+ Post New Thread
Results 1 to 4 of 4

3rd December 2019, 14:23 #1
 Join Date
 Dec 2019
 Posts
 1
 Helped
 0 / 0
 Points
 14
 Level
 1
How to make a coil to be resonance?
I made a helicail coil and have about 250 turns,
how can i made it to be natural resonance?

Advertisement

3rd December 2019, 21:32 #2
 Join Date
 Mar 2008
 Location
 USA
 Posts
 6,525
 Helped
 1914 / 1914
 Points
 40,444
 Level
 49
Re: How to make a coil to be resonance?
Every coil has a SRF (self resonant frequency) but you
may not like where it is. Usually people try to stay below
SRF when they care about inductance as a value.
A low frequency self resonant coil needs high interturn
capacitance which may be unlikely.
You could of course put highQ capacitor across the
entire length, or distribute caps along the winding. You
could even conceive of making them part of the structure
if the wire is bare and the caps don't space the windings
unacceptably.
The electrical length of the wire in total is your other
source of resonance, timeofflight. This is the Tesla
coil's deal. 1nS per foot or thereabouts, you might not
find this lands where you like if you wound the coil first.
If it's 250 turns and 4" circumference, that's maybe
1MHzish (consult your local Tesla coil construction
expert, he ain't me).

Advertisement

4th December 2019, 03:34 #3
 Join Date
 Nov 2012
 Posts
 3,267
 Helped
 815 / 815
 Points
 18,428
 Level
 32
Re: How to make a coil to be resonance?
It already have a natural resonance frequency; because of internal parasitic capacitance. You can either measure it directly or estimate it indirectly.
You have made an inductor; it needs some capacitance to be self resonant. You can put an external capacitor in series or in parallel and tune it for a desired frequency.
You can estimate the inductance from tables (geometric considerations of the solenoid) and also estimate the intrinsic capacitance.
To turn this into an active oscillator, you need an active element (e.g., a transistor) that can provide some gain to overcome losses and provide some measurable output. Without that, it is just a helical coil with a natural frequency determined by its geometry.

Advertisement

4th December 2019, 12:24 #4
 Join Date
 Apr 2014
 Posts
 2,295
 Helped
 921 / 921
 Points
 14,710
 Level
 29
+ Post New Thread
Please login