Abstract:
A visual alert system including at least two visual alert devices conductively connected to form an array. Each visual alert device includes a control circuit. The control circuits of the visual alert devices are connected by a flash mode interconnect line. The control circuits, thus interconnected are capable of sensing changes in voltage between the first and second control circuits across the flash mode interconnect line and therefore between the first and second visual alert devices. The visual alert devices, through their respective control circuits, may be programmed and selectively switched to operate in a variety of flash modes including an alternating mode or a synchronous mode.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to warning or hazard alert lighting systems and more particularly to a multiple visual alert device having variable mode operational capability. 
     2. Background 
     A wide variety of equipment, including mobile emergency, maintenance and law enforcement vehicles, employ a variety of signaling devices, both audible and visual. Visual alert devices commonly used in connection with these types of applications include flashing or flash simulating devices. Flashing devices may include strobe lights, rotating halogen devices, rotating sealed beam devices, flashing incandescent devices and devices which may include an array of light emitting diodes (LED). 
     The prior art recognizes generally the benefit in providing strobe pulse control, see Pacelli, U.S. Pat. No. 5,602,522, Visual Signaling System. In particular, the prior art recognizes that providing for a constant flash rate for strobe lights connected in an array may be of benefit. According to the prior art, constant flash rate for strobe lights has been achieved utilizing a single control circuit electrically connected to more than one strobe which signals each strobe individually to discharge simultaneously and at a constant rate. This type of system has a distinct disadvantage of relying on an additional and external component to trigger and therefore control strobe operation. 
     It may be desirable to provide a visual alert system that has either an alternating mode operational capability or a synchronous mode operational capability or in the alternative, both an alternating mode operational capability and a synchronous mode operational capability. It may also be desirable to provide either an alternating mode operational capability or a synchronous mode operational capability for strobe lights or other visual alert devices which are connected in an array which eliminates the need for a separate control device to operate and control the array of visual alert devices. In addition, it may be desirable to provide a visual alert system that has both an alternating mode operational capability and a synchronous mode operational capability which eliminates the need for a separate control device to operate and control an array of visual alert devices. 
     SUMMARY OF THE INVENTION 
     Accordingly, these and other objectives are achieved by a visual alert system having variable mode operational capability that includes two or more visual alert devices electrically interconnected to form an array. By variable mode it is meant alternating mode, both single and multiple pulse, synchronous mode both single and multiple pulse as well as the variations that may be achieved employing the present invention. 
     In one embodiment of the invention, the array may include a first visual alert device including a first control circuit and a second visual alert device including a second control circuit. The first and second control circuits are interconnected by way of a flash mode interconnect line. The first and second control circuits, thus interconnected are capable of sensing changes in voltage between the first and second strobe control circuits and therefore between the first and second visual alert devices. 
     In one embodiment of the invention, the first visual alert device includes a first strobe and a second strobe. In this embodiment of the invention, the first visual alert device includes a first strobe control circuit and the second visual alert device includes a second strobe control circuit. The first strobe control circuit and the second strobe control circuit, specifically, a first strobe control circuit microcontroller and a second strobe control circuit microcontroller, are interconnected by a flash mode interconnect line which, in the case of alternating mode operation is designated as an alternating flash mode interconnect line. 
     In one embodiment of the invention, the visual alert system the system operates in an alternating mode. In this embodiment of the invention, the visual first and second visual alert devices flash in a sequential manner wherein a first visual alert device is energized or discharges, followed by an interval between the energization or discharge of the first visual alert device and the second first visual alert device, followed by the energization or discharge of a second visual alert device. In the alternating mode the first and second visual alert devices may alternate flashing in single as well as multiple flash mode i.e. dual, quad, etc. 
