PCB mono coil

[Tec]

I'm going to make a PCB mono coil, anyone done this ?

I expect it to be easier and tidier and have better performance than one I can wind:

Specifications of PCBCOIL-1 are:

Diameter 250mm
Turns 25,
Track width 0.5mm
Layers 2

Shielding: mesh ground plane built in.

Solderable Links available to short out coil to have less windings.

Any suggestions or comments ?

[Qiaozhi]

This has been discussed previously ->
http://www.geotech1.com/forums/showt...ghlight=spiral

[bernte_one]

hello

im on the way to make a pcb flat spiral coil but i don´t expect much.
the thin copper layer has a high resistance for hole coil
you could solve this with solder the copper-lines to make them stronger
a spiral coil in diameter to a us letter format or european A4 you can print them by using
some pcb drawing programms they has a option "Spezialformen" "Sonderformen" (german)
specialforms etc.
with a greater diameter you should print at a copy shop or draw it by hand (like i - good action in the commercial breaks on tv)

[taliesin]

try inkscape freeware graphics

i think inkscape has a good spiral drawing facility if i remember

[bklein]

I wonder what a 10"x10" 6 layer board would cost....

[Tepco]

Except this is most expensive way to make coil, you will have very large ohmic resistance (calculate, tracks are only 35u thick). What type of mesh you intend to use for shielding? (unclear from text, but coil on one layer, grid on another?) Not sure this is a good idea, putting more metal into searchcoil, and this will slow it down for sure, loosing all advantage of spiral design (maybe very thin line mesh, 4-8mil or something, and not too dense, i never tried this way) From my experience, 2:1 OD:ID shape works best, turn number is about OK, will hit something around 200uH or somewhat more depending on design.

Please report your results whit finished coil, and even better, comparison whit similar geometry coil made using , say teflon or PVC insulated wire.

[bernte_one]

insulated wire is also my favorit you can make also good planar coils from it
and it is much easier
https://fotoalbum.web.de/gast/bernd....o-Planar-Spule

[mikebg]

Bernd, according wire type LiY 0,25/1,3 printed in the box, your coil is made of Litzendraht having conductor area 0.25 sq mm and outer diameter 1.3 mm. Is this true?

[bernte_one]

hello mike

thats right (catch that photo for that reason everybody can see)
this wire is the most wanted in german pulsdetektor forum

[Tepco]

One easy to find alternative is transparent insulation "speaker" type cable, like in 5-1 home theaters etc, 2x0.25mm litz, 1.8mm insulation on each, i use both wires in parallel to reduce resistance.

[Tec]

Ok here it is, a pcb coil

Ok here is the PCB coil.

It seems pretty good.
It turned out very close to calculations for a spiral coil.

• http://www.circuits.dk/calculator_fl...l_inductor.htm

Inductance = 310 uH (using oscillations when in parallel with 1uF capacitor)
Resistance = 4.7 ohms
Capacitance to shield 2.5nF

The physical dimensions:
20cm inner, 30cm outer (5mm fatter on one side than the other, due to minor variation)
Copper thickness = 2oz , required to get the low resistance.
28 turns, 1.4mm wide track.

Made using circle shapes then breaking them with a drill hole and connecting them.


Note the shielding:
It is fingers of copper, giving capacitance, but confounding to eddy currents similar to slotted al foil.
* It is broken at one end (does not make a full current loop of course)


Testing:
on my pi, without changing the damping resistor (335 ohm) a nice shaped discharge curve starting at about 20uSec (after amplifier curve, i.e the curve looks good, as fast as the bundle coils I made)

At the beach:
shielding worked (minimal effect when move up and down on wet sand).
*Very touchy when edge is dug in to sand, or sand gets on top.

This is due to I believe the close contact between sand and coil and will be solved by SPACING, a buffer around the coil to put space between it and the capacitive/conductive sand resting on top and edges...

Depth is as good (or better) than my hand wound coil !
It is very light, and consistent (symmetrical and 'clean' on targets)

(I found four targets: bobby pin, AU 20c piece, Au $1 coin, bottle cap)


Pretty good for first version (version a) !

[Qiaozhi]

Made using circle shapes then breaking them with a drill hole and connecting them.

Instead of making the coil with circle shapes, you could use a spiral.
Here's an example I've created using Easy-PC (Gerber file attached).
28 turns, 60 thou tracks with 80 thou spacing.

The image looks somewhat coarse, as it was taken from a screenshot. However, the Gerber file is completely smooth.

[Tec]

Thanks,
Spiral is nicer, if Easy PC does a spiral, then I might have to use that.

If I change to spiral, it shouldn't change the specs, maybe make it a bit better (symmetrical)

How is the performance of this ?
Do you sell your printed coils ?

[6666]

Somebody from here has uploaded a very good spiral coil design but I think it was a pdf.

[Davor]

Because it is the current turns and enclosed area in question, it would be very nice to get a square PCB coil with minimum groove between turns. Maybe a little mitering at corners?