How to use FEMM?

Spasticteapot · 25th September 2008, 03:56 AM

I'm trying to build a very small high-excursion ribbon driver for headphone use, and I've been having a dickens of a time trying to figure out how to use FEMM. Anyone have a good tutorial?

el`Ol · 25th September 2008, 06:55 PM

Unfortunately German, but this helped me a lot:
http://www.michaelgaedtke.de/SubMenu...M-Tutorial.htm

Andrew Steele · 25th October 2008, 11:20 AM

If you run it through Google translate , most of it is understandable. If you have any more questions - shoot away.

One thing to remember is to get as much triangulation (nodes) in the gap as possible, it seems that the topic is covered in the tutorial. But I remember I learnt the hard way when I thought I had designed the perfect motor but I had just two triangles in the gap so it wasn't true at all...

valveitude · 25th October 2008, 05:49 PM

I found the Yahoo Group for FEMM to be a valuable resource. They have (or had..been a while since I looked) a tutorial in English in the files section, and the guy who wrote the program is the moderator...

http://tech.groups.yahoo.com/group/F...ec=group&slk=1

Casey

jaya000 · 7th April 2009, 06:21 AM

Anybody uv simulated loudspeaker magnet assembly?
If yes, then how about giving guidance to fellow members here.
waiting for response.

Andrew Steele · 7th April 2009, 11:29 AM

Hi Jaya000

UV as I understand is short for ultraviolet, do you mean something else? I use FEMM for simulating loudspeaker magnet assemblies, I'm happy to answer any questions that I think I can answer.

jaya000 · 7th April 2009, 01:06 PM

Sorry Andrew Steele.
I mean to say hv & not uv.
Typing mistake.
Hope u understand

Andrew Steele · 7th April 2009, 01:30 PM

What is HV?

If you could use full words and not abbreviation it might help.

I understand these are some common things you would simulate in a speaker motor with FEMM -

(B) - Tesla - A unit of measure for the amount of magnetic energy/force.

Bl - The sum of (B) multiplied by the length in meters of the voice coil in the gap. This measure is commonly presented in Thiele-Small parameters.

Xmax - not so much FEMM but can calculate where Bl drops to 80% of original Bl.

There are more things you can do. But if you can try to explain a bit more possibly someone can help.

el`Ol · 7th April 2009, 02:43 PM

A short description:
File New - magnetic or electrostatic problem
Problem - define units, planar/radial
Grid Set Grid - define grid size (units per dot)
Grid Snap to Grid - defined points are aligned with grid dots
set points (with mouse)
select line icon
define lines by selecting two points
Properties Material Library
select materials by drag and drop to the right side
strange green icon is the material marker
set markers with mouse (better with deactivating snap to grid)
select marker with right mouse button
press blank on the keyboard
dialog opens, let femm choose mesh size is only recommended for air, 0.5mm is good for usual audio devices (you have to draw a frame around everything and label the inside with air)
File Save
yellow botton is for creating mesh, the wheel for calculation and the glasses for viewing
in the viewer press the colour icon and select "show density plot" to get everything nice and colourful
with the line icon you can draw a line and display a graph of the flux density over its length (typically define extra points in the editor before calculation)
press the blue graph icon for showing the graph
exporting pictures is done with Copy Paste

jaya000 · 7th April 2009, 04:23 PM

Thanks Andrew Steele & el`Ol,
I want to simulate magnet assembly of loudspeaker.
Many of us must have done it.
I just want the info to get started in FEMM.
Initial settings, selection of properties & analyzing magnetic flux bl linearity etc.
more info will help to learn more.
waiting for guidance from gurus here.

25th September 2008, 03:56 AM	#1
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	How to use FEMM? I'm trying to build a very small high-excursion ribbon driver for headphone use, and I've been having a dickens of a time trying to figure out how to use FEMM. Anyone have a good tutorial?

