1. Assignment#01: Literature Survey on Sensors and Actuators 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

2. 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-2 Outline –Reference List –Further Information –Major Applications –Basic Working Principle –Design Considerations –Materials –Production –Loudspeaker Application –Limitations & Failure Modes –Vendors & Cost Information

3. 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-3 Reference List (1) 1.http://circuitcellar.com/wp- content/uploads/2012/02/AX-march-Klasco.pdfhttp://circuitcellar.com/wp- content/uploads/2012/02/AX-march-Klasco.pdf 2.http://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Voice_coil 3.http://www.consult- g2.com/papers/paper8/paper.htmlhttp://www.consult- g2.com/papers/paper8/paper.html 4.http://www.pwr-con.com/voice-coil-motor.htmhttp://www.pwr-con.com/voice-coil-motor.htm

4. Reference List (2) 5.http://hackedgadgets.com/2007/10/02/hard-disk- drive-voice-coil-laser-shutter-actuator/http://hackedgadgets.com/2007/10/02/hard-disk- drive-voice-coil-laser-shutter-actuator/ 6.http://www.speakers.net/dloudspeakers.asphttp://www.speakers.net/dloudspeakers.asp 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-4

5. 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-5 Further Information http://en.wikipedia.org/wiki/Loudspeaker

6. 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-6 Major Applications Speakers Hard-disk read/write heads Other linear actuator applications Image 1 – Disk Drive Cutaway (5)

7. Basic Working Principle (1) Consists of: –Bobbin (Former) –Collar –Winding 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-7 Image 2 – Voice Coil Pieces (1)

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-8

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-9 Image 3 – Linear Voice Coil Motor (4)

10. Basic Working Principle (4) Overhung vs. Underhung Designs –Two ways in which the voice coil is immersed in the magnetic field 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-10 Image 4 – Overhung vs. Underhung Coils (2)

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-11

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-12

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-13

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) 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-14

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-15

16. Loudspeaker Application (1) Electro-acoustic transducer (produces sound in response to a electrical audio signal input) 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-16 Image 5 – Speaker Cutaway (6)

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-17

18. Limitations & Failure Modes (1) Mechanical Failure –Crushing of the bobbin if materials and their thicknesses are not sufficient –Poor adhesive bonding 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-18

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 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-19

20. Limitations & Failure Modes (3) Thermal Failure Example 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-20 Image 6 – Good voice coil vs. burned voice coil (1)

21. Vendors & Product Information H2W Technologies –http://www.h2wtech.com/Pages/Voice-Coil-Linear- Actuators.aspx?gclid=CPqu0e6v064CFakERQodTX_ ddQhttp://www.h2wtech.com/Pages/Voice-Coil-Linear- Actuators.aspx?gclid=CPqu0e6v064CFakERQodTX_ ddQ BEI Kimco Magnetics –http://www.beikimco.com/actuators_linear_CYL_unh oused.phphttp://www.beikimco.com/actuators_linear_CYL_unh oused.php 4/23/2015 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators Slide-21