Patent Publication Number: US-11034329-B2

Title: Wheel fastener alarm

Description:
RELATED APPLICATIONS 
     The present patent document is a continuation of U.S. Non-Provisional patent application Ser. No. 16/127,999, filed Sep. 11, 2018 (now U.S. Pat. No. 10,421,433), which is a continuation of U.S. Non-Provisional patent application Ser. No. 15/788,204, filed Oct. 19, 2017 (now U.S. Pat. No. 10,099,655), which claims the benefit of the filing date under 35 U.S.C. § 119(e) of Provisional U.S. Patent Application Ser. No. 62/414,444, filed Oct. 28, 2016. All of the foregoing applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present inventions relate generally to wheel fasteners, and more particularly, to a wheel fastener alarm. 
     Wheel fastener locks are used on many types of vehicles to prevent unauthorized removal and theft of vehicle wheels. Conventional wheel fastener locks require a special tool to remove the wheel fastener attached to the wheel. Thieves may circumvent the need for a special tool to remove conventional wheel fastener locks by breaking the wheel fastener off the wheel stud, such as with a strike bar. Accordingly, there is a need for an improved wheel fastener lock. 
     SUMMARY 
     A wheel fastener alarm is described, including a nut body comprising a cavity extending longitudinally through the nut body and comprising an internal thread along at least a bottom portion of the cavity; a cap disposed around a top portion of the nut body and secured to the nut body, wherein the cap has an opening in the end of the cap, the opening disposed over the cavity; a non-metallic cover disposed over the opening; and a sensor array disposed within the cavity, the sensor array including a sensor configured to detect an attribute of a wheel stud within the nut body and generate output information, a processor configured to generate a signal based on the output information, a transmitter configured to send the signal to a remote location, and a power supply configured to provide power to the sensor, processor, and transmitter. 
     The inventions herein may include any of the following aspects in various combinations and may also include any other aspect described below in the written description or in the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       The invention may be more fully understood by reading the following description in conjunction with the drawings. 
         FIG. 1  is a schematic of a wheel fastener alarm. 
         FIG. 2  is a schematic of a sensor array of a wheel fastener alarm. 
         FIGS. 3A and 3B  are a side cross-sectional view and an end view of a capped wheel nut of a wheel fastener alarm. 
         FIGS. 4A-4C  are end and side views of a wheel nut cap of a wheel fastener alarm. 
         FIG. 5  is a schematic of a sensor array of a wheel fastener alarm. 
         FIG. 6  is a schematic of a sensor array of another wheel fastener alarm; 
         FIG. 7  is a flow chart of a method of operating a wheel fastener alarm. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures, wheel fastener alarm  100  includes a capped automotive wheel nut  102 , as shown in  FIG. 1 . In some embodiments, the capped automotive wheel nut  102  may be a stainless steel capped automotive wheel nut. The top portion of the nut body  104 , including the wrenching surfaces  106 , may be covered by cap  108  that could be made of stainless or another appropriate capping material. Thus, when the wheel nut  102  is installed on a wheel stud  112 , the nut body  104  itself is not visible to casual observers, and the cap  108  is the only part of the nut that is readily visible. However, the bottom portion of the nut body  110  is not covered by the cap  108  so that the nut  102  can be threaded onto the wheel stud  112  without the cap  108  interfering with the engagement of the nut threads  114  and stud threads  116 . 
     Wheel fastener alarm  100  also includes a sensor array  118  to detect an attribute of wheel stud  112  within wheel nut  102 . The attribute may be information used to detect an alarm condition related to wheel nut  102 , such as if wheel nut  102  is being removed from wheel stud  112 . Attributes may include, for example, the position or location of the wheel stud within the wheel nut, an acceleration value of the wheel nut, a magnetic field around the wheel nut, shock value of wheel nut, a vibration value of the wheel nut on the wheel stud, or a temperature of the wheel nut. Sensor array  118  may be designed to fit within cavity  120  in wheel nut  102 . Sensor array  118  may be integral with wheel nut  102 . Wheel nut  102  may be sized similarly to a conventional wheel nut. For example, the amount of space within cavity  120  to house sensor array  118  may be a cylindrical space approximately 15 mm wide by 14 mm long. Depending on the length of wheel stud  112 , the amount of available space may be reduced to approximately 9 mm. Sensor array  118  may use a variety of methods (as discussed below) to detect the attribute of wheel stud  112 . 
