Abstract:
In a method and system for detecting a particular AC circuit from among a plurality of AC circuits at a circuit box, a transmitter is plugged into the particular AC circuit to be detected, the transmitter creating a high amplitude high-frequency current pulse. With a receiver, sensing the particular circuit at the circuit box by use of a sensing coil and employing a variable gain stage in conjunction with a threshold comparator and latch to pick off a signal caused by the high amplitude high frequency current pulse. The signal is latched so that a microprocessor can read the signal to activate an indication to a user when the particular AC circuit has been located at the circuit box. The microprocessor can be programmed after it is mounted into the receiver by use of a computer which transfers a program to the microprocessor. In an alternate embodiment of the invention, instead of the latch, the threshold comparator connects to an interrupt input of the microprocessor.

Description:
RELATED APPLICATION 
     This is a Continuation-In-Part of earlier application Ser. No. 09/420,502, filed Oct. 19, 1999 entitled “Improved Automatic Circuit Breaker Detector” by the same inventors as the instant application, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to automatic circuit breaker detectors. 
     It is known in prior art automatic circuit breaker detectors to provide a relaxation oscillator transmitter which creates high frequency high amplitude current pulses with a transmitter which plugs into a conventional AC outlet such as in a house wired for 110 AC. The high current amplitude high frequency pulses are transmitted via the 110 AC wiring to a circuit breaker box, located in a designated area within a home or business. Typically the circuit breaker box has a plurality of circuit breaker switches arranged in a column or a row. 
     Prior art automatic circuit breaker detector receivers are known which emit an audible indication when the receiver unit is brought adjacent to the particular circuit breaker or a line associated with the particular circuit breaker corresponding to the circuit in which the transmitter is plugged at the remote outlet. When the receiver unit begins to emit an audible sound, then the user has identified, without the need for switching off the circuit breaker switch, the particular circuit in which the transmitter has been remotely plugged. This has the known advantage that circuits can be identified without the need of actually switching off the circuit breaker detector. Thus, for example, electronic equipment does not have to be reset after a resumption of power. 
     It is a significant disadvantage of such prior art automatic circuit breaker detectors that they can provide false indications at the receiver when attempting to locate the circuit breaker corresponding to the remotely plugged in transmitter unit. For example, the receiver unit may emit an audible indication when it is placed adjacent more than one of the circuit breakers in the circuit breaker box, thus providing a false indication. Also, the receiver unit might not provide any indication, despite the presence of the current pulses on the particular circuit which is being located. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to improve the reliability and performance of automatic circuit breaker detectors so as to minimize the presence of false indications, and to maximize sensitivity automatically without manual calibration so that detection of a particular circuit breaker can be reliably detected in most or virtually all instances. 
     According to the present invention, a method and system are provided for detecting a particular AC circuit from among a plurality of AC circuits at a circuit box. A transmitter is plugged into the particular AC circuit to be detected and which creates a high amplitude high frequency current pulse. With a receiver unit, the particular circuit is sensed at the circuit box by use of a sensing coil. A variable gain stage is employed in conjunction with a threshold comparator and a latch to pick off the signal and latch the signal so that a microprocessor can read the signals and activate an indication to a user when the appropriate circuit has been located. Calibration occurs immediately by decreasing the gain of the variable gain stage automatically until the signal can no longer be detected, and then the gain is increased slightly so that the variable gain stage operates right at a threshold of the threshold comparator. 
