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General => General Discussion => Topic started by: Donaldwfc on May 21, 2009, 15:53:08 pm

Title: Coil design Questions
Post by: Login to see usernames on May 21, 2009, 15:53:08 pm
What would happen if I used a solid steel rod, maybe 1" diameter, as a coil core? will it still work in the frequency range required?

How do you determine the inductance when winding a simple coil so that you can wind several different coils and have the same resonant frequency for each, even when they are made of different sized wire?

ei
-If all the coils have the same diameter, and same number of turns, would they resonate at the same frequency even when made of different gauge? (or how would you accomplish this?)


Title: Re: Coil design Questions
Post by: Login to see usernames on May 21, 2009, 20:40:01 pm
What would happen is that it would not function well at high frequency.
What happens is that the bar becomes one large magnet, when the pulse is cut, there is magnetic lag, caused by vortexes called "Eddy" currents.
In a core that has many laminations or made of many small pieces (compressed ferrite powder core) the effect is many small magnets adding up. So when the pulse is cut each individual lamination demagnetizes. This produces a much sharper change in field. The result is much higher voltage and cleaner waves.

A solid core will work, just not as good
Title: Re: Coil design Questions
Post by: Login to see usernames on May 24, 2009, 02:57:07 am
What would happen if I used a solid steel rod, maybe 1" diameter, as a coil core? will it still work in the frequency range required?

How do you determine the inductance when winding a simple coil so that you can wind several different coils and have the same resonant frequency for each, even when they are made of different sized wire?

ei
-If all the coils have the same diameter, and same number of turns, would they resonate at the same frequency even when made of different gauge? (or how would you accomplish this?)

Here are some results of different core materials
Using the same bobbin with 300 turns per gap (pic 4) of my bifilar yeilded the following Henry readings
AIR
                     0.076 H leg 1
                     0.075 H leg 2
Ferrite
   0.152 H leg 1
   0.150 H leg 2
CRGO
   2.954 H leg 1
   2.933 H leg 2
IRON rod
                     0.349 H leg1
                     0.346 H leg 2
Good luck BR