Transient protection and current control of devices

Abstract

An apparatus including an electrical device electrically coupled to a power source and transient suppression and current control circuitry electrically coupled to the electrical device. The circuitry includes a negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge. The circuitry also includes a positive temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to a change in electrical current to maintain the electrical current below an acceptable threshold level.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of pending U.S. patent application Ser. No. 10/617,641 filed on Jul. 11, 2003, the contents of which are incorporated herein by reference.

BACKGROUND

The present invention relates to transient protection and current control of various devices, and more particularly but not exclusively relates to the utilization of temperature sensitive devices to eliminate or at least reduce any adverse consequences caused by power surges and increased current levels on various devices.

It is frequently desirable to interface various devices, such as sensor assemblies, to controllers. In many instances, the controller interface provides electrical power to operate such devices. Unfortunately, this arrangement sometimes generates transients that can damage the device or other circuit components connected to the controller. A similar problem can result when powering the device with a dedicated power supply or other source. Typically, general-purpose surge protectors are not adequate to provide the desired level of circuit protection. Moreover, increased current levels that are sometimes caused by an internal drop in circuit resistance may lead to excessive current levels that can damage the device, the controller, or other circuit components connected to the controller. Accordingly, there is a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique technique for transient protection and current control of various devices including, for example, sensor assemblies. Other embodiments include unique systems, devices, apparatus, and methods for protecting such devices from transients and excess current levels.

One embodiment of the invention includes a sensor operable to detect one or more physical characteristics and a transient suppression and current control circuit electrically coupled between a power source and the sensor. This circuit includes at least one thermistor that is responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge, and at least one thermistor that is responsive to a change in electrical current to maintain the electrical current below a threshold level.

In another embodiment of the invention, an apparatus includes an electrical device electrically coupled to a power source and transient suppression and current control circuitry electrically coupled to the electrical device. The circuitry includes a first negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge, and a first positive temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to a change in electrical current to maintain the electrical current below a threshold level.

In another embodiment of the invention, a method is directed to providing transient suppression and current control which includes providing electrical power to an electrical device, suppressing a transient power surge by dissipating at least a portion of the surge using a negative temperature coefficient thermistor, and maintaining electrical current below a threshold level using a positive temperature coefficient thermistor.

In another embodiment of the invention, an apparatus includes an electrical device, a connector configured to electrically couple the electrical device to a power source, and first and second thermistors electrically coupled between the connector and the electrical device, with one of the first and second thermistors being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge, and with another of the first and second thermistors being responsive to a change in electrical current to maintain the electrical current below a threshold level.

In another embodiment of the invention, a system includes a sensor operable to detect a change in one or more physical characteristics and to provide a corresponding sensor signal, a controller including a power source electrically coupled to the sensor, and transient suppression and current control circuitry electrically coupled between the sensor and the power source of the controller. The circuitry includes a first negative temperature coefficient thermistor responsive to an electrical power surge condition to dissipate at least a portion of the electrical power associated with the surge, and a first positive temperature coefficient thermistor responsive to a change in electrical current to maintain the electrical current below a threshold level.

It is one object of the present invention is to provide a unique technique for transient protection and current control associated with various devices including, for example, sensor assemblies.

Another object is to provide a unique system, method, device, or apparatus for protecting various devices from transients and increased current levels.

Other objects, embodiments, forms, features, advantages, aspects and benefits of the present invention shall become apparent from the detailed description and drawings included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system according to one embodiment of the present invention which includes a device having transient suppression circuitry.

FIG. 2 is a schematic view of the device of FIG. 1 shown in greater detail.

FIG. 3 is a schematic view of a system according to another embodiment of the present invention which includes a device having transient suppression and current control circuitry.

FIG. 4 is a schematic view of the device of FIG. 3 shown in greater detail.

DETAILED DESCRIPTION

While the present invention may be embodied in many different forms, for the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is hereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.

