ferrofluids

Arduino code to read proximity from 2 infrared sensors, drive 2 electromagnets and animate a ferrofluid sculpture.

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Ferrofluid sculptures

• Ferrofluids + 2 electromagnets + IR proximity sensors + Arduino.

Electromagnet

• 10cm * 1cm screws, smoothed edges.
• 4-layer coil, 60 turns per layer. Insulated copper wire (1mm / 2.8 Amps).
• 12V / 2Amps DC supply from an IDE-to-USB adaptor.
• Magnetic field shall be strong at the top, its gradient pulls the fluid up.
• Tight wiring to canalize it though the screw.
• First 2 layers are the most important ones. Top loops must be as close as possible to the fluid.

Power control

• Arduino's Pulse Width Modulation (500Hz, max ratio = 10% to stay < 2.5A).
• R3 motorshield or optocoupler + low Rds(on) MOSFET.

Code

• Last version : ferro3states2FerrosMotorShieldNoSin.ino
• Edited on codebender.cc

Prototypes

• DC supply directly wired to one electromagnet with a 5 Ohms power resistor
  • ON/OFF switch + 5 Ohm power resistor => 2 Amps.
  • Need a 'power' resistor dissipating 24W. It gets hot.
• Arduino with home made PWM power board (optocouplers and MOSFET)
  • Removed the hot resistor and added spikes modulation.
  • Power is controlled via Pulse Width Modulation (alpha max = 10% to stay below 2.5A)
  • With analogwrite (500Hz) + optocoupler + a low Rds(on) MOSFET.
  • Field strength is controlled by hand proximity (IR sensor).
• Addition of a second electromagnet
• Using a motorshield to be able to inverse polarities

Misc

• Magnetic fields are difficult to generate and canalize.
• Better start with a small screw and and a simple design.
  • Make a tight, clean wiring.
  • First 2 layers are the most important ones.
  • Use glue to fix layers.
  • Do not damage wires with sharp edges or with the glue.
  • Wire loops must be very close to the ferrofluid.

Parts

• https://www.supermagnete.de/eng/physics-magnets/ferrofluid-10-ml-magnetic-fluid-for-experiments_FER-01
• http://www.conrad.fr/ce/fr/product/605237/Bobine-de-fil-de-cuivre-100-mm-28-A-Block-CUL-100100/SHOP_AREA_17416?
• http://www.arduino.cc/en/Tutorial/PWM
• http://www.datasheetcatalog.com/datasheets_pdf/4/N/3/5/4N35.shtml
• https://www.fairchildsemi.com/datasheets/RF/RFP50N06.pdf
• http://www.farnell.com/datasheets/1496354.pdf