A bifilar coil is a parallel LC and a normal coil is a series LC

If we have a cap and charge it to 5v, the cap reads 5v.  2 caps in series, charge with 5v and each cap will have 2.5v. And the capacity goes down as you put more in series. 100 caps in series, charge with 5v and each cap will have .05v.  Same reduction as a normal coil when you add turns. A series LC.


Now put 2 caps in parallel and charge with 5v. Each cap will have 5v. 100 caps, 5v each. That is a bifi coil. More turns, same voltage in each cap as less turns. A parallel LC.

Just in case someone posted otherwise.

Mags

Bifi Trivia!!

A bifi coil takes less time to wind than a normal coil because 3000 total turns only takes 1500 revolutions of the bobbin. 

Mags

Quote from: Farmhand on January 14, 2014, 04:33:17 PM
Conrad, can you please give us a break down of the results of the series  test as compared to the parallel test, what is the difference if any ? Is the series resonant frequency of the bifilar coil lower than the series resonant frequency of the monofilar coil ? Is it the same as the parallel resonant frequency ?

I measured the resonance frequency of a series LC circuit (C = 10 nF), see http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383070/#msg383070

The measurement circuit for a series LC tank is from Gyula, see http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383065/#msg383065, see also Gyula's explication http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383103/#msg383103  The measurement in a series LC tank is less "indicative". (I want to note that Gyula posts good explanations and is often providing expert help, not only in this thread.)

Theory says that parallel and series LC circuit have the same resonance frequency.

The resonance frequency is defined by L = inductance of the coil and C = "external capacitance plus self capacitance". If the "external capacitance" = 0, we have "self resonance" and if the "external capacitance" = large, "self capacitance" becomes negligible.

Also for parallel and series LC circuit: The resonance effect occurs when inductive and capacitive reactances are equal in magnitude.

See http://www.allaboutcircuits.com/vol_2/chpt_6/2.html and http://www.allaboutcircuits.com/vol_2/chpt_6/3.html (the formula for f = frequency is the same in parallel and series LC circuit).

Important facts about parallel LC circuits:

In the parallel configuration, resonance occurs when the complex electrical impedance of the circuit approaches infinity, meaning that the circuit draws no current from the AC power source.

A prallel resonant circuit provides voltage magnification.

Important facts about series LC circuits:

In the series configuration, resonance occurs when the complex electrical impedance of the circuit approaches zero, the result is a short circuit across the AC power source at resonance.

A series resonant circuit provides current magnification.

(I restated in very short form what MileHigh explained in detail, read his posts, he is a good teacher.)

Quote from: Farmhand on January 14, 2014, 04:33:17 PM
Here is a thought Conrad, to test my theory that the applied voltage can vary the extra capacitance secured by the bifilar coil or any coil I guess, I intend to make a bifilar coil with the turns spaced so that with only a few volts or the meter used shows the capacitance secured between the two open windings is less than when they are wound closer together, thicker insulation more plate gap in the capacitor.

That will allow me to attempt to get a resonant frequency with only the few volts with the increased "plate gap", then also to get a resonant frequency with a higher voltage that should secure a higher capacitance between turns and therefore a lower resonant frequency of the coil for a higher applied voltage, within limits. If the gap that makes the capacitor is too wide for the applied voltage the capacitance secured should be less, just like if the plates of a capacitor are brought closer the capacitance reading increases. A parallel plate capacitor with a plate gap of 10 mm will give less capacitance secured in practice when only charged with 1 volt than when charged with 1000 volts, is what I am imagining to describe an extreme. If I'm right or wrong is another matter.

I am a beginner, but I would say that C = capacitance (the ability to store a charge) is a constant for a given capacitor or between two wires in a coil (independent of Voltage)? But the higher V = Voltage the more Q = charge can be stored in a capacitor. Formula C = Q/V or V*C = Q. So, the resonance frequency will not change with Voltage, but the charges pushed back and forth will be higher if Voltage is higher. See, http://en.wikipedia.org/wiki/Capacitor#Overview.

Greetings, Conrad

Some great clips from Itsu:

Pick-up coil for a pulse motor configured in parallel resonance:

http://www.youtube.com/watch?v=syxL4f2OsPg
http://www.youtube.com/watch?v=yNtnLAVk9Og

Pick-up coil for a pulse motor configured in serial resonance:

http://www.youtube.com/watch?v=K-avee5Z1oU

@MileHigh: Again, great explanations, thank you. The nebula in front of my eyes when looking at LC circuits and coils is lifting.

So, I will wind two helical coils with "many turns and many layers of turns" (one bifilar the other monofilar) to bring my tests into the 100 KHz region.

The planned coil parameters:

- core diameter 10 mm (interchangeable: air core, fitting Ferrite core and bundle of soft wire sticks)

- length of coil 30 mm

- outer diameter of coil 40 mm

- 31 AWG wire (wire diameter 0.22 mm)


I would also say to Farmhand and all other pan cake coil builders to wind a big pan cake coil with many turns for the same reason.

My two pan cake coils are a bit small and have too few wires and therefore introduced problems when testing caused by the MHz frequencies involved (the 1 pF decoupling capacitor for my scope probe became an important issue which was expertly solved by Gyula).

It is much easier to wind a pan cake coil with thick wire, but it will then have relatively few turns. It takes some craftsmanship to wind a pan cake coil and it needs a support plate (may be Plexiglass or some other plastic sheet, may be a very dry wood board).

For measurements please see my posts:

http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383043/#msg383043
http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383045/#msg383045
http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383070/#msg383070
http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg383084/#msg383084
http://www.overunity.com/13460/teslas-coil-for-electro-magnets/msg382906/#msg382906

and videos at http://www.youtube.com/user/conradelektro/videos

Good calculators:

http://www.1728.org/resfreq.htm
http://daycounter.com/Articles/How-To-Measure-Inductance.phtml
http://www.qsl.net/in3otd/inductors.html

This kind of concludes my measurements with my two pan cake coils. For the time being I move on to helical coils. But if some tangible and understandable claim concerning pan cake coils materialises I am ready to go back.

Greetings, Conrad