In one embodiment of the present invention, a sensing device is used to detect one or more physical characteristics. The sensing device is electrically coupled to a controller and a power source. The power source can be included in the controller. The connection of the sensing device to the controller is made through a corresponding interface. The controller is further connected electrically to an output device. The controller receives input from the sensing device and generates an output, which is sent to the output device. Transient suppression and/or current control circuitry is utilized in the connection between the sensing device and the controller. The circuitry utilizes thermistors to suppress power surges and/or to maintain current levels below certain threshold levels.

Referring to FIG. 1, shown therein is one embodiment of the present invention that is directed to a system 20 including controller 30, output device 40, and sensing device 50. Sensing device 50 is electrically coupled to sensing interface 32 of controller 30. Controller 30 is electrically coupled to output device 40.

FIG. 2 depicts controller 30 and sensing device 50 of FIG. 1 in more detail. Sensing device 50 includes sensor assembly 52 coupled to connector 54. Sensing interface 32 includes electrical power source 34, which is operable to supply electrical power to sensing device 50. Interface 32 electrically couples to connector 54 of sensing device 50. Assembly 52 and connector 54 are provided as an integral sensing device unit 56. Sensor assembly 52 includes transient suppression circuitry 60, sensing circuitry 74, and indicators 72. Transient suppression circuitry 60 includes two negative temperature coefficient thermistors 62, that are more specifically designated thermistors T1 and T2. Indicators 72 of assembly 52 are more specifically designated indicators I1 and I2. Sensing circuitry 74 includes sensor 70. Sensor 70 is operable to detect one or more physical characteristics relative to its environment in a standard manner.

Sensor 70 is connected in series with thermistor T2 of transient suppression circuitry 60. Indicators 72 are electrically connected in parallel between sensor 70 and thermistor T1. Each individual thermistor 62 is connected to a different contact, and correspondingly a different electrical node, of connector 54. This connection topology results in two distinct electrical branches of circuitry 60, each having a different one of thermistors 62.

Referring generally to FIGS. 1 and 2, sensor 70 of circuitry 74 is operable to detect one or more physical characteristics when powered through connector 54 with power source 34. One example of a physical characteristic that can be detected with sensor 70 is the occurrence of a change in a magnetic field. Alternatively or additionally, sensor 70 can be operable to detect temperature, electrical conductivity, pressure, velocity, acceleration, pH, intensity of one or more wavelengths of electromagnetic radiation, acoustic vibration, and/or mass fluid flow, to name just a few nonlimiting examples. Signals representative of detected physical characteristics are output from sensor 70 to indicators 72, and through transient suppression circuitry 60 and connector 54 to controller 30. Indicators 72 respond to a desired change in the sensor signal to display appropriate data to a user of system 20. In one arrangement, one of indicators 72 is arranged to indicate that device 50 is properly connected to and powered by controller 30 via interface 32 and the other of indicators 72 indicates when sensor 70 detects a characteristic level that exceeds a desired threshold. In a further embodiment, one or more of indicators 72 is activated to indicate a failure condition. In other embodiments, indicators 72 can be differently arranged, including more or fewer indicators. In one alternative, indicators 72 are absent with sensor 70 being electrically coupled in series between thermistors T1 and T2.

Controller 30 receives signals from sensor 70, and selectively transmits an output signal to output device 40 in response thereto. In one nonlimiting example, controller 30 is a programmable logic controller and output device 40 is a power relay that is activated when a characteristic detected with sensor 70 exceeds a desired level. For this embodiment, device 50 operates as a discrete, two-state device. In other embodiments, device 50 can be configured to operate in more than two discrete states and/or in a continuous manner over one or more continuous ranges of values.

