Abstract:
In a method of applying an electrical stimulus to an animal, at least one electrode is in contact with the animal and is fixedly and electrically coupled with a voltage detector circuit. A stimulus signal is carried by the at least one electrode. Using the voltage detector circuit, it is determined whether the stimulus signal exceeds a predetermined voltage level. An indicator signal, indicative of the determining step, is transmitted from the voltage detector circuit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to animal behavior modification systems, and, more particularly, animal behavior modification systems which apply an electrical shock to an animal. 
     2. Description of the Related Art 
     Animals such as dogs may be fitted with a collar which carries a receiver unit and a pair of electrodes for applying electrical stimulation to the skin of the dog in order to control its behavior. For example, a conventional pet containment system includes a stationary transmitter which is connected to an endless wire placed around the confinement area under the surface of the ground. Over the endless wire, the stationary transmitter transmits a radio frequency(RF) signal which is received by the receiver unit if the dog approaches too close to the wire. In response to receiving the signal, a voltage is applied across the electrodes, which causes an electrical current to flow through the dog&#39;s skin between the two electrodes. Alternatively, the trainer may carry a portable transmitter which selectively transmits an RF signal to the receiver unit for electrical stimulation when the animal exhibits undesirable behavior. As another option, a stationary transmitter may transmit an RF signal which is received by the receiver so long as the dog is in the confinement area. If the dog strays from the confinement area, the RF signal is no longer received and electrical stimulation is applied to the dog through the electrodes. 
     A problem is that the animal owner sometimes incorrectly installs the electroshock device on the animal so that the electroshock contacts do not make adequate contact with the animal&#39;s skin. More particularly, the collar is often not tightened enough so that the electrodes may be sufficiently biased against the animal&#39;s skin. As a result, the electroshock corrections that are generated by the device either are not detected by the animal or have a minimal effect on the animal and fail to provide the necessary correction. In other cases, the electroshock device is malfunctioning, for various reasons, and is not capable of producing an adequate electroshock correction, even when correctly installed. 
     It is known for the user to connect an audible or visible device to the output electrodes in order to determine whether an electroshock stimulus output is being generated. The user places the device in an environment capable of producing an electroshock stimulus output and watches or listens for the output to occur. A problem is that there is no indication of magnitude of the output level; the audible or visible device only indicates the presence or absence of the output. Thus, there is no indication of whether an adequate electroshock stimulus is being applied to the animal as installed, or whether the electroshock device is capable of producing an adequate electroshock stimulus, even when the electroshock device is correctly installed. 
     What is needed in the art is a device which allows the user to verify that the electroshock device is operating correctly, and that the electroshock device is installed correctly such that it may apply an adequate electroshock correction to the animal. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus which allows the animal owner to verify that the collar is correctly installed by performing an installation test which determines whether the electroshock probes are making proper contact with the animal&#39;s skin. The user may also perform a self test, with the electroshock device removed from the animal, to verify that the electroshock device is capable of providing an acceptable stimulation level. 
     The invention comprises, in one form thereof, a method of applying an electrical stimulus to an animal. At least one electrode is in contact with the animal and is fixedly and electrically coupled with a voltage detector circuit. A stimulus signal is carried by the at least one electrode. Using the voltage detector circuit, it is determined whether the stimulus signal exceeds a predetermined voltage level. An indicator signal, indicative of the determining step, is transmitted from the voltage detector circuit. 
     An advantage of the present invention is that the user is able to perform a functional self test of the electroshock device and measure whether the output level is within specified limits without the need for attaching additional external indicator devices. 
     Another advantage is that, while the electroshock device is being worn by the animal, the self test may be performed to verify that the device has been properly installed. 
     Yet another advantage is that data relating to the output level of the electroshock device may be stored in a memory for later analysis. 
     A further advantage is that the electroshock stimulus applied to the animal may be continually monitored or stored in a memory for later analysis so that the user can determine the number of times a correction stimulus has been performed, the time interval between shocks, the voltage level of the applied shocks, and whether the correction stimulus was properly applied to the animal&#39;s skin. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a transmitter and one embodiment of a receiver/transmitter unit of the present invention; 
     FIG. 2 is a block diagram of the transmitter and receiver/transmitter of FIG. 1 coupled with a receiver unit; 
     FIG. 3 is a schematic diagram of the receiver/transmitter and receiver of FIG. 2; and 
     FIG. 4 is a schematic diagram of another embodiment of a receiver/transmitter unit of the present invention. 
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to FIG. 1, there is shown an animal behavior modification system including a transmitter  10  and an animal shock collar  12  carrying one embodiment of a remote receiver/transmitter unit  14  of the present invention. Remote receiver/transmitter unit  14  includes at least two probes or electrodes  16  and  18  projecting from a hermetically sealed box  20 . Receiver/transmitter  14  receives a transmitted signal, indicated at  22 , from transmitter  10 . An optional receiver unit  24  (FIG. 2) receives a second transmitted signal, indicated at  26 , from receiver/transmitter  14 . 
