Abstract:
An apparatus for the independent control of the amount of heat produced by a right and a left side heated hand grip includes a control panel with various input buttons and a pair of LEDS that each indicates a relative power setting of one of the heated hand grips. A microprocessor receives input instructions from the input buttons and provides a first pulsed DC output having a desired duty cycle to one of the heated hand grips and a second pulsed DC output having either the same or a different duty cycle to a remaining one of the heated hand grips, thereby controlling the amount of heat produced by each respective heated hand grip. This improves comfort. Reverse polarity protection, a return to previous power settings, including a remembrance of a differential between the two heated hand grips, and automatic shutoff when battery voltage reaches a predetermined value are described.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention, in general, relates to hand grips, such as are found on the handlebars of motorcycles, snowmobiles, etc. and, more particularly, to heated types of handlebar hand grips. 
   Devices that require two hands to grip each side of a handlebar are well-known and include all manner of machines, including but not limited to bicycles, motorcycles, snowmobiles, and even yard tools, such as snow blowers and garden roto-tillers. 
   Often, the hands get cold when grasping the handlebars on certain of these types of devices. Accordingly, heated handlebar hand grips have been invented to help ameliorate cold hands when, for example, a person is driving a motorcycle on a chilly day. 
   At best, current heated grips include two positions, a low heat and a high heat position. Both hand grips (i.e., simultaneously both the right and left sides of the handlebars) are then set to produce the same amount of heat. While certainly better than nothing, these types of devices do not provide the degree of control or regulation that is necessary to maintain the hands at an optimum temperature. 
   There is, at times, a need to supply a different amount of thermal energy to one side of a handlebar grip than to the opposite side. This can be a function of the control levers that each hand may, at times, be required to operate. It may also be a function of the type of grip that is required on each side of the handlebars, where a firmer grip is required on one side and a less firm grip is required on the other side. Or, one side may offer greater protection from the wind than the other. 
   For example on a motorcycle, the right hand operates a rotary throttle. As such, the right hand wraps around the throttle control, squeezing and rotating it as required. This position is maintained for the majority of time, changing only on rare occasion when a front brake is applied. Otherwise, the grip around the throttle ensures ample area for contact between the right hand and the heated throttle grip. A large area for physical contact between the hand and the right side heated grip provides good thermal transfer of heat energy from the heated throttle grip to the right hand. 
   However, the left hand is also used to operate the clutch lever which is used during each successive gear change, whether increasing or decreasing the gear ratio. Many riders constantly maintain some or all of the fingers of their left hand in contact with the clutch lever, extending the fingers away from the left side grip. The clutch lever is not heated. The extended fingers, rather than absorbing heat from the grip, are now exposed to ambient air where they release what little thermal energy they may have to the ambient air. Only a small portion of the palm of the hand remains in constant contact with the heated left side handlebar grip, where heat can be absorbed. 
   Accordingly, when the same amount of heat energy is applied to both the right and left hand sides of a motorcycle handlebar, the left hand will often feel colder than the right. If the heat setting for both sides is set to its highest setting sufficient to heat the left hand, then the right hand often becomes too hot. 
   A similar uneven heating and cooling situation occurs whenever a chilly crosswind is removing heat from an exposed hand faster than from a downwind hand that is shielded from the wind. 
   Additionally, the heat setting for current devices requires the operator to remember to turn it off, lest it come on again the next time the machine i.e., the motorcycle, is used. This is undesirable for at least two reasons. First, heating may not be required the next time the machine is used. If the heated handlebar grips were turned and left on for a chilly evening ride home and then the next ride occurs on a following warm sunny afternoon, heat will not be required. Unless the operator remembers to turn the heat off after his or her ride, it will automatically resume again the next time the motorcycle is used. 
   Second, leaving the hand grips in a heated “on” position when heat is not required imposes a needless drain on the battery. The charging system must compensate for that drain and the ultimate source of that energy is the fuel that is consumed by the engine. Accordingly, fuel economy is compromised. 
   There is another related need that previous heated handlebar grips have not addressed. As mentioned above, there is a natural differential in the amount of thermal energy that is typically required between a right and left hand due to the normal position of the hand. If a left and a right side could be adjusted for a difference in temperature that felt comfortable at a particular ambient temperature, when the ambient temperature rises or falls, it is desirable to be able to increase or decrease the heat that is applied while still preserving the basic differential between the left and right hand sides. 
