Post by thread:[EE]: Coil Imprinted on PCB

Hi Werner, Sorry, I don't have formulas, but I doubt that you will get anywhere near 150uH with a coil printed on a PCB. Those are usually in the nH range, as far as I know. 150uH is not really a "low value", that is around the inductance of small DC motors (which have a fair number of turns wound on a metal core). Sean At 09:06 AM 11/30/00 +0200, you wrote: {Quote hidden}>Hi > >I'm designing an application that requires a few small coils with low values >1uH to 150uH. I've seen a few designs where the coil is part of the layout >on the PCB, and was wondering if anyone has any formulas for these coils. Or >is it a try your luck and see what value pops out thing? > >Thanks! > >Friendly Regards, >Werner Soekoe >.....WernerSKILLspam@spam@fsl.gov.za > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

I made a slight mistake. The values are not in uH, but supposed to be nH. Therefore, the values reange from 1nH to 150nH. Sorry! > Hi > > I'm designing an application that requires a few small coils with low values > 1uH to 150uH. I've seen a few designs where the coil is part of the layout > on the PCB, and was wondering if anyone has any formulas for these coils. Or {Quote hidden}> is it a try your luck and see what value pops out thing? > > Thanks! > > Friendly Regards, > Werner Soekoe > WernerSKILLspamfsl.gov.za > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Werner, What you are referring to is called microstriping. The formulas that apply are very intense. There are a few programs that you can down load free, that will help. I don't have them handy, if I find one I will forward the info to you. Remember that even the type of fiberglass used in the circuit board will effect your calculations. The location of other components around the coil will also have an effect. I assume that you meant nH for the coils, you will not have any problems implementing the inductors with the aid of a good program and a little knowledge of microstriping. Good luck. Gordon Varney > Hi > > I'm designing an application that requires a few small coils with low values > 1uH to 150uH. I've seen a few designs where the coil is part of the layout > on the PCB, and was wondering if anyone has any formulas for these coils. Or {Quote hidden}> is it a try your luck and see what value pops out thing? > > Thanks! > > Friendly Regards, > Werner Soekoe > EraseMEWernerSspam_OUTTakeThisOuTfsl.gov.za > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Hi Werner It's not easy to make a 'wound' inductor flat on a PCB. Making use of the fact that all conductors have inductance, based on their length and cross section, you lay out a PCB with a track length based on the inductance you need. Rule of thumb ids 1nH / mm, so a track 100mm long has an inductance of 100nH. The track can be zigzagged to fit it into the required space, but according to your earlier post, you need to fit 150mm of track onto your board for 150uH. Does this help? Mark ------------------------------------------------------------------- Mark Hull Engineering/Technical EMS (Africa) (Pty) Ltd PO Box 1026, Melville, 2109, South Africa Ph +27 11 482 4470 Fax +27 11 726 2552 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 04:22 PM 11/30/00 +0200, Mark Hull wrote: >Hi Werner > >It's not easy to make a 'wound' inductor flat on a PCB. >Making use of the fact that all conductors have inductance, based on their >length and cross section, you lay out a PCB with a track length based on the >inductance you need. >Rule of thumb ids 1nH / mm, so a track 100mm long has an inductance of >100nH. >The track can be zigzagged to fit it into the required space, but according >to your earlier post, you need to fit 150mm of track onto your board for >150uH. Shouldn't this be 150 metres ? Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" speffspam_OUTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 01:07 PM 11/30/00 +0200, you wrote: >Mark, > >You have totally confused me now. I don't have the feintest idea what the >ohms/mm is all about. But lets put it this way. I will be using the >oscillator circuits in transmitters and receivers. The one will transmit at >+- 100MHz (FM Band) and the other at approxiamately 280 MHz. > >What can you tell me about this? You can definitely get there, but there's some things to watch out for.. Coils built in this manner couple easily to external circuits, and nearby components will affect their inductance. A conventional inductor (toko, from digikey) is way more predictable, if not lower cost. You can get to larger values too, just clamp an RM-4 core around it, through cutouts in the PCB. -- Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

