PATENT DOCUMENT

Publication Number: US-8193781-B2
Application Number: US-55455009-A
Country: US
Kind Code: B2

Title: Harnessing power through electromagnetic induction utilizing printed coils

Abstract:
Systems for harnessing power through electromagnetic induction utilizing printed coils are provided. A system can include one or more moveable magnets adjacent to printed coils on a circuit. For example, a system can include one or more magnets that are operative to move alongside a circuit board that includes printed coils. The one or more magnets may move, for example, when a user shakes the system or when the user walks or runs while holding the device. The movement of the one or more magnets may create an electromotive force (e.g., a voltage) across the printed coils, and this force may be used to generate electric power.

Claims:
1. A system for harnessing power through electromagnetic induction, the system comprising:
 a first circuit board comprising:
 a plurality of layers comprising a first layer and a second layer adjacent to the first layer; 
 a plurality of printed coils comprising a first coil printed on the first layer and a second coil printed on the second layer; and 
 a first via between the first layer and the second layer, the first via operative to electrically couple the first coil with the second coil; and 
 
 at least one magnet adjacent to the first circuit board and operative to move alongside the plurality of printed coils to generate an electromotive force across the plurality of printed coils. 
 
     
     
       2. The system of  claim 1 , wherein:
 the plurality of layers comprises a third layer adjacent to the second layer; 
 the plurality of printed coils comprises a third coil printed on the third layer; and 
 the first circuit board comprises a second via between the second layer and the third layer, the second via operative to electrically couple the second coil with the third coil. 
 
     
     
       3. The system of  claim 2 , wherein:
 the first circuit board comprises a periphery; and 
 the second via is closer to the periphery than the first via. 
 
     
     
       4. The system of  claim 2 , wherein:
 each of the plurality of printed coils comprises an inner turn and an outer turn; 
 the first via couples the inner turn of the first coil with the inner turn of the second coil; and 
 the second via couples the outer turn of the second coil with the outer turn of the third coil. 
 
     
     
       5. The system of  claim 1 , wherein the first circuit board further comprises a printed trace printed on the first layer and electrically coupling the first coil with circuitry operative to condition power harnessed by the system. 
     
     
       6. The system of  claim 1 , wherein the first circuit board further comprises a dielectric material covering the first coil. 
     
     
       7. The system of  claim 1 , further comprising an enclosure mounted to the first circuit board and operative to retain the magnet in close proximity to the first circuit board. 
     
     
       8. The system of  claim 1 , wherein the at least one magnet comprises a plurality of magnets coupled together. 
     
     
       9. The system of  claim 1 , further comprising ferrofluid covering at least a portion of at least one of the at least one magnets, wherein the ferrofluid is operative to lubricate the covered magnet when it moves alongside the plurality of printed coils. 
     
     
       10. The system of  claim 1 , further comprising:
 a second circuit board comprising:
 a plurality of layers comprising a third layer and a fourth layer adjacent to the third layer; 
 a plurality of printed coils comprising a third coil printed on the third layer and a fourth coil printed on the fourth layer; and 
 a second via between the third layer and the fourth layer, the second via operative to electrically couple the third coil with the fourth coil; and 
 
 a conductive path electrically coupling the second coil with the third coil. 
 
     
     
       11. The system of  claim 1 , wherein:
 the first circuit board comprises:
 a top side; and 
 a bottom side opposite the top side; and 
 
 the at least one magnet comprises:
 a first portion adjacent to the top side of the first circuit board; 
 a second portion adjacent to the bottom side of the first circuit board; and 
 a third portion extending between the first portion and the second portion. 
 
 
     
     
       12. A system for harnessing power through electromagnetic induction, the system comprising:
 a circuit board comprising:
 a top side; 
 a bottom side opposite the top side; 
 a plurality of layers disposed between the top side and the bottom side and comprising a first layer and a second layer adjacent to the first layer; 
 a plurality of printed coils comprising a first coil printed on the first layer and a second coil printed on the second layer; and 
 a via between the first layer and the second layer, the via operative to electrically couple the first coil and the second coil; 
 
 a top magnet adjacent to the top side of the circuit board and operative to move alongside the plurality of printed coils; and 
 a bottom magnet adjacent to the bottom side of the circuit board and operative to move alongside the plurality of printed coils, wherein the top magnet and the bottom magnet are operative to generate an electromotive force by moving across the plurality of coils. 
 
     
     
       13. The system of  claim 12 , wherein:
 the plurality of layers comprises a third layer adjacent to the second layer; 
 the plurality of printed coils comprises a third coil printed on the third layer; and 
 the first circuit board comprises a second via between the second layer and the third layer, the second via operative to electrically couple the second coil with the third coil. 
 
     
     
       14. The system of  claim 12 , wherein the top magnet is coupled with the bottom magnet. 
     
     
       15. The system of  claim 12 , further comprising:
 a first enclosure mounted to the top side of the circuit board and operative to retain the top magnet in close proximity to the circuit board; 
 a second enclosure mounted to the bottom side of the circuit board and operative to retain the bottom magnet in close proximity to the circuit board. 
 
     
     
       16. The system of  claim 12 , further comprising a support structure coupled with the circuit board and comprising at least one slot operative to guide the top magnet and the bottom magnet when they move alongside the plurality of coils. 
     
     
       17. The system of  claim 16 , further comprising a bracket extending through one of the at least one slots and coupling the top magnet with the bottom magnet. 
     
     
       18. The system of  claim 12 , wherein the circuit board further comprises at least one slot operative to guide the top magnet and the bottom magnet when they move alongside the plurality of coils. 
     
     
       19. The system of  claim 18 , further comprising a bracket extending through one of the at least one slots and coupling the top magnet with the bottom magnet. 
     
     
       20. A method for manufacturing a system for harnessing power through electromagnetic induction, the method comprising:
 manufacturing a circuit board comprising a plurality of layers, a plurality of coils printed on the plurality of layers, and at least one via coupling a first coil of the plurality of coils with a second coil of the plurality of coils; and 
 providing a first magnet adjacent to the circuit board, wherein the first magnet is operative to move alongside the plurality of coils and generate an electromotive force across the plurality of coils. 
 
     
     
       21. The method of  claim 20 , further comprising attaching an enclosure to the circuit board, the enclosure being operative to retain the first magnet in close proximity to the circuit board while allowing the first magnet to move alongside the plurality of coils. 
     
     
       22. The method of  claim 20 , wherein:
 the circuit board comprises a top side and a bottom side; 
 providing the first magnet comprises providing the first magnet adjacent to the top side of the circuit board; and 
 the method further comprises providing a second magnet adjacent to the bottom side of the circuit board, wherein the second magnet is operative to move alongside the plurality of coils and generate an electromotive force across the plurality of coils. 
 
     
     
       23. The method of  claim 22 , further comprising coupling the first magnet with the second magnet. 
     
     
       24. The method of  claim 20 , further comprising applying ferrofluid to the first magnet, wherein the ferrofluid is operative to lubricate the first magnet when it moves alongside the plurality of coils. 
     
     
       25. The method of  claim 20 , further comprising machining a slot in the circuit board, wherein the slot is operative to guide the first magnet when it moves alongside the plurality of coils. 
     
     
       26. The method of  claim 20 , further comprising attaching the circuit board to a support structure that comprises a slot operative to guide the first magnet when it moves alongside the plurality of coils.