Source 34 (included in controller 30) supplies electrical power to sensing circuitry 74 via transient suppression circuitry 60. Both the detection signals from sensor 70 and electrical power are transferred along the same electrical pathways through transient suppression circuitry 60. Fluctuation in the power supplied to controller 30, a change in operating state of controller 30, connection or disconnection of unit 56 from interface 32, shifts in one or more environmental characteristics (such as temperature), device failures, and the like can cause transient increases in power output from source 34 to device 50 via interface 32 and connector 54. In one particular example, a transient results from initially powering device 50 through interface 32, which abruptly provides an electric potential to assembly 52. Sensing circuitry 74 and sensor 70 may be susceptible to damage by such transient power surges. Transient suppression circuitry 60 is utilized to protect sensing circuitry 74 from power surges, including but not limited to, power surges that can result when cycling electrical power to system 20, including device 50 or some part thereof.

Transient suppression circuitry 60 utilizes thermistors 62 of a negative temperature coefficient type to suppress power surges. Prior to applying power to sensing device 50 from electrical power source 34, sensing device 50 and thermistors 62 are typically at or near ambient room temperature. When at or near room temperature, thermistors 62 are characterized by high electrical resistance. Thus, when power is applied to sensing device 50, the high electrical resistance of thermistors 62 dissipates power surges encountered by thermistors 62, thus protecting sensor 70. As energy flows through thermistors 62, the temperature of thermistors 62 increases. The increase in temperature of the thermistors 62 results in decreased electrical resistance. Thus, after sensing device 50 reaches a desired operating temperature, the electrical resistance in thermistors 62 decreases allowing signals from sensor 70 to be provided to controller 30 without undesired interference from transient suppression circuitry 60.

Although the operation of system 20 has been described utilizing negative coefficient thermistors, other thermistor types may be utilized in which electrical resistance is initially low at room/starting temperature to shunt power around the sensor device or devices to be protected from transients, and then electrical resistance is increased to allow sufficient current for operation of sensor 70 at a desired temperature. In still other embodiments, a combination of different thermistor types can be utilized. In one preferred embodiment, transient suppression circuitry 60 is capable of suppressing power surges having a duration of at least 250 microseconds and a peak current of at least 500 milliamperes. In a more preferred embodiment, transient suppression circuitry 60 is capable of suppressing a power surge of up to 500 microseconds and a peak current of up to 1 ampere. Nonetheless, in other embodiments, a different power surge suppression capability is provided.

Transient suppression circuitry 60 can be utilized with different types of electrical power sources. For example, transient suppression circuitry 60 can be utilized with alternating current or direct current power sources. The utilization of two thermistors 62 in the manner illustrated provides for the suppression of power spikes originating from either electrical node of connector 54 before reaching sensor 70. In embodiments where it is desired to suppress spikes through only one of these nodes, only a respective one of thermistors 62 may be utilized. In other embodiments of the invention, one or more of connector 54, circuitry 74, and/or indicators 72 is separate from one or more other portions of device 50 such that they are not collectively provided as an integral operating unit 56. Alternatively or additionally, power source 34 and/or interface 32 can be separate from controller 30 in further embodiments.

Referring to FIG. 3, shown therein is another embodiment of the present invention which is directed to a system 120 including a controller 130, an output device 140, and an electrical device 150. Electrical device 150 is electrically coupled to interface 132 of controller 130. Controller 130 is electrically coupled to output device 140.

FIG. 4 depicts controller 130 and electrical device 150 of FIG. 3 in more detail. In one embodiment, electrical device 150 comprises an input device configured to provide an input signal to the controller 130. In a specific embodiment, the controller 130 comprises a programmable logic controller including a number of I/O cards. However, other types of controllers and interfaces are also contemplated as would occur to one of skill in the art, such as, for example, a computer or other types of computing devices. In another specific embodiment, the input device 150 comprises a sensing device configured to detect one or more physical characteristics relative to its environment in a standard manner. However, it should be understood that other types of electrical devices are also contemplated as falling within the scope of the present invention including, for example, various types of actuators, transducers, or other electrically driven devices. Interface 132 includes electrical power source 134 which is operable to supply electrical power to input device 150. The power source 134 can be of the alternating type (AC) or the direct type (DC). The interface 132 electrically couples to connector 154 of input device 150 in a standard manner.