   Similarly, if an ideal and typical setting for each side were obtained and the motorcycle (machine) were shut off, it would be desirable for the device to remember and to automatically return to the previous settings for both the right and left hand sides the next time the heated hand grip control is activated. This would ensure that the remembered setting was either the ideal or close to ideal from which one could easily fine tune the previous settings. It would be especially ideal to remember and restore the differential amount between the right and left heated hand grips, as well. 
   As mentioned above, it is common to forget to turn heated hand grips off at the end of a ride or other type of usage. An automotive type of battery, when fully charged and during charging, will express a voltage that typically is above 12.75 VDC. When the alternator stops supplying electrical power to the battery the voltage begins to drop. Before the battery begins to substantially drain and lose its reserve capacity, it is desirable to sense this condition. It would be ideal for heated grips to automatically shut off when the battery voltage drops to about 12.75 volts. 
   This capability would provide the expected benefit of not draining the battery when the motorcycle (machine) was not in use. It would also provide the unexpected benefit of preventing use of the heated handlebar grips when a defect in the vehicle&#39;s charging system is occurring. 
   Under such a failure condition, the battery would not be properly charged by the alternator during normal use and it would begin to lose its charge. Once its output voltage fell below a predetermined level (12.75 volts), the heated hand grip control would, ideally, cease to operate. 
   This would reduce current drain on the battery which in turn would extend the distance that the vehicle could be used (driven). It would also alert the operator by tactile feedback to the fact that an electrical failure is occurring. The operator would sense the cooling hands and a lack of indicator lights on a control panel of the heated handlebar grips, which would inform the operator that an electrical failure was occurring. The operator would then hasten home or to a repair facility. The operator might not notice the illumination of a battery charging warning light in the vehicle&#39;s instrument cluster when the electrical failure occurred because the operator might be concentrating on road conditions, however, the resultant chilly hands would soon attract his or her attention. 
   It is also desirable to provide ease in adjusting the left and right hand sides to produce the desired level of heat output as well as to provide a visual indication of the relative settings of each side. 
   Accordingly, there exists today a need for a heated hand grip control that helps ameliorate the above-mentioned problems and difficulties. 
   Clearly, such an apparatus would be a useful and desirable device. 
   2. Description of Prior Art 
   Heated motorcycle and snowmobile hand grips are, in general, known. While the structural arrangements of the above described devices may, at first appearance, have certain similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a heated hand grip control that allows setting a left and a right hand heated handlebar grip to a different setting. 
   It is also an important object of the invention to provide a heated hand grip control that allows setting a left and a right hand heated handlebar grip to a variety of different settings, thereby providing optimum comfort for the conditions at hand. 
   Another object of the invention is to provide a heated hand grip control that provides a visual indication of the relative heat settings for a right and a left hand grip. 
   Still another object of the invention is to provide a heated hand grip control that is adapted to provide an optimum amount of heat to each hand for a given ambient condition. 
   Still yet another object of the invention is to provide a heated hand grip control that is adapted to automatically shut itself off when a battery voltage falls to a predetermined value. 
   Yet another important object of the invention is to provide a heated hand grip control that is adapted to remember a previous left and right setting and which, when energized again, returns to the previous settings. 
   Still yet another important object of the invention is to provide a heated hand grip control that remembers a relative differential that is set between a right and a left hand side and which, when coarsely adjusted either up or down in heat output, automatically maintains that differential. 
   A first continuing object of the invention is to provide a heated hand grip control that allows for both coarse setting adjustments as well as fine tuning between each coarse setting. 
   A second continuing object of the invention is to provide a heated hand grip control that includes a microprocessor and a memory or a microcontroller. 
   A third continuing object of the invention is to provide a heated hand grip control that includes protection for reverse polarity connection. 
   A fourth continuing object of the invention is to provide a heated hand grip control that includes protection for excessive current (i.e., an overload condition) on each of two output signal lines. 