Description:
BACKGROUND OF THE INVENTION 
     This is directed to systems for harnessing power through electromagnetic induction. 
     Traditional systems for harnessing power through electromagnetic induction involve wire coils, a magnet, and relative movement between the two. To achieve meaningful output power, a traditional system typically includes thick coils of wire that add to the system&#39;s overall size. Moreover, the wire coils and magnet of a traditional system are often housed in an inefficient manner that further adds to the system&#39;s overall size. 
     SUMMARY OF THE INVENTION 
     Systems for harnessing power through electromagnetic induction utilizing printed coils are provided. A system can include one or more moveable magnets adjacent to printed coils on a circuit. For example, a system can include one or more magnets that are operative to move alongside a circuit board that includes printed coils. The one or more magnets may move, for example, when a user shakes the system or when the user walks or runs while holding the device. The movement of the one or more magnets may create an electromotive force (e.g., a voltage) across the printed coils, and this force may be used to generate electric power. 
     Printed coils can be formed using any suitable technique for printing circuit boards. For example, printed coils can be formed by depositing copper on a substrate to form traces in the shape of coils or selectively etching copper from a substrate to form traces in the shape of coils. In some embodiments, a circuit board may include multiple layers and printed coils can be formed on two or more of the layers. In such embodiments, the coils may be electrically coupled using vias to create a coil array. In some embodiments, multiple circuit boards with printed coils may form stacks of circuit boards that are electrically coupled together to form a coil array. 
     One or more moveable magnets may be used to harness power through electromagnetic induction. For example, a system may include a single magnet adjacent to one side of a coil array. In another example, a system may include a first magnet adjacent to a side of a coil array and a second magnet adjacent to an opposite side of the coil array. The two magnets may move freely alongside the printed coils or they may be coupled together so that they move in unison. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of the present invention, its nature and various advantages will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 2  is a schematic view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 3A  is a perspective view of an illustrative, partially exploded circuit board in accordance with one embodiment of the invention; 
         FIG. 3B  is a cross-sectional view of an illustrative circuit board in accordance with one embodiment of the invention; 
         FIG. 4  is a cross-sectional view of an illustrative circuit board array in accordance with one embodiment of the invention; 
         FIG. 5  is a perspective view of an illustrative circuit board in accordance with one embodiment of the invention; 
         FIG. 6  is a cross-sectional view of an illustrative circuit board in accordance with one embodiment of the invention; 
         FIG. 7  is a schematic view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 8  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 9  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 10  is a schematic view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 11  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 12  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 13  is a schematic view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 14  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 15  is a schematic view, including exemplary magnetic field lines, of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 16  is a perspective view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 17  is a perspective view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; 
         FIG. 18  is a cross-sectional view of an illustrative electromagnetic induction system in accordance with one embodiment of the invention; and 
         FIG. 19  is a flowchart of an illustrative process for manufacturing an electromagnetic induction system in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electromagnetic induction can cause an electromotive force across an array of printed coils on a circuit board when the array moves through a magnetic field. For example, a voltage potential may be measured when an array of printed coils moves relative to a magnet. The magnitude of the electromotive force, and the associated electrical power, may be the result of various factors. For example, the magnitude of the electromotive force may be based on the length of the conductor moving through the magnetic field (e.g., the number of turns in a printed coil). In some embodiments, coils can be printed on a circuit board in dense configurations that offer a greater concentration of coil turns. Moreover, coils printed on a circuit board may be more efficiently integrated with other components of a system and, therefore, allow for a generally smaller system. 
       FIG. 1  includes electromagnetic induction system  100  in accordance with one embodiment of the invention. System  100  can include circuit board  110  with coil  122  and coil  124  printed thereon. System  100  can also include magnet  140  that may be operative to move adjacent to circuit board  110  and, therefore, coils  122  and  124  (see, e.g., arrows in  FIG. 1 ). For example, magnet  140  may move adjacent to coils  122  and  124  when system  100  is shaken (e.g., through a user deliberately shaking the system). In another example, magnet  140  may move adjacent to coils  122  and  124  when a user carrying system  100  is walking or running (e.g., through movement created by the user&#39;s footfalls or arm swinging). Due to electromagnetic induction, an electromotive force may be generated in coils  122  and  124  when magnet  140  moves adjacent to circuit board  110 . 
     Circuit board  110  can include one or more suitable substrates and traces may be formed on the substrate or substrates using any suitable process. For example, circuit board  110  can include a dielectric substrate bonded to a layer of copper and selected portions of the copper layer may be removed to form traces. Circuit board  110  can include multiple layers and each layer can include different traces. For example, circuit board  110  can include layer  112  with traces and layer  114  with different traces. Traces on circuit board  110  can be formed from any suitable conductive material (e.g., copper) using any suitable technique (e.g., etching). Circuit board  110  can include one or more vias for electrically coupling traces on different layers. For example, circuit board  110  can include via  130  that electrically couples one or more traces on layer  112  with one or more traces on layer  114 . Vias in circuit board  110  can be formed from any suitable conductive material (e.g., copper) using any suitable technique (e.g., electroplating). 
     A circuit board can include one or more coils. For example, circuit board  110  can include coil  122  and coil  124 . A trace can be printed in a pattern to form a relatively flat coil on a substrate of a circuit board. For example, each of coils  122  and  124  may be formed from one or more traces printed on circuit board  110 . Different coils may be located on different layers of a circuit board. For example, one or more traces printed on layer  112  can form coil  122 , and one or more traces printed on layer  114  can form coil  124 . Coils located on different layers may be electrically coupled through one or more vias. For example, coil  122  may be electrically coupled with coil  124  through via  130 . Electrically coupled together, coil  122  and coil  124  may form a coil array. 
     An electromagnetic induction system may include a magnet moveable adjacent to one or more coils. For example, system  100  can include magnet  140  moveable alongside circuit board  110 . As a magnet moves adjacent to one or more coils, electromagnetic induction may generate an electromotive force across the coils. Any suitable type of magnet can be used to harness power in an electromagnetic induction system. For example, magnet  140  may include any object that produces magnetic fields. In some embodiments, magnet  140  may include a permanent magnet. 
     In some embodiments, an electromagnetic induction system may include circuitry in addition to a circuit board with printed coils and a magnet.  FIG. 2  includes electromagnetic induction system  200  in accordance with one embodiment of the invention. System  200  can include circuit board  210  with coil  222  printed on layer  212 , coil  224  printed on layer  214 , and via  230  electrically coupling coils  222  and  224 . Board  210 , layers  212  and  214 , coils  222  and  224 , and via  230  may be substantially similar to board  110 , layers  112  and  114 , coils  122  and  124 , and via  130  (see  FIG. 1 ), and the previous description of the latter can be applied to the former. 
     An electromagnetic system can include power conditioning circuitry for regulating power harnessed by the system. For example, system  200  can include power conditioning circuitry  260 . In some embodiments, power conditioning circuitry  260  may stabilize the voltage of an electromotive force generated across a coil. In some embodiments, power conditioning circuitry  260  may rectify electric power generated by electromagnetic induction. In some embodiments, power conditioning circuitry  260  may limit the current flowing through coils  222  and  224 . Power conditioning circuitry  260  may be electrically coupled with the coils in circuit board  210 . Power conditioning circuitry may couple with the coils in a circuit board to complete a conductive loop through the coils. For example, power conditioning circuitry  260  may be electrically coupled with coil  222  through conductive path  262  and coil  224  through conductive path  268 . Conductive path  262  and conductive path  268  can include any suitable conductor. For example, conductive paths  262  and  268  can include traces on a circuit board, connectors, wires, or any combination thereof. While the embodiment shown in  FIG. 2  portrays coil  222  and coil  224  configured in series and coupled with power conditioning circuitry  260 , it is understood that any suitable configuration of coils can be coupled with power conditioning circuitry. For example, coils can be coupled in series, parallel, or any combination thereof to form an array of coils, and the coil array can be coupled with power conditioning circuitry. 
