Self accelerating reed switch magnet spinner.

[MileHigh]

A little extra comment:  Looking again at your last scope shot, you can clearly see that the rotor magnet responsible for the third "zero cross" waveform is stronger than the previous two magnets.

[TinselKoala]

TK:

The angular adjustment for the sensor coil looks great!

How can I tell it's operating in attraction mode from the scope shot?  In looking at the sensor coil waveform I can see the "zero cross" is the center of the steep negative slope between the positive and negative humps.  That's also top-dead-center for the rotor magnet fly-by.

In looking at the drive coil waveform I can see that the switching is ON BEFORE the "zero cross" and it switches OFF at the "zero cross."  Hence the motor is running in attraction mode.

If I saw the drive coil being switched ON at the moment of the "zero cross" and it then switched OFF a certain amount of time AFTER the "zero cross" then I would know the motor was running in repulsion mode.

You can also see the switching angle of course.  To be more precise, you can clearly see that your actual switching threshold is actually set below the "zero cross" of approximately six volts.  Your switching threshold is set to let's say rougly five volts.  i.e.; negative one volt relative to the "zero cross."  Again, this is impossible to do with a conventional Bedini motor.

MileHigh

Yes, you are right all the way, I think. Actually the switching voltage level is about 5 1/2 volts, the sense trace is at 1 V/div and AC coupled, the "baseline" or "zero" is the 6 volt level.
(Since the coil's "reference" voltage is half the opamp supply because of the 22k dividing resistors, no matter what the opamp supply is, the thing is stable and switches at the same point even if the supply voltage changes. I tested it and it's good from 8 1/2 volts to 15 volts supply.)

Thanks for the clear description of how to tell repulsion from attraction. It is all coming back to me now, these are things I explained back in 2011 during the Orbette core effect motor days, when I was showing the difference between the three basic types of PMs: attractive, repulsive, and core effect. (My Marinov slab works on a fourth principle, repultraction.) Hopefully I'll be able to demonstrate the scope trace differences you describe, a bit later today or this evening.

I want to thank you again for your ideas, your help and your advice. This certainly is turning out to be a neat project. The controlled starting and the LED strobe just tickle me silly whenever I look at it. Yep, it is Way More Fun than the Bedini SGM. But it does like long duty cycles for max RPM. I wonder if it's possible to reproduce any of the effects or claims of Bedini with this driver/motor configuration. Any ideas on that?

I'm also wondering about the optimum mosfet to use. I've got the IRFP360 in there now. I just received some IRF3205  but they are low voltage high current units. Looking at the data sheets and what I have on hand, I might have chosen the best one already, by accident.

[TinselKoala]

A little extra comment:  Looking again at your last scope shot, you can clearly see that the rotor magnet responsible for the third "zero cross" waveform is stronger than the previous two magnets.

Yes, that's right, you'd be surprised at the rotor magnet arrangement. I don't want to take it apart right now, but glued to the inside of the rotor edge there are two round ceramic disks and two little ceramic flat bars, and then each has a tiny NdBFe button on top of it. So the rotor magnet fields are ... not all that well equalized, nor is the rotor very well mass-balanced. But it works anyhow!

Good catch on the scope traces. You can also see some little differences in the slopes of the individual magnets too. This is actually the reason for the four separate tape markings over the magnets: I was using a phototransistor to look at the reflective tape on one scope channel, and the Bedini pulses on the other channel. So I would see one, two, three, or four little pips and I could tell which magnet position was making which drive coil pulse.

[Pirate88179]

But it does like long duty cycles for max RPM. I wonder if it's possible to reproduce any of the effects or claims of Bedini with this driver/motor configuration. Any ideas on that?

TK:

Can you change the duty cycle on the fly on the op-amp while the rotor is running?  In other words, at max rpm can you then begin to shorten the duty cycle?  Sort of like the timing advance on the older cars of my youth.  My best Bedini set-up hit what I called second gear when the pots were all the way open, and then I began to add resistance again and it continued to accelerate ending up at 2 times the max rpm than if I just had the pots in that position from the start.

Just wondering.

Bill

[TinselKoala]

TK:

Can you change the duty cycle on the fly on the op-amp while the rotor is running?  In other words, at max rpm can you then begin to shorten the duty cycle?  Sort of like the timing advance on the older cars of my youth.  My best Bedini set-up hit what I called second gear when the pots were all the way open, and then I began to add resistance again and it continued to accelerate ending up at 2 times the max rpm than if I just had the pots in that position from the start.

Just wondering.

Bill

Yes, the current setup allows complete control of timing (by varying the position of the sense coil) and duty cycle (the setpoint control) while running "live". You can vary the timing so far you can even change magnets you are triggering on, and you can vary the duty cycle from 0 to 100 percent. It is fully controllable. The strobe will show the exact sweet spot, and the brightness of the neon does too, but is less precise.
The scope traces allow instant determination of RPM increasing or decreasing, by showing the frequency changing. More pulses = faster, and v.v.

Here's an annotated scopetrace with the Drain trace lowered and superimposed on the Sense coil trace. This clearly shows the switching points that MH pointed out above, and it shows a little hysteresis, which surprises me, but it's not too much. This is with the NE-2 from coil to Batt positive.

The Drain spike peaks are at a bit over 400 volts, off screen at the top. They would go even higher if I disconnected the neon.