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?
Unfortunately German, but this helped me a lot:
http://www.michaelgaedtke.de/SubMenu_Tutorials/FEMM-Tutorial.htm
http://www.michaelgaedtke.de/SubMenu_Tutorials/FEMM-Tutorial.htm
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...
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...
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/Femm/?v=1&t=search&ch=web&pub=groups&sec=group&slk=1
Casey
http://tech.groups.yahoo.com/group/Femm/?v=1&t=search&ch=web&pub=groups&sec=group&slk=1
Casey
Anybody uv simulated loudspeaker magnet assembly?
If yes, then how about giving guidance to fellow members here.
waiting for response.
If yes, then how about giving guidance to fellow members here.
waiting for response.
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.
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.
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.
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.
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
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
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.
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.
Have a look at the sample speaker design in the program folder > C:\Program Files\femm42\examples - That is a good starting point.
Make sure you save a copy before making any changes to it. FEMM seems to save as you go.
Make sure you save a copy before making any changes to it. FEMM seems to save as you go.
Thanks u Andrew Steele,
I will try now.
But still guidance to know about various testings to consider for loudspeaker magnet assembly are required.
I will try now.
But still guidance to know about various testings to consider for loudspeaker magnet assembly are required.
Can you post your design goals? Possibly some of us could try simulating the motor too. Give us details like
Voice coil diamater
voice coil winding height
Target xmax
Target Bl
Magnet material - Neodymium or Ceramic
A drawing would probably help too
Voice coil diamater
voice coil winding height
Target xmax
Target Bl
Magnet material - Neodymium or Ceramic
A drawing would probably help too
el`Ol :
yellow botton is for creating mesh, the wheel for calculation and the glasses for viewing
What calculations r done with this?
in the viewer press the colour icon and select "show density plot" to get everything nice and colourful
Done it.
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
Can u explain this in more details?
I hv attached my drawing in the my earlier post.
How to check the motor linearity with FEMM?
yellow botton is for creating mesh, the wheel for calculation and the glasses for viewing
What calculations r done with this?
in the viewer press the colour icon and select "show density plot" to get everything nice and colourful
Done it.
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
Can u explain this in more details?
I hv attached my drawing in the my earlier post.
How to check the motor linearity with FEMM?
Hello Jaya000,
The mesh generator is an extra program that needs a file for input and output. I find it practical to have the mesh displayed before the finite element calculation (wheel), so one can see if the mesh size is adequate for the problem (in your case not, "let triangle choose mesh size" gives a result that is not fine enough for checking the field linearity).
For checking the linearity you first set two extra points in the editor, one right above and one right below the gap. A new mesh has to be generated and a new calculation has to be done. In the viewer you press the red line icon and then you can connect the two extra points. Then press the blue graph icon to display the graph (flux density over the drawn line).
BTW,
your flux density is not very impressive, here is an example, not directly comparable because it is field coil, but very well done.
http://home5.inet.tele.dk/f-hammer/
Regards,
Oliver
The mesh generator is an extra program that needs a file for input and output. I find it practical to have the mesh displayed before the finite element calculation (wheel), so one can see if the mesh size is adequate for the problem (in your case not, "let triangle choose mesh size" gives a result that is not fine enough for checking the field linearity).
For checking the linearity you first set two extra points in the editor, one right above and one right below the gap. A new mesh has to be generated and a new calculation has to be done. In the viewer you press the red line icon and then you can connect the two extra points. Then press the blue graph icon to display the graph (flux density over the drawn line).
BTW,
your flux density is not very impressive, here is an example, not directly comparable because it is field coil, but very well done.
http://home5.inet.tele.dk/f-hammer/
Regards,
Oliver
Thanks el`Ol.
"your flux density is not very impressive"
Yes because there is very bog gap in the top plate & tyoke.
This is to accommodate 4 layer voice coil to get more BL.
I hv now added the voice coil in the gap.
How to go ahead now?
new to this field. learning from guidance.
Thanks in advance.
"your flux density is not very impressive"
Yes because there is very bog gap in the top plate & tyoke.
This is to accommodate 4 layer voice coil to get more BL.
I hv now added the voice coil in the gap.
How to go ahead now?
new to this field. learning from guidance.
Thanks in advance.
Sorry, I am no expert, either, I never simulated both magnets and coils in one simu. Just one hint: The important figure is not Bl, but Bm, wherre m is the copper mass. The copper mass in the gap can only increase linearly with the width, whereas the reduction of B is non-linear with the gap width (I don´t know the exact relation).
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