     An electromagnetic induction system can include power storage circuitry for storing power harnessed by the system. For example, system  200  can include power storage circuitry  265  that can be electrically coupled with power conditioning circuitry  260 . Power storage circuitry  265  may include one or more circuit elements suitable for storing electrical power. For example, power storage circuitry  265  may include a large capacitor or battery. In some embodiments, power storage circuitry  265  may include circuitry limiting the flow of power out of a circuit element (e.g., a capacitor or battery). For example, power storage circuitry  265  may include circuitry for limiting the speed at which power can be drained from a circuit element. 
     An electromagnetic induction system can include application circuitry for using power harnessed by the system. For example, system  200  can include application circuitry  270 . Application circuitry  270  can be electrically coupled with power storage circuitry  265 , power conditioning circuitry  260 , or both. Application circuitry  270  can include any suitable circuitry for performing electronic functions using power harnessed by the system. For example, application circuitry  270  may include a processor, memory, an input/output interface, any other suitable circuitry, or any combination thereof. In some embodiments, application circuitry  270  may include circuitry for playing media, circuitry for conducting wireless communications (e.g., cellular or 802.11x), any other suitable function, or any combination thereof. In some embodiments, system  200  can be incorporated into an electronic device. For example, system  200  can be incorporated into a media player such as an iPod® available from Apple Inc., of Cupertino, Calif., a cellular telephone, a personal e-mail or messaging device (e.g., a Blackberry® or a Sidekick®), an iPhone® available from Apple Inc., pocket-sized personal computers, personal digital assistants (PDAs), a laptop computer, a cyclocomputer, a music recorder, a video recorder, a camera, or any other suitable electronic device. 
       FIGS. 3A and 3B  include circuit board  310  in accordance with one embodiment of the invention. Circuit board  310  can include multiple layers (see, e.g., layers  112  and  114  shown in  FIG. 1 ). Each layer of circuit board  310  can include a conductive trace forming a coil for electromagnetic induction (see, e.g., coils  122  and  124  shown in  FIG. 1 ). 
     A circuit board may include multiple layers, and two or more of the layers may include traces forming coils for electromagnetic induction.  FIG. 3A  is a perspective, partially exploded view of circuit board  310  in which the top two layers of circuit board  310  have been lifted to show conductive traces forming coils. While only the top two layers of circuit board  310  have been lifted in  FIG. 3A  and  FIG. 3B  shows only seven layers, it is understood that circuit board  310  can include any number of layers. 
     Circuit board  310  can include layers  312 ,  314 , and  316 , and each layer may include a printed coil formed from a conductive trace. For example, layer  312  may include coil  322 , layer  314  may include coil  324 , and layer  316  may include coil  326 . A conductive trace can be printed on a layer in any suitable pattern to form a coil. For example, circuit board  310  includes coils  322 ,  324 , and  326  formed from conductive traces printed in a square pattern. In another example, a circuit board can include coils formed from conductive traces printed in a circular pattern. Printed coils can include inner turns and outer turns. For example, a printed coil can include an inner turn which has the smallest radius of any turns in the coil and an outer turn which has the largest radius of any turns in the coil. In some embodiments, each circuit board may include a periphery (e.g., a side edge) and a coil&#39;s outer turn may runs alongside the periphery of the board (see, e.g., coils  322 ,  324 , and  326  extending to the periphery of circuit board  310 ). In such embodiments, the coils may have a larger size, and potentially more turns, by extending to the periphery of the circuit board. In other embodiments, a circuit board may include other circuit or components and coils may not extend all the way to the periphery of the board. 
     A circuit board may include vias to electrically couple coils on different layers (see, e.g., via  130  shown in  FIG. 1 ). A via may include a conductive path extending through a layer so that a trace on that layer is electrically coupled with a trace on an adjacent layer. For example, circuit board  310  may include via  333  to electrically couple coil  322  with coil  324 . In another example, circuit board  310  may include via  335  to electrically couple coil  324  with coil  326 . A circuit board can include a via at any suitable location on a layer. For example, circuit board  310  can include via  333  at the center of coil  322  (e.g., at an inner turn of the coil) and via  337  at the center of coil  326  (e.g., at an inner turn of the coil). In another example, circuit board  310  can include via  336  along the periphery of coil  324  (e.g., at the outer turn of the coil). In the embodiment shown in  FIGS. 3A and 3B , the coils may be positioned directly on top of one another, and the location of the vias may alternate between the center of a coil and the periphery of a coil. In other embodiments, the coils may be positioned so that the each layer&#39;s coil is offset from the previous layer, and the vias may be located in the same relative position on each layer (e.g., the center of each coil). 
     A circuit board may include endpoint traces for electrically coupling coils with circuitry (see, e.g., conductive paths  262  and  268  shown in  FIG. 2 ). For example, a circuit board may include endpoint traces for coupling an array of coils with power conditioning circuitry (see, e.g., circuitry  260  shown in  FIG. 2 ). A circuit board may include an endpoint trace for electrically coupling a coil on a top layer with circuitry and another endpoint trace for electrically coupling a coil on a bottom layer with circuitry. For example, as seen in  FIGS. 3A and 3B , circuit board  310  may include endpoint trace  362  for coupling coil  322  with circuitry (not shown). Continuing the example, as seen in  FIG. 3B , circuit board  310  may include endpoint trace  368  on bottom layer  318  for coupling coil  328  with circuitry (not shown). If each coil in a circuit board is electrically coupled with coils on adjacent layers through vias and the top and bottom layers are coupled with power conditioning circuitry, the array of coils may form a closed loop through the power conditioning circuitry. As previously discussed, the coils may be coupled in series, parallel, or any combination thereof to form an array of coils, and such an array may be coupled with power conditioning circuitry through endpoint traces. 
     While the pattern of a conductive trace may vary, it may be advantageous for a conductive path to extend in the same general angular direction (e.g., clockwise or counter-clockwise) over an entire coil array. In the embodiment shown in  FIG. 3A , the conductive path of circuit board  310  can extend in a counter-clockwise direction through each layer of circuit board  310 . Starting from endpoint trace  362 , the conductive path can wind through coil  322  in a counter-clockwise direction towards the center of layer  312 . Upon reaching via  333 , the conductive path can extend to layer  314 , where it can wind through coil  324  in a counter-clockwise direction towards the periphery of layer  314 . Upon reaching via  335 , the conductive path can extend to layer  316  where it can wind through coil  326  in a counter-clockwise direction towards the center of layer  316 . The conductive path can continue moving through the coil array in a generally counter-clockwise angular direction until reaching endpoint trace  368  (see  FIG. 3B ), where it can electrically couple with circuitry (see, e.g., conductive path  268  and power conditioning circuitry  260 ). In other embodiments, a conductive path may extend in a generally clockwise direction. It may, however, be disadvantageous for a conductive path to switch between extending in a clockwise and a counter-clockwise direction. For example, the electromotive forces generated through electromagnetic induction may cancel each other if the conductive path changes angular directions. 
     In some embodiments, multiple circuit boards can be stacked and an array of coils can extend from one circuit board to another. For example, circuit boards in a stack can be electrically coupled through a conductor that allows a coil array to extend across multiple circuit boards.  FIG. 4  includes circuit board stack  410  in accordance with one embodiment of the invention. Circuit board stack  410  can include multiple circuit boards, and each circuit board can include multiple layers (see, e.g., layers  112  and  114  shown in  FIG. 1 ). Each layer of a circuit board in stack  410  can include a conductive trace forming a coil for electromagnetic induction (see, e.g., coils  122  and  124  shown in  FIG. 1 ), and each coil may be coupled with adjacent coils through vias (see, e.g., via  130  shown in  FIG. 1 ). 
     The top circuit board of stack  410  can be substantially similar to circuit board  310  (shown in  FIGS. 3A and 3B ) and can include layers  412 ,  414 ,  416 , and  418 , coil  422 , and endpoint trace  462 , which each correspond to, respectively, layers  312 ,  314 ,  316 , and  318 , coil  322 , and endpoint trace  362  of circuit board  310 . The top board of stack  410 , however, can include via  439  extending through bottom layer  418  of the top circuit board. Another potential difference between circuit board  310  (shown in  FIGS. 3A and 3B ) and the top circuit board of stack  410  may be the absence of an endpoint trace along bottom layer  418 . The function of an endpoint trace may be replaced by endpoint trace  468  located on bottom layer  488  of the bottom circuit board. 