     In the alternating mode operation, whenever either strobe flashes, it pulls the voltage across the alternating flash mode interconnect line low. Upon power up, each strobe begins operating norm ally, pulling the alternating flash mode interconnect line low when flashing. At this point, both the first and second strobe lights are flashing simultaneously. When the strobes are not flashing, their respective strobe control circuits monitor the alternating flash mode interconnect line to see if it gets pulled low. After an unspecified interval, the strobes will be slightly out of sequence. The first of the two strobes to detect a drop in voltage across the alternating flash mode interconnect line assumes operation as a slave strobe, with the other serving as a master strobe. The slave strobe monitors the alternating flash mode interconnect line for a preselected higher value indicating that the master strobe has completed its flash or flash sequence. Before discharging, the slave strobe delays a preselected delay interval depending upon the operational characteristics of the particular preselected flash program, i.e. single, dual or quad mode. During the slave strobe&#39;s flashing sequence, the master strobe monitors the alternating flash mode interconnect line for a preselected higher value indicating that the slave strobe has completed its flash or flash sequence. Flash intervals and delay intervals may be timed in incremental intervals. 
     The master strobe delays a preselected delay interval, once again depending upon the operational characteristics of the particular preselected flash program, before energizing. The system thereby achieves alternating flash mode and remains in that mode and the process sequence is repeated until the system power is switched off or the operational mode is changed. 
     In an alternate embodiment of the invention, the visual alert system the system operates in a synchronous mode. In this embodiment of the invention, the first strobe control circuit and the second strobe control circuit are interconnected by the flash mode interconnect line which in the case of synchronous mode operation is designated as a synchronous flash mode interconnect line. Whenever either strobe flashes, it pulls the voltage across the synchronous flash mode interconnect line low. In the case of synchronous mode operation, the first and second visual alert devices flash in a substantially synchronous mode wherein a first visual alert device is energized or discharges, in some cases more than once, followed by the substantially synchronous energization or discharge of a second visual alert device, followed by a dead interval between energization or discharge of the first and second visual alert devices. In the synchronous mode the first and second visual alert devices may flash in single as well as multiple flash mode, i.e. dual, quad, etc. 
     In the synchronous mode, upon power up, each strobe begins operating normally, pulling the synchronous flash mode interconnect line low when flashing. At this point, both the first and second strobe lights are flashing simultaneously. When they aren&#39;t flashing, their respective strobe control circuits monitor the synchronous mode interconnect line to detect if it gets pulled low. After a few seconds of operation, the strobes will be slightly out of sequence, and a second strobe will detect that the first strobe is pulling the line low. When the predefined low voltage is detected by the second strobe control circuit across the synchronous flash mode interconnect line indicating that the first strobe has discharged before the preselected dead interval has lapsed, the second strobe control circuit jumps to the beginning of its flash sequence and triggers the second strobe. The effect is that the second strobe discharges at a very short time following the discharge of the first strobe, creating the impression of synchronous mode operation. If a low voltage is not detected across the synchronous flash mode interconnect line prior to the end of the dead interval, both strobe control circuits will trigger a flash at the preselected time. The system thereby achieves synchronous flash mode and remains in that mode until the system power is switched off or the operational mode is changed. The strobe may be programmed to flash in a single or multiple mode, i.e. dual or quad etc. 
     In one embodiment of the invention, the visual alert system is capable of operation in either alternate or synchronous mode operation. 
     In an alternate embodiment of the invention, the array may include more than two interconnected visual alert devices. Various patterns may be achieved in this manner. For instance, first and second strobe lights may be interconnected for synchronous flash mode. Similarly, third and fourth strobe lights may be interconnected for synchronous flash mode. With the addition of a third interconnect line, for instance an alternating flash mode interconnect line between second and third strobe lights, a pattern, wherein first and second strobes flash in synchronous mode operation with respect to one another while third and fourth strobes flash in synchronous mode operation with respect to one another is achieved. However, first and second strobes flash in an alternating mode with respect to third and fourth strobes. In this manner a wide variety of patterns may be created employing a number of alert devices restricted only by the limitations of the electrical system as a whole. 
     Other advantages will become apparent to those skilled in the art from the following detailed description read in conjunction with the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective representational view of a vehicle employing a variable mode visual alert system according to the present invention; 
     FIG. 2 is a schematic representation of a variable mode visual alert system according to the present invention; 
