Replication of Mini Radiant Exciter circuit of Nelson Rocha

[Vortex1]

Dear Vortex1,

Something to think about with the two electrolytic capacitors connected in front of the
base of the TIP122...

Is it written anywhere that the two connections on a capacitor must be charged with
opposite charge?  What would happen if you applied like-charge to each plate?  So
instead of opposite charges attracting within the capacitor, they are repelling.

Just something to ponder...

OK I'll ponder that, Matt. My first impression is to create charge you must flow current into the capacitor and have a potential difference between the plates. So how do you apply like charge to each terminal? if Charge implies a potential difference between plates  this must be Nelson's top semantic secret. You could try shorting the two ends of the capacitor then they will have the same (0) charge. You could also elevate the capacitor to a few hundred volts with respect to earth ground with the leads tied together and the capacitor will be "like" charged on each plate with respect to ground.....but I know that's not what you are looking for soooo........ask Nelson.
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Regarding C3, the first capacitor, since it has a diode D2 in series it will charge to some positive value with respect to it's negative terminal  and then just sit there with that charge in place since there is no way for the +charge to go back out, it is blocked by the diode. It's internal leakage would  cause a very slight drop in charge over time, except for the fact that it is being replenished very slightly on each cycle when the diode is forward biased.  The charge just sits in the capacitor with nowhere to go, like it would in a half wave rectifier with no load on it.

At one point I mused that Nelson might be using the diode capacitance as part of a Drift Step Recovery configuration, using the capacitance of the diode to generate fast pulses, but that didn't wash because the pulses would be absorbed by the other capacitor C4.

Regarding the C4 capacitor with the R1 pot across it, this one will charge at the rate of current delivery from the coil and discharge at the RC time constant of the potentiometer setting.
The charging current for this capacitor is a function of supply voltage and duty cycle. This capacitor has an good chance of frying the base of the first transistor in the Darlington pair, since there is nothing to limit the high peak current if the voltage supply input is turned up too far. 120 mA is the max gate current allowed on that base.
The other problem is there is nothing to limit current into the base when the voltage reverses, so the 5 volt reverse limit may be exceeded again taking out the base.

I'm sure Nelson probably had very good reasons for designing it that way, so someone should talk to him and find out why he would stress the parts in such a manner. If only a couple of volts of supply are used, probably not a problem but 12 to 24 volts it probably would fail over time.

Now my question to you if I may ask:
What exactly are the operating specifications for this circuit, power input, voltage input, charger power output and HV power output? Also what type loads is it designed to drive? or is it just to demonstrate that you can charge a capacitor with a wire to the HV or light a neon lamp (400uA).

Kind Regards

P.S. You might wish to ask Nelson to put phasing dots on his schematics besides just being good form it is very helpful for replicators. As you are aware, the operation of the oscillator is quite different with the phase reversed so it is good to know which mode you are shooting for.

[Dog-One]

OK I'll ponder that, Matt. My first impression is to create charge you must flow current into the capacitor and have a potential difference between the plates. So how do you apply like charge to each terminal? if Charge implies a potential difference between plates  this must be Nelson's top semantic secret. You could try shorting the two ends of the capacitor then they will have the same (0) charge. You could also elevate the capacitor to a few hundred volts with respect to earth ground with the leads tied together and the capacitor will be "like" charged on each plate with respect to ground.....but I know that's not what you are looking for soooo........

I mentioned it because of Jack's comment in his thread.  He declares three states of charge:  positive, negative and neutral.   This is a variation I guess I either took for granted or didn't conceptualize well.  When we talk about stray capacitance, stray to what?  A neutral charge potential or something else?

I recall all the electrostatic videos with the Leyden Jar & electrometer, but never seemed to think of it in common electronic circuits.  Maybe because we rarely have those levels of voltages associated.  But when we compress a quantity of energy release into microseconds or shorter, something has to drastically increase.