     The bottom circuit board of stack  410  can also be substantially similar to circuit board  310  (shown in  FIGS. 3A and 3B ) and can include layers  482 ,  484 ,  486 , and  488 , coil  492 , and endpoint trace  468 , which each correspond to, respectively, layers  312 ,  314 ,  316 , and  318 , coil  322 , and endpoint trace  362  of circuit board  310 . A potential difference between circuit board  310  (shown in  FIGS. 3A and 3B ) and the bottom circuit board of stack  410  may be the absence of an endpoint trace along top layer  482 . The function of an endpoint trace may be replaced by endpoint trace  462  located on top layer  412  of the top circuit board. 
     A circuit board stack may include one or more conductors for electrically coupling the circuit boards. For example, stack  410  may include conductor  481  for coupling via  439  with the periphery of coil  492 . Accordingly, the coil array can extend in series from the top circuit board to the bottom circuit board. Conductor  481  can be a solder ball or any other suitable type of conductor for electrically coupling circuit boards. 
     A circuit board stack may include one or more mechanical couplings for holding the circuit boards together. For example, stack  410  may include bracket  480  coupled with both the top and bottom circuit boards in the stack. While the embodiment shown in  FIG. 4  includes a bracket along an edge of the stack, it is understood that any other suitable mechanical coupling or combination of couplings can be used. For example, circuit boards may be coupled together using brackets along multiple edges of a stack. In another example, circuit boards may be coupled together using adhesive injected in gap  495  between the boards. 
     In some embodiments, it may be advantageous for a circuit board (see, e.g., circuit board  310  shown in  FIGS. 3A and 3B ) or a stack of circuit boards (see, e.g., stack  410 ) to include an even number of layers. This is because such a configuration may allow an endpoint trace (see, e.g., conductive paths  262  and  268  shown in  FIG. 2 , endpoint traces  362  and  368  shown in  FIGS. 3A and 3B , and endpoint traces  462  and  468 ) to couple with the coil array at the periphery of a coil and, therefore, efficiently share a layer of a circuit board with the coil. On the other hand, if a coil array spans an odd number of layers, an extra layer may be necessary for an endpoint trace to couple with the coil array at the center of a coil. 
     In some embodiments, multiple coils can be provided on a single layer of a circuit board. For example, two or more coils can be provided adjacent to each other on a single layer of a circuit board. In such embodiments, two or more layers of a circuit board can each include multiple coils, and some of the coils on adjacent layers may be electrically coupled through vias. 
       FIG. 5  includes circuit board  510  in accordance with one embodiment of the invention. Circuit board  510  can include any suitable type of circuit board (see, e.g., circuit board  110  shown in  FIG. 1 ). For example, circuit board  510  can include any number of layers and may be manufactured using any suitable technique. Circuit board  510  can include at least layer  512  (see, e.g., layer  112  shown in  FIG. 1 ) with conductive traces printed thereon. As previously discussed, a layer of a circuit board can include multiple printed coils adjacent to each other. For example, layer  512  can include coil  521 , coil  522 , coil  523 , and coil  524  formed from conductive traces (see, e.g., coils  122  and  124  shown in  FIG. 1 ). Each of coils  521 - 524  may be substantially similar to coil  322  shown in  FIGS. 3A and 3B , and the previous description of the latter can be applied to the former. 
     A circuit board with multiple coils on a single layer can include multiple vias on the same layer and each via may correspond to one of the coils. For example, circuit board  510  may include vias  531 - 534 , each of which may electrically couple with one of coils  521 - 524 . Vias  531 - 534  can include any suitable conductor passing through layer  512  (see, e.g., via  130  shown in  FIG. 1 ). Each of vias  531 - 534  may electrically couple one of coils  521 - 524  with coils on a layer below layer  512  (see, e.g., vias  333  and  335  shown in  FIGS. 3A and 3B ). In this manner, a circuit board may include adjacent coils that span multiple layers by providing each layer with multiple, adjacent coils. 
     A circuit board with multiple coils on a single layer can include multiple endpoint traces on the same layer and each endpoint trace may correspond to one of the coils. For example, circuit board  510  may include endpoint traces  561 - 564 , each of which may electrically couple with one of coils  521 - 524 . Endpoint traces  561 - 564  can each include any suitable conductive path for electrically coupling a coil with circuitry (see, e.g., conductive paths  262  and  268  and power conditioning circuitry  260  shown in  FIG. 2 ). In some embodiments, endpoint traces  561 - 564  may be provided on top layer  512  of circuit board  510  and similar endpoint traces (see, e.g., endpoint trace  368  shown in  FIG. 3B ) may be provided on the bottom layer of circuit board  510 . 
     As previously discussed, coils can be coupled in series, parallel, or any combination thereof to form an array of coils. The resulting coil array can then be coupled with circuitry (e.g., power conditioning circuitry). In some embodiments, endpoint traces may be electrically coupled together (not shown) to form a parallel coil array of adjacent coils spanning multiple layers. In some embodiments, endpoint traces may be selectively coupled to form a series coil array of adjacent coils spanning multiple layers. For example, an endpoint trace may couple with an endpoint trace of an adjacent coil so that the conductive path can extend back through the circuit board. In such embodiments, it may be advantageous to reconfigure the angular direction of an adjacent coil so that the conductive path can maintain the same general angular direction throughout the array. For example, a coil may have a pattern that is a mirror image of an adjacent coil to which it is electrically coupled in series so that the conductive path can extend in the same general angular direction. 
       FIGS. 3A-5  show circuit boards with a single coil on each layer, stacks of circuit boards with a single coil on each layer, and circuit boards with multiple coils on each layer. It is understood, however, that any combination of these features can be used for electromagnetic induction without deviating from the disclosure. For example, a stack of circuit boards with multiple coils on each layer may be used for electromagnetic induction. In another example, rather than including multiple, adjacent coils on each layer of a circuit board, multiple circuit boards can be located adjacent to each other to provide adjacent coils for electromagnetic induction. 
     In some embodiments, a circuit board may be covered with a material on a side of the board adjacent to a magnet that is moveable relative to the board. For example, a circuit board may be covered with a dielectric material to insulate one or more traces on the top layer of the circuit board from the magnet. In another example, a circuit board may be covered with a relatively durable material to protect a circuit board from physical wear-and-tear due to the movement of a magnet alongside the board. In yet another example, a circuit board may be covered with a low-friction material to allow a magnet to move alongside the board with minimal resistance. Accordingly, a material with dielectric properties, durable properties, low-friction properties, any other suitable properties, or any combination thereof may cover one or more sides of a circuit board. 
       FIG. 6  includes circuit board  610  in accordance with one embodiment of the invention. Circuit board  610  can include multiple layers (see, e.g., layers  112  and  114  shown in  FIG. 1 ). Each layer of circuit board  610  can include a conductive trace forming a coil for electromagnetic induction (see, e.g., coils  122  and  124  shown in  FIG. 1 ), and each coil may be coupled with adjacent coils through vias (see, e.g., via  130  shown in  FIG. 1 ). 
     Circuit board  610  can be substantially similar to circuit board  310  (shown in  FIGS. 3A and 3B ) and can include layers  612 ,  614 ,  616 , and  618 , coil  622 , and endpoint trace  662 , which each correspond to, respectively, layers  312 ,  314 ,  316 , and  318 , coil  322 , and endpoint trace  362  of circuit board  310 . Circuit board  610 , however, can also include cover layer  611  over layer  612  and cover layer  619  below layer  618 . 
     A layer can be formed on a side of a circuit board adjacent to a magnet that is moveable relative to the board (see, e.g., magnet  140  shown in  FIG. 1 ). For example, layer  611  can be provided over layer  612 . In some embodiments, layer  611  may be operative to insulate traces on layer  612  (e.g., coil  622  and endpoint trace  662 ) from a magnet moving adjacent to circuit board  610 . In some embodiments, layer  611  may be operative to protect circuit board  610  from physical wear-and-tear due to the movement of a magnet alongside the board. In some embodiments, layer  611  may be operative to provide a smooth surface for a magnet to move alongside circuit board  610 . Layer  611  can be formed from any suitable material. For example, layer  611  can be formed from a material with dielectric properties, durable properties, low-friction properties, any other suitable properties, or any combination thereof. In another example, layer  619  can be provided below layer  618 . Layer  619  may be substantially similar to layer  611 , and the previous description of the latter can be applied to the former. Layer  619  may be provided in embodiments when a magnet below a circuit board is moveable relative to the board. A more detailed description of such embodiments can be found, for example, in the discussion corresponding to  FIGS. 10-18 . 
     A layer can be formed on a side of a circuit board using any suitable technique. In some embodiments, a material may be applied to a side of the circuit board to form a layer. For example, a material may be applied to the top side of circuit board  610  to form a layer over coil  622  and endpoint trace  662 . Such material may be applied so that it can fill in any uneven surfaces or gaps created by coil  622  and endpoint trace  662 . A material may be applied to the side of a circuit board using any suitable process. For example, a material can be applied to the side of a circuit board using a technique that includes depositing, sputtering, painting, gluing, adhering, spray-coating, immersion-coating, any other suitable technique, or any combination thereof. 