     Sensor array  118  may transmit a signal to receiver  122  regarding the attribute, such as detection or lack of detection of wheel stud  112  within wheel nut  102 . The signal may indicate that wheel nut  102  is attached to or detached from wheel stud  112 . Accordingly, the signal may be an indication that wheel nut  102  is being removed from wheel stud  112 . Receiver  122  may relay the signal to an alarm controller  124 . Alarm controller  124  may be a controller for a vehicle alarm system. Accordingly, wheel fastener alarm  100  may be in communication with the vehicle&#39;s electronic systems, such as the vehicle&#39;s alarm system. Alarm controller  124  may activate the vehicle&#39;s alarm system based on the signal received from sensor array  118  regarding the status of wheel nut  102 . Attempting to remove or tamper with wheel fastener alarm  100  may activate the vehicle alarm system. When wheel fastener alarm  100  is removed improperly, the vehicle alarm may generate sounds and initiate flashing lights. Similarly, if wheel fastener alarm  100  is damaged, sensor array  118  may send a signal indicating damage to alarm controller  124  through receiver  122 . Alarm controller  124  may then activate the vehicle&#39;s alarm system. Additionally or alternatively, alarm control  124  may transmit a signal regarding the vehicle&#39;s alarm system to a remote device, such as a mobile phone, a tablet, or a computer. Receiver  122  and alarm controller  124  may be located remotely from wheel nut  102  and wheel stud  112 , such as in a different part of the vehicle or remote from the vehicle. Receiver  122  may include CAN and LIN buses to allow receiver  122  to be used as a development platform in some applications, such as when wheel fastener alarm  100  is installed by original equipment manufacturers. 
     Wheel fastener alarm  100  may use distributed processing to determine if the vehicle alarm system should be activated based on the signal from sensor array  118 . Wheel fastener alarm  100  may rely on alarm controller  124  to process the signal from receiver  122  to determine if the attribute measured by sensor array  118  warrants activing the vehicle alarm system based on other information not available to wheel fastener alarm  100 , such as other sensors associated with the vehicle. For example, sensor array  118  may measure a temperature of wheel nut  102  that deviates from a reference value, such as being lower than a reference value, and may transmit a signal to receiver  122  indicating the measured temperature. Receiver  122  may send the signal to alarm controller  124 . Alarm controller  124  may process the received signal and determine that the vehicle alarm system does not need to be activated because other sensors on the vehicle are also measuring a temperature deviation, indicating that other portions of the vehicle are at the lower temperature, as opposed to just wheel nut  102  being at a lower temperature. Other portions of the vehicle being at the lower temperature may indicate that wheel nut  102  is not being removed from the vehicle, but may indicate instead that the vehicle is in a cold location. 
     Wheel fastener alarm  100  may include a cover  126  placed over an opening  127  in the end of cap  108 . Cover  126  may be non-conductive or non-metallic to allow the signal from sensor array  118  to pass through cover  126  and reach receiver  122 . Cover  126  may, for example, be composed of a polymer. Cover  126  may include any color or pattern to provide a visual indication of the presence of wheel fastener alarm  100  in order to decrease the probability that a thief attempts to steal the wheel that wheel fastener alarm is attached to. The color may be highly visible to an observer in comparison to the vehicle wheel and remainder of wheel fastener alarm  100 . For example, cover  126  may be composed of a blue colored polymer to easily show an observer that the wheel nut attached to the wheel is a wheel fastener alarm  100 . 
     Attenuation of the signal from sensor array  118  to receiver  122  due to the metallic nature of wheel nut  102  and cap  108  may be minimized by adequately sizing opening  127  in the end of cap  108 . The amount of attenuation is dependent on the size of opening  127  and can be approximated as:
 
