referring to fig1 - 6 , in a first preferred embodiment a medical headlamp assembly 10 includes a headband 12 , supporting a mounting column 14 . a low intensity headlamp assembly 16 includes a low intensity headlamp 18 , a linkage 20 , a slider 22 . also included is an electrical conductor 26 terminating in a four pole audio plug 28 , which plugs into a four pole audio jack 30 . as shown in fig2 , when a user decides that he would like to remove assembly 16 from mounting column 14 , he pulls assembly 16 upwardly to disengage slider 22 from column 14 and unplugs plug 28 from jack 30 . he may do this simply to replace a worn out assembly 16 , or ( referring to fig3 ) to install an assembly having different characteristics , such as medium intensity assembly 16 ′, having medium intensity light 18 ′ and plug 28 ′ which is plugged into jack 30 . referring to fig5 and 6 , in like manner assembly 16 ′ can be switched out and assembly 16 ″ having high intensity light 18 ″ and plug 28 ″, can be installed onto with slider 22 on column 14 , and with plug 28 ″ plugged into jack 30 . referring to fig7 , although plugs 28 , 28 ′ and 28 ″ appear identical , each one has a different active pin ( longitudinally arranged electrical contact ) that is electrically connected to the light emitting diode ( not shown ) of lamp 18 , 18 ′ or 18 ″, respectively , and serving as the return , with the current being delivered into lamp 18 , 18 ′ and 18 ″ in all cases through the ground . pin 1 of plug 28 serves as the led return for lamp 18 , pin 2 serves as the led return for lamp 18 ′ and pin 3 serves as the led return for lamp 18 ″. pin 1 , pin 2 and pin 3 of plug 28 connects to pin 2 , pin 3 and pin 4 of jack 30 , respectively . pin 1 of jack 30 connects to the ground of plug 28 . referring to fig8 , a dc - to - dc converter 50 acts as a power supply to whichever one of lamps 18 , 18 ′ or 18 ″ is connected to jack 30 . a feedback loop is formed by the output of converter 50 powering the led line , all of the current in which flows to the led return line , and at least a portion of which pass through a current sense resister r 1 , which in turn drives the feedback pin fb of converter 50 . ( the modification of the voltage at feedback pin fb through a voltage increase circuit 54 is described below .) the output of converter 50 increases if the voltage of feedback pin fb is below 0 . 5 volts and decreases if the voltage of feedback pin fb is above 0 . 5 volts , thereby setting that voltage at pin fb at 0 . 5 volts . accordingly , when the voltage increase circuit 54 is not active , the voltage across resister r 1 is set at 0 . 5 volts , and accordingly , i r1 = r1 / 0 . 5 vdc . for the 800 mamp lamp , for which the return current exits at pin 2 of the jack 30 , a few equations apply : i r ⁢ ⁢ 1 = 800 ⁢ ⁢ mamps - i r ⁢ ⁢ 2 i r ⁢ ⁢ 1 = 800 ⁢ ⁢ mamps * ( r 2 + r 3 + r 4 ) r 1 * ( r 2 + r 3 + r 4 + 1 ) for the 1 . 1 amp lamp ( from jack 30 pin 3 ) these equations become : i r ⁢ ⁢ 2 , r ⁢ ⁢ 1 = 1 . 1 ⁢ ⁢ mamps - i r ⁢ ⁢ 3 , r ⁢ ⁢ 4 i r ⁢ ⁢ 2 , r ⁢ ⁢ 1 = 1 . 1 ⁢ ⁢ mamps * ( r 3 + r 4 ) ( r 1 + r 2 ) * ( r 3 + r 4 + 1 ) for the 1 . 4 amp lamp ( from jack 30 pin 4 ) these equations become : i r ⁢ ⁢ 3 , r ⁢ ⁢ 2 , r ⁢ ⁢ 1 = 1 . 4 ⁢ ⁢ mamps - i r ⁢ ⁢ 4 i r ⁢ ⁢ 3 , r ⁢ ⁢ 2 , r ⁢ ⁢ 1 = 1 . 4 ⁢ ⁢ mamps * ( r 4 ) ( r 1 + r 2 + r 3 ) * ( r 4 + 1 ) in addition , for no lamp 18 , 18 ′ or 18 ″ may the voltage drop through the lamp and the resistive network composed of r 1 , r 2 , r 3 and r 4 must not exceed a maximum , that in one embodiment is about 3 . 4 volts . in addition , the power consumption of this resistive network must be minimized for all the lamps , leading to low values for all of the resistors , on the order of a little more than an ohm . the voltage output of the brightness adjust rheostat 40 is fed into a pin of a microprocessor 56 , resulting in a periodic waveform having a duty factor that is related to the rheostat output voltage , appearing on an output pin of the microprocessor 56 . when the rheostat 40 is moved to a “ dim ” setting , this causes microprocessor 56 to produce a waveform that causes voltage increase circuitry 54 to amplify the voltage at its input , thereby reducing the current ( and voltage ) out of the dc - to - dc converter 50 , and reducing the current through resister r 5 . in an alternative preferred embodiment voltage increase circuitry is set to always amplify its input signal , thereby permitting a lower value for the voltage drop across r 1 , when the lamp 18 , 18 ′ or 18 ″ is not being dimmed . this permits a lower value of resistance for r 1 , and lower power loss through r 1 and through the entire resistance network r 1 , r 2 , r 3 and r 4 . for dimming positions of rheostat 40 , this amplification is increased . when the brightness adjust knob 40 is set at its maximum , causing a voltage increase circuit 54 ( described below ) to pass the voltage from a current sense resister r 1 , unchanged , then the voltage through the current sense resister r 1 is forced to 0 . 5 volts by the feedback loop implemented by the converter 50 feedback pin fb ( driven directly or indirectly by the current sense resister r 1 , and the converter 50 output powering the lamp 18 , 18 ′ or 18 ″, with the led return line powering resister r 1 . the while a number of exemplary aspects and embodiments have been discussed above , those possessed of skill in the art will recognize certain modifications , permutations , additions and sub - combinations thereof . it is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications , permutations , additions and sub - combinations as are within their true spirit and scope .
a medical headlamp assembly has a headband subassembly , including an electrical network , including a battery and an electrical jack and a headlamp mount . an electrical headlamp subassembly , has a mounting element that is matingly and removably engaged to the headlamp mount , and an electrical plug that is matingly and removably engaged to the jack and an electrical headlamp , electrically connected to the plug .