circuits).  
This one gives a negative resistance to ground.  A both-ends-floating 
negative resistor can be made by adding another op-amp.
>  An old friend of
> mine humorously referred to this as "joule cooling". I have built
> such a circuit, but before you guys get too excited, the energy source
> doing the "inserting" was a DC pulse. From the point of view of
> the circuit, there would be a positive current and a negative voltage,
> a true negative resistance. When this circuit element was put into
> a passive LC network, the whole circuit would ring up at the resonant
> frequency at the expense of the DC driving pulse.
I believe you can do the same with a neon lamp - provided you bias it 
with DC to its negative resistance region.  An AC tank circuit wired 
around it will ring-up just as you describe.
> It's tempting
> to write this up for the website, but I did this work years ago
> so I don't have pics of the device, just the scope shots. 
>    
> Not to put words in Ron's mouth, but I think when he asks you to
> forget everything you know and build the circuit what's he's
> doing in effect is to say, "look, I could spend a month
> arguing with you about this thing, but if
> you build a copy and play with it most of the discussion can
> be avoided and we'll be on the same page pretty quickly". It
> is in fact the quality that makes Ron welcome here; his
> constant exhorting of people to actually build up some hardware
> and play with it. I would take his advice;
Yes I am getting there.  I was really hoping that the dozen or so clever 
hobbyists and one or two PhDs that Ron has already had looking at the 
problem would have come up with some resolutions by now.  By rights I 
should not be able to add much to such an effort except possibly to be 
able to see things from a physics point of view instead of just from an 
electronics viewpoint.  What also puts me off a little is the special 
inductor and the fact that one might get everything apparently working 
(ie oscillating) only to find that it is not working in "SEC mode".  But 
if there is something I can identify as unquestionably anomalous, I do 
intend to get my hands dirty with a protoboard or something.

J.