Attenuation (dB)=20 log(Δ/2 a ),
 
where λ=wavelength and a=largest opening dimension.
 
The required transmit power can be approximated as:
 
Tx Power (dBm)=Rx Sensitivity (dBm)+2×antenna gain+path loss+cavity loss+vehicle attenuation.
 
For an approximately 7.5 mm diameter opening  127 , the transmit power is estimated as:
 
Tx Power (dBm)=−112 dBm+(2×17 dB)+39.2 dB (at 5 meters)+33.3 dB+10 dB (estimated)
 
Tx Power (dBm)=4.5 dBm minimum.
 
Transmit power of approximately 4.5 dBm is achievable with many low power transmitters in the appropriate frequency range. The size of opening  127  may be adjusted to reduce the required transmit power.
 
     Wheel fastener alarm  100  may be removed from wheel stud  112  without any special tools beyond the tools that are normally required to remove a conventional wheel nut. Wheel fastener alarm  100  does not require a special key, socket, or wrench to be removed. Wheel fastener alarm  100  may be designed to operate on any type of vehicle and may tolerate the environmental and operating stresses associated with being mounted on the tire/wheel assembly of any vehicle. Wheel fastener alarm  100  may be capable of operating within a temperature range of −40° C. to +85° C. 
     Wheel fastener alarm  100  is located on the wheel of a vehicle; accordingly, wheel fastener alarm  100  complies with design and test requirements suitable for applications associated with vehicle wheels. Wheel fastener alarm  100  is compatible with steel and aluminum wheel materials, such as high strength low allow steel, hot rolled low carbon steel, AA 356 aluminum, 6061 T6 aluminum, AA 5454 aluminum, and chrome clad wheels. Wheel fastener alarm  100  can withstand corrosion testing, such as 60 cycles of CETP: 00.00-R-311, or equivalent, without loss of function, serviceability, or significant degradation in appearance, including any galvanic contribution to degraded wheel appearance. An example matrix of tests that wheel fastener alarm  100  may pass is listed below. 
     
       
         
           
               
               
             
               
                   
               
               
                 Test Description 
                 Example Criterion 
               
               
                   
               
             
            
               
                 100% Functional Evaluation 
                 Full parametric characterization 
               
               
                   
                 −40 to +85 C. 
               
               
                 Shipping/Storage 
                 −50 to +90 C. for 160 hrs 
               
               
                 Low Temperature Endurance 
                 −20 C. for 1000 hrs 
               
               
                 Low Temperature Operation 
                 −40 C. for 250 hrs 
               
               
                 High Temperature Endurance 
                 +85 C. at 85% humidity for 500 hrs 
               
               
                 High Temperature Operation 
                 +85 C. for 800 hrs 
               
               
                 Powered Thermal Cycle 
                 500 cycles 
               
               
                 Thermal Shock Resistance 
                 100 cycles 
               
               
                 Powered Vibration 
                 20 hrs 
               
               
                 Mechanical Shock And Drop 
                 10 shocks per axis, 10 drops from 1 m 
               
               
                 Humidity/Temperature Cycle 
                 −10 C. to +60 C. at 95% humidity 
               
               
                   
                 for 250 hrs 
               
               
                 Water/Fluids Ingress 
                 IP X5 
               
               
                 Salt Mist Atmosphere 
                 96 hrs 
               
               
                 Chemical Resistance 
                 Various 
               
               
                 Dust Test 
                 IP 5KX 
               
               
                 High Pressure Steam Jet 
                 IP X9K 
               
               
                 Thermal Shock Endurance 
                 −40 to +85 C. for 500 hrs 
               
               
                 FCC Part 15 Compliance 
                 Various 
               
               
                 EMC Compatibility/Immunity 
                 Various 
               
               
                   
               
            
           
         
       
     