Regarding C3, the first capacitor, since it has a diode D2 in series it will charge to some positive value with respect to it's negative terminal  and then just sit there with that charge in place since there is no way for the +charge to go back out, it is blocked by the diode. It's internal leakage would  cause a very slight drop in charge over time, except for the fact that it is being replenished very slightly on each cycle when the diode is forward biased.  The charge just sits in the capacitor with nowhere to go, like it would in a half wave rectifier with no load on it.

At one point I mused that Nelson might be using the diode capacitance as part of a Drift Step Recovery configuration, using the capacitance of the diode to generate fast pulses, but that didn't wash because the pulses would be absorbed by the other capacitor C4.

You also have the standard diode voltage drop which may somehow be used for proper biasing.  But your DSR thought may be right on track.

Regarding the C4 capacitor with the R1 pot across it, this one will charge at the rate of current delivery from the coil and discharge at the RC time constant of the potentiometer setting.
The charging current for this capacitor is a function of supply voltage and duty cycle. This capacitor has an good chance of frying the base of the first transistor in the Darlington pair, since there is nothing to limit the high peak current if the voltage supply input is turned up too far. 120 mA is the max gate current allowed on that base.
The other problem is there is nothing to limit current into the base when the voltage reverses, so the 5 volt reverse limit may be exceeded again taking out the base.

I'm sure Nelson probably had very good reasons for designing it that way, so someone should talk to him and find out why he would stress the parts in such a manner. If only a couple of volts of supply are used, probably not a problem but 12 to 24 volts it probably would fail over time.

He did mention he has never had any component failures in his tuned version.  So I have to suspect for anyone that has wrecked components, something isn't quite right.

Now my question to you if I may ask:
What exactly are the operating specifications for this circuit, power input, voltage input, charger power output and HV power output? Also what type loads is it designed to drive? or is it just to demonstrate that you can charge a capacitor with a wire to the HV or light a neon lamp (400uA).

For power input I set the current limit way down and bring the voltage up slowly from about two volts.  As you slowly increase input, adjust the pot in between small voltage steps.  At some point below ~9 volts, you will see a characteristic change in behavior.  Instead of an oscillator, the circuit becomes a pulse generator.  It's this pulse generator I assume Nelson wants us to study and see the effects it is able to manifest.  In my testing, I only went a volt or two higher from when I saw the behavior change, so I don't know what might happen beyond that.  Maybe that's how people are blowing components.

If you look closely at this video, you will begin to recognized what Nelson has morphed his pulse generator into.  Then if you look at his most recent videos, you'll see what he is able to do with this concept.  Maybe I'm just overly optimistic or clairvoyant, but I see the progression clearly.  I see the improved (higher power) pulse generator and his method of harnessing those pulses via his pancake coils, which all goes back to Jack's open ended bifilar coils.  Now whether Nelson and Jack are actually doing the same thing or not...?   I can't say, but if they are, a lot pieces fall into place.

[Vortex1]

With an  open mind I will give the videos another good look per your suggestion.

I do think this would all be a lot easier for the attempts at replication if a good document were put together(like Jack's) rather than all the guesswork, but I'll keep my opinions out of it from here forward.......as Jack Friday would say..."just the facts ma'm".

Kind Regards

[Jimboot]

[size=78%] started working on this again yesterday. Given myself quite a few belts. Need to tie one hand behind my back. Something interesting I found by accident was if I connected a lamp and a spark gap in series between the dc ground of my fwbr and the "ground" of my mot output, I could dimly light my incandescent 12watt lamp and get a neon to partially light with single wire. The mot puts out around 800volts with 7v 200ma input which I'm using instead of the 25/240v transformer. It did make my garage rf remote openers inoperable when running as my wife discovered when returning from the shops. I'll try and do a video tonight. Need a csr on the output as my meters said it was 12ma at 785volts which is wrong as my lamp should have been a lot brighter if that was correct.[/size]