     FIG. 3 is a schematic representation of a variable mode visual alert system according to the present invention; 
     FIG. 4 is a schematic representation of first and second strobe lights employed in the present invention; 
     FIG. 5A is a graphic representation of pulse timing for one embodiment of the present invention operating in dual alternating mode; 
     FIG. 5B is a graphic representation of pulse timing for one embodiment of the present invention operating in quad alternating mode; 
     FIG. 6A is a graphic representation of pulse timing for one embodiment of the present invention operating in dual synchronous mode; and 
     FIG. 6B is a graphic representation of pulse timing for one embodiment of the present invention operating in quad synchronous mode. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows maintenance vehicle V including variable mode visual alert system  10 . In the embodiment of the invention shown in FIG. 1, variable mode visual alert system  10  includes strobe lights  25  and  26  mounted atop the cab of maintenance vehicle V. The system also may also include switching and control circuit  15 , in this case mounted within the cab of maintenance vehicle V. 
     FIG. 2 shows variable mode visual alert system  10  including power source  11  which provides switchable electrical current through switch SW 1  to system components including switching and encoding circuit  12  and control circuit  13 . Power source  11  is conductively connected to switching and control circuit  15 . Switching and control circuit  15  includes control circuit  13  and switching and encoding circuit  12 . First strobe light  25  is connected to control circuit  13  by first conductor  30  and second conductor  31  through output switches  14 A and  14 B. Second strobe light  26  is similarly shown connected to control circuit  13  by third conductor  32  and fourth conductor  33  through output switches  14 C and  14 D. First strobe light  25  and second strobe light  26  are conductively connected by alternating flash mode interconnect line  34  and synchronous flash mode interconnect line  35 . 
     Switching and encoding circuit  12  includes encoder U 3  connected to switch SW 2 . Encoder U 3  in the embodiment shown includes an integrated circuit manufactured by the Motorola Company and identified as part number MC14532B. SW 2  is conductively connected to the plurality of input pins of encoder U 3  and permits the user of the system to switch the device between a plurality of pre-programmed flash modes. The output pins of encoder U 3  are conductively connected to microcontroller U 1  of control circuit  13  as shown. Microcontroller U 1  converts the input signal from encoder U 3  to activate the system through output switches shown generally,  14 A through  14 D to activate and operate the system in a variety of preprogrammed flash modes. Microcontroller U 1 , in the embodiment shown, includes an integrated circuit manufactured by the Microchip Company and identified as part number PIC16C54. 
     Referring to FIG. 3, variable mode visual alert system  10  is shown including power source  11  connected to switching and control circuit  15 . Switching and control circuit  15  includes control circuit  13  conductively connected to switching and encoding circuit  12 . As shown in FIG. 3, control circuit  13  includes microcontroller U 1  having a plurality of input pins which are connected to switching and encoding circuit  12 . The output pins of microcontroller U 1  are connected to a plurality of output switches shown generally as output switch  14 A, output switch  14 B, output switch  14 C and  14 D. FIG. 3 shows variable mode visual alert system  10  including first strobe light  25  connected to output switch  14 A by first conductor  30  and to output switch  14 B by second conductor  31 . Similarly, second strobe light  26  is connected to output switch  14 C by third conductor  32  and to output switch  14 D by fourth conductor  33 . 
     Each of the output switches  14 A,  14 B,  14 C and  14 D include transistors Q 1 A, Q 1 B, Q 1 C and Q 1 D respectively, which provide switching of low voltage power to first strobe light  25  and second strobe light  26 . 
     FIG. 4 is a schematic representation showing first strobe light  25  and second strobe light  26 . First strobe light  25  is shown including first power input circuit  16 A, first low voltage power supply circuit  17 A, first flash mode input circuit  18 A, first strobe control circuit  19 A, first charging power supply circuit  20 A and first trigger circuit  21 A. First conductor  30  is conductively connected to first charging power supply circuit  20 A and first trigger circuit  21 A through first flash mode input circuit  18 A and first strobe control circuit  19 A. Similarly, second conductor  31  is conductively connected to first charging power supply circuit  20 A through first power input circuit  16 A. First flash tube  22 A is conductively connected to first charging power supply circuit  20 A and first trigger circuit  21 A. 
     Second strobe light  26  is shown including second power input circuit  16 B, second power supply circuit  17 B, second flash mode input circuit  18 B, second strobe control circuit  19 B, second charging power supply circuit  20 B and second trigger circuit  21 B. Third conductor  32  is conductively connected to second charging power supply circuit  20 B and second trigger circuit  21 B through second flash mode input circuit  18 B and second strobe control circuit  19 B. Similarly, fourth conductor  33  is conductively connected to second charging power supply circuit  20 B through second power input circuit  16 B. Second flash tube  22 B is conductively connected to second charging power supply circuit  20 B and second trigger circuit  21 B. 