The sensor device 150 includes a sensor assembly 152 coupled to connector 154. In one embodiment, sensor assembly 152 and possibly the connector 154 are provided as an integral unit packaged within an outer body or housing 156. Sensor assembly 152 includes transient suppression and current control circuitry 160, sensing circuitry 174, and indicators 172. Indicators 172 are also designated as I1 and I2. In one embodiment of the invention, transient suppression and current control circuitry 160 includes two negative temperature coefficient thermistors 162 that are also designated as NTC₁ and NTC₂, and two positive temperature coefficient thermistors 164 that are also designated as PTC₁ and PTC₂. In a specific embodiment, the thermistors 162, 164 are unipolar so as to suppress both positive and negative incoming pulses. However, it should be understood that other types, configurations and arrangements of thermistors are also contemplated as would occur to one of skill in the art.

As will be discussed more fully below, the negative temperature coefficient thermistors NTC₁ and NTC₂ are electrically coupled between the power source 134 of controller 130 and the sensing circuitry 174 of input device 150, and are responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge. Additionally, the positive temperature coefficient thermistors PTC₁ and PTC₂ are also electrically coupled between the power source 134 of controller 130 and the sensing circuitry 174 of input device 150, and are responsive to a change in electrical current to maintain the electrical current below a threshold level.

In the illustrated embodiment, the first negative temperature coefficient thermistor NTC₁ and the first positive temperature coefficient thermistor PTC₁ are electrically connected in series between the power source 134 and the sensing circuitry 174. Specifically, the first negative temperature coefficient thermistor NTC₁ is electrically connected to a first node of the power source 134, and the first positive temperature coefficient thermistor PTC₁ is electrically connected between the first negative temperature coefficient thermistor NTC₁ and the sensing circuitry 174. Additionally, the second negative temperature coefficient thermistor NTC₂ and the second positive temperature coefficient thermistor PTC₂ are electrically connected in series between the power source 134 and the sensing circuitry 174. Specifically, the second negative temperature coefficient thermistor NTC₂ is electrically connected to a second node of the power source 134, and the second positive temperature coefficient thermistor PTC₂ is electrically connected between the second negative temperature coefficient thermistor NTC₂ and the sensing circuitry 174. However, it should be understood that other arrangements and positioning of the thermistors 162 and 164 are also contemplated as falling within the scope of the present invention.

In one embodiment of the invention, the negative temperature coefficient thermistors NTC₁ and NTC₂ are connected to a different contact, and correspondingly to a different electrical node, of connector 154. This connection topology thereby results in two distinct electrical branches of the transient suppression and current control circuitry 160, each including a corresponding pair of negative and positive temperature coefficient thermistors. In a further embodiment of the invention, at least one of the indicators 172 is electrically coupled in series with the sensor 170 and the thermistors 162 and 164. In a specific embodiment, indicators 172 are electrically connected in parallel between sensor 170 and the first positive temperature coefficient thermistor PTC₁. However, it should be understood that other arrangements and positioning of the thermistors 162 and 164, the sensor 170 and/or the indicators 172 are also contemplated as falling within the scope of the present invention.