     In some embodiments, an electromagnetic induction system can include an enclosure adjacent to a circuit board for guiding a moveable magnet. For example, an enclosure may be mounted onto a circuit board for guiding a moveable alongside the circuit board. An enclosure may prevent a magnet from moving too far away from the circuit board. For example, an enclosure may prevent a magnet from falling away from the circuit board if the board is flipped upside-down. In some embodiments, an enclosure may create a sealed environment for a moveable magnet to move through. For example, an enclosure may create a sealed environment and the environment may be filled with a lubricant to reduce the friction created by a moveable magnet. 
       FIG. 7  includes electromagnetic induction system  700  in accordance with one embodiment of the invention. System  700  can include coil array  710  that may include any number of coils printed on any number of circuit boards (see, e.g., coils  122  and  124  and circuit board  110  shown in  FIG. 1 ). For example, coil array  710  can include coils printed on different layers of a circuit board (see, e.g.,  FIGS. 3A and 3B ), coils printed on different circuit boards in a stack (see, e.g.,  FIG. 4 ), coils printed on the same layer of a circuit board (see, e.g.,  FIG. 5 ), any other suitable configuration of coils, or any combination thereof. 
     As previously discussed, an electromagnetic induction system can include a magnet moveable adjacent to printed coils. For example, system  700  can include magnet  740  that can move along coil array  710 . Magnet  740  can include any object that produces magnetic fields (see, e.g., magnet  140 ). In some embodiments, magnet  740  may include a permanent magnet. 
     An electromagnetic induction system can include an enclosure adjacent to printed coils. For example, system  700  can include enclosure  742  adjacent to coil array  710 . Enclosure  742  may be shaped to guide magnet  740  alongside coil array  710  when it moves. For example, width  746  of enclosure  742  may be set so that magnet  740  moves alongside coil array  710  at a relatively close distance. Accordingly, enclosure  742  may retain magnet  740  in close proximity to coil array  710  while still allowing magnet  740  to move alongside coil array  710 . An enclosure for guiding a magnet can be formed from any suitable material. For example, enclosure  742  can include plastics, polymers, polycarbonates, metals, any other suitable materials, or any combination thereof. In some embodiments, an enclosure for guiding a magnet may include a ferrite sheet for blocking a portion of the magnetic field from the magnet. For example, enclosure  742  may include a ferrite sheet to block the portion of the magnetic field from magnet  740  that extends away from coil array  710 . It may be advantageous to block some of the magnetic field from a magnet in an electromagnetic induction system because stray magnetic fields may interfere with other circuitry in the induction system or an electronic device into which the induction system is integrated. For example, an electromagnetic induction system may be integrated into a small, portable electronic device that includes other circuitry (see, e.g., application circuitry  270  shown in  FIG. 2 ) and the operation of the other circuitry may be disrupted by the magnetic field from the induction system&#39;s magnet. 
     In some embodiments, an enclosure in an electromagnetic induction system can be mounted to a physical structure in the system. For example, an enclosure may be mounted directly to a coil array or a bracket supporting the coil array. In some embodiments, an enclosure can be mounted to a physical structure at locations that provide mechanical support to prevent the enclosure from separating from the coil array. For example, an enclosure can be mounted to a physical structure at locations that include brackets for mechanical support. In the embodiment shown in  FIG. 7 , enclosure  742  may be mounted to coil array  710 . An enclosure may be mounted to a coil array at any suitable location. For example, an enclosure may be mounted to one or more circuit boards that form a coil array. In some embodiments, an enclosure may be mounted to the periphery of one or more circuit boards that form a coil array (see, e.g., the periphery of layer  312  shown in  FIG. 3A ). For example, an enclosure may be mounted to the periphery of one or more circuit boards using a bracket that attaches to the edge of the circuit board. Mounting an enclosure to the periphery of a circuit board may be advantageous because it may expose the largest area of coils to the magnetic field. In some embodiments, an enclosure may be mounted to a layer covering a circuit board (see, e.g., layers  611  and  619  sown in  FIG. 6 ). 
     In some embodiments, an enclosure in an electromagnetic induction system can be mounted to a physical structure in a manner that creates a sealed environment for a magnet to move through. For example, an enclosure may be airtight, a coil array may be formed on an airtight circuit board or include an airtight layer covering the circuit board, and the enclosure can be mounted to a physical structure at locations that include airtight seals. In the embodiment shown in  FIG. 7 , enclosure  742  may be mounted to coil array  710  at seal  743  and seal  744 . Seals  743  and  744  may include any suitable material for forming an airtight seal. For example, seals  743  and  744  may include an adhesive, epoxy, glue, resin, sealant, solder, any other suitable material, or any combination thereof. Accordingly, magnet  740  can move through a sealed environment. 
     In some embodiments, an electromagnetic induction system may include a lubricant in a sealed environment created by an enclosure. For example, a system may include a lubricant to reduce the friction experienced by a moveable magnet. In some embodiments, a system may include a lubricant that includes a ferrofluid. For example, system  700  can include ferrofluid  745  in enclosure  742  for lubricating the movement of magnet  740 . Ferrofluid  745  can include any liquid with one or more ferromagnetic properties. For example, ferrofluid  745  may be magnetically attracted to magnet  740  so that magnet  740  is coated by ferrofluid  745 . Ferrofluid  745  may have lubricating properties to reduce the friction created by the movement of magnet  740 . It may be advantageous to use a lubricant that includes ferrofluid because such a lubricant will be attracted to the magnet and, therefore, follow the magnet as it moves adjacent to the coils. 
     In some embodiments, the poles of a movable magnet may be positioned to maximize the magnetic field perpendicular to the printed coils in an electromagnetic induction system. The electromotive force (i.e., voltage) generated by electromagnetic induction may be proportional to the rate at which the flux passing through the coils changes. Accordingly, it may be advantageous to maximize the magnetic field perpendicular to the coils so that the change in flux is maximized when the magnet moves adjacent to the coils. 
       FIGS. 8 and 9  include, respectively, electromagnetic induction systems  800  and  900 . Systems  800  and  900  may each include a coil array and a moveable magnet. For example, systems  800  and  900  may include, respectively, coil array  810  and coil array  910 . Coil arrays  810  and  910  may each include any number of coils printed on any number of circuit boards (see, e.g., coils  122  and  124  and circuit board  110  shown in  FIG. 1 ). Moreover, systems  800  and  900  may include, respectively, moveable magnet  840  and moveable magnet  940 . Moveable magnets  840  and  940  may each include any object that produces magnetic fields (see, e.g., magnet  140  shown in  FIG. 1 ). Magnets  840  and  940 , however, may have different pole positions in  FIGS. 8 and 9 . For example, the poles of magnet  840  may be positioned vertically with the north pole directly over its south pole while the poles of magnet  940  may be positioned horizontally with its north pole to the left of its south pole. Therefore,  FIGS. 8 and 9  display different magnetic field lines due to the different pole positions. As shown in the figures, a greater portion of the magnetic field of magnet  840  may be perpendicular to coil array  810  than the portion of the magnetic field of magnet  940  that is perpendicular to coil array  910 . Accordingly, it may be advantageous to provide a magnet with poles positioned vertically, in a manner similar to magnet  840 . But much of the magnetic field of magnet  840  may still go unused because it is either parallel with coil array  810  or returning to the side of magnet  840  that is opposite coil array  810 . 
     In some embodiments, an electromagnetic induction system can include multiple moveable magnets adjacent to printed coils, at least two of which can be on different sides of the printed coils. For example, one moveable magnet may be adjacent to the top side of the printed coils and another moveable magnet may be adjacent to the bottom side of the printed coils. In some embodiments, the poles of magnets on opposite sides of printed coils may be positioned so that opposite poles face each other and the magnetic fields can extend in a relatively straight line between the magnets. It may be advantageous to position magnets on opposite sides of printed coils so that opposite poles face each other because such a configuration may cause the magnetic field to extend through the coils in a relatively straight line that is perpendicular to the coils. 
       FIG. 10  includes electromagnetic induction system  1000  in accordance with one embodiment of the invention. System  1000  may be substantially similar to system  700  (shown in  FIG. 7 ) and the previous description of the latter may be applied to the former. For example, system  1000  may include coil array  1010 , magnet  1040 , enclosure  1042 , seals  1043  and  1044 , and ferrofluid  1045 , which may each correspond to, respectively, coil array  710 , magnet  740 , enclosure  742 , seals  743  and  744 , and ferrofluid  745 . System  1000 , however, may also include magnet  1050  adjacent to the bottom surface of coil array  1010 . In some embodiments, magnet  1050 , and any accompanying enclosures, seals, or ferrofluid near the bottom surface of coil array  1010  may be similar to magnet  1040 , enclosure  1042 , seals  1043  and  1044 , and ferrofluid  1045  near the top surface of coil array  1010 . For example, enclosure  1052  may be substantially similar to enclosure  1042 , and seals  1053  and  1054  may be substantially similar to seals  1043  and  1044 . Moreover, ferrofluid  1055  may be substantially similar to ferrofluid  1045 . 