     Wheel fastener alarm  100  can be tested and programmed prior to installation on a vehicle. For example, a low power, low frequency receiver may be included in wheel fastener alarm  100  to allow testing and programming to occur on the assembly line or during service at a vehicle&#39;s dealership. 
     Wheel fastener alarm  100  may use sensor array  118  to detect if wheel nut  102  is loose or loosening from wheel stud  112 . If sensor array  118  detects the distance between sensor array  118  and wheel stud  112  is increasing, sensor array  118  may transmit a signal to alarm controller  124  indicating that wheel nut  102  is loose or loosening from wheel stud  112 . The signal may be an early indication of wheel nut  102  loosening, such that a vehicle operator may take corrective action and tighten wheel nut  102  before wheel nut  102  detaches from wheel stud  112 . Similarly, wheel fastener  100  may indicate if an entire wheel is loose or loosening from a vehicle if wheel fastener  100  is installed on all the wheel studs  112  of a vehicle&#39;s wheel. If one or more wheel fastener alarms  100  are loose or loosening, alarm controller  124  may determine that the wheel is loose and may signal the vehicle operator to take corrective action. 
     Referring to  FIG. 2 , sensor array  118  may include components such as processor  228 , transmitter  230 , power supply  232 , wheel stud sensor  234 , motion sensor  236 , shock sensor  238 , accelerometer  250 , geomagnetic sensor  252 , and temperature sensor  254 . 
     Processor  228  may be implemented as a microprocessor, microcontroller, application specific integrated circuit (ASIC), discrete logic, or a combination of other types of circuits or logic. Numerous options exist for processor  228 . For example, processor  228  may be a Microchip PIC16LF1824T39A family of microcontrollers that include integrated radio frequency transmitters. Processor  228  may be a Infineon SP370-25-106-0, a Freescale FXTH871511DT1, or a Melexis MLX91801. Freescale FXTH71511DT1 may be the best of the integrated chip solutions, but may be more expensive than other options. The Microchip PIC16LF1824T39A may provide a low cost solution with ample radio frequency output power, low frequency receive capability for service, the ability to auto arm/disarm in original equipment manufacturer applications, and other options to reduce system power consumption. Microchip PIC16LF1824T39A may also interface easily with the sensors used in wheel fastener alarm  100 . 
     Power supply  232  may include a replaceable or rechargeable source of power, such as one or more batteries. The power supply  232  may be sufficient to power wheel fastener alarm  100  for many years and in some instances approximately 10 years. Additionally or alternatively, power supply  232  may be sufficient to power wheel fastener alarm  100  for the amount of time it typically takes for a vehicle carrying wheel fastener alarm  100  to travel approximately 100,000 miles. Power supply  232  may fit in a cylindrical space approximately 12 mm in diameter and 5 mm deep. Alternative spaces for power supply  232  may also be used. Power supply  232  may be a custom designed battery or may be an off the shelf battery, such as a CR1225 coin cell battery. Power supply  232  may be a rechargeable lithium-ion battery that is charged remotely, such as by a low frequency receiver. Sensor array  118  may include additional circuitry and software to regulate charging power supply  232 . Additionally or alternatively, an external charging station may be used. 
     Wheel stud sensor  234  may detect the position of wheel stud  112  within wheel nut  102 . The position of wheel stud  112  within wheel nut  102  may be determined with an accuracy of approximately 1 mm. Wheel stud sensor  234  may transmit a signal to processor  228  regarding the detection or lack of detection of wheel stud  112  within wheel nut  102 . Processor  228  may then utilize transmitter  230  to wirelessly send a signal to a remote location, such as receiver  122 , regarding the position of wheel stud  112  within wheel nut  102 . As discussed previously, the vehicle&#39;s alarm system may activate if wheel stud sensor  234  does not detect wheel stud  112  within wheel nut  102 . Processor  228  may also periodically utilize transmitter  230  to transmit a signal indicating that wheel stud  112  is located within wheel nut  102  and confirm that wheel fastener alarm  100  is operational. 
     Transmitter  230  may communicate with the vehicle&#39;s alarm system using the existing vehicle systems, such as the tire pressure management system or remote keyless entry system. Communication with the vehicle&#39;s systems may utilize the vehicle&#39;s low power radio frequency data link at approximately 315 MHz or 434 MHz. The use of existing vehicle communication systems by wheel fastener alarm  100  may not interfere with existing vehicle systems because wheel fastener alarm  100  may transmit most often when the existing vehicle systems are not transmitting. For example, the tire pressure management system transmits most often when the vehicle is moving, whereas wheel fastener alarm  100  may only transmit when the vehicle is stationary. Additionally or alternatively, a separate radio frequency receiver may be used to establish communication between transmitter  230  and the vehicle&#39;s systems. 
     Wheel stud sensor  234  may use a variety of methods to detect the position of wheel stud  112  within wheel fastener alarm  100 . The table below provides characteristics for capacitive, magnetic, inductive, and optical methods of detection. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                   
                 Inductance to 
                   
               
               
                   
                 Design 
                   
                 Inductive Hall 
                 Digital 
               
               
                 Description 
                 Requirement 
                 Capacitive 
                 Effect 
                 Converter 
                 Optical 
               
               
                   
               
             
            
               
                 Equipment 
                   
                 Microchip 
                 TI DRV5013 
                 TI 
                 AMS TMD 
               
               
                   
                   
                 PIC16LF1824T39A 
                 and Microchip 
                 LDC1101DR 
                 27723 
               
               
                 Package Size 
                   
                 N/A (part of control 
                 L: 2.9 mm 
                 L: 3 mm 
                 L: 3.94 mm 
               
               
                   
                   
                 IC) 
                 W: 2.37 mm 
                 W: 3 mm 
                 W: 2.36 mm 
               
               
                   
                   
                   
                 H: 1 mm 
                 H: 0.9 mm 
                 H: 1.35 mm 
               
               
                   
                   
                   