Referring generally to FIGS. 3 and 4, sensor 170 of circuitry 174 is operable to detect one or more physical characteristics when powered through connector 154 via power source 134. One example of a physical characteristic that can be detected with sensor 170 is the occurrence of a change in a magnetic field. Alternatively or additionally, sensor 170 can be operable to detect temperature, electrical conductivity, pressure, velocity, acceleration, pH, intensity of one or more wavelengths of electromagnetic radiation, acoustic vibration, and/or mass fluid flow, to name just a few nonlimiting examples. Signals representative of detected physical characteristics are output from sensor 170 to indicators 172, and through transient suppression and current control circuitry 160 and connector 154 to controller 130. Indicators 172 respond to a desired change in the sensor signal to display appropriate data to a user of system 120. In one arrangement, one of indicators 172 is arranged to indicate that input device 150 is properly connected to and powered by controller 130 via interface 132, and the other of indicators 172 indicates when sensor 170 detects a characteristic level that exceeds a desired threshold. In a further embodiment, one or more of indicators 172 may be activated to indicate a failure condition. In other embodiments, indicators 172 can be differently arranged, including a single indicator or three or more indicators. Additionally, in a further embodiment, indicators 172 are absent and sensor 170 is directly coupled in series between positive temperature coefficient thermistors PTC₁ and PTC₂.

Controller 130 receives signals from sensor 170 and selectively transmits an output signal to output device 140 in response thereto. In one non-limiting example, controller 130 is a programmable logic controller and output device 140 is a power relay that is activated when a characteristic detected with sensor 170 exceeds a desired level. For this embodiment, device 150 operates as a discrete, two-state device. In other embodiments, device 150 can be configured to operate in more than two discrete states and/or in a continuous manner over one or more continuous ranges of values. In still other embodiments, the output device 140 may comprise a switch or an electrical component associated with a machine that is configured to perform some type of work.

The power source 134 (included in controller 130) supplies electrical power to the sensing circuitry 174 via the transient suppression and current control circuitry 160. The detection signals from the sensor 170 and the electrical power from the source 134 are each transferred along the same electrical pathways, and more specifically through the transient suppression and current control circuitry 160. Fluctuation in the power supplied to controller 130, a change in operating state of controller 130, connection or disconnection of unit 156 from interface 132, shifts in one or more environmental characteristics (such as temperature), device failures, and the like can cause transient increases in power output from source 134 to device 150 via interface 132 and connector 154. In one particular example, a transient results from initially powering device 150 through interface 132, which abruptly provides an electric potential to the assembly 152. Sensing circuitry 174, sensor 170 and/or other components or devices electrically coupled to the power source 134 may be susceptible to damage by such transient power surges. The transient suppression and current control circuitry 160 is utilized to protect sensing circuitry 174 from power surges, including but not limited to, power surges that can result when cycling electrical power to system 120, including input device 150 or some part thereof. As a result, the likelihood of damage and/or destruction of one or more components associated with the input device 150 as a result of overheating is significantly reduced. Additionally, the circuitry 160 is configured and arranged to minimize current or voltage drop across the input device 150.

Transient suppression and current control circuitry 160 utilizes thermistors 162 of a negative temperature coefficient type to suppress power surges. Prior to applying power to input device 150 from electrical power source 134, input device 150 and the negative temperature coefficient thermistors NTC₁ and NTC₂ are typically at or near ambient room temperature. When at or near room temperature, thermistors NTC₁ and NTC₂ are characterized by a relatively high electrical resistance. Thus, when power is applied to input device 150, the high electrical resistance associated with the thermistors NTC₁ and NTC₂ dissipates power surges encountered by thermistors 162, thus protecting sensor 170 and indicators 172 from overheating and possible damage or destruction. As energy flows through thermistors NTC₁ and NTC₂, the temperature of the thermistors increases. This increase in the temperature of the thermistors 162 correspondingly results in decreased electrical resistance. Thus, after input device 150 reaches a threshold operating temperature, the electrical resistance in thermistors NTC₁ and NTC₂ decreases, thereby allowing signals from sensor 170 to be provided to controller 130 without undesired interference from transient suppression and current control circuitry 160.

