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Prepared by: Dave Call Dept. of Electrical and Computer Engineering Utah State University

ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Voice Coil Actuators. Prepared by: Dave Call Dept. of Electrical and Computer Engineering Utah State University. 3/9/2012. Outline. Reference List Further Information Major Applications

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Prepared by: Dave Call Dept. of Electrical and Computer Engineering Utah State University

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  1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Voice Coil Actuators Prepared by: Dave Call Dept. of Electrical and Computer Engineering Utah State University 3/9/2012

  2. Outline • Reference List • Further Information • Major Applications • Basic Working Principle • Design Considerations • Materials • Production • Loudspeaker Application • Limitations & Failure Modes • Vendors & Cost Information ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  3. Reference List (1) • http://circuitcellar.com/wp-content/uploads/2012/02/AX-march-Klasco.pdf • http://en.wikipedia.org/wiki/Voice_coil • http://www.consult-g2.com/papers/paper8/paper.html • http://www.pwr-con.com/voice-coil-motor.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  4. Reference List (2) • http://hackedgadgets.com/2007/10/02/hard-disk-drive-voice-coil-laser-shutter-actuator/ • http://www.speakers.net/dloudspeakers.asp ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  5. Further Information • http://en.wikipedia.org/wiki/Loudspeaker ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  6. Major Applications • Speakers • Hard-disk read/write heads • Other linear actuator applications Image 1 – Disk Drive Cutaway (5) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  7. Basic Working Principle (1) • Consists of: • Bobbin (Former) • Collar • Winding Image 2 – Voice Coil Pieces (1) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  8. Basic Working Principle (2) • Bobbin – provides a rigid structure to wind the coil on • Collar – secures the wire leads and reinforces the bobbin • Winding – path for the electrical current to produce EM field • *Note: Most voice coils use this structure. A less common type is a monolithic (self-supporting) voice coil that does not use a bobbin or collar ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  9. Basic Working Principle (3) • How it Works • By driving a current through the voice coil, an electromagnetic field is produced • This EM field reacts to the EM field of a permanent magnet that is fixed in place • This results in the voice coil (and whatever is attached to it) moving Image 3 – Linear Voice Coil Motor (4) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  10. Basic Working Principle (4) • Overhung vs. Underhung Designs • Two ways in which the voice coil is immersed in the magnetic field Image 4 – Overhung vs. Underhung Coils (2) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  11. Basic Working Principle (5) • Overhung (most common) • Coil height is greater than gap height • Higher coil mass, medium to high sensitivity • Soft non-linearity as the coil exceeds limits • Underhung (high-end speakers) • Gap height is greater than coil height • Low coil mass, low to medium sensitivity • Hard non-linearity as the coil exceeds limits ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  12. Design Considerations (1) • Effect of Materials Used • Materials used will affect performance of the voice coil • Eg., For loudspeaker applications, materials chosen can affect distortion, sensitivity, and sound quality • Lightweight materials, better voice coil performance • Designers must use appropriate materials and thickness for the bobbin and collar to prevent bobbin crushing for the application ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  13. Design Considerations (2) • Overheating • Passing too much power through a coil can cause it to overheat • Many low frequency voice coils include vents that allow air cooling • Typical voice coils employ materials that can withstand temperatures up to 150 C • Some magnet designs have aluminum heat sink rings above and below the ‘gap’ to better dissipate heat ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  14. Materials • Bobbin Materials • Polyimide(PI), Glass fiber, Carbon fiber composite • Collar Materials • Paper • Winding Materials • Copper (low cost, good conductor, most common) • Aluminum/CCA (good for low mass applications) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  15. Production • Bobbin and collar are coated with a thin layer of adhesive on one side • They are then cut to the required dimensions • The bobbin is wetted with a solvent • The winding, which also has an adhesive coating, is wound onto the bobbin • The solvent activates the adhesives creating a secure bond between all components • The collar is placed over the winding leads ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  16. Loudspeaker Application (1) • Electro-acoustic transducer (produces sound in response to a electrical audio signal input) Image 5 – Speaker Cutaway (6) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  17. Loudspeaker Application (2) • Speaker cone is driven by voice coil • The electrical audio signal is input into the windings of the voice coil • The EM field generated in the winding reacts to the EM field from the permanent magnet thus moving the voice coil and in turn the diaphragm of the speaker • Movement of the speaker diaphragm at the correct frequency results in the produced sound ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  18. Limitations & Failure Modes (1) • Mechanical Failure • Crushing of the bobbin if materials and their thicknesses are not sufficient • Poor adhesive bonding ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  19. Limitations & Failure Modes (2) • Thermal Failure • Current driven through the windings will cause heating • Materials soften when heated up (including the bobbin, collar, and wire insulation) • Too much current can cause failure of the materials and the device ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  20. Limitations & Failure Modes (3) • Thermal Failure Example Image 6 – Good voice coil vs. burned voice coil (1) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

  21. Vendors & Product Information • H2W Technologies • http://www.h2wtech.com/Pages/Voice-Coil-Linear-Actuators.aspx?gclid=CPqu0e6v064CFakERQodTX_ddQ • BEI Kimco Magnetics • http://www.beikimco.com/actuators_linear_CYL_unhoused.php ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

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