Forums

printed inductors

Started by Tom Del Rosso May 13, 2013
When an inductor is printed on a PCB in the shape of a 'square wave' or 
square zigzag, each time it zags the trace doubles back on itself.  Doesn't 
this cancel the magnetic field to an extent?  How much does the coil 
structure matter to a coiled inductor, or would the straight wire have the 
same inductance?


-- 

Reply in group, but if emailing remove the last word. 


On May 13, 10:34=A0pm, "Tom Del Rosso" <tomd...@verizon.net.invalid>
wrote:
> When an inductor is printed on a PCB in the shape of a 'square wave' or > square zigzag, each time it zags the trace doubles back on itself. =A0Doe=
sn't
> this cancel the magnetic field to an extent? =A0How much does the coil > structure matter to a coiled inductor, or would the straight wire have th=
e
> same inductance? > > -- > > Reply in group, but if emailing remove the last word.
perhaps it is a high frequency inductor which is more like a distributed transmission line inductor?
On Mon, 13 May 2013 22:34:01 -0400, Tom Del Rosso wrote:

> When an inductor is printed on a PCB in the shape of a 'square wave' or > square zigzag, each time it zags the trace doubles back on itself. > Doesn't this cancel the magnetic field to an extent? How much does the > coil structure matter to a coiled inductor, or would the straight wire > have the same inductance?
When it doubles back it'll reinforce the magnetic field, and only destructively interfere on the next line over (with the current going the same way). But I have no clue how much difference it makes, or how much it acts like a straight wire of the same length. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Mon, 13 May 2013 22:34:01 -0400, "Tom Del Rosso"
<tomd_u1@verizon.net.invalid> wrote:

> >When an inductor is printed on a PCB in the shape of a 'square wave' or >square zigzag, each time it zags the trace doubles back on itself. Doesn't >this cancel the magnetic field to an extent? How much does the coil >structure matter to a coiled inductor, or would the straight wire have the >same inductance?
The ones you see on PC boards may be delay lines. When you route a differential pair and turn a corner or something, one trace gets longer than the other. So some people wigwag the shorter one to make the electrical lengths equal. Like this: https://dl.dropboxusercontent.com/u/53724080/PCBs/T165_zigzag.jpg I doubt that a tight wigwag has a time delay that exactly corresponds to the geometric trace length that the PCB layout software reports. Real RF inductors are usually proper spirals. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
"Tim Wescott"

>> When an inductor is printed on a PCB in the shape of a 'square wave' or >> square zigzag, each time it zags the trace doubles back on itself. >> Doesn't this cancel the magnetic field to an extent? How much does the >> coil structure matter to a coiled inductor, or would the straight wire >> have the same inductance? > > When it doubles back it'll reinforce the magnetic field, and only > destructively interfere on the next line over (with the current going the > same way).
** Tim has no idea just how stupid he is. .... Phil
On May 13, 10:34=A0pm, "Tom Del Rosso" <tomd...@verizon.net.invalid>
wrote:
> When an inductor is printed on a PCB in the shape of a 'square wave' or > square zigzag, each time it zags the trace doubles back on itself. =A0Doe=
sn't
> this cancel the magnetic field to an extent? =A0How much does the coil > structure matter to a coiled inductor, or would the straight wire have th=
e
> same inductance? > > -- > > Reply in group, but if emailing remove the last word.
We make spiral coils on PCB to 'shim' magnetic fields. I'm not sure what you mean by zig-zagging back... maybe a picture? Re: a coil versus a length of wire. You get more inductance from the coil. I think if you have a fixed length of wire and wanted to make the largest inductance then you'd wind it as one big single turn coil. (hopefully someone will correct me if that is wrong.) George H.
George Herold Inscribed thus:

> On May 13, 10:34&Acirc;&nbsp;pm, "Tom Del Rosso" <tomd...@verizon.net.invalid> > wrote: >> When an inductor is printed on a PCB in the shape of a 'square wave' >> or square zigzag, each time it zags the trace doubles back on itself. >> &Acirc;&nbsp;Doesn't this cancel the magnetic field to an extent? &Acirc;&nbsp;How much does >> the coil structure matter to a coiled inductor, or would the straight >> wire have the same inductance? >> >> -- >> >> Reply in group, but if emailing remove the last word. > > We make spiral coils on PCB to 'shim' magnetic fields. > I'm not sure what you mean by zig-zagging back... maybe a picture? > > Re: a coil versus a length of wire. You get more inductance from the > coil. I think if you have a fixed length of wire and wanted to make > the largest inductance then you'd wind it as one big single turn > coil. (hopefully someone will correct me if that is wrong.) > > George H.
I suspect the OP is refering to the meander lines on a pcb used to match signal timing over varying trace lengths. -- Best Regards: Baron.

"Tom Del Rosso" <tomd_u1@verizon.net.invalid> wrote in message 
news:kms7un$4bl$1@dont-email.me...
> > When an inductor is printed on a PCB in the shape of a 'square wave' or > square zigzag, each time it zags the trace doubles back on itself. > Doesn't this cancel the magnetic field to an extent? How much does the > coil structure matter to a coiled inductor, or would the straight wire > have the same inductance?
The only zig-zag inductors' I've seen, were tacho generators in "pancake" motors such as the spindle drive in a disk drive or similar. Maybe a service manual for that kind of kit would throw some light.
On 5/14/2013 8:02 AM, George Herold wrote:

 > We make spiral coils on PCB to 'shim' magnetic fields.

PCB inductors appear to have poor Q.
They are convenient to make, but lacking performance.

 > I'm not sure what you mean by zig-zagging back... maybe a picture?
 >
 > Re: a coil versus a length of wire.  You get more inductance from the
 > coil.  I think if you have a fixed length of wire and wanted to make
 > the largest inductance then you'd wind it as one big single turn
 > coil.  (hopefully someone will correct me if that is wrong.)

That is incorrect. Using same piece of wire, max. inductance is achieved 
with max. number of turns.


Vladimir Vassilevsky
DSP and Mixed Signal Designs
www.abvolt.com

John Larkin wrote:
> On Mon, 13 May 2013 22:34:01 -0400, "Tom Del Rosso" > <tomd_u1@verizon.net.invalid> wrote: > > > > > When an inductor is printed on a PCB in the shape of a 'square > > wave' or square zigzag, each time it zags the trace doubles back on > > itself. Doesn't this cancel the magnetic field to an extent? How > > much does the coil structure matter to a coiled inductor, or would > > the straight wire have the same inductance? > > The ones you see on PC boards may be delay lines. When you route a > differential pair and turn a corner or something, one trace gets > longer than the other. So some people wigwag the shorter one to make > the electrical lengths equal.
I should have said that this definitely is an inductor. It's a choke connected to the power trace on a 4GHz board. -- Reply in group, but if emailing remove the last word.