   Briefly, a heated hand grip control that is constructed in accordance with the principles of the present invention has a user-accessible control panel conveniently mounted and connected to a microprocessor&#39;s (or microcontroller&#39;s) input. The control panel includes a course up button that is depressed to raise, in course increments, the overall energy that is supplied to both the right and left hand grips. The control panel includes course down button that is depressed to lower, in course increments, the overall energy that is supplied to both the right and left hand grips. A pair of indicator lights, one for each the right and left hand side grips, progressively change in appearance to provide an indication of the temperature settings for each hand and of the changes made thereto. A left grip button is used to make fine adjustments, intermediate each course adjustment, for the left hand grip. A right grip button is used to similarly make fine adjustments for the right hand grip. The microprocessor responds to the input settings by varying a first pulsed DC output signal to the right hand heated grip and by varying a second pulsed DC output signal to the left hand heated grip. The microprocessor includes a non-volatile memory that remembers the previous settings for both sides and when reactivated, automatically returns to those settings. The microprocessor&#39;s memory is also used to remember a differential between the right and left hand sides and when course adjustments to the amount of heat output are made, the microprocessor maintains the differential as the course settings are modified. The microprocessor also preferably senses battery voltage and automatically turns itself either off or enters into a quiescent state when the battery voltage falls to or below a predetermined level. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagrammatic view of a heated hand grip control and its connection to a pair of heated grips on a handlebar. 
       FIG. 2  is a block wiring diagram of the heated hand grip control of  FIG. 1 . 
       FIG. 3  is a plurality of a few possible waveforms of a pulsed DC output of the heated hand grip control of  FIG. 1 . 
       FIG. 4  is a flowchart of a main routine, and  FIG. 5  is a flowchart of an interrupt routine of the heated hand grip control of  FIG. 1 . 
       FIG. 6  is a schematic of the heated hand grip control of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring on occasion to  FIG. 1  and  FIG. 2 , is shown, a heated hand grip control, identified in general by the reference numeral  10 . Refer also on occasion to  FIG. 3  which shows only a few of the many possible outputs of the heated hand grip control  10 . 
   A control panel, identified in general by the reference numeral  12 , is conveniently mounted on or near a handlebar  14 . 
   The handlebar  14  includes right side heated hand grip  16  and a left side heated hand grip  18 . The heated hand grips  16 ,  18  are either factory installed, dealer installed, or an aftermarket add on. The heated hand grips  16 ,  18  includes some resistive means that produces heat in proportion to the electrical energy each heated hand grip  16 ,  18  receives. 
   The control panel  12  includes a first pulsed DC output signal  20  that is supplied to the right hand heated grip  16  and a second pulsed DC output signal  22  that is supplied to the left hand heated grip  18 . These each include current limiting means  24 ,  26 , such as a fuse to protect against an over current condition, for example, if either of the pulsed outputs  20 ,  22  were to become shorted. 
   The control panel  12  preferably includes an enclosure  28 , such as a plastic container, inside of which all components, as are described in greater detail hereinafter, are contained. However, if preferred, any of the components may be located remote with respect to the control panel  12 . 
   Typically when factory installed, each of the heated hand grips  16 ,  18  is grounded on one electrical wire (i.e., lead) side thereof and a remaining electrical wire side is where electrical voltage energy (i.e., positive voltage) is applied. If one lead each of the heated hand grips  16 ,  18  is not grounded, then both leads are discretely wired, as shown. 
   When the heated hand grips  16 ,  18  each include one lead that is grounded, then a corresponding ground lead of each of the pulsed outputs  20 ,  22  is grounded and a remaining (+VDC out) lead is connected to the “hot” lead of each of the heated hand grips  16 ,  18 , as is well known in the electrical arts. 
   The control panel  12  is connected to a vehicle 12 VDC battery  30 . A microprocessor  32  and a non-volatile memory  34  are included, preferably in the enclosure  28 , and are used to receive input and to control the pulsed DC outputs  20 ,  22  accordingly, as well as to store settings and a differential value in the memory  34 . The memory  34  is operatively connected to the microprocessor  32 . 
   The term microprocessor  32 , as used herein, is intended to include any type of microprocessor or microcontroller (i.e., a similar type of processor with the memory  34  as an integral part thereof) sufficient to perform the required tasks. 
   The control panel  12  includes four input control functions that are selected by an operator and a left grip LED  36  and a right grip LED  38 , which serve as indicators for the present relative power output settings of the heated hand grip control  10 . 
   The four input controls include a coarse up button  40 , a coarse down button  42 , a left grip button  44 , and a right grip button  46 . The four input control buttons  40 – 46  include any preferred type of pressure switch, membrane switch, or other type of electrical momentary switch. 
   The four input control buttons  40 – 46  are used to energize (i.e., turn on) the heated hand grip control  10  as well as to regulate all coarse and fine output controls. 
