BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to electrically-heated devices, more specifically, to an electronic circuit for controlling electrically-heated devices.

The Prior Art

Portable electrically-heated devices are used for a variety of purposes, including heated grips for vehicles, heated grips for power tools and eguipment, heated gloves, heated wraps, heated clothing, heated insoles, etc. Most such devices are made with a specific control circuit either embedded within the heated device or within the device's power cable and are designed specifically for and only to operate that device. Some devices which are separate from the device being heated (as in some heated insoles) are connected to the heating device using a cable with a

connector, but they are still designed to heat that one and only heated device. They are not able to operate heated devices across multiple vehicles, for multiple heated devices, or for multiple sources of power. In each case they are designed for one specific power source. Some are designed to operate on a 12-volt vehicle system. Others are mated with a specific battery.

With some exceptions, including the invention disclosed in U.S. patent No. 6,844,524, devices typically do not measure the actual temperature of the device being heated. It is desirable to measure the actual temperature of the device in order to regulate the temperature and account for heat loss due to varying conditions such as ambient

temperature and airflow.

Most heated devices either vary the electrical current through the heating element by use of an additional resistor or resistors which are switched in or out of the circuit, or by turning the heating element on and off at a fixed rate. This is typically done with two or three settings m a Low, Medium, and High fashion. In both cases, when the user selects a setting of Low, Medium, or High, the heater generates a fixed amount of heat corresponding to the setting. As a result, as conditions change, such as the ambient temperature or airflow, the temperature of the heating device can fluctuate greatly. This means that users are forced to freguently change between the fixed heat settings as the device gets too hot or too cold.

An additional problem with operating with fixed amounts of heat is that if the device is heating up at less than the device's maximum heating capability, the device will take longer to heat up. A better solution is to heat up at the maximum rate possible by generating as much heat as possible and then to subseguently decrease the amount of heat

generated as the desired temperature is reached. This is not possible with devices that output a fixed amount of heat per setting .

Heated devices typically are capable of completely draining the voltage of the battery they are connected to. This can happen especially if a user forgets to turn off the heated device on a vehicle without an alternator, on a vehicle in which the alternator is not running, or on a vehicle that the alternator is not producing a sufficient charge current. This can cause permanent damage to many types of batteries. In cases where the battery is reguired to start the vehicle, this can leave a user stranded. One solution is disclosed in U.S. patent Nos . 6,844,524 where the heated device is wired to the vehicle's ignition circuit so that the device can monitor and determine when the vehicle is running. This reguires additional wiring and added

complexity. Some vehicles do not have an ignition wire or other appropriate wire that indicates when the alternator is operating, or the wire may be unavailable or difficult to access . Most heated devices only give the user one, two, or three heat settings to choose from. As stated previously, each setting typically corresponds to a constant amount of heat. Many users would prefer a different temperature - a

temperature other than one of the fixed settings - of the heated grip depending on many conditions, including how cold they feel, what they are wearing (jacket, gloves, etc.), and/or what the environmental conditions are (snow, rain, etc.) . Many users prefer to have a greater range of options as to how much their hands, feet, or body is heated.

No known heated device notifies the user that the device has heated up to a desired temperature, that the user has changed a setting, or that the temperature of the device is changing. Most devices have no ability to determine the temperature of the device, so this information cannot be presented to the user.

Many heated devices cause electromagnetic interference (EMI) by switching an inductive load or a load drawing a large amount of current on and off in an effort to provide a certain amount of heating capability less than the maximum available. This EMI can interfere with radio eguipment, cellular phones, and other electrical eguipment on the person or vehicle. Some devices attempt to reduce radiated and conducted EMI with complex or costly filtering elements on the input power wires.

Many devices have a button or multiple buttons which provide one function each. In some cases, as disclosed in U.S. Patent Nos . 7,064,292 and 7,214,906, one button

increases the amount of heat while another button decreases the amount of heat or the current heat setting.