25th October 2008, 05:49 PM	#4
valveitude diyAudio Member Join Date: Apr 2005 Location: Naches,WA	I found the Yahoo Group for FEMM to be a valuable resource. They have (or had..been a while since I looked) a tutorial in English in the files section, and the guy who wrote the program is the moderator... http://tech.groups.yahoo.com/group/F...ec=group&slk=1 Casey __________________ Experience is a wonderful thing. It enables you to recognize a mistake when you make it again.

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25th September 2008, 06:55 PM	#2
el`Ol diyAudio Member Join Date: May 2005 Location: Bavarian Forest	Unfortunately German, but this helped me a lot: http://www.michaelgaedtke.de/SubMenu...M-Tutorial.htm

25th October 2008, 11:20 AM	#3
Andrew Steele diyAudio Member Join Date: Jan 2002 Location: Queensland, Australia	If you run it through Google translate , most of it is understandable. If you have any more questions - shoot away. One thing to remember is to get as much triangulation (nodes) in the gap as possible, it seems that the topic is covered in the tutorial. But I remember I learnt the hard way when I thought I had designed the perfect motor but I had just two triangles in the gap so it wasn't true at all...

7th April 2009, 06:21 AM	#5
jaya000 diyAudio Member Join Date: Dec 2006	Anybody uv simulated loudspeaker magnet assembly? If yes, then how about giving guidance to fellow members here. waiting for response.

7th April 2009, 11:29 AM	#6
Andrew Steele diyAudio Member Join Date: Jan 2002 Location: Queensland, Australia	Hi Jaya000 UV as I understand is short for ultraviolet, do you mean something else? I use FEMM for simulating loudspeaker magnet assemblies, I'm happy to answer any questions that I think I can answer.

7th April 2009, 01:06 PM	#7
jaya000 diyAudio Member Join Date: Dec 2006	Sorry Andrew Steele. I mean to say hv & not uv. Typing mistake. Hope u understand

7th April 2009, 01:30 PM	#8
Andrew Steele diyAudio Member Join Date: Jan 2002 Location: Queensland, Australia	What is HV? If you could use full words and not abbreviation it might help. I understand these are some common things you would simulate in a speaker motor with FEMM - (B) - Tesla - A unit of measure for the amount of magnetic energy/force. Bl - The sum of (B) multiplied by the length in meters of the voice coil in the gap. This measure is commonly presented in Thiele-Small parameters. Xmax - not so much FEMM but can calculate where Bl drops to 80% of original Bl. There are more things you can do. But if you can try to explain a bit more possibly someone can help.

7th April 2009, 02:43 PM	#9
el`Ol diyAudio Member Join Date: May 2005 Location: Bavarian Forest	A short description: File New - magnetic or electrostatic problem Problem - define units, planar/radial Grid Set Grid - define grid size (units per dot) Grid Snap to Grid - defined points are aligned with grid dots set points (with mouse) select line icon define lines by selecting two points Properties Material Library select materials by drag and drop to the right side strange green icon is the material marker set markers with mouse (better with deactivating snap to grid) select marker with right mouse button press blank on the keyboard dialog opens, let femm choose mesh size is only recommended for air, 0.5mm is good for usual audio devices (you have to draw a frame around everything and label the inside with air) File Save yellow botton is for creating mesh, the wheel for calculation and the glasses for viewing in the viewer press the colour icon and select "show density plot" to get everything nice and colourful with the line icon you can draw a line and display a graph of the flux density over its length (typically define extra points in the editor before calculation) press the blue graph icon for showing the graph exporting pictures is done with Copy Paste

7th April 2009, 04:23 PM	#10
jaya000 diyAudio Member Join Date: Dec 2006	Thanks Andrew Steele & el`Ol, I want to simulate magnet assembly of loudspeaker. Many of us must have done it. I just want the info to get started in FEMM. Initial settings, selection of properties & analyzing magnetic flux bl linearity etc. more info will help to learn more. waiting for guidance from gurus here.

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