Rotating Magnetic Field's and Inductors.

[Dog-One]

The results of the heat dissipation test-with and without rotor.
https://www.youtube.com/watch?v=E0d6tb67oLM

Looks pretty scientific to me Brad.  Nice work.

On the power supply common ground...

I had always thought the same thing as you, but I did some testing on my BK PSU and discovered the black terminal isn't hard connected to the green terminal which is actually linked to the frame ground through the third prong on the mains plug.  Digging around in the original box for the power supply, I happened onto a little metal clip that is designed to link the black and green terminals together for when one truly wants the ground to be reference to earth.  You may want to confirm your PSU is the same, but I think it is fairly safe to say your PSU and scope are probably not tied together via a common earth ground.  It would be nice if typical oscilloscopes had the same little metal clip, but I haven't run into one yet that does.

Another comment about grounding...

Most of our closed-circuit testing completely ignores earth grounding as in electrostatic potential.  When I see devices that supposedly require a solid earth ground to operate, I always become a little suspicious of the huge electrostatic potential & capacitance connected to the circuit.  If you happen to dig into some of the old documents describing electrostatics, you will notice charge accumulates only on the outside of the metallic object; never on the inside.  This is basically the Faraday Cage principal.  Personally I'm not able to throw-out these effects on what would otherwise be considered a closed-circuit, UNLESS the entire closed-circuit including test equipment and power sources are all INSIDE a Faraday Cage.  What I'm getting at is we have a coil that is being continuously energized and dissipated--is it not possible this action is pulling/pushing electrostatic charge from the environment asymmetrically.  If it is, could this charge somehow be doing work within the circuit?  What I need to experiment with is electrostatics in concert with magnetic fields--which may help to explain what the rotor brings to the table with this experiment.

Anyway, I have no gripes about your testing Brad--all really looks good and thorough to me.  Just wanted to pop a few ideas into your thinking and consideration.

[picowatt]

Tinman,

Consider building a strobe to observe the rotor.

Use the second channel of your FG to drive an NPN (or MOSFET) to turn on and off a bright white LED via a current limit resistor and additional battery or supply.  Connect the emitter (or source) and LED supply to the FG/common ground point.

For a quick test, you could just connect an LED across the coil using a current limit resistor and reverse polarity protection diode.  However, using the second FG channel will allow you to adjust the strobe's duty cycle and phase to optimize viewing brightness/clarity and allow you to observe the rotor position at various portions of the coil drive waveform.

Keep in mind that LED's can handle peak currents well in excess of their continuous rating.  At low duty cycles, you can hit them pretty hard.  If you can switch the LED fast enough and with enough current, using a very narrow pulse width will allow you to resolve more position related details while maintaining apparent brightness.  I do not know what the persistence is with regard to the LED phosphors, or what effect it might have on visual clarity (motion blur), but if that becomes problematic, consider a monochrome LED (blue, etc) with rotor labeling/marks appropriate for the color used.

I'd probably try a bright white LED first.  To be bright enough to video the results, you might consider something like a star mounted 3-5 watt LED or just cobble up a cheap flashlight so you can use the reflector (and possibly the battery) as well.  Pick one without a boost converter/electronic drive or bypass that circuitry if it does.  For the ultimate cool, use a flashlight with a tail switch and replace it with a BNC connector.  Use the internal battery and mount the switching components inside the tail cap.     

Thought it might be interesting, at the least it should be fun...

PW

[tinman]

Tinman,

Consider building a strobe to observe the rotor.

Use the second channel of your FG to drive an NPN (or MOSFET) to turn on and off a bright white LED via a current limit resistor and additional battery or supply.  Connect the emitter (or source) and LED supply to the FG/common ground point.

For a quick test, you could just connect an LED across the coil using a current limit resistor and reverse polarity protection diode.  However, using the second FG channel will allow you to adjust the strobe's duty cycle and phase to optimize viewing brightness/clarity and allow you to observe the rotor position at various portions of the coil drive waveform.

Keep in mind that LED's can handle peak currents well in excess of their continuous rating.  At low duty cycles, you can hit them pretty hard.  If you can switch the LED fast enough and with enough current, using a very narrow pulse width will allow you to resolve more position related details while maintaining apparent brightness.  I do not know what the persistence is with regard to the LED phosphors, or what effect it might have on visual clarity (motion blur), but if that becomes problematic, consider a monochrome LED (blue, etc) with rotor labeling/marks appropriate for the color used.

I'd probably try a bright white LED first.  To be bright enough to video the results, you might consider something like a star mounted 3-5 watt LED or just cobble up a cheap flashlight so you can use the reflector (and possibly the battery) as well.  Pick one without a boost converter/electronic drive or bypass that circuitry if it does.  For the ultimate cool, use a flashlight with a tail switch and replace it with a BNC connector.  Use the internal battery and mount the switching components inside the tail cap.     

Thought it might be interesting, at the least it should be fun...

PW

Hi PW

No problem with the strobe,as i have done it many times before to see where the magnet is in relation to the coil when the transistor closes/coil is switched on.

What is the purpose of this exercise ?

P.S
The FG will drive an LED by it self, no problem at all.
As you are talking about using the FG to drive a strobe LED,then i am guessing you are referring to the test where the pulsed inductor driven by the FG is spinning the rotor,and not the test i just posted,where the rotor is being spun in pulse motor mode--no FG ?.


Brad

[tinman]

post removed

[picowatt]

Hi PW

No problem with the strobe,as i have done it many times before to see where the magnet is in relation to the coil when the transistor closes/coil is switched on.

What is the purpose of this exercise ?

P.S
The FG will drive an LED by it self, no problem at all.
As you are talking about using the FG to drive a strobe LED,then i am guessing you are referring to the test where the pulsed inductor driven by the FG is spinning the rotor,and not the test i just posted,where the rotor is being spun in pulse motor mode--no FG ?.


Brad

Tinman,

Yes, I was referring to the FG driven tests.  Do you know for certain to which polarity you are synch'ed (i.e., which polarity and position at turn on)?

Having looked at your waveforms a bit more, the rotor inertia/magnet interaction with the drive coil appears to increase the effective inductance of the coil.  Coil current rises more slowly due to the effective inductance increase, hence less input current.

I am somewhat reminded of an Orbo...

PW