Patent Publication Number: US-2004056651-A1

Title: System for detecting a flip-lid position of a personal electronic device

Description:
FIELD OF INVENTION  
       [0001] The present invention relates to personal electronic devices. More particularly, the present invention relates to a system for detecting a flip-lid position of a personal electronic device.  
       BACKGROUND  
       [0002] Many personal electronic devices, such as cellular telephones, personal digital assistants (“PDAs”), and walkie-talkies, are packaged with flip-lids. Opening the flip-lid typically turns on the electronic device, and closing the flip-lid typically turns off the electronic device or places the electronic device in a “sleep” mode. The flip-lid may be moveably connected to a base unit of the electronic device through a hinge or other pivoting or swiveling mechanism to allow the flip-lid to move between the open and closed positions. Alternatively, the flip-lid may slide along the base unit to move between the open and closed positions.  
       [0003] Moreover, the flip-lids may include components of the electronic device. For example, the flip-lid of a cellular telephone typically includes an earpiece. The base unit of the cellular telephone typically includes a microphone so that the earpiece may be positioned at the user&#39;s ear and the microphone may be positioned at the user&#39;s mouth when the cellular telephone is in the open position. Alternatively, the flip-lid may include the microphone and the base unit includes the earpiece.  
       [0004] In the closed position, the cellular telephone is more compact for carrying because of the reduction in length. As another example, the flip-lid of the cellular telephone may include buttons for dialing telephone numbers and activating other functions of the cellular telephone. In the closed position, the flip-lid may protect the buttons and a display built into the base unit. Opening the flip-lid may activate the display, which is revealed upon opening the flip-lid, or activate other functions of the electronic device, such as activating illumination of the buttons and display.  
       [0005] Typically, the flip-lid includes at least one speaker, such as an earpiece of a cellular telephone, and a discrete permanent magnet, where the base unit includes a sensor that is sensitive to magnetic fields. When the flip-lid is in the closed position, the sensor detects the magnetic field of the permanent magnet due to the proximity of the permanent magnet. The permanent magnet and sensor avoid the use of mechanical switches for detecting the flip-lid position.  
       [0006] The permanent magnet is typically mounted in the flip-lid without regard to polarity, and therefore the sensor must have the capability of detecting magnetic fields of both north and south polarity. Additionally, the permanent magnet may have sufficient strength to erase information encoded on magnet strip cards, such as credit cards or identification cards. Further, the permanent magnet is another cost component of the electronic device in terms of the component and the labor costs of mounting the permanent magnet in the flip-lid. Yet further, the permanent magnet adds weight to the electronic device and uses space that could otherwise be used for electronic components or a larger sized battery. Therefore, there is a need for detecting the flip-lid position of the personal electronic device that dispenses with the inclusion of the permanent magnet in the flip-lid. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007]FIG. 1 is a diagram illustrating a side view of an electrical device;  
     [0008]FIG. 2 is a diagram illustrating a side view of an alternate configuration of the electrical device of FIG. 1;  
     [0009]FIG. 3 is a diagram illustrating a side view of one embodiment of an electrical device that includes a magnetic transducer in the flip-lid; and  
     [0010]FIG. 4 is a diagram illustrating dimensions of the personal electronic device of FIG. 3.  
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
     [0011]FIG. 1 is a diagram illustrating a side view of an electrical device  10 . The electrical device  10  has a flip-lid  12  and a base unit  14  that are moveably connected at a moveable connection  16 . The moveable connection  16  may be a pivot, such as a hinge. Another pivotable connection  16  is a swivel, where the flip-lid  12  and base unit  14  rotate relative to each other along a common perpendicular axis in moving from the open to closed position. A further moveable connection  16  is a slideable connection  16 , where the flip-lid  12  and base unit  14  remain parallel along a common longitudinal axis but are relatively translated along the common longitudinal axis in moving from the open to closed position. The flip-lid  12  may fully overlap the base unit  14  in the closed position or may partially overlap the base unit  14  in the closed position.  
     [0012] In the case of the pivotal connection  16 , for example, the flip-lid  12  is in the closed position when the flip-lid  12  is substantially parallel to the base unit  14 , i.e., the angle between the longitudinal axes of the flip-lid  12  and base unit  14  is essentially zero. In the open position, the longitudinal axes of the flip-lid  12  and base unit  14  are at an angle that allows the user to view the top surface  24  of the base unit  14 .  
     [0013] Flip-lids  12  are known to include a permanent magnet  18  while the base unit  14  includes a sensor  22 , sensitive to magnetic fields, mounted on a circuit board  20 . The permanent magnet  18  is typically composed of a rare earth magnetic material, such as Samarium-Cobalt or Neodymium-Iron-Boron, or a non-rare earth material, such as Alnico or ceramic ferrites.  