     FIG. 4 also shows first strobe control circuit  19 A and second strobe control circuit  19 B conductively connected by alternating flash mode interconnect line  34  and synchronous flash mode interconnect line  35 . More particularly, the first end of alternating flash mode interconnect line  34  is shown connected at pin  2  of microcontroller U 10  of first strobe control circuit  19 A and the second end of alternating flash mode interconnect line  34  is shown connected at pin  2  of microcontroller U 10  of second strobe control circuit  19 B. Similarly, the first end of synchronous flash mode interconnect line  35  is shown connected at pin  6  of microcontroller U 10  of first strobe control circuit  19 A and the second end of synchronous flash mode interconnect line  35  is shown connected at pin  6  of microcontroller U 10  of second strobe control circuit  19 B. Microcontroller U 10 , in the embodiment shown, includes an integrated circuit manufactured by the Microchip Company and identified as part number PIC12C508. 
     FIG. 5A is a graphic representation of pulse timing for an embodiment of the present invention operating in dual flash alternating mode. FIG. 5A shows relative pulse timing for first strobe light  25  and second strobe light  26  and corresponding relative voltage across alternating flash mode interconnect line  34 . It may be noted that at the termination of flash interval DA 1  of first strobe light  25 , voltage rises at V 1  to a preselected higher voltage across alternating flash mode interconnect line  34 . Timing of delay interval DA 1  begins for the sequential flash of second strobe light  26  in flash interval DA 2 . Flash interval DA 2  is followed by delay interval DI 2  and so on. In this embodiment of the invention, flash interval DA 1  and flash interval DA 2  both equal 210 ms±50 ms and delay interval DI equals 180 ms±25 ms. Flash interval DA 1  and flash interval DA 2  and delay intervals Dl 1  and DI 2  may be varied in intervals of 30 ms. 
     FIG. 5B is a graphic representation of pulse timing for one embodiment of the present invention operating in quad flash alternating mode. FIG. 5B shows relative pulse timing for first strobe light  25  and second strobe light  26  and corresponding voltage across alternating flash mode interconnect line  34 . It may be noted that at the termination of flash interval QA 1  of first strobe light  25 , voltage rises at V 2  to a preselected higher voltage across alternating flash mode interconnect line  34 . Timing of delay interval DI 3  begins for the sequential flash of second strobe light  26  in flash interval QA 2 . Flash interval QA 2  is followed by delay interval DI 4  and so on. In this embodiment of the invention, flash interval QA 1  and flash interval QA 2  both equal 420 ms and delay interval DI equals 60 ms. Flash interval QA 1  and flash interval QA 2  and delay intervals DI 3  and DI 4  may be varied in intervals of 30 ms. 
     FIG. 6A is a graphic representation of pulse timing for one embodiment of the present invention operating in dual synchronous mode. FIG. 6A shows relative pulse timing for first strobe light  25  and second strobe light  26  and corresponding voltage across synchronous flash mode interconnect line  35 . It may be noted that when voltage V 3  drops to a preselected low voltage level as a result of the discharge of first strobe light  25  in flash interval DS 1 , the discharge of second strobe light  26  follows at an interval indicated by lapse L 1 . Since lapse L 1  is measured in microseconds the apparent visual effect is one of synchronous flash. FIG. 6A also illustrates the concept that either first strobe light  25  or second strobe light  26  may discharge first as in the case of the second impulse DS 2  which is led by the discharge of second strobe light  26  followed at an interval indicated by lapse L 2  by the discharge of first strobe light  25 . In this embodiment of the invention, DS 1  and DS 2  both equal 210 ms±60 ms and dead period DP 1  between flashes equals equal 540 ms±60 ms. Flash DS 1  and DS 2  and dead period DP 1  may be varied in intervals of 30 ms. 
     FIG. 6B is a graphic representation of pulse timing for one embodiment of the present invention operating in quad synchronous mode. FIG. 6B shows relative pulse timing for first strobe light  25  and second strobe light  26  and corresponding voltage across synchronous flash mode interconnect line  35 . It may be noted that when voltage V 4  drops to a preselected low voltage level as a result of the discharge of first strobe light  25  in flash interval QS 1 , the discharge of second strobe light  26  follows at an interval indicated by lapse L 3 . In this embodiment of the invention, QS 1  and QS 2  both equal 420 ms±60 ms and dead period DP 2  between flashes equals equal 540 ms±60 ms. Flash QS 1  and QS 2  and dead period DP 2  may be varied in intervals of 30 ms. 
     The following is an identification of various components of the circuits described herein, it being understood that specified components may be varied and/or replaced by other suitable components depending upon the particular application, and that any such replacement or substitution still falls within the scope of the present invention. 
     Power source  11  as shown in FIG. 2 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 capacitor C1 
                 100μF 50V 
               
