Claimed OU circuit of Rosemary Ainslie

[TinselKoala]

If there is anything useful to you all here, feel free to
repost:
http://www.energeticforum.com/renewable-energy/4314-cop-17-heater-rosemary-ainslie.html

Hmm. Interesting thread, full of ideas.
I do note one thing, though--those who are reporting lots of heat in the load seem to be using longer duty cycles. I like Stiffler's calorimeter setup, but I think I can do even better. And I guess I'll have to try Lindeman's circuit too.
Now, I have a question: In the original circuit in the pdf, Ainslie uses a 555 timer circuit, not specified, to drive the MOSFET gate. What voltage is being applied? I'm using as much as 10 volts, which is more than spec, but not enough yet to cause shoot-through. Could her drive voltage be even higher? I am having trouble getting my load to heat up, because of the short duty cycle.
Or is it possible that the 3.7 percent figure is a misprint?
It's hard for me to imagine that the MOSFET type itself would make that much difference. The one I'm using is an exact replacement for about 90 percent of all applications of the IRFPG50, has the internal diode and everything. But I'm ordering the IRFPG50 anyway, now that I don't think I'll smoke it (ten bucks!) right off the bat. No telling when it will arrive.

Anyway, I replaced my original 2.5 ohm shunt with a 0.25 ohm shunt as specified, and it made a lot of difference in the behaviour of the circuit. I'm uploading a video now, and I'll post a link when it's up.

[Groundloop]

@TinselKoala,

She used 12 volt to drive the 555 circuit.

Groundloop.

[TinselKoala]

OK, thanks, I'll build it and compare.
But can you explain the notations on the resistors like
"[R]/50   k ohm/50%"
I don't understand what that means.

But from that, it certainly looks like my gate voltage isn't the problem. However the output of that circuit is likely to be less "clean" than my FG, which might be a good thing as it could help drive the MOSFET into the "O-zone", where the horizontal becomes vertical and the vertical goes ballistic...

So far:
http://www.youtube.com/watch?v=trip8gjoxMQ

[Groundloop]

@TinselKoala,

Here is a cleaned up drawing of the circuit.

[EDIT] Added the Eagle CAD files. (For those of you that uses Cadsoft Eagle.)

GL.

[TinselKoala]

It's so pretty! Thanks, much easier to work with. I get the resistor values now.