Stubblefield coils (bifilar) and speculations

[libra_spirit]

Jeanna,

Thanks for the URL

"Parallel Differential Electromagnet"

There is the Stubblefield winding design.
Brings up some intresting questions, since they were using this coil in telephony, why?
Cancelling a magnetic field with current still flowing would seem to be the reason, it would drop the relay without taking down the DC circuit. The coil would still resist AC. Today we would see this as simply wasting energy, but having a background in telephone I can see the reason may be to keep the switchtrain up while dropping the relay switching circuit to a different path through a matrix.

My question for the Stubblefield cells is that if we set up a DC current in a coil that cancels the magnetic field what is left?
Does a pulsed cancelling field still radiate an A vector field?

Dave L

[Pirate88179]

@ libra_spirit:

My understanding is that when pulsing the primary, the secondary emits high voltage ac. I assume the magnetic field collapses momentarily while disconnected via the switching mechanism, but the frequency of these disconnections is what determines the frequency of the resultant ac.  This idea seems  so simple that to me it is beautiful.  Now, If only we can get it to work.  I don't know if this answers your last question or not.  I learned more form reading the first 30 pages of Jeanna's book link than I ever knew so, I can't wait to finish reading.

I am still leaning toward the rotary make/break devices for the primaries.  Many advantages as I see it and no metal fatigue.  I have still not built one but I have the parts for one as of now.

Bill

[storre]

I see a rotary type of switch not switching fast enough. You have design in mind?

[Pirate88179]

Sure.  Actually Localjoe came up with the idea of a rotary switch.  My approach may be a little different, but basically the same.

I was thinking of using a cd disk with conducting lines painted across it in an axial manner. (from the center hole outward) Like pc board paint.  Spin this with a variable resistor controlled motor and use two "brushes" made from stranded copper wire positioned up against the spinning cd such that a connection is made and unmade every several degrees of cd rotation.  By varying the rpm many different frequencies could be explored.  One can also very the number and space between the conducting lines as well.

We first had hopes of possibly self-powering the motor with the primary but, to uncomplicate things, I am just going to use a AAA battery for this for now.  I am using a small motor salvaged from a vibrating electric toothbrush. (the brush cost $5.00 3 years ago)  These are the same motors they put into shaving razors that vibrate as well.  They just have a small weight on the shaft to remove which is what causes the vibrations.  These are advertised as "ultra-sonic" but I really doubt they vibrate in the 20,000 Hz range which they would have to for this to be true.

We have posted some drawings of our switching ideas on Joe's topic somewhere way back.  I hope this makes some sense.

Bill

[storre]

I have about 20 NC reed switches arriving in a few days so hopefully I will be successful enough to test out the fatigue problem

Anyone have any ideas about using a Hall IC in place of the reed switch? Not sure if it could duplicate a NC reed switch action.

http://www.asahi-kasei.co.jp/ake/en/product/ic/outline.html