     Also according to the present invention, in the receiver unit a variable gain stage is employed in conjunction with a threshold comparator and a microprocessor and wherein the microprocessor has an interrupt input connected to an output of the threshold comparator so as to pick off the signal so that the microprocessor can read the signals and activate an indication to a user when the appropriate circuit has been located. Calibration occurs immediately by decreasing the gain of the variable stage automatically until the signal can no longer be detected, and then the gain is increased slightly so that the variable gain stage operates right at a threshold of the threshold comparator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a front view of a typical wall socket having the transmitter used in the automatic circuit breaker detector system of the invention plugged into it; 
     FIG. 1B is a perspective view of an automatic circuit breaker detector receiver of the system according to the invention employed in locating a particular circuit breaker or circuit associated with that breaker in a circuit breaker box; 
     FIG. 2 is a block diagram of the improved automatic circuit breaker detector system of the invention; 
     FIG. 3 is a schematic diagram of a transmitter portion used with the improved automatic circuit breaker detector system of the invention; 
     FIG. 4 is a schematic diagram of a first embodiment of the inventive receiver portion of the improved circuit breaker detector system of the invention; 
     FIG. 5 is a block diagram flow chart of the software program employed in the first embodiment of the present invention; 
     FIG. 6 is a block diagram of the improved automatic circuit breaker detector system of the invention employing an interrupt input on the microprocessor in a second embodiment of the invention; 
     FIG. 7 is a schematic diagram of the inventor receiver portion of the improved circuit breaker detector system of the invention corresponding to the second embodiment block diagram of FIG. 6; 
     FIG. 8 is a block diagram flow chart of a software program employed in the second embodiment of FIGS. 6 and 7; and 
     FIG. 9 is an alternate embodiment software block diagram for use with the second embodiment shown in FIGS.  6  and  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The transmitter used in the improved circuit breaker detector system of the invention as shown in FIG. 1A at  12 . It is housed in a box having two prongs  12   a  and  12   b  protruding from one face thereof which are plugged into one of the sockets  10   a  or  10   b  of the wall outlet  10  connected to a particular electrical 110 volt AC circuit  11  formed of two circuit lines  11   a  and  11   b . The transmitter has an LED  87  which is illuminated when the transmitter is functioning to create high current high frequency current pulses in the AC line  11  as described hereafter. 
     To locate the particular circuit into which the transmitter is plugged, as shown in FIG. 1B a receiver  13  is provided such as in a pistol grip casing having on its backside a power switch  18  and a light such as an LED  19  for indicating when the receiver is turned on. The receiver has slots  9  through which an audible sound can be emitted as described hereafter. 
     At the front face of the pistol grip unit, a sensor surface  21  having an associated sensing coil  24  (see FIGS. 2 and 4) is provided. This sensing face  21 , located at on the end of a tapered projection  22  at the top portion  23  of the pistol grip having a lower handle portion  20 , is positioned adjacentvarious circuit breakers  11   c ,  15   c ,  16   c , and  17   c  provided in respective AC line circuits  11 ,  15 ,  16  and  17  in a circuit breaker box  14 . The receiver senses the voltage drop which occurs at the circuit breaker, such as may result due to internal resistance of the circuit breaker, or as a result of the internal inductance of the circuit breaker. Since the current pulses are very high frequency and very high amplitude current, even small circuit breaker resistances or switch inductances can be detected. The receiver unit also will detect the current pulses on the AC line itself, although in the preferred mode the unit is detecting voltage drops at the circuit breakers. 
     When the receiver is positioned adjacent the circuit breaker such as  11   c  corresponding to the circuit  11  into which the transmitter is plugged at a remote location, then the receiver unit will emit an audible sound only when the detecting face  21  of the receiver unit is adjacent the proper circuit breaker. When it is moved away from the designated circuit breaker, then no sound is emitted. 
     In the block diagram of FIG. 2, the transmitter  80  is shown transmitting the high frequency high amplitude pulses along the AC line. This signal is picked up by the sensing coil  24  when the sensing coil  24  at the sensing face is positioned adjacent to the appropriate circuit breaker corresponding to the circuit in which the transmitter  80  is plugged. In addition to the sensing coil  24 , the receiver has a variable gain stage  25  which amplifies the signal from the sensing coil  24 . The amplified signal from the variable gain stage  25  is fed into a threshold comparator  26 . If the output of the variable gain stage  25  meets or exceeds the voltage reference of the threshold comparator  26 , latch  27  will be set. The microprocessor  28  monitors the status of the latch  27 . If the latch  27  is set, the microprocessor  28  will adjust the value of the digital-to-analog converter  29  which, through the feedback line  30 , will decrease the sensitivity of the variable gain stage  25 . The microprocessor  28  will then clear the latch  27  via line  90  and alert the user. If the microprocessor  28  determines that a signal is out of range it will compensate by increasing the gain of the variable gain stage amplifier  25  by a predetermined value output to the digital to analog converter  29  through feedback line  30 . 