Most devices have a single indicator or multiple

indicators, such as an LED, lamp, light, mechanical position, etc., each of which indicate one thing to the user. For example, one LED might indicate that the heated device is operating in the High setting and another LED might indicate that the device is operating m the Low setting. Another LED might indicate that the device is on or off.

Most devices are not capable of detecting the failure of a critical component and instructing the user to replace that component. Typically, the component cannot even be replaced because the heating system may be permanently integrated with the control circuit. Such a failure would reguire the replacement of the complete heating system.

SUMMARY OF THE INVENTION

The present invention is an adaptive thermal regulator which can regulate the temperature of many heating and/or cooling devices (hereinafter, "HC device") such as grips for vehicles, power tools, gloves, clothing, insoles, helmets, or any device with a heating and/or cooling element

(hereinafter, "HC element") and a sensor with a resistance which varies with temperature, such as a thermistor.

The regulator is connected to a power source, optionally by mating connectors . The power source may be a battery, alternator, or combination of the two.

The regulator is connected to the HC element on an HC device, optionally by a connector. The HC element is of the type wherein the amount of heating or cooling it provides varies with the current flow. Typically, this means either a resistive device for heating or a Peltier effect device for heating or cooling. The regulator is connected to the sensor on the HC device, optionally by a connector. Use of

connectors allows for independent replacement of the HC device and the regulator and to enable the regulator to control many different types of HC devices. The HC element and sensor are arranged in such a way that the sensor is nearly the same temperature as the HC device being

heated/cooled by the HC element.

The power source connects to the regulator. The

regulator is controlled by the microcontroller and the program that it runs . One output of the microcontroller controls a switching circuit that provides power to the HC element. Another output controls an LED indicator. One microcontroller input reads that state of a momentary-contact switch. Another input reads the power supply voltage and another reads the thermistor resistance.

When switch is pressed and released, the temperature setting is increased by a predetermined amount. When the temperature is at the highest setting and switch is pressed, the setting wraps back to the lowest setting. When switch is held closed for greater than 1.5 seconds, the regulator and HC element are turned off. Pressing switch for more than 0.1 second when the regulator is off turns the regulator on at the lowest temperature setting.

In another configuration of the thermal regulator 10, the regulator 10 has a single predetermined temperature setting and there is no switch.

The LED conveys status information to the operator by using different intensity levels and flashing rates.

Optionally, the LED can be either replaced or augmented by a sound transducer, such as a piezoelectric speaker.

The power supply voltage is read by the microcontroller every two seconds and compared to a low-voltage threshold value. If the voltage is below this value, a counter increments . If the voltage is above a high-voltage threshold value, the counter is cleared to zero. If the counter reaches a predetermined value, the microcontroller turns the HC element and LED off and enters a low power state. After the regulator has shut down due to a low voltage, the microcontroller resumes operation periodically for a few milliseconds to measure the source voltage. When the source measurement is above a high-voltage threshold, the

microcontroller resumes normal operation. BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the nature and object of the present invention, reference is made to the accompanying drawings, wherein:

FIG. 1 is a block diagram of the adaptive thermal regulator of the present invention;

FIG. 2 is an electrical schematic diagram of the control circuit ;

FIG. 3 is a example of a heated device for use with the present invention;

FIG. 4 is a example of a cooling device for use with the present invention; and

FIG. 5a-f is a flow diagram of the program run by the microcontroller .

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an adaptive thermal regulator 10 which is capable of regulating the temperature of many heating and/or cooling devices 12 (hereinafter, "HC device") including, but not limited to, grips for vehicles, grips for power tools and eguipment, gloves, clothing, insoles, helmets, or any device with a heating and/or cooling element 14 (hereinafter, "HC element") and a sensor 16 with a resistance which varies with temperature, such as a

thermistor. References in the present specification and claims to a HC device, a HC element, a heating/cooling device, and a heating/cooling element are intended to mean any device or element that can heat only, cool only, or both heat and cool .

