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Biomagnetic Field Generation. Project #10 Brett Duncan & Tanvi Patel ECE 445 Senior Design December 1, 2005 Introduction. Biomagnetics – the study of applied magnetic fields on living tissue.

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biomagnetic field generation
Biomagnetic Field Generation

Project #10

Brett Duncan & Tanvi Patel

ECE 445 Senior Design

December 1, 2005

  • Biomagnetics – the study of applied magnetic fields on living tissue.
  • Design and implement a biological research device which allows for the application of magnetic fields to cell culture chambers
  • Allow for the application of magnetic field to cell cultures (normal, cancer cells) to determine the magnetic field effects on cell growth, differentiation and repair.
  • Magnetic fields are being used along with iron-containing antibodies as an alternative to Flow Cytometry for cell sorting and identification.
  • The overall goal is to create a reliable and accurate device which can provide a uniform magnetic field throughout a specified volume over a culture dish.
  • Also, to characterize this field in a way that will be useful for studies of cell cultures placed inside the magnetic field.
  • Magnetic Field range between 1 and 100 Gauss with a resolution of one Gauss.
  • User friendly display showing current field strength.
  • Quick and easy ability to “dial in” desired magnetic field.
  • Adaptable to different sized cell culture containers.
device overview1
Device Overview
  • Agilent 25 Watt Power Supply

- Provide + 5 Volt for PIC and LCD

  • Xantrex 1000 Watt Power Supply

- Provide 14 Volt and 0 – 7.2 Amps to Buck Converter and Magnetic Chamber

buck converter
Buck Converter
  • Allows for tunable current supplied to Magnetic Chamber for control over magnetic field strength
magnetic field chamber
Magnetic Field Chamber
  • Generates magnetic field for application to a variety of cell culture containers
pic microcontroller lcd
PIC Microcontroller/LCD
  • PIC Microcontroller

- Receives reference voltage as an input and uses a stored calibration equation to calculate magnetic field in chamber

  • LCD Display

- Displays calculated magnetic field from PIC for the user

power supply noise testing
Power Supply Noise Testing
  • Vmax = 14.438 V
  • Vmin = 13.578 V
  • Max Ripple:

850 mV

noise effects on device performance
Noise Effects on Device Performance

Top Left : Agilent Power Supply

Top Right : Xantrex Power Supply

Bottom Left : Xantrex Power Supply after noise reduction

device testing
Device Testing
  • Determination of maximum field strength and an optimum usable range for the device
  • Set device at 100% duty cycle and increased supply voltage while monitoring magnetic field strength and state of components
field strength and resolution testing
Field Strength and Resolution Testing
  • Maximum field strength of 177 Gauss
  • Determined a usable range of 0 to 100 Gauss with a resolution of one Gauss
magnetic field strength vs current measurement
Magnetic Field Strength vs. Current Measurement
  • Vary the duty cycle of the Buck Converter to determine field strength vs. current
  • Compare results versus theoretical calculation


calibration curve
Calibration Curve
  • Varying the duty cycle corresponds with:
    • A change in Magnetic Field Strength
    • A change in current through the sensing resistor
      • This results in a change in voltage across the resistor
  • Therefore a voltage across the sensing resistor can be related to a field strength
  • A calibration curve was established using these 2 parameters
magnetic field characterization
Magnetic Field Characterization
  • An x,y,z,coordinate system was defined
    • 10 x 16 cm stage area
    • 4 cm above and below stage
  • Measurements of Magnetic field strength were taken throughout the stage area in two cm intervals
  • Usable range of 0-100 Gauss Magnetic Field with 1 Gauss resolution
  • Uniform Magnetic Field of 30 cm3
  • Magnetic Field Strength Displayed within 1.8% accuracy of exterior magnetometer
  • Linear Amplifier circuit unable to handle large power dissipation
  • Power dissipation considerations with components, heatsinks, and wiring
  • Limitations due to high currents
  • Magnetic Chamber Construction
  • Mathematical limitations with PIC
  • Current Design
    • Use of a PIC with advanced math functions
    • Less noisy power supply
    • Use of Custom printed circuit boards
  • To achieve 1000 Gauss field
    • Power Dissipation Considerations
      • Minimize MOSFET RDS(on)
      • Minimize Diode Vf
      • Larger heatsinks, cooling fans
    • Magnetic Chamber Design
      • Switch to magnetic wire
      • Increase wire size
      • Cooling for coils
  • We successfully created a variable magnetic chamber for biological research
  • Applicability determined by research demands for
    • Cancer research
    • Normal cell healing and growth
    • Cell sorting and identification
  • Professor Ray Fish
  • Professor Jonathan Kimball