     In some embodiments, magnets on opposite sides of printed coils may be mechanically free to move along printed coils independently of each other. For example, there may be no brackets mechanically coupling magnet  1040  with magnet  1050 . In such embodiments, the force of the magnets&#39; magnetic fields may have a partially coupling effect by exerting forces that pull the magnets towards each other. In some embodiments, magnets on opposite sides of printed coils may be mechanically coupled to move along printed coils in unison. For example, system  100  may include a bracket mechanically coupling magnet  1040  with magnet  1050 . A more detailed description of such embodiments as well as other embodiments to move magnets in unison can be found, for example, in the discussion corresponding to  FIGS. 16-18 . 
     In some embodiments, the poles of movable magnets on opposite sides of printed coils may be positioned to maximize the magnetic field perpendicular to the coils in an electromagnetic induction system.  FIGS. 11 and 12  include, respectively, electromagnetic induction systems  1100  and  1200 . Systems  1100  and  1200  may each include a coil array and moveable magnets on opposite sides of the coils. For example, systems  1100  and  1200  may include, respectively, coil array  1110  and coil array  1210 . Coil arrays  1110  and  1210  may each include any number of coils printed on any number of circuit boards (see, e.g., coils  122  and  124  and circuit board  110  shown in  FIG. 1 ). Moreover, systems  1100  and  1200  may include, respectively, moveable magnets  1140  and  1150  and moveable magnets  1240  and  1250 . Moveable magnets  1140 ,  1150 ,  1240 , and  1250  may each include any object that produces magnetic fields (see, e.g., magnet  140  shown in  FIG. 1 ). Magnets  1140 ,  1150 ,  1240 , and  1250 , however, may have different pole positions in  FIGS. 11 and 12 . For example, the poles of magnets  1140  and  1150  may be positioned vertically with the south pole of magnet  1140  facing the north pole of magnet  1150 . On the other hand, the poles of magnets  1240  and  1250  may be positioned horizontally with the north pole of magnet  1240  facing the south pole of magnet  1250  and the south pole of magnet  1240  facing the north pole of magnet  1250 . Therefore,  FIGS. 11 and 12  display different magnetic field lines due to the different pole positions. As shown in the figures, a greater portion of the magnetic fields of magnets  1140  and  1150  may be perpendicular to coil array  1110  than the portion of the magnetic field of magnets  1240  and  1250  that is perpendicular to coil array  1210 . Accordingly, it may be advantageous to provide magnets with poles positioned vertically and opposite poles facing each other, in a manner similar to magnets  1140  and  1150 . Moreover, as seen by comparing system  1100  to system  800  (shown in  FIG. 8 ), the addition of a magnet on the opposite side of printed coils can increase the density of the magnetic fields. 
     In some embodiments, an electromagnetic induction system may include printed coils and multiple moveable magnets adjacent to opposite sides of the printed coils. For example, an electromagnetic induction system may include two or more magnets adjacent to the top side of a printed coil array and two or more magnets adjacent to the bottom side of a printed coil array. It may be advantageous to include multiple moveable magnets adjacent to opposite sides of printed coils because the magnetic field passing through the printed coils may be increased by each additional magnet. 
       FIG. 13  includes electromagnetic induction system  1300  in accordance with one embodiment of the invention. System  1300  may be substantially similar to systems  700  (shown in  FIG. 7) and 1000  (shown in  FIG. 10 ) and the previous description of the latter systems may be applied to the former. For example, system  1300  may include coil array  1310 , magnet  1340 , enclosure  1342 , seals  1343  and  1344 , ferrofluid  1345 , magnet  1350 , enclosure  1352 , seals  1353  and  1354 , and ferrofluid  1355 , each of which may each correspond to, respectively, coil array  1010 , magnet  1040 , enclosure  1042 , seals  1043  and  1044 , ferrofluid  1045 , magnet  1050 , enclosure  1052 , seals  1053  and  1054 , and ferrofluid  1055 . Moreover, the magnets, enclosures, seals, and ferrofluid on opposite sides of coil array  1310  may correspond, respectively, to the magnet, enclosures, seals, ferrofluid on the top side of coil array  710  in system  700  (see, e.g., magnet  740 , enclosure  742 , seals  743  and  744 , and ferrofluid  745 ). System  1300 , however, may include an additional magnet adjacent to opposite sides of printed coils. For example, system  1300  may include magnet  1341  adjacent to the top side of coil array  1310  and magnet  1351  adjacent to the bottom side of coil array  1310 . 
     In some embodiments, multiple magnets adjacent to a single side of printed coils may be of similar types and sizes. For example, magnet  1341  may be substantially similar to magnet  1340 . In another example, magnet  1351  may be substantially similar to magnet  1350 . In some embodiments, an enclosure may be shaped to guide multiple magnets alongside one side of printed coils. For example, enclosure  1342  may be shaped to guide magnet  1340  and magnet  1341  alongside the top side of coil array  1310 . In another example, enclosure  1352  may be shaped to guide magnet  1350  and magnet  1351  alongside the bottom side of coil array  1310 . In some embodiments, a system may include enough ferrofluid in an enclosure to lubricate multiple magnets. For example, ferrofluid  1345  may include enough ferrofluid to cover both magnet  1340  and magnet  1341  so that each magnet can move smoothly alongside coil array  1310 . In another example, ferrofluid  1355  may include enough ferrofluid to cover both magnet  1350  and magnet  1351  so that each magnet can move smoothly alongside coil array  1310 . 
     In some embodiments, multiple magnets adjacent to one side of printed coils may be coupled together so that they move across the coils in unison. For example, the magnets may be part of an assembly that moves as a single unit alongside the printed coils. Moreover, assemblies on opposite sides of printed coils may be coupled so that both assemblies move across the coils in unison. For example, in the embodiment shown in  FIG. 13 , magnets  1340  and  1341  may be coupled together so that they move in unison and magnets  1350  and  1351  may be coupled together so that they move in unison. In other embodiments, multiple magnets adjacent to one side of printed coils may move independently. For example, the magnets may move independently alongside the printed coils. 
     In some embodiments, the poles of multiple magnets located on the same side of printed coils may be positioned to maximize the magnetic field perpendicular to the coils.  FIGS. 14 and 15  include, respectively, electromagnetic induction systems  1400  and  1500 . Systems  1400  and  1500  may each include a coil array and multiple moveable magnets on opposite sides of the coils. For example, systems  1400  and  1500  may include, respectively, coil array  1410  and coil array  1510 . Coil arrays  1410  and  1510  may each include any number of coils printed on any number of circuit boards (see, e.g., coils  152  and  154  and circuit board  110  shown in  FIG. 1 ). Moreover, systems  1400  and  1500  may include, respectively, moveable magnets  1440 ,  1441 ,  1450 , and  1451  and moveable magnets  1540 ,  1541 ,  1550 , and  1551 . Moveable magnets  1440 ,  1441 ,  1450 ,  1451 ,  1540 ,  1541 ,  1550 , and  1551  may each include any object that produces magnetic fields (see, e.g., magnet  140  shown in  FIG. 1 ). Magnets  1440 ,  1441 ,  1450 ,  1451 ,  1540 ,  1541 ,  1550 , and  1551 , however, may have different pole positions in  FIGS. 14 and 15 . In some embodiments, the pole positions of magnets  1440 ,  1441 ,  1450 , and  1451  may be similar to the pole positions of magnets  1140  and  1150  (shown in  FIG. 11 ), and the pole positions of magnets  1540 ,  1541 ,  1550 , and  1551  may be similar to the pole positions of magnets  1240  and  1250  (shown in  FIG. 12 ). For example, the poles of magnets  1440 ,  1441 ,  1450 , and  1451  may be positioned vertically with the south poles of magnets  1440  and  1441  facing the north poles of magnet  1450  and  1451 . On the other hand, the poles of magnets  1540 ,  1541 ,  1550 , and  1551  may be positioned horizontally with the north pole of magnet  1540  facing the south pole of magnet  1550 , the south pole of magnet  1540  facing the north pole of magnet  1550 , the north pole of magnet  1541  facing the south pole of magnet  1551 , and the south pole of magnet  1541  facing the north pole of magnet  1551 . Therefore,  FIGS. 14 and 15  display different magnetic field lines due to the different pole positions. As shown in the figures, a greater portion of the magnetic fields of magnets  1440 ,  1441 ,  1450 , and  1451  may be perpendicular to coil array  1410  than the portion of the magnetic field of magnets  1540 ,  1541 ,  1550 , and  1551  that is perpendicular to coil array  1510 . Accordingly, it may be advantageous to position the poles of the magnets vertically with opposite poles facing each other across the printed coils, in a manner similar to magnets  1440 ,  1441 ,  1450 , and  1451 . Moreover, the portion of the magnetic fields of magnets  1440 ,  1441 ,  1450 , and  1451  that is perpendicular to coil array  1410  may be greater than the portion of the magnetic fields of magnets  1140  and  1150  that is perpendicular to coil array  1110  (shown in  FIG. 11 ). Accordingly, it may be advantageous to provide multiple magnets on each opposite side of printed coils. 