     As shown in FIG. 3, the transmitter  80  connects at terminals  81   a  and  81   b    81 A and  81 B to the AC line  11 . Terminal  81  a connects through a capacitor  86  and resistor  85  to a DIAC  84 . The DIAC  84  periodically triggers to discharge capacitor via SCR  82  controlled by  84  to create the high frequency high current pulse which is sent over the AC line  11 . 
     Now referring to FIG. 4, the receiver has a power supply comprising a battery  33 , a diode  32 , the power switch  18 , the power indicating LED  19 , and a resistor  31 . A V++ terminal indicates the voltage outlet to the remaining circuitry of the receiver 
     At the bottom of FIG. 4 at the lower left a voltage regulator  65  is indicated for converting the V++ voltage to a lower voltage V+ which is filtered at  66 . Additional filters  67 ,  68  and  69  are also provided which connect to various integrated circuits to provide a filtered source of V+ or V++ voltage. 
     The variable gain stage  25  is formed of the coil  24 , capacitor  35 , resistor  36 , resistor  37 , resistor  38 , and transistor  39 . Also the transistor  39  connects to a capacitor  40 , a resistor  41 , and a resistor  42  as shown. 
     The output of the variable gain stage  25  has a high frequency filter capacitor  43  which improves the sensitivity and reliability of the system in detecting a signal on a single circuit breaker among a plurality of circuit breakers. This typically has a relatively small capacitance value such as 47 pf. 
     The signal from the variable gain stage  25  is connected to the threshold comparator  26  having a voltage reference provided by resistors  44  and  45 , and resistor  47  at its output. 
     The latch  27  is formed of resistors  51 ,  52 ,  56 , and transistor  48  connected to resistor  49 . The latch  27  receives a clear signal on line  90  through resistor  51  from microchip  58 . An amplifier stage  53  having an associated feedback resistor  54  is provided fed with power from resistor  55 . Resistor  56  connects the amplifier  53  to transistor  57  having an associated resistor  59 . 
     The transistor  57  has its output connected to a microprocessor chip. This microprocessor is externally programmable via a program connection block  63 . 
     The microprocessor chip is connected to provide an output to a piezo element  61  which provides an audible signal such as about 2000 Hz and which is driven by a transistor  60  controlled by voltage coming in through resistor  62  from the microprocessor. This piezo-element provides the audible sound when a detected signal is present. 
     The output of the microprocessor connects to the digital-to-analog converter  29 . 
     In order to program the microprocessor chip  58  with the program shown in FIG. 2, a computer  78  connects to the program connections  63  and which downloads the program from a disk  79 , for example, to the microprocessor chip  58 . 
     A start block  70  indicates power-up and the beginning of program execution. The initialize I/O block  71  sets the microprocessor pins as inputs and outputs. The set to max gain block  72  outputs a value to the D/A converter that sets the variable-gain stage to its maximum sensitivity. The calibrate-to-ambient (tare) block  73  decreases the gain of the variable gain stage until no signal is present, thus preventing false signals from being validated. If an out-of-range condition occurs, then the compensate block  88  increases the value that is output to the D/A converter to increase the gain of the variable gain stage, thereby preventing a loss-of-signal condition. The gain value is stored block  89  and the program loops back to the out-of-range decision block  74 . The latch-set decision block  75  will loop back to the out-of-range decision block  74  if the input signal has not set the latch. If the latch is set, then the program proceeds to the beep/decrement gain block  76 , which will decrement the output value to the D/A converter, thereby decreasing the sensitivity of the variable gain stage, and then annunciates to the user. The gain value is stored in block  77  and the latch is cleared  87 . The program then flows back to the out-of-range decision block  74 . 
     With the present invention, by use of the threshold comparator  26  and latch  27 , the microprocessor can pull in a signal more reliably and does not miss pulses. This results in higher receiver accuracy and more reliability with fewer false indications. 
     Moreover, the microprocessor is programmed after it is soldered into the circuit. This has a distinct advantage over the prior art system where microprocessors would have to be programmed prior to mounting into the circuit. This results in higher production efficiency and ease of handling of the microprocessor. The programming is thus more reliable and easier to accomplish. 
     There is also the dual benefit that the program connection block also provides terminals at which a function test can be performed to determine whether the receiver unit is properly functioning. 