   The left grip LED  36  provides a relative indication of the duty cycle of the second pulsed DC output signal  22  that is supplied to the left hand heated grip  18 . This is described in greater detail hereinafter. The right grip LED  38  similarly provides a relative indication of the duty cycle supplied to the first pulsed DC output signal  20  that is supplied to the right hand heated grip  16 . 
   A preferred physical layout of the four input buttons  40 – 46  and of the two LEDs  36 ,  38  are shown in the control panel  12  of  FIG. 1 . 
   Referring now also on occasion to  FIG. 3 , five possible waveforms A, B, C, D, and E are shown that are supplied along either the first pulsed DC output signal  20  to the right hand heated grip  16  or to the second pulsed DC output signal  22  to the left hand heated grip  18  (or to both simultaneously, if that happens to be preferred). Many other waveforms, not shown, are also possible. 
     FIG. 3  illustrates how varying the duty cycle from zero percent on duty cycle at A (off entirely) to one-hundred percent on duty cycle at E (on all the time) is possible. A 25% on duty cycle at B, a 50% on duty cycle at C, and a 75% on duty cycle at D are also shown. 
   As illustrated, waveform C supplies twice the electrical energy to the corresponding heated grip (either  16  or  18 ) that it is connected to than would waveform B. Similarly, waveform D supplies three times the electrical energy of waveform B. Waveform E supplies four times the electrical energy of waveform B. Waveform E supplies twice as much electrical energy as waveform C. 
   There is considerable design variability as to the number of possible waveforms possible as outputs for the pulsed DC output signals  20 ,  22  that are supplied to the heated hand grips  16 ,  18 . 
   The thermal energy released by either hand grip  16 ,  18  is proportional to the amount of electrical energy that is supplied to it. Accordingly, by varying the duty cycle of the pulsed DC output signals  20 ,  22  a way is provided to provide variable adjustment capability to the heat output of the heated hand grips  16 ,  18 . 
   The number of variable settings (i.e., different duty cycles) is a design variable that can vary from application to application, as well as from one version of the heated hand grip control  10  to another version. 
   To provide an optimum variable range without the burden of forcing an operator to forge through too many possible selections, a preferred setting is to use the coarse up and down buttons  40 ,  42  to provide five course settings, for example, a 20%, 40%, 60%, 80%, and maximum 100% duty cycle that is applied to either of the pulsed DC output signals  20 ,  22 . Of course, more or less coarse settings are also possible. 
   It is also preferred to use the left and right grip buttons  44 ,  46  to fine tune the amount of overall energy (i.e., duty cycle) that is applied to either of the pulsed DC output signals  20 ,  22 . Five fine settings are preferably provided intermediate each of the five coarse settings. 
   The right and left grip LEDs  38 ,  36  are preferably similarly energized in a pulsed output pattern that corresponds generally with the setting of each corresponding pulsed DC output signal  20 ,  22 . Accordingly, the brighter the corresponding grip LED  38 ,  36 , the higher is the duty cycle of the pulsed DC output signal  20 ,  22  to which it appertains. 
   It is also desirable to provide each grip LED  36 ,  38  with more than one color capability. Preferably, from green to red spectrum color capability are provided for each of the right and left grip LEDs  38 ,  36 , as is well known. There is considerable variability in how the colors can be set to indicate the relative power settings of the heated hand grip control  10 . 
   A preferred way is for each grip LED  36 ,  38  to illuminate at a brightest red color for a maximum or 100% duty cycle. Each progressively cooler setting corresponds with a progressive lowering of the duty cycle. The color of the affected grip LED ( 36  or  38 ) changes its color (hue) with each progressive lowering of the duty cycle. Preferably, a 50% duty cycle will cause the affected grip LED ( 36 , or  38 ) to glow in an amber color (intermediate red and green). 
   The next possible lowering of the duty cycle causes the color of the grip LED ( 36 ,  38 ) to begin to shift slightly away from amber and toward a green color. 
   This progression continues until the coolest setting that is possible (either the lowest power setting possible or, if preferred completely off) is shown by a bright green LED  36 ,  38  for either the left grip Led  36  or the right grip LED  38 . 
   Accordingly, the duty cycles of  FIG. 3  can be used to energize either the red to amber to green portions of either of the LEDs  36 ,  38  to provide any desired visual indication of a duty cycle that is applied to a corresponding one of the pulsed DC outputs  20 ,  22 . 