Although the operation of system 120 has been described utilizing thermistors of a negative coefficient type, other thermistor types may be utilized in which electrical resistance is initially low at room/starting temperature to shunt power around the sensor device or devices to be protected from transients, and then electrical resistance is increased to allow sufficient current for operation of sensor 170 at a desired temperature. In still other embodiments, a combination of different thermistor types and configurations can be utilized. In one embodiment of the invention, transient suppression and current control circuitry 160 is capable of suppressing power surges having a duration of at least 250 microseconds and a peak current of at least 500 milliamperes. In a further embodiment, transient suppression circuitry 160 is capable of suppressing a power surge of up to 500 microseconds and a peak current of up to 1 ampere. Nonetheless, in other embodiments, a different power surge suppression capability is provided.

As should now be appreciated, utilization of one or both of the negative temperature coefficient thermistors NTC₁ and NTC₂ in the manner illustrated and described above dissipates at least a portion of the power associated with a power surge, thereby providing for the suppression of power spikes or surges originating from the power source 130 or other powered components before reaching sensor 170. In embodiments where it is desired to suppress spikes through only one of the nodes of the power source 130 or the connector 154, only one of the negative temperature coefficient thermistors NTC₁ and NTC₂ need be utilized.

As discussed above, the power source 134 supplies electrical power to the sensing circuitry 174 via the transient suppression and current control circuitry 160. The detection signals from the sensor 170 and the electrical power from the source 134 are each transferred along the same electrical pathways, and more specifically through the transient suppression and current control circuitry 160. Under certain circumstances, the current passing through the circuitry 160 to and/or from the sensing circuitry 174 may increase to a level that may cause damage or destruction to the sensing circuitry 174, the controller 130 and/or any other electrical component in electrical communication with the circuitry 160. For example, a drop in internal circuit resistance may lead to an increase in the current levels passing through the sensing circuitry 170 and/or the controller 130. Additionally, increased current levels may be associated with the abnormal operation of the power source 134, a change in the operating state of controller 130, shifts in one or more environmental characteristics (such as temperature) and/or device failures. The transient suppression and current control circuitry 160 is thereby utilized to protect the sensing circuitry 174, the controller 130 and/or any other electrical component in electrical communication with the circuitry 160 from current levels that exceed an unacceptable threshold level.

Transient suppression and current control circuitry 160 utilizes thermistors 164 of a positive temperature coefficient type to control current flow and to maintain current levels below a threshold level that might otherwise lead to the damage and/or destruction of one or more electrical components that are in electrical communication with the circuitry 160. Prior to applying power to input device 150 from electrical power source 134, input device 150 and the positive temperature coefficient thermistors PTC₁ and PTC₂ are typically at or near ambient room temperature. When at or near room temperature, thermistors PTC₁ and PTC₂ are characterized by relatively low electrical resistance. Thus, when power is applied to the input device 150, the low electrical resistance of the positive temperature coefficient thermistors PTC₁ and PTC₂ will not appreciably effect current flow to/from the sensing circuitry 174 and the controller 130. However, if current levels exceed a threshold level upon the initial application of power to the device 150, the resistance of the positive temperature coefficient thermistors PTC₁ and PTC₂ will increase to control the current level passing therethrough. As a result, the circuitry associated with the sensing circuitry 174 and/or the controller 130 is protected from overheating and possible damage or destruction.

As current flows through the positive temperature coefficient thermistors PTC₁ and PTC₂, the temperature of the thermistors will increase. This increase in the temperature will correspondingly result in increased electrical resistance, thereby reducing the level of current passing through the positive temperature coefficient thermistors PTC₁ and PTC₂. Thus, the thermistors PTC₁ and PTC₂ are responsive to changes in electrical current to maintain the current level within a normal and acceptable range of current and below a select threshold level to protect the components in electrical communication with the circuitry 160 from damage or destruction (e.g., sensing circuitry 174 and controller 130). The thermistors PTC₁ and PTC₂ thereby operate to provide a relatively stable current level that does not exceed a threshold level over a large temperature range and without undesired interference from transient suppression and current control circuitry 160.

