N.R.M.R.E. An investigation.

[Grumage]

Dear TinselKoala.

Excellent.....

I'll reply later, this last fortnight has been a seemingly never ending childminding session!!
Last day today, at least for this week.

Nice rising bounce..... As Dog-One has mentioned already be very vigilant as you raise the input voltage.

Kind regards, Graham.

[Jimboot]

No, not the same gauge, the thin stuff is #27 and I don't know what the thicker stuff is. I would have used the thicker stuff all around but I ran out after one winding of 50 turns.

The core is a small CRT deflection yoke. I also have some smaller ferrite toroids wound and ready to swap in.

Wow that's bright. Are your cap values similar to Nelson's or the same? Is that an audio transformer? That trace is interesting, the ringing begins to rise just before the next pulse. Sorry for the dumb question but is there an easy way to alter the duty cycle with this build? I'm still waiting for a few parts.

[TinselKoala]

Capacitance values are the same but I chose higher voltage ratings for the caps. I'm using UF3003 diodes instead of MUR440. I have some MUR1560 on reserve just in case but so far nothing has failed.  The little transformer is some random thing I pulled from a TV chassis, it has about the right turns ratio I think. I didn't connect the FWBridge on the output yet, just testing with the neon to show some output in a dramatic way. I imagine that open-circuit the output will rise to "HV radiant" status if the little transformer can take the strain.
The pot varies all kinds of things: duty cycle, frequency, that weird ringing, input current draw, peak voltage at collector.... the interplay between input voltage and what the pot does is very interesting. I put a heatsink on the transistor and have tried input voltages up to 5 v but it seems to work "better" at much lower voltages. Depending of course on your definition of "better". I put a switch in series with the base connection to make it easy to "unplug" the base but I have not seen any oscillations continuing after base is disconnected. Yet.

[tinman]

First light.

Well, it makes one hell of a Joule Thief, I'll say that much for it. 2.1 volts and about 210 mA input, lights up a NE-2 neon brilliantly. One "typical" Collector trace shown on the scopeshot. Adjusting the pot causes some radical changes. Still exploring.

TK
The ringing amplitude seems to be increasing,before your transistor switches on again.
Is this correct?.


Brad

[TinselKoala]

TK
The ringing amplitude seems to be increasing,before your transistor switches on again.
Is this correct?.


Brad

Yes, that is correct. And if that's what one wants to emphasize, one can fiddle with input voltage and pot setting to get this effect to show up more strongly than in the scopeshot above.