As shown in FIG. 1, the adaptive thermal regulator 10 includes a circuit board 20 comprising several electrical components. The regulator 10 may be mounted within an enclosure 22 or may be used without an enclosure. The regulator 10 is connected to a power source 24 by means of a positive wire 26 and a negative or ground wire 28. The power source wires 26, 28 may be connected by mating connectors 30. The power source 24 may be one of many different varieties including a battery, alternator, or combination of the two. The battery may be of any type that is capable of supplying a sufficient voltage and current to the regulator 10. In one embodiment, the regulator 10 is powered from any battery supplying a voltage between 8 volts and 18 volts at any current up to 2 amperes .

The regulator 10 is connected by two wires 34, 36 to the HC element 14 within or mounted on an HC device 12. The present invention assumes that the HC element 14 is of the type wherein the amount of heating or cooling the HC element 14 provides varies with the current flow (or duty cycle) through the HC element 14. For heating, this means that the HC element 14 is "resistive." For cooling or heating, the HC element 14 is a Peltier effect device.

The HC device 12 also includes a sensor 16 having a resistance that varies with temperature, such as a

thermistor, which is connected to the regulator 10 by means of two wires 38, 40. The two HC element wires 34, 36 and two sensor wires 38, 40 may be connected to the regulator 10 by one or two mating connectors 44, 46. Use of the connector (s) 44, 46 allows for independent replacement of the HC device 12 and the regulator 10. It also enables the regulator 10 to control many different types of HC devices 12 as long as they have the same mating connector (s) 44, 46. This is

advantageous as it allows for a relatively small number of versions of the regulator 10 to be produced and used to control a wide range of HC devices 12 for different markets.

The HC element 14 and thermistor 16 are arranged in the HC device 12 in such a way and within such proximity that the sensor 16 is nearly the same temperature as the HC device 12 being heated/cooled by the HC element 14. One example of a HC device 12 for heating is disclosed in United States

Provisional Patent Application No. 61/504,776, entitled Heating Wrap, incorporated herein by reference, and shown in FIG. 3. In summary, the wrap 12 is designed to wrap around a handle bar or hand grip and includes an insulating base 50, a heating element 14, a thermistor 16, a heat-conducting film 52, and a sheath 54. The base 50 is a thin ribbon of heat- insulating material that substantially reduces heat transfer to what the heated device is attached to so that more heat is transferred to the user's hands. The resistive heating element 14 lays against and extends substantially the length of the base 50. The thermistor 16 lays on the base 50 and is located away from the ends of the base 50. The thermistor 16 is positioned on the base 50 such that, when the wrap 12 is installed on the handlebar, the thermistor 16 is where the user normally grips the handlebar. A heat-conductive film 52 is adhered to the base 50 to cover and secure the heating element 14 and thermistor 16. The subassembly of base 50, heating element 14, thermistor 16, and conductive film 52 is covered by a sheath 54. Wires 58, 60, 62, 64 extend from the heating element 14 and thermistor 16 to a connector 66, 68 that mates with the regulator connector 44, 46.

One example of a HC device 12 for cooling is shown in

FIG. 4. The device 12 is designed as a carrying case for a small volume of medicine, such as insulin or pills, which it cools to a proper temperature while carried in an environment that may become warm enough to damage the medicine . It incorporates a thermo-electric cooler (hereinafter, "TEC") 14, a thermally-insulative enclosure 72, a heat sink 74, a thermally-conductive base plate 76, and a thermistor 16. The enclosure 72 is made from a thermally-insulative material and can take any shape that allows for one side wall 78 to be flat with the thermally-conductive base plate 76 extending substantially along the inside of that wall 78 The enclosure 72 contains one or more openings (not shown) which allow the medicine or pills to be placed into the enclosure 72. In one configuration, the enclosure 72 is rectangular, with an opening at one end and is made from glass-filled plastic. The TEC 14 is mounted within the flat wall 78 of the

enclosure 72 with the cool side 80 pressed against the base plate 76 and the warm side 82 pressed against the small heat sink 74 which is exposed to the outside 84 of the enclosure 72. The thermistor 16 is adhered to the base plate 76 on the side 86 exposed to the inside of the enclosure 72. Wires 88, 90 extend from the TEC 14 and wires 92, 94 extend from the thermistor 16 to a connector 96, 98 that mates with the regulator connector 44, 46.

