Patent Publication Number: US-2013234618-A1

Title: Single Input Power Wire - Multi Function Control

Description:
BACKGROUND 
     The present disclosure relates to control of electronic circuits and specifically to control of electronic circuits in situations where access to the circuit is limited. 
     For example, a typical manual articulating light mounted on the “A” pillar of a police vehicle only has one function, which would be a high intensity halogen spotlight. The wiring from this light bulb to the ON\OFF switch inside the vehicle must travel through a very small conduit and typically uses only one wire for power, with ground supplied through the vehicle chassis. An exemplary articulating light is shown in  FIG. 1 . With the advent of LED technology, this spot light could support multiple functions, such as a flashing warning light or California steady red light in combination with the traditional high intensity spotlight. This multiple feature light poses the problem of how to control functionality and supply power to a multifunction electronic circuit with only a single wire. 
     SUMMARY OF THE DISCLOSURE 
     A solution to this problem comprises incorporating a circuit including a microcontroller (μC) into the head of the light assembly (the head being that portion of the articulating light positioned outside the vehicle). The μC is configured to monitor the input voltage delivered to the head, looking for a gap in the input voltage of a pre-determined duration, which indicates to the μC that the second (or additional) function is desired. The μC, filters the voltage drop out pulse width and determines whether the pulse is less than 50 ms (noise), or greater than 500 ms, (OFF Command) pulse. A voltage gap of between 50 ms and 500ms is the signal to activate the second function. The 5 volt regulator delivering power to the μC is configured such that the 5 volts will “hold up” approximately 1.5 seconds to guarantee that the μC will operate during a “valid” “drop out” voltage pulse. The μC needs a minimum of 2 outputs which will drive current regulators for the “Warning” LED&#39;s and the steady WHITE spotlight LED&#39;s. 
     An alternative solution is a circuit arranged to monitor the polarity of the input voltage applied to the light. A first polarity applied results in a first function being activated, while the opposite polarity activates the alternative, second function. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a manual articulating spotlight incorporating a single wire multifunction control circuit and LED combination warning and spot light according to aspects of the present disclosure; 
         FIG. 2  schematically illustrates a first embodiment of a single wire input multifunction control circuit according to aspects of the disclosure; 
         FIG. 3  graphically illustrates input voltage, power output of the voltage regulator and output of the μC for the circuit of  FIG. 2 ; 
         FIG. 4  schematically illustrates an alternative embodiment of a single wire control circuit configured to monitor the polarity of the input power according to aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS 
       FIG. 1  illustrates a spotlight configured for mounting in the A pillar of an emergency vehicle. A hollow shaft  10  passes through the A pillar and defines a passage for a single wire  11  which supplies power to the light generator in spotlight. A first exemplary embodiment of a circuit permitting multifunction control and power through a single wire is illustrated in  FIG. 2 . The voltage regulator  12  is provided with capacitors that store sufficient electrical power that the μC has power for approximately 1.5 seconds after voltage +V is removed from the input/power wire. The relationship between input power +V and power delivered to the μC is shown in  FIG. 3  in the graphical presentation labeled +5. Every time this circuit is powered up, (Cold Start), the μC flashes the Warning LED&#39;s (MODE 1), with μC output  20  active. As illustrated in  FIG. 3 , if the input voltage drops out for a time period of between 50 ms and 500 ms, the μC will switch from the flashing Warning mode, (MODE 1), to a Steady Spot light mode, (MODE 2), with μC output  22  active. If the input voltage drops out again between 50 ms and 500 ms, the uC will switch back to the flashing Warning light mode, (MODE  1 ) and μC output  20  is active again. If the input voltage drops out for less than 50 ms, the μC is programmed to ignore this event and consider it as noise. If the input voltage drops out for more than 500 ms, the μC will consider it as an OFF command and is programmed to reset the circuit to the flashing Warning light mode, (MODE 1) and shut down. If the input voltage drops out for a duration greater than 1.5 seconds, at which time the +5 volt regulator  12  will drop below 2 volts, the μC will reset and will start from a “(Cold Start)” start when the input voltage is applied to the circuit again. The timing and functionality set forth with respect to this embodiment can be adjusted, depending upon the intended use of the multifunction control circuit. 
     In an alternative second embodiment of a circuit for multifunction control through a power delivery wire is illustrated in  FIG. 4 , the circuit  25  employs a bridge rectifier input  30 , a microcontroller (μC)  32 , LED arrays  34 ,  36  and current regulators  38 . The bridge rectifier  30  allows the circuit  25  to work with the input voltage V in  connected in a positive or negative polarity. A logic circuit  31  connected to the positive input side of the bridge rectifier  30  allows the circuit  25  to be responsive to only the positive polarity input. The μC  32  monitors this logic signal at input F and can make a determination whether the input polarity is positive or negative. If the circuit powers up and the input logic signal F at the μC  32  is low, “0”, the uC will output a “Steady White Spotlight” function with output  2  of the μC  32  active. If the power input is reversed or negative, the μC  32  will sense a logic high at F and the μC  32  will output a “Flashing Warning Signal” function with output 1 of the μC  32  active. 
     This circuit operation is very simple. An input “Positive” polarity will cause the light to activate the White Spotlight mode of operation. An input “Negative” polarity will cause the light to activate the flashing RED or BLUE mode of operation. Either a small relay circuit or “H” bridge output driver circuit will be needed to drive this lamp to make it seamless to the operator. Switches are available which apply alternative polarity to the circuit. This circuit may require two wires through the A pillar.