PCB Coil?

[omega]

Hi all,

what is about PCB coils? Have anyone try this? I mean to make a coil on PCB and not with wire.

Thanks, omega

[Carl-NC]

Tesoro uses PCB coils on their Sandshark PI. Someone else (on this forum I believe) did a PCB coil for an IB design. It has the advantages of lower parasitics and exact reproducibility, but worse resistance and a poorer magnetic field.

[omega]

thanks Carl.

[bugwhiskers]

Tesoro uses PCB coils on their Sandshark PI. Someone else (on this forum I believe) did a PCB coil for an IB design. It has the advantages of lower parasitics and exact reproducibility, but worse resistance and a poorer magnetic field.

Using 2oz board and tin plating it will over come the high resisitance/low inductance problem. I have an autocad lisp routine that creates spirals...I tried to attach it to this reply but get a message "error on page".

bugwhiskers

[chemelec]

Using 2oz board and tin plating it will over come the high resisitance/low inductance problem. I have an autocad lisp routine that creates spirals...I tried to attach it to this reply but get a message "error on page".

bugwhiskers

The Inductance problem can be overcome with Lots of Turns, But Even With Two Ounce Copper and Tin Plating, The Resistances are STILL Quite High.

I always use 2 ounce PCB on everything I do and I have etched Numerous ones of these coils.

But they Don't come out Near as good as my Radial wound Coils, at least Not for a PI Detector.

Unless you use Very Wide Traces, you have a High Resistance trace and with Wide Traces, Your Limiting your amount of Inductance.

[Esteban]

Yes, this is a 4 ohm coil! :mad:

I copy this over copper via film technic. I found in a magazine. Was many years ago.

[chemelec]

Yes, this is a 4 ohm coil! :mad:

I copy this over copper via film technic. I found in a magazine. Was many years ago.

And What was the Inductance?

[Esteban]

I'll measure and post it.

[chemelec]

I'll measure and post it.

Taking a Wild Guess from the looks of it I would say about 120uH at most.

[Esteban]

This coil is 9.5 cm diam, 30 turns + center point (decreasing in diameter, of course), each turn wide 1 mm and spaced 0.85 mm, resistence 4.1 - 0.2 (this is cable's resistance of tester) = 3.9 ohms, inductance shows here .023 mH = 23 uH, but no contrasted with other instrument.

I'll post photos of the film (no find at this moment yet!) and original photo in magazine. This coil was designed for wideband electromagnetotherapy.

[Sean Goddard]

What about multi layer PBC's?? No one thought of that yet?

[Carl-NC]

I expect taking the spiral all the way to the center will hurt performance. You want at least 50% of the diameter open.

"What about multi layer PBC's?? No one thought of that yet?"

I laid out a 2-layer PCB coil years ago, but never made it.

- Carl

[chemelec]

Here is one PCB coil that I have on hand.

This one was done by a friend of mine on 1 ounce pcb. It measures 7.75 inches by 2.875 inches.

It has an Inductance of 126uH and a DC Resistance of 25.77 Ohms.

Even if it was done with 2 Ounce copper and Tin Plated, it would Still be about 12 Ohms.

Gary

This coil is 9.5 cm diam, 30 turns + center point (decreasing in diameter, of course), each turn wide 1 mm and spaced 0.85 mm, resistence 4.1 - 0.2 (this is cable's resistance of tester) = 3.9 ohms, inductance shows here .023 mH = 23 uH, but no contrasted with other instrument.

I'll post photos of the film (no find at this moment yet!) and original photo in magazine. This coil was designed for wideband electromagnetotherapy.

[bugwhiskers]

I made another PCB coil on the weekend, capsule shaped, semicircle on the ends with straight sides.

L: 285 mm
W: 147 mm
Tracks: 36
Track width: 1.33 mm
Track spacing: 2 mm
PCB: 1 oz copper
DC Impedance: 7.6 ohms
Inductance:~ 200 uH

The inner tracks are only 10 mm apart and it doesn't seem to affect performance. I will have to make a similar one with inner tracks further apart to see if it makes any difference but will be hard to compare as there will be fewer tracks, lower inductance and impedance.

The high impedance doesn't worry me as my PIMD has a SMPS and I am hitting the coil with 15.7 volts. The 15.7 volts was chosen as it fitted within the spread of Electrolytic capacitor voltage ratings. One day I will up the voltage to 25V, 35V & 50V to see if there is any benefit apart from a shorter MOSFET on time.

Wuth the coil decsribed above and 15.7 volts for 37 uS I can take my first sample 8.65uS after MOSFET shutoff. (flat top on flyback is about 0.5 uS)

[bugwhiskers]

I made another PCB coil on the weekend, capsule shaped, semicircle on the ends with straight sides.

L: 285 mm
W: 147 mm
Tracks: 36
Track width: 1.33 mm
Track spacing: 2 mm
PCB: 1 oz copper
DC Impedance: 7.6 ohms
Inductance:~ 200 uH

The inner tracks are only 10 mm apart and it doesn't seem to affect performance. I will have to make a similar one with inner tracks further apart to see if it makes any difference but will be hard to compare as there will be fewer tracks, lower inductance and impedance.

The high impedance doesn't worry me as my PIMD has a SMPS and I am hitting the coil with 15.7 volts. The 15.7 volts was chosen as it fitted within the spread of Electrolytic capacitor voltage ratings. One day I will up the voltage to 25V, 35V & 50V to see if there is any benefit apart from a shorter MOSFET on time.

Wuth the coil decsribed above and 15.7 volts for 37 uS I can take my first sample 8.65uS after MOSFET shutoff. (flat top on flyback is about 0.5 uS)