Referring to the schematic diagram of FIG. 2, the power source 24 connects to the circuit at Jl . Diodes Dl and D2 provide reverse-polarity protection to the control circuit in the event that the power leads 26, 28 are reversed at Jl . U2/C1/C2 provide a regulated 5 VDC to the circuit.

Ul is a microcontroller with integral processor, volatile and non-volatile memory, analog-to-digital converters (ADC), and input/output connections. Microcontroller Ul also refers to any combination of separate components that function in the same way as a microcontroller, for example, a combination of a microprocessor, non-volatile memory, volatile memory,

ADCs, input/output devices, clock, and connecting components. Microcontroller Ul provides control of the regulator 10 through inputs II, 12, 13, and outputs 01 and 02.

Microcontroller Ul runs a program, described below, that controls the operation of the regulator 10.

Output 01 of microcontroller Ul provides the output signal to a switching circuit comprised of Q1/R3/R4/C4 to control power conducted through the HC element 14. The HC element 14 is connected to J2 so that the high side of the HC element 14 is connected to power and the low side is

connected to field-effect transistor (FET) Ql of the

switching circuit. Power is supplied to the HC element 14 by switching output 01 and, conseguently FET Ql, on. The amount of power supplied to the HC element 14 is regulated by pulsing output 01 at selected duty cycles. Resistor R3 and capacitor C4 form a low-pass filter at the gate of FET Ql in order to increase the switching time of FET Ql to reduce radiated EMI caused by the resistive and/or inductive load being switched on and off. Resistor R4 pulls the gate of FET Ql low to ensure that FET Ql is off when output 01 is off or when the microcontroller Ul is not running.

The temperature of the HC device 12 is measured using the thermistor 16 to allow for thermostatic control. The thermistor 16 and resistor R8 form a resistor divider that generates a voltage at input II that the microcontroller Ul translates into a temperature using fixed-point 16-bit linearized eguations or alternatively a look-up table.

In one configuration, the user controls operation of the regulator 10 by a single-pole, normally-open, momentary- contact switch SI that is connected to microcontroller Ul at input 12. A pull-up resistor internal to microcontroller Ul and connected to input 12 in conjunction with capacitor C5 keeps microcontroller Ul from reading switch bounce as more that one switch actuation and filters out momentary voltage changes possibly caused by electro-magnetic interference.

When switch SI is pressed and released, the temperature setting is increased by a predetermined amount. When the temperature is at the highest setting and switch SI is pressed, the setting wraps back to the lowest setting. By operating in this manner, the operator is able to select between any number of preprogrammed temperature settings . In the current embodiment implementing a heating-only HC device 12, there are six temperature settings: 95 °F, 105 °F, 115 °F, 125 °F, 140 °F, and 155 °F .

When switch SI is held closed for greater than a

predetermined time, typically 1.5 seconds, the regulator 10 and HC element 14 are turned off. When the regulator 10 is off, pressing switch SI for more than 0.1 second turns the regulator 10 on at the lowest temperature setting. In another configuration of the thermal regulator 10, the regulator 10 has a single predetermined temperature setting. There is no input like switch SI through which the user can change the setting. The regulator merely controls the HC element 14 to maintain the predetermined setting. The regulator turns off when there is no power to the regulator and on when power is available. Optionally, there is a switch to turn power on and off.

In one configuration, a visual indicator, LED D3, at output 02 is illuminated to convey status information to the operator. By turning LED D3 on and off at a fast rate, 70 Hz in the present embodiment, and varying the duty cycle, the intensity of LED D3 is controlled. In the present

embodiment, LED D3 has twenty intensity levels but can have more or less in other embodiments. The intensity of LED D3 is varied over time to create different effects. One effect is blinking, where the intensity alternates between off and on. The rate of blinking and the number of blinks indicates different status information to a user. Another effect is glowing, where the intensity slowly increases to a maximum before decreasing slowly to a minimum and repeating.

Alternatively, LED D3 can remain lit at any intensity value.