As should now be appreciated, utilization of one or both of the positive temperature coefficient thermistors PTC₁ and PTC₂ in the manner illustrated and described above controls the amount of current passing therethrough to maintain current below a threshold level, thereby protecting the components electrically connected to the circuitry 160 from unacceptably high current levels. In embodiments where it is desired to control/maintain current levels through only one of the nodes of the power source 130 or the connector 154, only one of the positive temperature coefficient thermistors PTC₁ and PTC₂ need be utilized. Although the operation of system 120 has been described utilizing thermistors of a positive coefficient type, other thermistor types may be utilized in which electrical resistance is initially low at room/starting temperature and which increases to control the level of current passing therethrough.

In one embodiment of the invention, the transient suppression and current control circuitry 160 and the sensing circuitry 174, including sensor 170 and indicators 172, are incorporated into an integral sensing package or operating unit. In a further embodiment, the connector 154 may also be incorporated into the integral sensing package. However, it should be understood that in other embodiments of the invention, one or more of the transient suppression and current control circuitry 160, the sensing circuitry 174, and the connector 154 may be separate from one another such that they are not collectively provided as an integral operating unit. Additionally, in one embodiment, the transient suppression and current control circuitry 160 is located at a remote location relative to the controller 130. However, other embodiments are also contemplated wherein the circuitry 160 is directly connected or positioned in close proximity to the controller 130.

Any theory, mechanism of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention, and is not intended to limit the present invention in any way to such theory, mechanism of operation, proof, or finding. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only selected embodiments have been shown and described and that all equivalents, changes, and modifications that come within the spirit of the inventions as defined herein or by the following claims are desired to be protected.

Claims

1. An apparatus, comprising:

an electrical device electrically coupled to a power source; and

transient suppression and current control circuitry electrically coupled to the electrical device, including: a first negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge; and a first positive temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to a change in electrical current to maintain the electrical current below a threshold level.

2. The apparatus of claim 1, wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are electrically connected in series between a first node of the power source and the electrical device.

3. The apparatus of claim 2, wherein the first negative temperature coefficient thermistor is electrically connected to the first node of the power source and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the electrical device.

4. The apparatus of claim 1, wherein the transient suppression and current control circuitry further includes a second negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and a second positive temperature coefficient thermistor electrically coupled between the power source and the electrical device.

5. The apparatus of claim 4, wherein the second negative temperature coefficient thermistor and the second positive temperature coefficient thermistor are electrically connected in series between a second node of the power source and the electrical device.

6. The apparatus of claim 5, wherein the second negative temperature coefficient thermistor is electrically connected to the second node of the power source and wherein the second positive temperature coefficient thermistor is electrically connected between the second negative temperature coefficient thermistor and the electrical device.

7. The apparatus of claim 1, wherein the electrical device comprises a sensor operable to detect one or more physical characteristics and to provide a corresponding electrical sensor signal.

8. The apparatus of claim 7, wherein the one or more physical characteristics include a change in a magnetic field detectable with the sensor.

9. The apparatus of claim 7, further comprising a controller including the power source, the controller being responsive to the sensor signal.

10. The apparatus of claim 9, further comprising an output device coupled to the controller, the controller being operable to provide an output signal to the output device in response to a change in the sensor signal.

11. The apparatus of claim 7, wherein the sensor and the transient suppression and current control circuitry are incorporated into an integral sensing device unit.

12. The apparatus of claim 7, further comprising at least one indicator electrically coupled to the sensor; and

wherein the sensor and the at least one indicator are electrically coupled in series with the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor.

13. The apparatus of claim 1, further comprising a controller including the power source;

an output device coupled to the controller; and

wherein the controller is responsive to a change in an electrical output signal provided by the electrical device; and

wherein the controller provides a corresponding control signal to the output device.

14. The apparatus of claim 1, wherein the electrical device and the transient suppression and current control circuitry are incorporated into an integral package assembly.