   If five coarse settings are provided and five fine settings are also possible intermediate each of the coarse settings for each of the pulsed DC outputs  20 ,  22 , then a total of 25 settings are possible. Similarly, 25 variations from dark green to bright red are possible for each grip LED  36 ,  38 . 
   If 25 settings are possible, the five coarse settings (20, 40, 60, 80, and 100%) can be varied in approximately four percent incremental changes in duty cycle. For example, it is possible to adjust the heated hand grip control  10  to provide a 4% output duty cycle, an 8% output cycle, a 12% output duty cycle, and so on up to a 100% duty cycle for either of the pulsed DC outputs  20 ,  22 . 
   It is important to note that the setting for either of the pulsed DC outputs  20 ,  22  may be adjusted independent of the other, as is described in greater detail hereinafter. 
   The pulsed DC outputs  20 ,  22  are connected directly to an output of the microprocessor  32  or alternately to a power transistor (not shown) or to any other intermediate circuit component, as is well known in the electrical arts, in order to deliver a desired amount of electrical power without causing damage to the component or to the microprocessor  32 . A preferred intermediate circuit component includes a MOSFET. 
   Preferably, a printed circuit board that includes the microprocessor  32 , memory  34 , buttons  40 – 46 , grip LEDs  36 ,  38 , and all other circuit components is provided in the enclosure  28 . 
   The microprocessor  32  also monitors a positive VDC input  48  compared to a ground input  50  and verifies that the voltage differential is at least 12.75 VDC, which typically indicates a fully charged battery. If the voltage differential falls below 12.75 VDC, the heated hand grip control  10  shuts itself off and stops supplying any power to either of the heated grips  16 ,  18 . 
   When the heated hand grip control  10  is used to control a motorcycle&#39;s heated grips  16 ,  18  (or other machine that includes the handlebar  14 ), the engine may have to be running and the charging system operating to maintain the battery  30  output at or above the required 12.75 volts. 
   Should a malfunction of the battery  30  or charging system occur the battery  30  will be drained and its output will soon fall below 12.75 VDC, at which time the heated hand grip control  10  will shut itself off. The resultant cold hands will provide tactile feedback sufficient to inform the operator of the electrical failure. 
   The heated hand grip control  10  preferably does not include an “on-off” control, although it certainly could. When the motorcycle (or other machine) is turned off, the battery  30  stops being charged and the output voltage soon drops to below 12.75 volts, still indicative of a full charge for the battery  30 , but not that which would normally occur while the motorcycle engine was running. The heated hand grip control  10  senses the drop in battery voltage (the differential between the positive VDC input  48  and the ground input  50 ) to 12.75 VDC and shuts the unit off (or puts it into a low current draw quiescent state) after storing the last settings in the memory  34 . 
   When any button  40 – 46  is momentarily depressed, the heated hand grip control  10  detects the depression and automatically restores both the right and left heated grips  16 ,  18  to their last settings by resuming the duty cycle that was present prior to shut down of the heated hand grip control  10  at each of the two pulsed DC outputs  20 ,  22 . Both LEDs  36 ,  38  are illuminated accordingly. 
   If the operator wants both of the heated grips to experience a proportional increase in temperature, the coarse up button  40  is depressed and released one time. Both LEDs  36 ,  38  will experience the same coarse magnitude change in brightness or color to indicate that the same change has occurred for both the right and left sides. 
   However, any differential in duty cycle between the two pulsed DC outputs  20 ,  22  that was there previously will remain after depressing the coarse up button  40 , or alternately the coarse down button  42 . 
   If the right pulsed DC output  20  was previously at a 40% duty cycle and the left pulsed DC output  22  was previously at a 36% duty cycle, then one depression of the coarse up button  40  will raise the duty cycle of the right pulsed DC output to 60% and it will also raise the duty cycle of the left pulsed DC output  22  to 56%, thereby preserving the same magnitude of temperature (energy) differential between the right and left heated grips  16 ,  18 . 
   This permits the operator to compensate for changes in ambient temperatures while still preserving optimum comfort for both the right and left hands. The operator&#39;s own preferences, which takes into account a combination of all other factors such as the normal position of the right and left hands, rate of heat loss from each hand, thermal conductivity of each hand, etc. once set in the form of an energy differential between the right and left hands is maintained unless the operator deliberately changes the differential. 
