Self accelerating reed switch magnet spinner.

[MileHigh]

Supposing that you decided that you wanted to have a voltage waveform averaging filter.... One way to do that is where you connect an AC voltage source to a resistor, and that connects to a capacitor that goes to ground.  The voltage that you would get at the junction of the resistor and the capacitor would be the average of the AC voltage waveform supplied by the voltage source if you provide enough filtering.

So, supposing that we want to use a resistor that is 1K ohm.  Supposing that we decide that if our filtering time constant is one second, then when the pulse motor is running at a normal speed then the averaging of some kind of mystery voltage waveform from the pulse motor will be excellent.

What we are really saying is that we want R x C = 1 second.

Therefore C = 1 / R.

Therefore C = 0.001 Farads.   That equals 1000 uF, which is a pretty standard electrolytic cap hat just about anybody should  have.  Likewise, just about anybody should have a 1K ohm resistor.

Connect the dots.....................

[MileHigh]

TK:

Now that you are in possession of the most flexible pulse motor I have have ever seen on YouTube, I will give you my thoughts on getting the highest RPM per input watt ratio.  In other words, not looking for highest RPM, instead looking for highest electrical efficiency to produce RPMs.  Standard disclaimer that I am not asking you to do this.

Permit me to discuss this in terms of a repulsion motor, but everything I will state applies equally to an attraction motor.

Also, we are going to "forget" about the energizing time constant of the drive coil and any possible influences on that energizing time constant by the passing rotor magnets.  This is just to make the discussion simpler.

So if you switch on the drive coil at top-dead-center it's useless to you.  You are not applying any torque to the rotor at TDC.

Likewise, if you switch on the drive coil at +45 degrees after TDC, that also useless for the same reason.  You are not applying any torque to the drive coil.

Somewhere in between there is a "torque sweet spot."

So, with your 10-turn potentiometer you can dial up any coil energizing pulse width (a.k.a conduction angle) you want.  Then, by changing the angular position of the sense coil, you can move that coil energizing pulse around and hunt for the "torque sweet spot" by checking your RPM.  You can also experiment with the width of the energizing pulse and hunt for the sweet spot and see how efficient you can make the pulse motor.

In theory, there is a "sweet energizing pulse with" and a "sweet angle past TDC" that lines up with the physical torque sweet spot that corresponds to how the energized coil and the rotor magnets interact.  i.e.; the good old repulsion between a magnet and an electromagnet.

Then, there is just a dumb brute force reality check.  Switch the coil on 100% of the time by changing the potentiometer setting.  Then take the rotor in your hand and hold the rest of the motor down with your other hand and simply feel for the angle with the most torque.  That will be were the sweet spot is.  In theory your "hunt" for the sweet spot by running the motor as described above, and the angle you feel with your brute force reality check, should correspond.

MileHigh

[Pirate88179]

MH:

I agree but,  (always a but) does the frequency not have to increase also or, in TK's set-up, does that happen automatically like in a Bedini motor?  In other words, on mine, I have to change the vr's to get it to accelerate.  This can be done continually until it reaches the max rpm for that configuration.

Perhaps you can explain this:

http://www.youtube.com/watch?v=LfprTzG5SY4

I never was able to figure out why this happened the way it did.  Some folks on Youtube offered their opinions which may, or may not have been correct.

This probably has nothing to do with TK's motor and for that, I am sorry.  (But it might)

Bill

PS  I had mounted the coil on a threaded rod assembly such that I could, with some precision, move the coil's position to the rotor.  I had already found the "sweet spot" in my earlier videos.

[TinselKoala]

Hey Bill, this whole discussion is kind of a "hijack" of the original thread on reed-switched magnet spinner, and I apologize for that. I would ask a moderator to transfer all this to a new thread but I don't have the foggiest idea how.

Maybe we should just start a new thread and carry on the MHOP discussion there.

Your little motor is really cooking! I don't have any idea why it is doing what it does with your resistance changing. What kinds of explanations did people give you?


MH, your AC voltage integrator is great... but will it work for a spiky, pulsed DC signal too? But I'm not sure if it is applicable here because any power taken off will be through a diode and put onto a big cap anyway, and there are losses in that process for sure.

And your explanation of the torque point is good, for the max RPM case under no load. I'm not sure if the same timing and dwell parameters will apply to the loaded rotor though, since it will stabilize at a slower speed.

I've made a new video showing the waveforms and how they change with setpoint setting; it's being processed and uploaded now, should be ready in an hour or so.

[Pirate88179]

TK:

Thanks for your understanding.

A fellow named Drevetoobe offered the following explanation:

"I'll take a stab at an explanation. For starters the motor is exhibiting "metastability", there are multiple speeds where everything stabilizes. That's were the electrical power coming from the coil is in balance with the mechanical power being burned off in the spinning rotor.
When you start to increase the resistance, less power is being burned off in the pick-up coil. This means there is more power left over to go towards spinning the rotor and it speeds up.
Now that you are spinning faster, the main drive coil is on less time, and the inductor's natural resistance to change in current is giving you another opportunity to add more power. If you can provide more voltage for a longer time you can pump a bit more power through the coil. So you lower the resistance again and the coil is on for a slightly longer time and the speed creeps up. And so on. Every time the motor stabilizes it is running at a new metastability point. A reasonable guess."

I did this video back in 2009 and it makes me feel a lot better that you are not sure (right away) why this worked the way it did.  It has always bugged me.  Oh, input was 12v in case it was not mentioned in this video.  (I started with a 9v battery in the first videos)

Also, I think that if that fellow's explanation above were correct, then I could do this again (3rd gear) and again (4th gear) etc.  But 2nd gear was all I could get out of it.

Thanks again,

Bill