     [0014] When the flip-lid  12  is in the closed position, the sensor  22  detects the magnetic field due to the proximity of the permanent magnet  18 . The sensor  22  and permanent magnet  18  may be situated respectively on the circuit board  20  and in the flip-lid  12  far from the moveable connection  16  as shown in FIG. 1. FIG. 2 is a diagram illustrating a side view of an alternate configuration of the electrical device  30  of FIG. 1. In the personal electronic device  30  of FIG. 2, the sensor  22  and permanent magnet  18  are situated respectively on the circuit board  20  and in the flip-lid  12  proximate to the moveable connection  16 .  
     [0015] The flip-lid  12  also typically contains a transducer (not shown), such as the earpiece or the microphone as described above. The transducer may comprise a voice coil connected to a diaphragm, wherein the voice coil includes another permanent magnet. The voice coil in an earpiece moves the diaphragm to produce sound waves in response to current. The voice coil in a microphone produces current in response to sound waves on the diaphragm. The other permanent magnet in the voice coil is distinct from the permanent magnet  18  in the flip-lid  12  and does not participate in the detection of the flip-lid  12  position. It is only the proximity of the separate permanent magnet  18  and sensor  22  that detects the closed or open position of the flip-lid  12 .  
     [0016] The sensor  22  is typically a Hall Effect Sensor (“HES”), which is a device that includes a semiconductor material exhibiting a Hall effect voltage in response to a magnetic field and also includes associated integrated circuitry that amplifies the voltage. The sensor  22  and permanent magnet  18  may be situated respectively on the circuit board  20  and in the flip-lid  12  far from the moveable connection  1   6  as shown in FIG. 1. FIG. 2 is a diagram illustrating a side view of an alternate configuration of the electrical device  30  of FIG. 1. In the personal electronic device  30  of FIG. 2, the sensor  22  and permanent magnet  18  are situated respectively on the circuit board  20  and in the flip-lid  12  proximate to the moveable connection  16  as shown in FIG. 2.  
     [0017] The permanent magnet  18  is typically mounted in the flip-lid  12  without regard to polarity. This mounting is done to reduce labor costs of consistently orienting the permanent magnet  18  and also to increase the reliability of manufacturing against incorrect orientation. Therefore the sensor  22  must have the capability to detect magnetic fields of both north and south polarity. Such a sensor  22  is a bipolar, or pole-independent, HES that detects the presence of the permanent magnet  18  regardless of which pole is facing the top surface  24  of the base unit  14 . Typically, bipolar HES sensors are more expensive than unipolar, or pole-dependent, HES sensors and so the indiscriminate mounting of the permanent magnet  18  increases the cost of the personal electronic device  10 ,  30 . Further, the permanent magnet  18  may have sufficient strength to erase information encoded on magnet strip cards, such as credit cards or identification cards. Therefore, there is a need for detecting the closed position of the personal electronic device  10 ,  30  that does not rely on a permanent magnet  18 .  
     [0018] These considerations and costs associated with the permanent magnet  18  and bipolar HES  22  may be reduced by detecting the field of a magnetic transducer already present in the personal electronic device. For example, the field of a magnetic earpiece in a cellular telephone may have sufficient strength that a HES can determine the position of the earpiece on the flip-lid  12  with respect to the base unit  14 . An advantage of using the magnetic field of the existing transducer to detect the closed position is that the transducer is mounted similarly on each personal electronic device and each transducer magnet has a common polarity. Because the sensor detects magnetic fields of one polarity, the sensor can be a unipolar HES of lower cost. Further, the magnetic field of the electronic device is reduced without the permanent magnet  18  and is less likely to damage magnetic strip cards.  
     [0019]FIG. 3 is a diagram illustrating a side view of one embodiment of an electrical device  40  that includes a magnetic transducer  42  in the flip-lid  12 . The transducer  42  has a front  44  and a back  46 , and is mounted in the flip-lid  12  so that the front  44  faces the top surface  24  of the base unit  14  when the flip-lid  12  is closed. Examples of transducers  42  include speakers of laptop computers, walkie-talkies, or PDAs, and earpieces or microphones of cellular telephones. Other examples include alarm devices such as buzzers on PDAs and tremblers of cellular telephones that are used for silently alerting the user to an incoming call by causing the cellular telephone to mechanically vibrate. The transducers  42  are typically manufactured with a common magnetic orientation such that the front  44  of each manufactured transducer  42  exhibits the same magnetic polarity. The transducers  42  typically cannot be properly mounted in the flip-lid  12  with an incorrect orientation.  
     [0020] The base unit  22  includes a magnetic field detector  48 , which may be mounted on a circuit board  20 . In one embodiment, the magnetic field detector  48  is a reed switch that closes in the presence of a sufficiently strong magnetic field. In another embodiment, the magnetic field detector  48  is a HES. A HES has some advantages over a reed switch in that the HES is typically smaller and is not sensitive to mechanical vibrations of the electronic device  40 .  