                 Plus Magnet 
               
               
                 Field Type 
                   
                 Electric 
                 Magnetic 
                 Magnetic 
                 Light 
               
               
                 Detection 
                 1-5 mm 
                 0-1.7 mm 
                 1-3.5 mm 
                 0-4.5 mm 
                 1-15 mm 
               
               
                 Range 
               
               
                 Supply Voltage 
                 2.5-3.0 VDC 
                 1.8-3.6 VDC 
                 2.5-5.5 VDC 
                 1.71-3.46 VDC 
                 2.6-3.6 VDC 
               
               
                 Supply Current 
                   
                 35 uA 
                 2.7 mA 
                 3.2 mA 
                 12.5 mA 
               
               
                 (Active) 
               
               
                 Detection Time 
                   
                 20 us 
                 50 us 
                 2 ms 
                 2.8 ms 
               
               
                 Wake From 
                 Desirable 
                 Yes 
                 Possibly 
                 No 
                 Yes 
               
               
                 Sleep 
               
               
                 Emitter/Detector 
                   
                 PCB Trace 
                 Magnet/IC 
                 PCB Trace 
                 LED 
               
               
                 Type 
               
               
                 I/O Control Pins 
                   
                 2 
                 2 
                 5 
                 4 
               
               
                 Required 
               
               
                 Complexity 
                   
                 Low 
                 High 
                 Low 
                 Low 
               
               
                   
                   
                   
                 (requires 
               
               
                   
                   
                   
                 custom 
               
               
                   
                   
                   
                 design 
               
               
                   
                   
                   
                 magnet) 
               
               
                 Operating 
                   
                 −40 C. to +85 C. 
                 −40 C. to +85 C. 
                 −40 C. to +85 C. 
                 −30 C. to +85 C. 
               
               
                 Temperature 
               
               
                 Range 
               
               
                 Base Cost (IC 
                   
                 $0 (part of control 
                 $0.29/3000 
                 $2.99/3000 
                 $1.15/2500 
               
               
                 only) 
                   
                 IC) 
                 (excluding 
               
               
                   
                   
                   
                 magnet) 
               
               
                   
               
            
           
         
       
     
