Electromagnet Question

[mondrasek]

So I learned very quickly that my long solenoid appears to have magnetic affects mostly at the ends, so the middle is kind of a dead zome, similar to the tri-force arrays.  Many of you probably knew that already.

I've been playing with a couple of Imhotep's Bedini fans and threw my new long solenoid into that circuit in place of the re-charge battery.  It seems to have resulted in a resonant circuit.  I have no idea how it is working so I am again asking for assistance with understanding this strange behavior.  The details are here:  http://imhotepslabs.freeforums.org/viewtopic.php?f=3&t=34

As always, I appreciate your input.

M.

[TinselKoala]

Hi Mond, glad to see you are still experimenting.
It's pretty easy to send that 2n3055 circuit into feedback self-oscillation; that's probably what's happening with yours. Also it's pretty easy to blow those transistors with these circuits, so buy a bunch. And they do vary some in their characteristics; sometimes an out-of-control oscillation can be fixed simply by trying a different transistor. Component layout, lead length, and so forth can also have a big effect on feedback oscillations.
I agree that you should use a current-monitoring resistor with your 'scope to do current measurements. If your scope is a modern DSO, it probably has math functions available that can do (roughly) correct power calculations for you, given the voltage vs. time from one channel and the current (voltage drop across the resistor) vs. time from the other channel. The digital multimeters like the Fluke can be pretty good at RMS values--in a certain frequency range!-- but doing the math in the DSO is usually more accurate, as the DMM usually assumes a sinusoidal input and yours won't be.
By connecting the two circuits of your bifilar wound coil in series, you have converted it into a monofilar coil.
The power to accelerate the PM out of the solenoid comes from the power supply, not the PM. You will be able to measure it eventually, as your technique and equipment improves.
You've gotten some very good answers in this thread.

[capthook]

mondrasek -

Any updates on your launching of a PM with a coil?

What are you final conclusions? 
Is there increased power draw from the air coil when the PM is present (and launched) vs. when it's not?
(The last I read is you had concluded the power draw may have actually decreased due to induction in the coil windings by the PM that was beneficial/power consumption decreasing)
What about using a long cylinder PM?

Any other thoughts, planned pursuits with this etc?

[mondrasek]

Sorry capthook, but I never got back to further testing on that.  What I ultimately wanted to do involved two new areas for me, one being launching the PM from a coil, and the other being reusing/reclaiming the electricity used to energize that coil.  I started a couple learning projects on the second part and never got back to the magnet launch (yet).  I am actually following your thread on winding a strong electromagnet very closely in the hopes that you and Xaverius might end up doing it for me!  I'd offer to help by continuing my original experiments but I find myself limited by the equipment and knowledge that I have at hand right now.  If I ever get back to it before you or someone else does, I'll be sure to let you know.

M.