   To increase in coarse increments the duty cycle of both the right and the left heated grips  16 ,  18 , the coarse up button  40  is repeatedly depressed and released a desired number of times, up to the maximum range in coarse adjustment. The temperature of both heated grips  16 ,  18  are simultaneously increased a proportionate amount for each depression of the coarse up button  40 . The two LEDs  36 ,  38 , in tandem, reflect that proportionate increase in temperature. 
   Conversely, to make coarse adjustments that proportionally cool both grips  16 ,  18  while still preserving the differential between them, the coarse down button  42  is repeatedly depressed and released until the desired setting is obtained. The two LEDs  36 ,  38 , in tandem, reflect that proportionate decrease in temperature. 
   To change the differential between the right and left hands, a number of design options are possible. A preferred way to change the differential is by repeatedly depressing and releasing either the left grip button  44  or the right grip button  46  to increase the duty cycle for the one that is being repeatedly pressed and released, as compared to the one that is not. 
   If, for example, it is desired to increase the temperature (i.e., the duty cycle) of the left side heated hand grip  18  as compared to that of the right side heated hand grip  16 , the left grip button  44  is repeatedly depressed and released. 
   The differential is thereby increased whereby the duty cycle for the left grip  18  is increased and the duty cycle for the right grip  16  is decreased for each depression and release. The left grip LED  36  will incrementally color shift toward the red while the right grip LED  38  will incrementally color shift toward the green, thereby indicating that the differential has shifted between the left grip  18  and the right grip  16  in such a manner that the left grip  18  is now warmer with respect to the right grip  16  than it was before the first repeated depression and release of the left grip button  44 . 
   Additional similar repeated depressions will proportionately increase the duty cycle of the left grip  18  (and its temperature) with respect to the right grip  16 . The left grip LED  36  will also continually incrementally color shift toward the red while the right grip LED  38  will incrementally color shift toward the green for each subsequent depression and release of the left grip button  44 . 
   If at any time the left grip  18  is already at a 100% duty cycle and therefore maximally warm, it is not possible to increase the duty cycle of the left grip  18  or to color shift the left grip LED  36  further toward the red end of the spectrum when it already is fully red. If this is the situation and the left grip button  44  is repeatedly depressed and released, this input command by the user is still interpreted as one that is intended to increase the differential between the left grip  18  making it warmer when compared to the right grip  16 . 
   The only way to do this when the left grip  18  is at a 100% duty cycle is maintain the left grip  18  at its 100% duty cycle and to proportionately lower the duty cycle of the right grip  16  from wherever it is for each repeated depression and release of the left grip button  44 . This process can be repeated until a desired differential is attained. The left grip LED  36 , in this example, would stay red while the right grip LED  38  would incrementally shift toward the green for each subsequent depression and release of the left grip button  44 . Of course, a maximum differential possible would be attained when the left grip  18  is at 100% duty cycle and with a fully red left grip LED  36  to indicate this state and the right grip  16  at 0% duty cycle (off) with the right grip LED  38  fully green. 
   If it is desired to increase the temperature (duty cycle) of the right grip  16  as compared to that of the left grip  18 , the process described above is mirrored for repeated depressions and releases of the right grip button  46 . 
   After establishment of the proper differential between the left grip  18  and the right grip  16 , if the overall temperature setting of both is not proper, the coarse up button  40  and the coarse down button  42  are then used to either raise or lower the overall temperature for each grip  16 ,  18  respectively while preserving any differential that was previously established and set. 
   Other program options for creating a differential between the right  16  and left grip  18  are certainly possible. For example, although not preferred operation of the microprocessor  32  can be modified (by program change), whereby either the left grip button  44  or the right grip button  42  is first initially depressed and released one time. The operator then momentarily depresses and releases either the coarse up button  40  or the coarse down button  42  repeatedly to make fine adjustments in the corresponding duty cycle for the side that was first selected. This process can continue to introduce any magnitude of offset between the duty cycle that is applied to the right and left sides. Either side can be made (i.e., set to) hotter or cooler, by any of the possible twenty-five settings (or other amount) as previously described. 
   If, to continue description of this modification, the operator wishes to further warm the left heated grip  18  and to further cool the right heated grip  16 , the operator may elect to first depress the left grip button  44  thereby selecting the left heated grip  18  and the left pulsed DC output  22  to first adjust. The operator would then repeatedly depress and release the coarse up button  40  which would now make fine adjustments (i.e. 4%) for each depression in the duty cycle of only the left pulsed DC output. The right pulsed DC output  20  is not affected. 