     There is the further advantage with the in circuit programmability of the microprocessor that if the program changes, old units in inventory do not have to be destroyed. Rather, engineering changes to the programming whereby new software is placed into the microprocessor can be accomplished with existing inventory units. 
     Also according to the present invention, with the in-circuit programmability of the microprocessor, inputs and outputs are initialized. 
     In an alternate embodiment of the invention as shown by the block diagram of FIG. 6, the transmitter  80  is shown transmitting the high frequency high amplitude pulses along the AC line. This signal is picked up by the sensing coil  24  when the sensing coil  24  at the sensing face is positioned adjacent to the appropriate circuit breaker corresponding to the circuit in which the transmitter  80  is plugged. In addition to the sensing coil  24 , the receiver has a variable gain stage  25  which amplifies the signal from the sensing coil  24 . The amplified signal from the variable gain stage  25  is fed into a threshold comparator  26 . If the output of the variable gain stage  25  meets or exceeds the voltage reference of the threshold comparator  26 , an interrupt signal will be present at the microprocessor. The microprocessor will act upon the interrupt by adjusting the value of the digital to analog to converter  29 , which through the feedback line  30  will decrease the sensitivity of the variable gain stage  25 . The microprocessor  28  will then alert the user. If the microprocessor  28  determines that a signal is out of range, it will compensate by increasing the gain of the variable gain stage amplifier  25  by a predetermined value through the digital to analog converter  29  and through feedback line  30 . 
     In the schematic diagram of FIG. 7 corresponding to the block diagram of FIG. 6, similar circuit elements which have been previously discussed in relation to FIG. 4 will not be discussed here. However, as can be seen in FIG. 7, the latch  27  of the first embodiments of FIGS. 2 and 4 is not present. Rather, the threshold comparator  26  output connects to a line  100  to an interrupt input  101  of the microprocessor chip  58 . 
     Two alternate embodiments of software can be employed with the alternate embodiment employing the interrupt input on the microprocessor as shown in FIG.  7 . In a first alternate embodiment as shown in FIG. 8, a start block  91  indicates power-up and the beginning of program execution. The initialize I/O and interrupts block  92  sets the microprocessor pins as inputs and outputs and enables the external hardware interrupt. The set-to-max-gain block  93  outputs the value to the D/A converter that sets the variable-gain stage to its maximum sensitivity. The calibrate-to-ambient (tare) block  9  decreases the gain of the variable-gain stage until no signal is present, thus preventing false signals from being validated. If an interrupt  98  occurs, then the program proceeds to the beep/decrement gain block  99  which will decrement the output value to the D/A converter, thereby decreasing the sensitivity of the variable gain stage. The gain value is then stored into memory  112 , and then execution returns to the main program loop. If an out-of-range condition  95  occurs, the compensate block  96  increases the gain value output to the D/A converter to increase the sensitivity of the variable gain stage, thus presenting a loss-of-signal condition. The gain value is then stored, and block  97  and the program loops back to the out-of-range decision block  95 . 
     In the embodiment of FIG. 9, a start block  91  indicates power-up and the beginning of program execution. The initialize I/O and interrupt block  92  sets the microprocessor pins as inputs and outputs and enables the external hardware interrupt. The set-to-max-gain block  93  outputs the value to the D/A converter that sets the variable-gain stage to its maximum sensitivity. The calibrate-to-ambient (tare block  94  decreases the gain of the variable-gain stage until no signal is present, thus preventing false signals from being validated. If an out-of-range condition  102  occurs, the compensate block  107  increases the gain value output to the D/A converter to increase the sensitivity of the variable-gain stage, thus preventing a loss-of-signal condition. The gain value is then stored, block  118 , and the program loops back to the out-of-range decision block  102 . Decision block flag set  103  will loop back to the out-of-range decision block  102  if the input signal has not triggered the interrupt  109  which sets the flag  110 , and then returns to execution of the main loop  111 . If the flag is set, then the program proceeds to the beep/decrement-gain block  104  which will decrement the output value to the D/A converter, thereby decreasing the sensitivity of the variable-gain stage, and then annunciates to the user. The gain value is stored in memory  105 , and the flag is cleared-block  106 . The program then flows back to the out-of-range decision block  102 . 
     Although various minor modifications might be suggested by those skilled in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come with the scope of our contribution to the art.