When switch SI is pressed and released, the temperature setting increases (or wraps to the lowest setting) , and LED D3 turns off briefly and then blinks the number of times that corresponds to the temperature setting. Then LED D3 turns off briefly and then glows while the HC device 12 is changing temperature. When the thermistor 16 shows that the HC device 12 has reached the desired temperature, LED D3 illuminates dimly and no longer glows.

If the thermistor 16 or the wiring to the thermistor 16 is damaged or disconnected thereby presenting a short or open circuit at input II, microcontroller Ul detects this

condition as a failure and LED D3 guickly flashes five times, turns off briefly, and then repeats as long as the failure condition remains. The same failure condition is indicated if the HC device 12 is disconnected from the regulator 10 at connector 44, 46. While this failure is present, output 01 remains off and the HC element 14 is not energized.

If the regulator 10 must turn off because the source voltage is too low, as described below, LED D3 also blinks guickly five times and then turns off as the regulator 10 powers off .

Optionally, LED D3 can be either replaced or augmented by a sound transducer, such as a piezoelectric speaker.

In another configuration, there is no visual or audio indicator of the status of the regulator 10.

In the current embodiment, resistors Rl and R2 with capacitor C3 form a voltage divider and low-pass filter which enables microcontroller Ul to measure the voltage of the power source 24 using an internal 10-bit analog-to-digital converter at input 13. Microcontroller Ul combines the results from multiple measurements using an infinite impulse response (IIR) low-pass software filter to reduce the effects of transient voltages. Voltage measurements are taken every two seconds and the HC element 14 is turned off for

approximately 143 milliseconds during the measurement so that no power for the HC element 14 is being drawn from the power source 24. The resulting filtered voltage measurement is compared to a low-voltage threshold value. When the source voltage measurement is below this value, a counter

increments . If the source voltage measurement is above a predetermined high-voltage threshold value, the counter is cleared to zero. If the counter reaches a predetermined value, microcontroller Ul turns the HC element 14 and LED D3 off and enters a low power state. The predetermined counter value corresponds to the desired amount of time that the regulator 10 operates below the low-voltage threshold voltage. The primary concern regarding the amount of time to allow is depletion of the battery. For example, if the HC device 12 is a set of heated grips on a motorcycle and the rider goes into a store for 10 minutes with the alternator off, it would be nice for the grips to still be hot when the rider comes out. However, if the rider goes in for 30 minutes, he does not want his battery to be depleted such that the motorcycle cannot be started. In some embodiments, the power source 24 is used solely to power the regulator 10 and contains an internal circuit to protect the power source from excessive discharge. Most lithium polymer batteries have this internal protection circuit. When used with this type of power source, it is desirable to use all of the available power stored in the battery and the low-voltage threshold value is set to zero such that the regulator 10 never turns off automatically and the power source will be depleted .

After the regulator 10 has shut down due to a low voltage, the microcontroller Ul resumes operation

periodically - about every two seconds in the current implementation - for a few milliseconds to measure the source voltage. When the filtered source voltage measurement is above a specified high-voltage threshold, the counter is cleared and microcontroller Ul resumes normal operation and blinks LED D3 the number of times to indicate the previously selected temperature setting which is being resumed.

The low-voltage threshold, high-voltage threshold, and predetermined counter value are programmable values stored in non-volatile memory. In one embodiment, the low-voltage threshold is 12.6 V and the high-voltage threshold is 13.1 V so that microcontroller Ul goes into its low power state when the source voltage is 12.6 V or less for 300 voltage

measurements (approximately 10 minutes) and resumes normal operation when the source voltage is 13.1 V or more. With programmable threshold and counter values, the present invention can be paired with most vehicles with a

battery/alternator system (e.g., motorcycle, dirt bike, ATV, snowmobile, personal watercraft, etc.)- Alternatively, the same hardware can be paired with a battery-only system such as an 11.1 V Li-Polymer battery, 14.8 V Li-Polymer battery, 12-volt lead-acid battery, or any battery with a nominal voltage between 9 V and 18 V. Alternatively, the regulator 10 can operate from a power source of a different voltage by optionally changing the values of resistors Rl and R2 and the threshold and counter values.