     Capacitive proximity sensors produce an electric field and can be used to sense a variety of materials such as metal, solids, liquids, or the human hand. Introducing an object into the electric field results in a change in capacitance that is measurable. A capacitive sensor can be implemented using PCB traces combined with a capacitor and series resistor as the sensing element. Only two processor pins are required for control resulting in a very inexpensive solution. In addition to the low cost and component count, capacitive proximity sensors consume very little power. Experiments with capacitive proximity sensors using a 5 mm PCB sensing element demonstrate a maximum detection range of a wheel stud in a wheel nut of 1.7 mm. Larger sensing elements increase the detection range. However, the nut body in close proximity to the larger sensing element may have the effect of shorting the electric field. This may make it difficult to differentiate between the wheel stud and the wheel nut, so the wheel stud position cannot be detected reliably. The shorting effect can be mitigated somewhat by the choice of a sensing element with small geometry relative to the wheel nut size. This smaller sensing element significantly affects range, resulting in a maximum detection of approximately 1.7 mm with a 5 mm sensing element. While the capacitive sensing method could normally be used to reliably detect the stud, the presence of the fastener body may make it impractical. One possible improvement would be the use of a less ferrous material such as stainless steel for the wheel nut body. 
     Magnetic (Inductive Hall Effect) sensors vary their output voltage in response to a magnetic field. The common implementation, such as a proximity switch, simply senses the presence of the field generated by a magnet. More complex implementations are possible where metallic objects in close proximity alter the magnetic field and cause a measurable change to the output voltage of the sensor. Operation of the sensor is dependent upon characteristics of the magnetic materials and lot to lot distribution of the magnets along with the physical placement of the magnet, electronics, and object being detected in the final system. Magnetic sensors are unaffected by harsh environments and can have a very long service life. Placing a magnet on the wheel stud so it can be easily detected by the Hall Effect element may present problems for use with wheel fastener alarm  100  due to the service aspect where the magnet could be damaged or the wheel fastener alarm  100  inadvertently installed on the wrong wheel stud. If the magnet were incorporated with the electronics, concerns may include the available packaging space, achieving the necessary spacing and geometry to detect the wheel stud properly, and the ability to calibrate out the effects of the wheel fastener body. 
     Inductive sensors typically utilize an oscillator in combination with a resonant LC (inductor-capacitor) coil as a means for sensing the presence of an object such as metal. The magnetic field radiated by the coil induces eddy currents in the conductive object which alters the oscillator performance. This performance change is directly related to the distance between the metal object and the LC coil. As an example of an inductive sensor, the TI LDC1101 can simultaneously measure the impedance and resonant frequency of an LC resonator with very high resolution allowing it to sense the proximity and movement of conductive materials. By monitoring the amount of power injected into the resonator, the LDC1101 determines the equivalent parallel resistance of the resonator which it returns as a digital value. It also measures the oscillation frequency of the LC circuit by comparing the sensor frequency to a reference frequency which can then be used to determine the inductance of the LC circuit. Tests show that presence of the wheel stud within the wheel nut is detectable over an approximately 1-4.5 mm range using the LDC1101. Calibration of the inductive sensor may be required to minimize the effects of the wheel nut body on detecting the wheel stud. Given the low component count and ability to compensate for the effects of the fastener body, an inductive sensor may be a good solution for sensing the position of the wheel stud. A further advantage is that the LDC1101 will operate to approximately 1.8V. If paired with the PIC16LF1824T39A processor option, the potential for significant reduction in current consumption is possible. 
     Optical sensors may have the potential for best detection range when sensing the wheel stud. For example, the AMS TMD 27723 integrates a highly focused LED light source and detector that will provide an approximately 15 mm sensing range. A primary concern with optical sensing is dust, dirt, or debris in the wheel nut cavity. Reflections from the inside wall of the wheel nut must also be accounted for with the possibility that the walls would require a non-reflective coating. In the case of the TMD 27723, current consumption at the lowest intensity setting is significantly more than other sensing options, which may require a custom power supply. 
     Motion sensor  236  may inhibit the wheel stud  112  sensing function of wheel fastener alarm  100  when the vehicle is in motion. Additionally or alternatively, motion sensor  236  may prevent transmitter  230  from sending a signal regarding the status of wheel stud  112  or may instruct alarm controller  124  to disregard the signal when the vehicle is in motion. Wheel fastener alarm  100  may only be activated and/or operate to signal theft of a wheel when the vehicle is parked. Accordingly, wheel fastener alarm  100  may automatically not be used when the vehicle is in motion and may automatically arm when the vehicle is stationary. Restricting the use of wheel fastener alarm  100  to when the vehicle is stationary may decrease power consumption. Motion sensor  236  may be a ball bearing type switch to sense motion to arm/disarm wheel fastener alarm  100 . A ball bearing style sensor has the advantage of being used in other vehicular applications and having low power consumption. Motion sensor  236  may also be an accelerometer to detect when wheel fastener alarm  100  is moving. 
