Testing the TK Tar Baby

[poynt99]

TK,

Try the original circuit again, with the 3.3V zener, and LED load, but place a 470p cap in parallel with the 1N4007. See if that gets it to oscillate and be more stable. In the sim, the Fo goes down.

What sort of weirdness are you seeing with your simple DC zener test?

[MileHigh]

TK:

I thought that I would mention in your first of the new round of scope shots you can see that when the MOSFET is on, there is a second higher-frequency oscillator running.  It completes about 7 or 8 cycles before the MOSFET switches off as part of the main cycle.

It would be nice to see the gate voltage waveform scoped also.  That's the link between the battery voltage waveform and the CVR voltage waveform.  You might remember my "tripod" offer.

It looks like you will find a nice configuration that shows gobs of power returning to the battery.  Then you can load mass quantities of Altoid cases into a shipping container!   

MileHigh

[Magluvin]

I wonder if this circuit has blown all my 3.3 V Zeners on first trial. They test good on the diode check test but give me weird results when I look at them with a power supply and a voltmeter.

I see the 3.3v zens check out.  Did you try 2 in series? 6.6v may show you if they are blown or 3.3v is not high enough to work here.

Mags

[TinselKoala]

What size capacitor was that you were using in place of the zener?

0.01 uF

Also, did you get a current measurement when it was working with the 3.3V zener and LED load?

I'm no longer sure it was ever working with the 3.3V zener, but anyway, no.

@Mags
No, I have not tried two in series...yet. I intended to go and get some fresh ones but didn't get around to it today. I'll try two of the ones I've got now in series.

I've posted a video showing some of the variations.
http://www.youtube.com/watch?v=jtped72pYZQ

[TinselKoala]

With two of my 3.3V Zeners in series and the single LED load,  the result is similar to the result with the 5.1 V Zener: a decrease in osc frequency to 1.875 MHz (philips pm6676) and a more pronounced ringing. And the LED brightens visibly over the "nothing in zener slot" level.

When I just look across the empty Zener socket with a voltmeter I get about 2.7 V DC or so.

(The battery is low, though, around 8 volts no-load).