   To further cool, according to this modification for example, the right heated grip  16 , the operator would then depress the right grip button  46  and then repeatedly depress and release the coarse down button  42  which, in this mode, would now make fine adjustments (i.e., 4%) that decrement the duty cycle that is applied to the right pulsed DC output  20 . 
   Accordingly, any differential between the duty cycle of the energy applied to the heated grips  16 ,  18  may be set. After selecting the left or right grip buttons  44 ,  46  for adjustment and after a short timeout without further input from the coarse buttons  40 ,  46 , the coarse buttons  40 ,  46  resume their primary function in providing coarse (i.e., 20%) adjustment of the overall duty cycle that is applied simultaneously to both heated grips  16 ,  18 . 
   The left LED  36  and right LED  38  always reflect, by a combination of color and brightness, the duty cycle of the left pulsed DC output  22  and the right pulsed DC output  20 , respectively. The operator is always able to tell by a glance of the LEDs  36 ,  38  on the control panel  12  the setting that each heated grip  16 ,  18  is set to. 
   Reverse polarity protection is provided in the enclosure  28  on the printed circuit board to ensure that if the operator reverses polarity of the ground input  50  and the positive voltage DC input  48 , no harm occurs. 
   An alternate way to shut the heated hand grip control  10  off (both sides) is by depressing and holding the coarse down button  42  in a depressed state for at least three seconds. The previous settings of both the left and right heated grips  18 ,  16  (i.e., the duty cycles that were applied to the left and right pulsed DC outputs  22 ,  20 ) are maintained in memory  34  and are restored when any button  40 – 46  is later again depressed and quickly released. 
   The heated hand grip control  10  may be factory installed on new motorcycles or it may be retrofitted to virtually all previously existing motorcycles. While a description of the preferred embodiment used a motorcycle to illustrate the features and benefits of the heated hand grip control  10 , it may be used on any machine or device that includes the handlebar  14 . It is also noted that the handlebar  14  does not have to be a “one-piece” contiguous unit. As long as a right hand of the operator grips a right side and a left hand of the operator grips a left side of the device, the heated hand grip control  10  is applicable to precisely regulate the heat that is applied individually to both the right and left hands simultaneously. 
   A convenient way is provided by the heated hand grip control  10  to precisely control the amount of heat that is applied to the right heated grip  16  independent of the heat that is applied to the left heated grip  18 . A minimum of control inputs (i.e., the four input buttons  40 – 46 ) allow for easy on-off control and setting of the desired temperatures of each heated grip  16 ,  18 . 
   It is noted that the coarse up button  40  and the coarse down button  42  provide coarse adjustment when they are used by themselves. In that mode, the coarse up and down buttons  40 ,  42  simultaneously adjust the duty cycle in a coarse manner (i.e., +/−20% per cycle) that is applied to both the right and left grips  16 ,  18 . 
   However, if either the left grip button  44  or the right grip button  46  is first depressed and released, then the coarse up and down buttons  40 ,  42  change their mode of function by independently adjusting the duty cycle in a finer manner (i.e., +/−4% per cycle) that is applied to either the right or left grip  16 ,  18 , depending upon which grip button  44 ,  46  was depressed first, and not by adjusting both of the grips  16 ,  18  at the same time. 
   Referring again to  FIG. 1 , a small amount of heat  52  is shown rising off from the right heated grip  16  and a large amount of heat  54  is shown rising off from the left heated grip  18 . This illustrates the ability of the heated hand grip control  10  to independently control the right heated grip  16  and the left heated grip  18  apart from each other. 
   When the heated hand grip control  10  powers off, the duty cycle of each grip  16 ,  18  and therefore the differential setting are retained in the memory  34  and are restored when the heated hand grip control  10  is activated by a depression of any button  40 – 46 . 
     FIG. 4  is one possible flowchart of a main routine, and  FIG. 5  is one possible flowchart of an interrupt routine of the heated hand grip control  10 . 
     FIG. 6  is a possible schematic of the heated hand grip control of the heated hand grip control  10 . 
   The invention has been shown, described, and illustrated in substantial detail with reference to the presently preferred embodiment. It will be understood by those skilled in this art that other and further changes and modifications may be made without departing from the spirit and scope of the invention which is defined by the claims appended hereto.