     As previously discussed, magnets on opposite sides of printed coils may be mechanically coupled to move along printed coils in unison in some embodiments. For example, one or more magnets on a top side of printed coils may be mechanically coupled with one or more magnets on the bottom side of printed coils. 
       FIG. 16  includes electromagnetic induction system  1600  in accordance with one embodiment of the invention. System  1600  can include coil array  1610  that may include any number of coils printed on any number of circuit boards (see, e.g., coils  122  and  124  and circuit board  110  shown in  FIG. 1 ). For example, coil array  1610  can include coils printed on different layers of a circuit board (see, e.g.,  FIGS. 3A and 3B ), coils printed on different circuit boards in a stack (see, e.g.,  FIG. 4 ), coils printed on the same layer of a circuit board (see, e.g.,  FIG. 5 ), any other suitable configuration of coils, or any combination thereof. 
     System  1600  can include moveable magnet  1640  and moveable magnet  1650  that may each be adjacent to coil array  1610 . Moveable magnet  1640  may be adjacent to a first side of coil array  1610 , and moveable magnet  1650  may be adjacent to a second side of coil array  1610 . Moveable magnets  1640  and  1650  may each include any material suitable for generating a magnetic field. For example, moveable magnets  1640  and  1650  may each be substantially similar to moveable magnets  1040  and  1050 , and the previous description of the latter can be applied to the former. 
     In some embodiments, magnets on opposite sides of a printed coil array may be mechanically coupled together using one or more brackets. For example, one or more brackets may mechanically couple magnets together so that the magnets move alongside the printed coils in unison. Such a configuration may be advantageous because it may increase the strength of the magnetic field passing perpendicularly through the printed coils. In the embodiment shown in  FIG. 16 , magnet  1640  may be mechanically coupled with magnet  1650  using brackets  1691 ,  1692 ,  1693 , and  1694 . Brackets  1691 - 1694  may be posts that couple with each magnet near the corner of the magnet. In some embodiments, brackets for coupling magnets may be integrated into carriers or housings for the magnets or the brackets may be adhered to the surface of the magnet. In some embodiments, one or more brackets may couple together assemblies of multiple magnets on opposite sides of printed coils. For example, brackets similar to brackets  1691 - 1694  may be provided in conjunction with system  1300  (shown in  FIG. 13 ) to couple magnets  1340  and  1341  together with magnets  1350  and  1350 . 
     In some embodiments, a system may include a structure for supporting a coil array and guiding one or more magnets moveable adjacent to the array. For example, a circuit board that includes a coil array may include additional substrate along the periphery of the array for support. In another example, a circuit board that includes a coil array may be embedded in a support structure of a different material (e.g., a chassis). In the embodiment shown in  FIG. 16 , system  1600  may include structure  1602  for supporting coil array  1610  and guiding magnets  1640  and  1650 . In some embodiments, structure  1602  may include an extension of the circuit board or stack of circuit boards that form coil array  1610 . In some embodiments, structure  1602  may include a support structure composed of a material different from a circuit board or stack of circuit boards that form coil array  1610 . For example, structure  1602  may include a chassis formed from a relatively rigid material. 
     In some embodiments, a system may include one or more slots in a support structure for guiding magnets moveable adjacent to printed coils. For example, a structure may include an extension of a circuit board or stack of circuit boards that form a coil array and the extension may include one or more slots for guiding adjacent magnets. In another example, a separate support structure in which a circuit board or stack of circuit boards may be mounted can include one or more slots for guiding magnets adjacent to the array. In some embodiments, the location and size of a slot may correspond to the location of one or more brackets used to couple magnets together. For example, a structure may include a slot overlapping the path of a bracket as magnets move alongside the printed coils. In the embodiment shown in  FIG. 16 , structure  1602  may include slot  1604  and slot  1606 . The locations of slots  1604  and  1606  may correspond to the locations of brackets  1691 - 1694  when magnets  1640  and  1650  move alongside coil array  1610 . For example, the location and size of slot  1604  may correspond to the path of brackets  1691  and  1694  as magnets  1640  and  1650  move adjacent to coil array  1610 . In another example, the location and size of slot  1605  may corresponding to the path of brackets  1692  and  1693  as magnets  1640  and  1650  move adjacent to coil array  1610 . 
     The brackets and corresponding slots shown in the embodiment of  FIG. 16  are merely illustrative and other suitable brackets, corresponding slots, or other support structure can be used without deviating from the disclosure. For example, a bracket could be used that extends along one side of a magnet (e.g., a continuous bracket running between the locations of brackets  1692  and  1693 ). In another example, a support structure may be narrow enough that one or more brackets run alongside the outer edge (e.g., periphery) of the support structure. 
     An electromagnetic induction system with magnets on opposite side of printed coils may include one or more enclosures. In some embodiments, a system may include a first enclosure covering a first side of a printed coil array (see, e.g., enclosure  1342  shown in  FIG. 13 ) and a second enclosure covering the second side of the printed coil array (see, e.g., enclosure  1352  shown in  FIG. 13 ). For example, system  1600  may include a first enclosure (not shown) mounted to structure  1602  and covering the top side of coil array  1610  and magnet  1640 . Continuing the example, system  1600  may include a second enclosure (not shown) mounted to structure  1602  and covering the bottom side of coil array  1610  and magnet  1650 . In some embodiments, a system may include a single enclosure covering both sides of a printed coil array. Such an enclosure may completely envelop a coil array, moveable magnets, and any support structure. For example, system  1600  may include an enclosure (not shown) encapsulating structure  1602  so that both sides of coil array  1610  as well as magnets  1640  and  1650  are covered. 
     In some embodiments, a magnet may extend from one side of printed coils to an opposite side of printed coils. For example, a single magnet can be positioned adjacent to both the top side of printed coils and the bottom side of the printed coils. In some embodiments, a magnet may include a first portion adjacent to the top side of printed coils, a second portion adjacent to the bottom side of the printed coil, and a third portion extending from the first portion to the second portion. In some embodiments, the third portion of the magnet can extend through a structure for supporting a coil array (see, e.g., structure  1602  shown in  FIG. 16 ). For example, a support structure may include one or more slots in a for guiding magnets moveable adjacent to printed coils and the third portion may extend through any of the one or more slots. 
       FIG. 17  includes electromagnetic induction system  1700  in accordance with one embodiment of the invention. System  1700  can include coil array  1710  that may include any number of coils printed on any number of circuit boards (see, e.g., coils  122  and  124  and circuit board  110  shown in  FIG. 1 ). For example, coil array  1710  can include coils printed on different layers of a circuit board (see, e.g.,  FIGS. 3A and 3B ), coils printed on different circuit boards in a stack (see, e.g.,  FIG. 4 ), coils printed on the same layer of a circuit board (see, e.g.,  FIG. 5 ), any other suitable configuration of coils, or any combination thereof. 
     System  1700  can include moveable magnet  1740  that may extend from one side of coil array  1710  to the opposite side of coil array  1710 . For example, moveable magnet  1740  may be adjacent to both the top side of coil array  1710  and the bottom side of coil array  1710 . Accordingly, moveable magnet  1740  may be operative to move alongside multiple sides of coil array  1710 . Moveable magnet  1740  may include any material suitable for generating a magnetic field (see, e.g., magnet  140  shown in  FIG. 1 ). 
     In some embodiments, a moveable magnet extending from one side of a coil array to an opposite side of the coil array may include multiple portions. For example, magnet  1740  may include first portion  1741  adjacent to the top side of coil array  1710 , second portion  1742  adjacent to the bottom side of coil array  1710 , and third portion  1743  extending from first portion  1741  to second portion  1742 . Third portion  1743  may, for example, function as a mechanical link between first portion  1741  and second portion  1742 . The length of third portion  1743  may be based at least partially on the thickness of coil array  1710 . For example, the length of third portion  1743  may be selected so that both first portion  1741  and second portion  1742  are within close proximity of coil array  1710 . 
     In some embodiments, a system may include a structure for supporting a coil array and guiding a magnet moveable adjacent to the array. For example, a circuit board that includes a coil array may include additional substrate along the periphery of the array for support. In another example, a circuit board that includes a coil array may be embedded in a support structure of a different material (e.g., a chassis). In the embodiment shown in  FIG. 17 , system  1700  may include structure  1702  for supporting coil array  1710  and guiding magnet  1740 . In some embodiments, structure  1702  may include an extension of the circuit board or stack of circuit boards that form coil array  1710 . In some embodiments, structure  1702  may include a support structure composed of a material different from a circuit board or stack of circuit boards that form coil array  1710 . For example, structure  1702  may include a chassis formed from a relatively rigid material. 