     In addition or alternative to motion sensor  236 , wheel fastener alarm  100  may be armed or disarmed based on the presence of a keyfob for the vehicle. Similar to the unlock/lock functions of the vehicle&#39;s doors, the presence of a keyfob within an adequate distance of the vehicle may arm/disarm wheel fastener alarm  100 . For example, if the owner of the vehicle has the keyfob near the vehicle, wheel fastener alarm  100  may automatically be disarmed to allow the owner to remove wheel fastener alarm  100  from wheel stud  112 , such as to change a tire, without setting off the vehicle&#39;s alarm system. 
     Wheel fastener alarm  100  may also be armed/disarmed through a remote device, such as a mobile phone, a tablet, or a computer. A user may also be able to determine the status of wheel fastener alarm  100  through a remote device, such as if it is operating properly or if it has initiated an alarm signal. Wheel fastener alarm  100  may also automatically inform a user through the remote device that an alarm signal has been initiated. 
     Additionally or alternatively, wheel fastener alarm  100  may include a low frequency receiver that receives a signal from a low frequency initiator associated with the tire pressure management system in the vehicle. The signal could instruct wheel fastener alarm  100  to arm or disarm. For example, the presence of the vehicle&#39;s keyfob may be detected by the tire pressure management system and the tire pressure management system may then send a signal to wheel fastener alarm  100  indicating the presence of the keyfob. Wheel fastener alarm  100  may then automatically disarm. 
     Additionally or alternatively, wheel fastener alarm  100  may be armed or disarmed manually from inside the vehicle, such as by a switch, to allow removal of the vehicle&#39;s wheels for any reason, such as tire replacement, tire rotation, or tire repair. Additionally or alternatively, wheel fastener alarm  100  may be automatically armed after the vehicle is stationary for a predetermined time period, such as a number of minutes or other time period. 
     Shock sensor  238  may detect if wheel fastener alarm  100  is being removed by force, such as being broken off with a strike bar used to shear off wheel nut  102 . The shock may be sensed as an overdamped vibration present on three axes (x, y, z). Tests show that the shock felt by wheel fastener alarm  100  from a strike bar or similar tampering force may last approximately 200 ms. Accordingly, shock sensor  238  may sample wheel fastener alarm  100  for force/vibration every 200 ms in order to detect a tampering force/vibration. The duration of the sampling/detection time may be extended based on ringing that may occur in wheel fastener alarm  100  after the tampering force/vibration or may be extended based on the vibration that occurs after wheel fastener alarm  100  falls to the ground as a result of a tampering force/vibration. Using an accelerometer for shock sensor  238  may require a high power capacity if a force/vibration sample is required approximately every 200 ms. Shock sensor  238  may be required to consume very low power in order to extend the operating life of wheel fastener alarm  100 . Accordingly, shock sensor  238  may be a ball bearing sensor, such as the SignalQuest SQ-MIN-200, that provides simple switch closures and is implemented carefully with interrupt pins. 
     Accelerometer  250  may detect tampering with wheel fastener alarm  100  by detecting movement or a change in position of wheel nut  102 . Processor  228  may use sensor array  118 , or some other means, to ascertain a reference position of wheel nut  102 , such as a position defined by X, Y, and Z coordinates, at the time wheel fastener alarm  100  is armed. Processor  228  may periodically ascertain the current position of wheel nut  102  and compare it to the reference position. Wheel fastener alarm  100  may activate the vehicle alarm system if the current position does not match the reference position within a predefined amount. 
     Geomagnetic sensor  252  may detect tampering with wheel fastener alarm  100  by detecting a change in the magnetic field around wheel nut  102 . Geomagnetic sensor  252  may measure a reference magnetic field around wheel nut  102  at the time wheel fastener alarm  100  is armed. Processor  228  may periodically compare a current magnetic field around wheel nut  102  with the reference magnetic field to detect if a magnetic object, for example a lug wrench, is being applied to wheel nut  102 . Wheel fastener alarm  100  may activate the vehicle alarm system if the current magnetic field differs from the reference magnetic field by a predefined amount. 
     Temperature sensor  254  may detect tampering with wheel fastener alarm  100  by detecting a change in temperature around wheel nut  102 . Processor  228  may periodically compare a current temperature measured by temperature sensor  254  around wheel nut  102  with the reference temperature to detect a change in temperature. A temperature change may indicate that wheel nut  102  is being subjected to extreme temperatures in an effort to remove wheel nut  102  from wheel stud  112 , such as by heating wheel nut  102  up with a blowtorch or freezing wheel nut  102  with dry ice. Extreme temperature changes may make it easier to remove wheel nut  102  from wheel stud  112 . Wheel fastener alarm  100  may activate the vehicle alarm system if the current temperature differs from the reference temperature by a predefined amount. 
     The arrangement and packaging of the components of sensor array  118  into wheel nut  102  are robust enough to provide protection to wheel fastener alarm  100  such that wheel fastener alarm  100  can detect a tampering force/vibration and send a signal indicating a tampering force/vibration is occurring before becoming irreparably damaged. For example, cap  108  and cover  126  provide enough protection to the components within wheel nut  102  to detect a tampering force/vibration before wheel fastener alarm  100  is rendered inoperable. The arrangement and packaging of the components of sensor array  118  into wheel nut  102  are also robust enough to prevent damage to wheel fastener alarm  100  and its components from the shock of an impact wrench being used to remove wheel fastener alarm  100 . Sensor array  118  may be seated within a plastic housing located in wheel nut  102  in order to easy assembly and to reduce the shock and vibration experienced by sensor array  118 . Additionally or alternatively, a flexible potting compound or liquid silicon rubber may be used for shock reduction. 