15. A method of providing transient suppression and current control, comprising:

providing electrical power to an electrical device;

suppressing a transient power surge by dissipating at least a portion of the surge using a negative temperature coefficient thermistor; and

maintaining electrical current below a threshold level using a positive temperature coefficient thermistor.

16. The method of claim 15, wherein the electrical device comprises a sensing device; and

wherein the method further comprises detecting a change in one or more physical characteristics with the sensing device.

17. The method of claim 15, further comprising:

coupling the electrical device and an output device to a controller;

providing an input signal from the electrical device to the controller; and

providing an output signal to the output device from the controller in response to an input signal from the electrical device.

18. The method of claim 15, wherein the suppressing is provided by a negative temperature coefficient thermistor; and

wherein the maintaining is provided by a positive temperature coefficient thermistor; and

wherein the negative temperature coefficient thermistor and the positive temperature coefficient are connected in series between the power source and the electrical device.

19. The method of claim 18, further comprising packaging the electrical device and the thermistors within an integral package body.

20. An apparatus, comprising:

an electrical device;

a connector configured to electrically couple the electrical device to a power source; and

first and second thermistors electrically coupled between the connector and the electrical device, one of the first and second thermistors being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge, another of the first and second thermistors being responsive to a change in electrical current to maintain the electrical current below a threshold level.

21. The apparatus of claim 20, wherein the first thermistor comprises a first negative temperature coefficient thermistor and wherein the second thermistor comprises a first positive temperature coefficient thermistor.

22. The apparatus of claim 21, wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are electrically connected in series between a first node of the connector and the electrical device.

23. The apparatus of claim 22, wherein the first negative temperature coefficient thermistor is electrically connected to the first node of the connector and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the electrical device.

24. The apparatus of claim 22, further comprising a second negative temperature coefficient thermistor and a second positive temperature coefficient thermistor; and

wherein the second negative temperature coefficient thermistor and the second positive temperature coefficient thermistor are electrically connected in series between a second node of the connector and the electrical device.

25. The apparatus of claim 24, wherein the second negative temperature coefficient thermistor is electrically connected to the second node of the connector and wherein the second positive temperature coefficient thermistor is electrically connected between the second negative temperature coefficient thermistor and the electrical device.

26. The apparatus of claim 20, wherein the electrical device comprises a sensor operable to detect one or more physical characteristics and to provide a corresponding electrical sensor signal.

27. The apparatus of claim 26, further comprising:

a controller operable to provide the power source and being responsive to the sensor signal; and

an output device coupled to the controller; and

wherein the controller is operable to provide an output signal to the output device in response to a change in the sensor signal.

28. The apparatus of claim 20, wherein the electrical device and the first and second thermistors are incorporated into an integral package body.

29. The apparatus of claim 28, wherein the connector is incorporated into the integral package body.

30. A system, comprising:

a sensor operable to detect a change in one or more physical characteristics and to provide a corresponding sensor signal;

a controller including a power source electrically coupled to the sensor; and

transient suppression and current control circuitry electrically coupled between the sensor and the power source of the controller, the circuitry including: a first negative temperature coefficient thermistor responsive to an electrical power surge condition to dissipate at least a portion of the electrical power associated with the surge; and a first positive temperature coefficient thermistor responsive to a change in electrical current to maintain the electrical current below a threshold level.

31. The system of claim 30, wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are connected in series between the power source and the sensor.

32. The system of claim 31, wherein the first negative temperature coefficient thermistor is electrically connected to a first node of the power source and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the sensor.

33. The system of claim 31, wherein the transient suppression and current control circuitry further includes a second negative temperature coefficient thermistor and a second positive temperature coefficient thermistor electrically connected in series between a second node of the power source and the sensor.

34. The system of claim 30, wherein the one or more physical characteristics include a change in a magnetic field detectable by the sensor.

35. The system of claim 30, wherein the sensor and the transient suppression and current control circuitry are incorporated into an integral sensing device unit.