               
                   
                 capacitor C2 
                 .1μF 400V 
               
               
                   
                 capacitor C3 
                 10μF 50V 
               
               
                   
                 diode D1 
                 1N4006, 1A, 800V 
               
               
                   
                 diode D2 
                 1N5233 zener, 6V 
               
               
                   
                 resistor R1 
                 2K 2W 
               
               
                   
                 transistor Q5 
                 MPSW 42 
               
               
                   
                 varistor VR1 
                 47V 
               
               
                   
                   
               
             
          
         
       
     
     Switching and encoding circuit  12  as shown in FIG. 2 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 encoder U3 
                 MC14532B 
               
               
                   
                 resistor R5 
                 10K 
               
               
                   
                   
               
             
          
         
       
     
     Control circuit  13  as shown in FIG. 3 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 microcontroller U1 
                 PIC16C54 
               
               
                   
                 reset circuit U2 
                 MC33064 
               
               
                   
                 capacitor C4 
                 18pf 
               
               
                   
                 capacitor C5 
                 18pf 
               
               
                   
                 resistor R2 
                 10K 
               
               
                   
                 resistor R3 
                 150 
               
               
                   
                 resistor R4 
                 10K 
               
               
                   
                 crystal X1 
                 4.0 MHZ 
               
               
                   
                   
               
             
          
         
       
     
     Output switch  14 A, which is typical of output switch  14 B,  14 C and  14 D as shown in FIG. 3 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 resistor R6A 
                 1K 
               
               
                   
                 resistor R7A 
                 1K 
               
               
                   
                 resistor R8A 
                 10K 
               
               
                   
                 transistor Q1A 
                 power mosfet, 60V 
               
               
                   
                 varistor VR1A 
                 22V 
               
               
                   
                   
               
             
          
         
       
     
     First power input  16 A, as shown in FIG.  4  and which is typical of second power input  16 B, includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 capacitor C10 
                 .01 1K 
               
               
                   
                 capacitor C11 
                 680 μF 50V 
               
               
                   
                 inductor L10 
                 100μH 
               
               
                   
                 diode D10 
                 FR605 
               
               
                   
                 varistor VR10 
                 68V 
               
               
                   
                   
               
             
          
         
       
     
     First low voltage power supply  17 A, which is typical of second low voltage power supply  17 B, as shown in FIG. 4 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 capacitor C23 
                 10μF 50V 
               
               
                   
                 diode D24 
                 1N5231B zener 5.1V 
               
               
                   
                 diode D25 
                 1N4741A zener 11V 
               
               
                   
                 transistor Q15 
                 MPSW42 
               
               
                   
                 resistor R34 
                 3.9K 1W 
               
               
                   
                 resistor R35 
                 1K 
               
               
                   
                   
               
             
          
         
       
     
     First trigger input  18 A, which is typical of second trigger input  18 B, as shown in FIG. 4 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 resistor R36 
                 200K 
               
               
                   
                 resistor R37 
                 35.7K 
               
               
                   
                 diode D26 
                 1N5231B zener 5.1V 
               
               
                   
                 capacitor C24 
                 .01 μF 
               
               
                   
                   
               
             
          
         
       
     
     First strobe control circuit  19 A, which is typical of second strobe control circuit  19 B, as shown in FIG. 4 includes the components: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 capacitor C15 
                 1μF 
               
               
                   
                 capacitor C16 
                 1μF 
               
               
                   
                 capacitor C17 
                 1μF 
               
               
                   
                 microcontroller U10 
                 P1C12C508 
               
               
                   
                 reset circuit Q13 
                 MC33064P 
               
               
                   
                   
               
             
          
         
       
     
     Circuit design for first charging power supply circuit  20 A, which is typical of second charging power supply circuit  20 B, is well known to those skilled in the art. Similarly, circuit design for first trigger circuit  21 A, which is typical of second trigger circuit  21 B, is well known to those skilled in the art. 
     While this invention has been described with reference to the described embodiments, this is not meant to be construed in a limiting sense. Various modifications to the described embodiments, as well as additional embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description, the drawings and the appended claims. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.