     An embodiment of wheel fastener alarm  100  cannot be disarmed by any external command or communication method in order to prevent unintended disarming of the system, such as by hacking, tampering, or other altering of the system. Because this embodiment of wheel fastener alarm  100  cannot be disarmed, an alarm condition of this embodiment of wheel fastener alarm  100  will only activate the vehicle alarm system if the vehicle alarm system is in the armed state. Accordingly, this embodiment of wheel fastener alarm  100  is always armed, but will only activate the vehicle alarm system if the vehicle alarm system is armed. 
     Referring to  FIG. 3 ,  FIG. 3A  is a side cross-sectional view of an embodiment of wheel fastener alarm  300 , including wheel nut  302 , cap  308 , opening  327 , and cover  326 .  FIG. 3B  is an end view of wheel fastener alarm  300 , showing cap  308  and cover  326 . Wheel fastener alarm  300  may include all the components and features of wheel fastener alarm  100 . Cover  326  may have a greater thickness at its center portion than its edge portions to provide protection to components contained within wheel nut  302 . The dimensions shown in  FIG. 3  may be varied to suit the application of wheel fastener alarm  300 . 
     Referring to  FIG. 4 ,  FIG. 4A  is an end view of an embodiment of wheel fastener alarm  400 , including cap  408  and opening  427 .  FIG. 4B  is a side view of cap  408 .  FIG. 4C  is an end view of cap  408  and opening  427 . Wheel fastener alarm  400  may include all the components and features of wheel fastener alarm  100 . The dimensions shown in  FIG. 4  may be varied to suit the application of wheel fastener alarm  400 . 
       FIG. 5  is a schematic of a sensor array  518  of an embodiment of a wheel fastener alarm. Wheel fastener alarm  500  may include all the components and features of wheel fastener alarm  100 . Sensor array  518  includes a rigid-flex PCB assembly. Rigid PCB  540  may be positioned near wheel stud  512  (not shown). Flex PCB  542  may be positioned near cover  526  (not shown) in order to optimize the performance of antenna  544 . Processor  528  may be located on rigid PCB  540 . Sensor array  518  may utilize one or more power supplies  532  to operate.  FIG. 5  shows two power supplies  532  located between rigid PCB  540  and flex PCB  542 . The power supplies  532  may be the same or different. For example, both power supplies  532  may be CR1225 coin cell batteries. Power supply  532  may be any off the shelf or custom designed battery. Sensor array  518  may also include vibration sensor  546 . Vibration sensor  546  may combine the components and features of motion sensor  236  and shock sensor  238  discussed above. Vibration sensor  546  may be a ball bearing switch. Sensor array  518  may include LF (low frequency) coil  548 , which may, for example, be similar to a Coilcraft 4513TC-725XGLB RFID transponder coil. 
       FIG. 6  is a schematic of a sensor array  618  of an embodiment of a wheel fastener alarm. Wheel fastener alarm  600  may include all the components and features of wheel fastener alarm  500 . Sensor array  618  may include only a rigid PCB  640  and may not include a flex PCB. Sensor array  618  may include sensor  650 . Sensor  650  may be any type of sensor used to detect attributes related to wheel nut  102 , such as, for example, a stud position/location sensor, a motion sensor, a shock sensor, an acceleration sensor, a geomagnetic sensor, and a temperature sensor. The other components of sensor array  618  may be the same as sensor array  518 . 
       FIG. 7  shows a flow chart of a method  700  of operating a wheel fastener alarm. The wheel fastener alarm used in conjunction with method  700  may have the same components and features as wheel fastener alarm  100 . The flow of method  700  may begin with step  760  by installing a wheel fastener alarm onto a wheel stud, such as by interlocking the threads on the wheel nut in the wheel fastener alarm with the corresponding threads on the wheel stud. Step  762  may include activating the sensor array in the wheel fastener alarm. Step  764  may include detecting an attribute to determine an alarm condition related to the wheel stud. Attributes may include the position of the wheel stud within the wheel nut, an acceleration value of the wheel nut, a magnetic field around the wheel nut, shock value of wheel nut, a vibration value of the wheel nut on the wheel stud, or a temperature of the wheel nut. Step  766  may include sending a signal from the wheel fastener alarm to the vehicle&#39;s alarm system regarding the status of the wheel stud within the wheel nut. The status may be determined by comparing the detected attribute with a reference value. Step  768  may include sounding the vehicle&#39;s alarm system if the status indicates that the detected attribute is outside a predetermined deviation from the reference value. The alarm may indicate that the wheel stud is not within the wheel nut. Such an alarm may indicate that the wheel of the vehicle is being stolen. 
     Methods or processes may be implemented, for example, using a processor and/or instructions or programs stored in a memory. Specific components of the disclosed embodiments may include additional or different components. A processor may be implemented as a microprocessor, microcontroller, application specific integrated circuit (ASIC), discrete logic, or a combination of other types of circuits or logic. Similarly, memories may be DRAM, SRAM, Flash, or any other type of memory. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, or may be logically and physically organized in many different ways. Programs or instruction sets may be parts of a single program, separate programs, or distributed across several memories and processors. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.