     [0021] A unipolar HES switches in response to a field of only one polarity. Examples of unipolar HES devices are the A3250 and A3251 devices manufactured by Allegro MicroSytems, Inc. of Worcester, Mass. A bipolar HES, however, responds to either magnetic polarity by reversing the directions of the current through the Hall element and/or reversing the voltage measurement points on the Hall element. Examples of bipolar HES devices are the A3209 and A3210 devices also manufactured by Allegro MicroSytems, Inc. of Worcester, Mass. Because the bipolar devices require more circuitry to be sensitive to magnetic fields of either polarity, the bipolar devices are typically more expensive than the unipolar devices.  
     [0022] Also, unipolar HES devices are typically more sensitive to magnetic fields than bipolar HES devices and may better detect the smaller magnetic field of the transducer  42 . As the transducer  42  alone has a weaker magnetic field than in combination with the permanent magnet  18  of FIG. 1 and FIG. 2, there is less of a risk of damaging the information on a magnetic strip card if the card is in close contact with the personal electronic device  40 . Further, in the embodiment illustrated in FIG. 3 there is reduced interference with the detection of the magnetic field of the transducer  42  from other magnetic field sources on the personal electronic device  40  because the permanent magnet  18  is absent.  
     [0023] In the closed position, the flip-lid  12  of the personal electronic device  40  is substantially parallel to the base unit  14 . The front  44  of the transducer  42  is at its closest position to the unipolar HES  48 . The magnetic field detected at the unipolar HES  48  is therefore at its highest value when the flip-lid  12  is in the closed position. As the angle at the moveable connection  16  between the flip-lid  12  and the top surface  24  of the base unit  14  increases, the distance between the front  44  of the transducer  42  increases and correspondingly the magnetic field strength at the unipolar HES  48  decreases. When the magnetic field strength at the unipolar HES  48  decreases below a predetermined trigger point value, the HES  48  switches to indicate to other components on the circuit board  20  that the flip-lid  12  is not in the closed position.  
     [0024]FIG. 4 is a diagram illustrating the dimensions of the personal electronic device  40  of FIG. 3. The distance between the moveable connection  16  and the transducer  42  is denoted L. The distance between the HES  48  and the transducer  42  in the closed position is denoted d. The angle between the flip-lid  12  and the base unit  14  is denoted α. The HES  48  switches to the state corresponding to the closed position when a falls below a closing angle α C . Also, the HES  48  switches to the state corresponding to the open position when α rises above an opening angle α O . Hysteresis of the HES  48  prevents an unstable trigger point. Increasing the hysteresis of the HES  48 , for example by programming the HES  48 , increases the difference between α O  and α C .  
     [0025] Table 1 displays the dimensions and opening and closing angles for three makes of cellular telephones. The three cellular telephones are the models designated “V3688,” “V66,” and “T720,” which are manufactured by Motorola, Inc. of Schaumberg, Ill. The opening and closing angles are dependent on the dimensions of the cellular telephones and the transducer  42  in each respective cellular telephone, and the sensor  48  is an A3210 bipolar HES.  
                               TABLE 1                       Model   L (mm)   d (mm)   α O     αhd C                                                    V3688   54   3   4°   3°       V66   65   2   5°   4°       T720   73   3   3°   2°                  
 
     [0026] It should be understood that the above dimensions and angles are for illustrative purposes only and that other angles and dimensions are possible for other models of cellular telephones. Also, other angles are possible if the magnetic field strength of the transducer  42  is changed or a different HES  48  is used.  
     [0027] In personal electronic devices  40  whose operative transducer  42  is closer to the moveable connection  16 , the opening and closing angles are expected to be larger because a larger angle a is required to separate the HES  48  and the transducer  42  to sufficiently weaken the magnetic field strength of the transducer  42 .  
     [0028] Therefore, employing the magnetic field of the transducer  42  to operate the unipolar HES  48  disposes with the need for mounting a permanent magnet  18  in the personal electronic device, and disposes with the need for using a bipolar HES to detect the magnetic field change. Cost savings are from eliminating the labor costs of mounting the permanent magnet, eliminating the cost the permanent magnet itself, and using the cheaper unipolar HES  48 . Additionally, the space and weight considerations of the separate permanent magnet are eliminated. The extra space may be used for including additional components of the electronic device  40 , or for creating acoustical structures that enhance the sound quality of the transducer  42 .  
     [0029] The foregoing detailed description is merely illustrative of several embodiments of the invention. Variations of the described embodiments may be encompassed within the purview of the claims. For example, the transducer  42  may be mounted in the base unit  14  and the sensor  48  mounted in the flip-lid  12 . Accordingly, any description of the embodiments in the specification should be used for general guidance, rather than to unduly restrict any broader descriptions of the elements in the following claims.