There is also the issue of patent infringement. Radio Electronics carried a contruction article many years ago ('80s) where the author used the PCB inductor method in the project (UHF TV Transmitter if I recall correctly). RE had to publish a notice some months later warning readers that using this project was infringing on a current patent. With luck the 17 year limit on that patenet has expired. The patent would also have details on computing the inductance I would think. R Werner Soekoe wrote: {Quote hidden}> > I made a slight mistake. The values are not in uH, but supposed to be nH. > Therefore, the values reange from 1nH to 150nH. Sorry! > > > Hi > > > > I'm designing an application that requires a few small coils with low > values > > 1uH to 150uH. I've seen a few designs where the coil is part of the layout > > on the PCB, and was wondering if anyone has any formulas for these coils. > Or > > is it a try your luck and see what value pops out thing? > > > > Thanks! > > > > Friendly Regards, > > Werner Soekoe > > @spam@WernerSKILLspamfsl.gov.za > > > > -- > > http://www.piclist.com hint: The PICList is archived three different > > ways. See http://www.piclist.com/#archives for details. > > > > > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Some info on coil on PCB: This person uses 4 pcbs to create a 20uH coil: hem.passagen.se/sm0vpo/info/pcb-coil.htm (no calculations) The Eagle web board has the following message: www.eagleware.com/wwwboard/messages/968.html Two recent articles I have written cover this subject. The September 1999 issue of RF Design magazine had an article entitled Designing a Low-Noise VCO on FR4. This article used a printed inductor and techniques for reducing effects associated with the poor dielectric of FR4. The October 1999 issue of Applied Microwave & Wireless had an article entitled High-Q Resonators on FR4. This article explained how to obtain printed inductors with Q higher than the inherent Q of FR4. Both articles may be downloaded at this site at the What's New page. Also the Examples manual of Version 7 includes a spiral inductor example in =EMPOWER=,the electromagnetic simulator. A demo of a magnetic, inductor and choke design software (with free schematic capture): http://www.i-t.com/engsw/intusoft/magdesgn.htm Looks like you can specify the inductor construction (planar), wire, core and everything. This may be your best bet. This message gives a simple example: http://fstewart.ne.mediaone.net/DaEtiCpesIdcosEtchedNews.shtml Another message idicates the book "Introduction to Microwave Engineering" has this info in it. There's a whole slew of papers on inductors and various methods of construction here: http://nickel.arai.riec.tohoku.ac.jp/yamaguti/general/j_papers.html There is an FM transmitter (100MHz) with three etched inductors on its PCB here: http://members.tripod.com/rclindia/trans.html (PCB inductors aren't necessarily spiral or even wound about themselves, every track features inductance) If you have a SUN workstation and lots of money you could use SPIRAL: solutions.sun.com/catalogs/now/Electronic_Design_Automation/Design_Analysis/34633.html A 3D inductor design package meant to deal with PCB inductors specifically. You can find a few other messages (including journals) to spiral inductors here: http://fstewart.ne.mediaone.net/DaEtiCpesIdcosSpiral.html#Spiral Here is a demo analog simulator that has a model for spiral inductors: http://www.ednmag.com/reg/download/analog.asp Someone wrote a bibliography of inductor calculations, including references to 22 works which include impedance calculations relating to spiral inductors specifically: http://members.aol.com/marctt/Technical/Inductance_References.htm Here's a short "Guesstimating inducatance of wire loops" http://members.aol.com/marctt/CV/Abstracts/inductance.htm And "Inducatance Calculation Techniques - Part II: Approximations and Handbook Methods" www.pcim.com/articles/1999/art0006/art1.html quote "Included are inductance calculations for polygons, disk coils, finite-length solenoids and flat planar spirals" This company appears to distribute shareware, one program (spirlind #2259) does the calculations for spiral inductors: http://www.marblehead.com/business/034/ The page referring to the program is here: http://www.marblehead.com/business/034/electron.htm There are others, I found these by doing various searchs on google for inductors, spiral, planar, etched, etc. I hope this helps. -Adam Werner Soekoe wrote: {Quote hidden}> > Hi > > I'm designing an application that requires a few small coils with low values > 1uH to 150uH. I've seen a few designs where the coil is part of the layout > on the PCB, and was wondering if anyone has any formulas for these coils. Or > is it a try your luck and see what value pops out thing? > > Thanks! > > Friendly Regards, > Werner Soekoe > KILLspamWernerSKILLspamfsl.gov.za > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

It occurs to me that tesla coils use a spiral wound primary. You might try going in that direction. In fact, here is the exact equation you're looking for: http://home.earthlink.net/~electronxlc/formulas.html#spiral And here is a javascript calculator for it: http://www.geocities.com/CapeCanaveral/Hangar/3108/calculat.html#Pancake (Found searching for "tesla coil equations" on google) -Adam For those interested in tesla coils (perhaps brought to this message by searching for tesla coil, there is a tesla coil designer program here: http://www.noonco.com/tesla/ And a tesla coil cookbook here: http://home.sprynet.com/~halldo/teslatc.htm Werner Soekoe wrote: {Quote hidden}> > Hi > > I'm designing an application that requires a few small coils with low values > 1uH to 150uH. I've seen a few designs where the coil is part of the layout > on the PCB, and was wondering if anyone has any formulas for these coils. Or > is it a try your luck and see what value pops out thing? > > Thanks! > > Friendly Regards, > Werner Soekoe > RemoveMEWernerSTakeThisOuTfsl.gov.za > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.