Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto...
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Transcript of Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto...
![Page 1: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/1.jpg)
Finite Element Model of a Magnet Driven Reed Switch
Bryan M. LaBarge1 and Dr. Ernesto Gutierrez-Miravete2
1Gems Sensors and Controls, 2Rensselaer at Hartford
![Page 2: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/2.jpg)
Scope
• Use COMSOL to predict and visualize a magnetic field
• Use further processing to determine field strength
• Correlate field strength to reed switch operation
![Page 3: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/3.jpg)
Background
• Magnet/reed switch systems are used extensively for proximity sensing
• Ability to predict reed switch operation reduces testing time, time to market
• Knowing magnet strength at any point allows designer to focus on reed switch selection
![Page 4: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/4.jpg)
What is a reed switch?
![Page 5: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/5.jpg)
Governing Equations
• Maxwell’s Equations
• Magnetization Equation
0
t
BE
JD
H
t
B = (H+M)
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Application Description
![Page 7: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/7.jpg)
Model Creation
• 2-D (r-z coordinate) magneto-static analysis• Magnet centerline bounds model• Magnet modeled as iron, bounded by air
– M = 1.6x105 A/m
– Relative permeability () = 4000
• Elements: 15,472 (triangular, 7859 nodes)• Static, stationary solver• Output = Gauss (r-, z-, normal direction)
![Page 8: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/8.jpg)
Model Validation
• Magnet mounted to XY table, Gauss probe stationary, 3.9 mm parallel to magnet centerline
• Measurements taken every 0.3 mm
• Results plotted vs. COMSOL output
![Page 9: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/9.jpg)
Procedure (in brief)
• Export COMSOL data to EXCEL
• Use EXCEL data as look-up table
• Calculate coordinates of switch movement along an arc
• Calculate magnetic field at coordinates using look-up table
• Determine switch operation
![Page 10: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/10.jpg)
Procedure (continued…)
• COMSOL data exported to EXCEL– 0.3 mm resolution in (x,y) coordinates
• Magnet/Switch location measured relative to pivot point (origin)
• Open/closed positions of switch measured for later reference
![Page 11: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/11.jpg)
Procedure (continued…)
• xmax defines arc radius• Coordinates calculated on 0.02 mm
resolution in x-direction• Coordinates are interpolated from the look-
up table to assign Gauss values to points on the arc
• Arc coordinates/Gauss values become second look-up table
![Page 12: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/12.jpg)
Results
• Reed switches are tested using a test coil, measuring operation in terms of Ampere-Turns (AT)
• AT = I n• I = current; n = number of coil turns• Test switch open/closed values:
– Open = 29.1 AT– Closed = 18.7 AT
![Page 13: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/13.jpg)
Results (continued…)
• Prior empirical testing shows Gauss/AT correlation
• G = 0.533AT – 0.857
• Open = 14.7 G
• Closed = 9.12 G
![Page 14: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/14.jpg)
Results (continued…)• Model Verification
– Red = COMSOL, Blue = Empirical
051015202530354045
0 5 10 15 20 25
Distance (mm)
Gau
ss (
G)
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Results (continued…)• COMSOL contour plot, normal direction
![Page 16: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/16.jpg)
Results (continued…)• COMSOL contour plot, z- direction
![Page 17: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/17.jpg)
Results (continued…)
• Using the values of Gauss on switch arc and the Gauss values for switch operation, switch location can be interpolated.
• Example: 29 AT = 14.57 G = (15.47, 8.72) mm
![Page 18: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/18.jpg)
Results (continued…)
• Actual switch points compared to calculated switch points
x, closed y, closed x, open y, open
Model 15.47 8.72 14.98 10.96
Observed 15.34 8.97 14.83 10.82
Error 0.84% -2.87% 1.00% 1.27%
![Page 19: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/19.jpg)
Conclusions
• COMSOL model agrees with empirical results to within 2%
• Increased error in y than x due to geometry
![Page 20: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/20.jpg)
Conclusions
• Application requires 20o maximum angle, switch should operate at 10o
• Model says switch will open at 18.3o and close at 9.9o
• Decrease in AT on switch will close switch over full arc.
![Page 21: Finite Element Model of a Magnet Driven Reed Switch Bryan M. LaBarge 1 and Dr. Ernesto Gutierrez-Miravete 2 1 Gems Sensors and Controls, 2 Rensselaer at.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649d4e5503460f94a2db41/html5/thumbnails/21.jpg)
Conclusions
• Model is a simplification of actual system
• Further work can be done to model effects of reed blades
• Speaker’s first COMSOL model