number of turns? (DD coil)

[ShinyGoldPT]

Hi, i'd like to know how many turns i have to make with a 0.25mm copper wire (copper + resin) to archive 6mH and 6.5mH. I tried to use the calculator posted by the administratorbut since im working with a D shape and is not a perfect D (see attachment) i don't know the radius.Could you guys help me?

Thank you all.

[Skippy]

Work out the circumference of your D-shaped coil. Then work out a radius, R, for a circular coil with that circumference ( use R = Circ / (2 * pi) ). Now use the coil calculator as normal, but try and achieve an inductance 2% greater than you want.

[kt315]

for D shape is not a formula, not still invented. you must calculate for a diameter of round form, wind and
measure by LC meter.

[Qiaozhi]

Hi, i'd like to know how many turns i have to make with a 0.25mm copper wire (copper + resin) to archive 6mH and 6.5mH. I tried to use the calculator posted by the administratorbut since im working with a D shape and is not a perfect D (see attachment) i don't know the radius.Could you guys help me?

Thank you all.

You can get a reasonably accurate result by adding the two diameters (255 and 137) and dividing by 4. Then use that figure as the radius in the calculation.
i.e. (255 + 137) / 4 = 98

[Tim]

Tesoro coil specs from THunting/homefire .25mm, 255x137mm.
TX 99 turns 6mH 18-25R 14.5kHz.
RX 104 turns 6.5mH 18-25R
RX resonance with 15nf is about 16.1 kHz.

[ShinyGoldPT]

Hi all,
thank you all for the quick replies.

Tim, thank you so much for these values now i can do my coil.
Qiaozhi, good idea to calculate the "radius" of the elipsoid and the value is a really good approximation (testing Tim numbers)
kt315, i don't own a LC meter nor a oscilloscope (i don't know how im gonna null the device without one)
Skippy, i understand your idea but i think i wouldn't get a accurate value of the radius, but i will try it and sharmy results.

The big question now is how im gonna null the circuit + coil without the oscilloscope.


Thank you all

[Skippy]

If you can, try and wind one extra isolated turn on your coils, so for example 99T + 1T. This allows you to create a coil of 98 / 99 / 100T as needed, which would be approx. 6.0 mH +/- 0.1 mH. Or go that bit extra and wind 99T + 2T + 1T, for +/- 0.3 mH.

[Tim]

Also to null coils, hook up TX coil only, then use a multimeter on AC volts to measure for lowest possible value across RX coil. (I think that's right-can someone correct me it I'm wrong?)
This info is in the TGSL and Raptor/ITMD build info I think.....

[homefire]

Using the Build Document those are the Numbers I came up with. Depending on your winding, they work out quite well. As you can see I deviated from the Original. A Good DVM can get you real close on the Null. Prepare to Learn New Cuss Words. They seem to come out of no place.

[ShinyGoldPT]

Hi all,

im waiting for more copper wire to come so i can finish Rx (Tx is already made). Will post where my progress has soon i finish Rx.

Tnk you all.

[kt315]

kt315, i don't own a LC meter nor a oscilloscope
---
you have to balance the coil only by o-scope. i can not suggest you another way.