     Within box  20  is contained a receiver circuit  28  which receives signal  22  from transmitter  10 . Receiver/transmitter  14  also includes a signal generator  30 , an input circuit  32 , and a voltage detector circuit  33  which includes a voltage divider circuit  34 , a pulse stretcher circuit  36 , a voltage comparator  38 , and a microcontroller  40 . Lastly, receiver/transmitter  14  includes a transmitting circuit  42  and a light emitting diode (LED)  44 . 
     Signal generator  30  is capable of generating a number of different input signals, one of which may be selected by the user depending on the intensity of the stimulus signal that the user wishes electrodes  16  and  18  to apply to the animal. For example, the user may operate a switch (not shown) to select one of seven different input signals which each have a different pulse duration which generates a different output voltage at electrodes  16  and  18 . In general, the shorter the pulse width, the lower the voltage level of the output signal. In one embodiment, the pulse width may range from 20 to 1000 microseconds, and the output voltage at electrodes  16  and  18  may range between 100 and 2000 volts. The input signal transmitted by signal generator  30  to input circuit  32  typically is a pulse having a time duration of less than  1  millisecond. 
     Input circuit  32  includes a transistor  46  and a transformer  48 . As signal generator  30  applies the input signal to the base of transistor  46 , current flows through primary winding  50 , thereby inducing a second current in secondary winding  52 . The voltage signal across secondary winding  52  provides a stimulus signal that is applied across electrodes  16 ,  18 . 
     Voltage divider circuit  34  includes a high value fixed resistor  54  and one or more parallel measurement resistors  56 , with three measurement resistors  56  being shown in the embodiment of FIG.  3 . The peak voltage of the stimulus signal across electrodes  16 ,  18  can be between approximately 1000 and 4000 volts, and preferably is between 1000 and 2000 volts. Voltage divider circuit  34  functions to reduce this voltage to a level that can be more easily measured and/or compared, such as between approximately one and five volts. By operating internal switches  58 , microcontroller  40  can select and combine measurement resistors  56  in order to determine the percentage by which the voltage of the stimulus signal is reduced at node  60 . Each of the possible combinations of measurement resistors  56  produces a different signal at node  60 , and each signal represents a respective percentage reduction of the stimulus signal at electrodes  16 ,  18 . Microcontroller  40  can select a combination of measurement resistors  56  that corresponds with the input signal selected by the user from signal generator  30  such that the peak voltage seen at node  60  is substantially constant regardless of which input signal has been chosen. If the total number of measurement resistors  56  is N, measurement resistors  56  can be combined in 2 N −N1 different ways. Thus, the three measurement resistors  56  shown in FIG. 3 can be combined in seven different ways, with each way corresponding to one of seven possible input signals to be chosen by the user. Microcontroller  40  can also select a combination of measurement resistors  56  based upon whether electrodes  16 ,  18  are loaded by the skin of the animal, i.e., whether collar  12  is being worn by the animal. 
     Voltage divider circuit  34  provides a high impedance test load for the high voltage output transformer  48  when electrodes  16 ,  18  are not in contact with an animal. Voltage divider circuit  34  is also designed to minimize any loading effects when an electroshock stimulus is applied to the animal through electrodes  16 ,  18 . The resistor values that are used in voltage divider circuit  34  are a function of the high voltage transformer  48  used to generate the electroshock stimulus, the desired load required to make the open circuit high voltage measurement, the high voltage present on transformer  48  when the electroshock stimulus is applied to animal skin, and the threshold voltage range capabilities of voltage comparator  38 . 
     The stimulus signal that appears at electrodes  16 ,  18  in response to an input signal from signal generator  30  has a voltage waveform that spikes up to a peak value and then exponentially decays relatively quickly. That is, the waveform has a relatively short decay time. The time period in which the waveform is at or near its peak voltage level may be too short for the peak value to be easily measured. Pulse stretcher circuit  36 , using the reduced stimulus signal at node  60  as an input, produces a modified signal which has a longer decay time, or slower exponential decay, than the reduced stimulus signal at node  60 . Pulse stretcher circuit  36  includes a transistor  62  in a voltage follower configuration with a capacitor  64  and a resistor  66  attached to the emitter. The RC circuit has a time constant that is long enough to allow required measurements of the short duration high voltage output pulses. That is, the modified signal produced by pulse stretcher circuit  36  remains at or near its peak value for a period of time sufficient for the peak value to be easily measured. 
     Voltage comparator  38  compares the peak value of the modified signal produced by pulse stretcher circuit  36  to a threshold voltage V ref . V ref  may be supplied by microcontroller  40 , or by a voltage divider or amplifier connected to +V. Microcontroller  40  determines if the output response of comparator  38  is proper for the input signal generated by signal generator  30  in order to determine whether receiver/transmitter  14  is operating correctly and/or collar  12  is correctly installed on the animal. 