The program run by microcontroller Ul is shown as a block diagram in FIGS. 5a-f. At startup 202, the hardware and software components are initialized, as at 204. Then the program enters the shutdown phase 206. First, the program waits for the button SI to be released 208 in case it is pressed, then clears the timer and enters the low power state, as at 210. At this point, the microcontroller Ul is placed into sleep mode 212 and remains that way until awakened due to a button press or timeout of the timer. If awakening was caused by the button SI being pressed 214, as described above, the program waits for the button SI to be released 220 and enters the wakeup phase 224. If awakening was caused by the timeout of the timer and the Resume flag is set 216, then the power supply voltage is sampled 218 at input 13 of the microcontroller Ul . If the voltage is above the high threshold 222, the program enters the wakeup phase 224. If awakening was not due to a button press and the Resume flag is not set, the program reenters the shutdown phase at 210. On wakeup, the LED D3 at output 02 is

initialized for the glow effect 226 and the main loop is entered 228.

In the main loop, the timer is started for 714

microseconds which causes the main loop to run at 1400 Hz. If the Shutdown flag is set 234, the program enters the shutdown phase at 206. If the Shutdown flag is not set, the program handles the HC element 14 pulse width modulation (PWM) , as at 236 and FIG. 5b. If it is at the beginning of the HC device PWM period 252 and the duty cycle is greater than zero 254, output 01 is set 256 to apply power to the HC element 14. If it is not at the beginning of a PWM period and it is at the end of the duty cycle 258, output 01 is cleared 260 to remove power from the HC element 14.

After the HC element PWM is handled, the LED D3 PWM is handled, as at 238 and FIG. 5c. If it is at the beginning of the LED D3 PWM period 264 and the duty cycle is greater than zero 266, output 02 is set 268 to apply power to the LED D3. If it is not at the beginning of a PWM period and it is at the end of the duty cycle 270, output 02 is cleared 272 to remove power from the LED D3.

After the LED PWM is handled, the button SI is checked 240, but only every 14 ^th time through the main loop, which is the same as once every 10 milliseconds. As in FIG. 5d, if the button SI is not pressed 276, the button check is ended. If the button SI is pressed but not held 278, the temperature is incremented and reset to zero if it is 6. The LED D3 is set to flash the number of times for the new setting 286 and then the LED D3 is set to glow 288 until the new temperature is reached. If the button SI is pressed and held, the Resume flag is cleared 280 and the Shutdown flag is set 282.

After the button check, the LED intensity is updated for the LED PWM 242, but only every 70 ^th time through the main loop, which is once every 50 milliseconds.

After the LED intensity is updated, the thermistor 16 is sampled 244, but only every 280 ^th time through the main loop, which is once every 200 milliseconds. As in FIG. 5e, the voltage at II is sampled 292. If the sample shows a short or open circuit for the thermistor 16, LED D3 is set to fast flash. Otherwise the result is stored for use in setting the HC element 14 duty cycle.

After the temperature is sampled, the auto shutoff is checked 246, but only every 2800 ^th time through the main loop, which is once every 2 seconds. As in FIG. 5f, the power source voltage is sampled 302. If the voltage is above the high threshold 304, the voltage counter is cleared 306. Otherwise, if the voltage is below the low threshold 308, the voltage counter is incremented 310. If the incremented counter is greater than the predetermined value 312, meaning that the regulator 10 has exceeded it maximum time at the low voltage, the LED D3 is set to fast flash 314, the Resume flag is set 316, and the Shutdown flag is set 318.

After auto shutoff is checked, the heater modulation (duty cycle) is recalculated based on the new temperature sample. This is done only every 280 ^th time through the main loop, which is once every 200 milliseconds, the same as the temperature sampling period.

The main loop is completed after the timer expires 250. Thus it has been shown and described an adaptive thermal regulator. Since certain changes may be made in the present disclosure without departing from the scope of the present invention, it is intended that all matter described in the foregoing specification and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense .