Tunnig circuit for Solenoid coil

[jameermanur]

Dear all.
I am designing the tuning circuit for the solenoid witch inductance of 6mH. I need a tuning circuit design for it. if any one has please share it, i am designing to tune the frequency of 1Khz-10Khz,with max 2 Amp current. and also please mention how to test and verify the function of the circuit. i have build up the circuit with op07 but not working properly.
i need it asap
thank you,
regards,
Jameer.

 

[FvM]

Explain more clearly what you try to achieve.

Are you talking about a real or simulated inductor (e.g. gyrator based)?

Tuning a resonant LC circuit over a 10:1 range by variable inductor involves 100:1 inductance variation, rather unrealistic for a real inductor, unless it uses a tapped winding.

If you are targetting to simulated inductors (active electronic circuits), you surely can't handle 2 A just with OPs. Designing active inductors as a linear circuit is questionable anyway, because the supply power will be a multiple of the transferred element power.

 

[jameermanur]

i am doing on real inductive coil.
it has 1200 turns and passing 1Amp current to produce 200-300 gauss magnetics field for Farady Rotation experiment.
and passing frequency of 1-10Khz.
for that frequency (Bandwidth)we need tuning circuit.
thank you

 

[jameermanur]

Hi!

The coil of 6mH is fixed not a variable inductor. The signal of various frequencies ranging from 10Hz-10kHz will pass through this coil. For this particular coil/inductor I want to design a tuning ckt. I'd like to mention the specification of this coil once again as: 6mH,1200 turns(13 layers), wire of 18 gauge,length of solenoid as 12.5cm, maximum allowable current thro' this coil~2A. The tuning ckt must have the high Q factor and if possible varying 'Q' facility will be and additional requirement to this.
Kindly suggest me on this, how to resolve it. (Considering circuit parameters: like Tank ckt/parallel RLC ckt).
Awaiting for your reply.
Thanks!

 

[FvM]

Tune to fulfill which criterion?

 

[jameermanur]

Pls refer the above details.
I want to tune it for whole frequency range, varying. Need high Q-factor.

 

[betwixt]

The only way I know of to tune a fixed inductor is with a capacitor. The formula is f=1/(2 * pi * SQRT(L * C)).

The 'Q' will not be very high anyway but you can reduce it by adding a parallel resistance.

Brian.

 

[BradtheRad]

For 6mH inductance:
To resonate at 10 Hz, add a capacitor of 42,000 uF.
At 10 kHz, a capacitor of 42 nF.

The sweep range is 1,000:1.
It is impractical to do this in one sweep. You'll need to switch in various capacitors. Tunable capacitors are becoming rare, and it will require effort and ingenuity to fabricate them with the Farad values you want.

Varactors (variable capacitance diodes) are tunable but they do not pass current, so they will not work.

 

[D.A.(Tony)Stewart]

6mH in series with 0.042F supercap yields 10 Hz @ 0.378 Ohms for Q of 10, your wire ESR and Cap ESR must be 0.0378, which might not be possible with miniature caps. Faraday used oil or parafin filled caps and Tesla used very large Mica Caps and thick wire transformers.

This Supercap has 35 mOhm ESR @ 0.04F.
But I suspect your wire is too thin, so the Copper ESR will be much greater than this.

You could use CRGO laminations to boost L with fewer turns CRGO is cold rolled grain oriented plastic coated steel. Or use an old microwave oven transformer core and wrap a dozen turns of magnet wire maybe.
But as it stands understand that Q is the ratio of reactive impedance to ESR for series and the opposite for parallel resonance using parallel load much higher than X, with ratio of Q. Search for a Nomograph of RLC Z vs f on web. Then Q is easily found vs F and ESR

 

[chuckey]

X6mh @10K ~2 X PI X 10^4 X 6 X 10^-3 ~ 360 ohms @ 1A = 360V !! So putting in a cap of -j 360, gets this down to the series loss resistance of the coil, at 5 KHZ, Xl = 180, Xc = 720, total Z = -j520, so now you need 520V for your current unless you times the C by 4. if we look at it the other way and say you have 200V available and arrange for the circuit to look capacitive at 10 KHZ, then Z = 200 or +j360 and -j 160, so at 5KHZ, its +j180 and -j320 or Z = -j140, which is OK. So with a200V supply you can possiblely squeeze a frequency range of 10KHZ to 4 KHZ, or 2.5 :1, you need 10:1, so you could just about get away with three auto switched in capacitors.
As explained high Q components need to be tuned to the correct frequency, you have a fixed L so you need a massive size (I = 2A) variable cap with range of 100 :1 , this is not possible.
With a huge voltage supply you can get the high frequency current, in fact it seems that you are having to trade PSU voltage against bandwidth or number of switched capacitors.
Frank