     In some embodiments, a system may include one or more slots in a support structure for guiding a magnet moveable adjacent to printed coils. For example, a structure may include an extension of a circuit board or stack of circuit boards that form a coil array and the extension may include one or more slots for guiding adjacent magnets. In another example, a separate support structure in which a circuit board or stack of circuit boards may be mounted can include one or more slots for guiding magnets adjacent to the array. In some embodiments, the location and size of a slot may correspond to the shape and size of a magnet extending from a first side of the coil array to a second side of the coil array. For example, a structure may include a slot overlapping the path of a magnet portion that extends from a first side of the coil array to a second side (see, e.g., third portion  1743 ) as the magnet moves alongside the printed coils. In the embodiment shown in  FIG. 17 , structure  1702  may include slot  1704 . The location of slot  1704  may correspond to the location of third portion  1743  of magnet  1740  when magnet  1740  moves alongside coil array  1710 . For example, the location and size of slot  1704  may correspond to the path of third portion  1743  as magnet  1740  moves adjacent to coil array  1710 . 
     The magnet shape and corresponding slot shown in the embodiment of  FIG. 17  are merely illustrative and other suitable magnet shapes, corresponding slots, or other support structures can be used without deviating from the disclosure. For example, a magnet shape can include a curved portion extending through a slot (e.g., a curved third portion connecting a first portion adjacent to a first side of a coil array and a second portion adjacent to a second side of a coil array). In another example, a support structure may be narrow enough that a magnet can extend from one side of a coil array to another by wrapping around the outer edge (e.g., periphery) of the support structure. 
     In embodiments where a magnet can extend from one side of printed coils to an opposite side of printed coils, the connecting portion of the magnet extending between the two sides (see, e.g., third portion  1743  shown in  FIG. 17 ) can serve multiple functions. In some embodiments, the connecting portion of the magnet can provide the functionality of a bracket that mechanically couples the first portion with the second portion (see, e.g., brackets  1691 - 1694  shown in  FIG. 16 ). In some embodiments, the connecting portion of the magnet can alter the magnetic field of the magnet to intensify the portion of the magnetic field that passes through the printed coils. For example, the poles of the magnet can be located in portions of the magnet on opposite sides of printed coils and the connecting portion can serve as a return path for the magnetic field. Such a return path may intensify the portion of the magnetic field passing through the printed coils. 
       FIG. 18  includes electromagnetic induction system  1800 . System  1800  may include a coil array and a moveable magnet adjacent to opposite sides of the coils. For example, system  1800  may include coil array  1810  and moveable magnet  1840 . Coil array  1810  may include any number of coils printed on any number of circuit boards (see, e.g., coils  152  and  154  and circuit board  110  shown in  FIG. 1 ). Moveable magnet  1840  may include any object that produces a magnetic field (see, e.g., magnet  140  shown in  FIG. 1 ). While no arrows are shown in  FIG. 18 , magnet  1840  may be moveable adjacent to coil array  1810  by moving perpendicular to the plane of  FIG. 18  in a manner similar to the movement of magnet  1740  adjacent to coil array  1710  (shown in  FIG. 17 ). Magnet  1840  may include multiple portions. For example, magnet  1840  may include first portion  1841  adjacent to the top side of coil array  1810  (see, e.g., first portion  1741  shown in  FIG. 17 ). Continuing the example, magnet  1840  may include second portion  1842  adjacent to the bottom side of coil array  1810  (see, e.g., second portion  1742  shown in  FIG. 17 ). Extending between the first and second portions, magnet  1840  may include third portion  1843  (see, e.g., third portion  1743  shown in  FIG. 17 ). 
     In some embodiments, the poles of a magnet extending from one side of printed coils to an opposite side of printed coils may be positioned to maximize the magnetic field perpendicular to the coils. For example, the poles of magnet  1840  may be positioned so that a first pole is adjacent to one side of coil array  1810  and a second pole is adjacent to the opposite side of coil array  1810 . In the embodiment shown in  FIG. 18 , the north pole is positioned in first portion  1841  adjacent to the top side of coil array  1810  and the south pole is positioned in second portion  1842  adjacent to the bottom side of coil array  1810 .  FIG. 18  displays magnetic field lines for magnet  1840 . 
     As shown in  FIG. 18 , a substantially large portion of the magnetic field of magnet  1840  may pass perpendicularly through coil array  1810  while extending from first portion  1841  to second portion  1842 . Moreover, a minimal amount of the magnetic field may extend back to the surfaces of magnet  1840  facing away from the coil array (see, e.g., magnetic fields shown in  FIGS. 11 and 14 ). Accordingly, it may be advantageous to provide a magnet extending from one side of printed coils to an opposite side of the printed coils the resulting magnetic field may be focused on the printed coils. 
     Any suitable methods can be used to manufacture electromagnetic induction systems in accordance with the disclosure. For example, one or more known circuit board manufacturing methods can be used to generate a printed coil array and then the remaining components of a system may be provided. For example, one or more moveable magnets may be provided adjacent to the coil array and then one or more enclosures can be coupled to the coil array or a support structure for covering the magnets. 
       FIG. 19  includes process  1900  for manufacturing an electromagnetic induction system in accordance with one embodiment. Process  1900  can be used to form an electromagnetic induction system that includes printed coils. At block  1910 , a circuit board can be manufactured that includes layers, coils printed on the layers, and at least on via coupling a first one of the coils with a second one of the coils. For example, a circuit board similar to circuit board  310  (shown in  FIGS. 3A and 3B ) or circuit board  510  (shown in  FIG. 5 ) can be manufactured. In some embodiments, a multi-layered circuit board with printed coils can be manufactured using any suitable technique. For example, each coil can be formed on each layer using an etching process, vias can be drilled in one or more layers, and then the layers can be combined to form a circuit board. The circuit board manufactured at block  1910  can include any suitable number of layers, coils, and vias. 
     At block  1920 , a first magnet can be provided adjacent to the circuit board so that the first magnet is operative to move alongside the coils and generate an electromotive force across the coils. For example, a magnet can be provided on one side of a circuit board, and the magnet can be moveable alongside the coils (see, e.g., magnet  740  shown in  FIG. 7 ). 
     In some embodiments, process  1900  can include attaching an enclosure to the circuit board. Such an enclosure may be operative to retain the first magnet in close proximity to the circuit board while it moves alongside the coils (see, e.g., enclosure  742  shown in  FIG. 7 ). 
     In some embodiments, process  1900  can include providing multiple magnets adjacent to the circuit board. For example, one magnet may be provided adjacent to the top surface of the circuit board and another magnet may be provided adjacent to the bottom surface of the circuit board (see, e.g., system  1000  shown in  FIG. 10 ). In some embodiments, process  1900  can include coupling a first magnet adjacent to a top side of a circuit board with a second magnet adjacent to a bottom side of a circuit board (see, e.g., system  1600  shown in  FIG. 16 ). 
     In some embodiments, process  1900  can include applying ferrofluid to a magnet. Such ferrofluid may serve as a lubricant to reduce friction as the magnet moves alongside the printed coils (see, e.g., ferrofluid  745  shown in  FIG. 7 ). 
     In some embodiments, process  1900  can include machining a slot in the circuit board. For example, a slot can be machined in the circuit board to guide the a magnet when it moves alongside the coils. Such a slot can be similar to slot  1604  (shown in  FIG. 16 ) or slot  1704  (shown in  FIG. 17 ). 
     In some embodiments, process  1900  can include attaching the circuit board to a support structure. Such a support structure may be formed from a rigid or durable material. In some embodiments, such a support structure may include a slot operative to guide the a magnet when it moves alongside the coils. Such a slot can be similar to slot  1604  (shown in  FIG. 16 ) or slot  1704  (shown in  FIG. 17 ). 
     The previously described embodiments are presented for purposes of illustration and not of limitation. It is understood that one or more features of an embodiment can be combined with one or more features of another embodiment to provide systems and/or methods without deviating from the spirit and scope of the invention. The present invention is limited only by the claims which follow.

Metadata:
Filing Date: 20090904
Publication Date: 20120605
Grant Date: 20120605
Priority Date: 20090904
Inventors: LIN GLORIA
RAHUL PAREET
ROSENBLATT MICHAEL
NAKAJIMA TAIDO
GERMANSDERFER BRUNO
DASGUPTA SAUMITRO
Assignee: APPLE INC
CPC Classifications: [{"code": "H02K3/47", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49826", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02K3/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02K35/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02K3/47", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4913", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4913", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02K35/02", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49826", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/4902", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02K3/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/4902", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 43647204