     The user can indicate to controller  40 , possibly by use of a switch (not shown), whether the device is being tested in the unloaded state, i.e., off of the animal, or in the loaded state, i.e., on the animal. The test may be initiated by either an airborne signal transmitted by transmitter  10  or by a test signal induced by the user via a switch (not shown) on box  20 . 
     If collar  12  has been correctly installed on the animal so that electrodes  16 ,  18  are in good electrical contact with the animal&#39;s skin, the peak value of the voltage signal at electrodes  16 ,  18  should be only approximately ⅓ of its value in the unloaded state. In one embodiment, this maximum voltage value in the loaded state has been empirically found to be approximately 800 volts. Thus, if the user has indicated that a test is being conducted with collar  12  on the animal, voltage comparator  38  compares the signal to a first threshold value V ref . If the peak value of the digital signal exceeds this first threshold value, it is indicative that electrodes  16 ,  18  are not making good electrical contact with the animal&#39;s skin. Microcontroller  40  then transmits an indicator signal to light emitting diode (LED)  44  in order to visually indicate to the user that collar  12  is not properly installed. For example, the indicator signal could cause LED  44  to flash on and off continuously. Upon seeing the flashing signal on LED  44 , the user can tighten collar  12  in order to increase the pressure with which electrodes  16 ,  18  are biased against the animal&#39;s skin. The test can then be repeated in the loaded state in order to verify that collar  12  is sufficiently tight. 
     If, on the other hand, the user has indicated to microcontroller  40  that the test is being conducted in the unloaded state with collar  12  off of the animal, then voltage comparator  38  compares the signal to a second threshold value V ref  which is higher than the first threshold value. If voltage comparator  38  determines that the signal is less than the second threshold value, it is indicative that receiver/transmitter  14  is malfunctioning and is not capable of producing an adequate stimulus signal across electrodes  16 ,  18 . Microcontroller  40 , in this mode too, transmits an indicator signal to LED  44  to indicate to the user that receiver/transmitter  14  is malfunctioning. For example, the indicator signal in this mode could cause LED  44  to flash on and off with a frequency that is different from the flashing frequency in the loaded test mode. 
     Data related to the signal from voltage comparator  38  may be stored in a memory  68 , which may be either in microcontroller  40  or in a separate memory device connected to microcontroller  40 . This data storage may be particularly useful when receiver/transmitter  14  is being operated in the field, rather than being in one of the two test modes. For instance, the data stored in memory  68  may be later analyzed in order to determine the number, frequency and intensity of the shocks which have been applied to the animal. 
     Data related to the signal from voltage comparator  38 , or the digital signal itself, can be transmitted to receiver  24  from transmitting circuit  42  through a RF link. Receiver  24  includes a memory  70  which is capable of performing the same functions as memory  68 . Receiver  24  can also include a microcontroller to perform the measuring and/or comparing of the digital signal. The indicator signal that is transmitted to LED  44  can also be transmitted to receiver  24  in order to be displayed on a LED  72  connected thereto. Receiver  24  can be separate from transmitter  10 , as shown, or can be integral with transmitter  10 . 
     Indicator devices  44  and  72  are shown as being in the form of LED&#39;s. However, indicator devices  44 ,  72  may also be audible devices, alpha/numeric displays, or any other type of device which indicates to the user that the output voltage is either within or outside of predetermined threshold limits. Receiver/transmitter  14  and receiver  24  are shown as communicating through a RF link. However, it is to be understood that they may also communicate through an acoustic data link, a magnetic data link, or an optic data link. For example, the data related to the digital signal may be transmitted via LED  44  to an optical receiver on receiver  24 . In this embodiment, receiver  24  may be part of a base unit that inductively recharges a battery within receiver/transmitter  14 . The battery supplies +V throughout receiver/transmitter  14 . The relatively close engagement between receiver/transmitter  14  and receiver  24  that is required for such inductive recharging is also particularly conducive for optical data transfer, such as through LED  44 . 
     In the embodiment described above, the amplitude of V ref  depends upon whether the user indicates that collar  12  is or is not being worn by the animal. In another embodiment, V ref  has a constant voltage amplitude regardless of whether collar  12  is being worn by the animal. In order to compensate for the effects of loading on the signal at electrode  16 ,  18 , microcontroller  40  selects one of two combinations of measurement resistors  56 , with the combination that is selected being dependent upon whether collar  12  is being worn by the animal. The two combinations of measurement resistors  56  are predetermined such that, with receiver/transmitter  14  operating properly, the voltage at node  60  when electrodes  16 ,  18  are unloaded is higher than the V ref  voltage and when electrodes  16 ,  18  are properly biased against the animal&#39;s skin the voltage at node  60  is lower than the V ref  voltage. Thus, regardless of whether electrodes  16 ,  18  are loaded, voltage comparator  38  can compare its input voltage to a same value of V ref . 
     In another embodiment (FIG.  4 ), microcontroller  40  is capable of directly measuring the digital signal from an A/D converter  74 , and measurement resistors  56  may be eliminated or shorted out. 
     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.