Abstract:
An electronic device for use by recreational divers, that uses ultrasonic signals to measure distance, to indicate relative direction, and to maintain contact between at least two diving partners during a diving session. One of the devices is worn and operated by each diving partner, and each device, through an arrangement of ultrasound transmitters and receiver pairs affixed thereto, monitors relative distance between itself and each other device in use by a diving partner. The device has a user interface, including a plurality of push-buttons and liquid crystal display, to set and indicate relative distance, relative direction, low battery fault, and chime or vibration warning mode. The warning mode alerts a diver when a distance limit between companion divers has been exceeded.

Description:
FIELD OF THE INVENTION 
     The present invention relates to underwater location and communication devices, and more specifically, to a device for use by recreational divers, that uses ultrasonic signals to measure distance, to indicate relative direction, and to maintain contact between diving partners during a diving session. 
     BACKGROUND OF THE INVENTION 
     A review of diving accident reports has shown that a majority of diving accidents occurs when a diver is out of contact with his or her diving partner or partners. Therefore, from a safety perspective, the availability of a compact, light weight, easily worn, and highly reliable means of contact between divers can help to greatly reduce the incidence of mishaps and fatalities sustained during underwater recreational activities. 
     The art includes a number of devices aimed at enhancing communication and navigational abilities for divers. Among such devices are those disclosed in U.S. Pat. Nos. 5,077,703 and 5,185,725. 
     U.S. Pat. No. 5,077,703 discloses a device that uses microwaves, radio waves, or the like to indicate the direction and distance between a diver and a home base transmitter. The home base transmitter creates a signal of a prescribed frequency. The diver wears the device on his or her wrist, similar to a watch. Upon receipt of the signals, the receiver indicates the direction of the base. The receiver also has a range indicator that will warn the diver when he or she has exceeded a prescribed distance from the home base. 
     U.S. Pat. No. 5,185,725 discloses an invention wherein a system of locator modules determine the range and bearing of the other modules in the system by sending out acoustic pulses. A diver carries a module that measures the range and bearing of other modules mounted on a boat or other underwater location. A console carried by the diver displays the information. 
     While the above described devices and others known in the art have desirable capabilities, the present invention affords divers a device having even greater safety features, including alerting the diver(s) when a preselected range limit from other divers in the group is exceeded. 
     SUMMARY OF THE INVENTION 
     The present invention is an ultrasonic transceiver (transmitter/receiver). As ultrasound is a popular method of underwater communication, the device of the present invention employs ultrasound to monitor relative distance between itself and other similar units. The device has a user interface to set and indicate relative distance, relative direction, low battery fault, and chime or vibration indicating mode. The unit is housed in a durable plastic, water proof case. The device runs on two coin cell batteries that are accessible via a rear panel battery compartment. 
     The device turns on and off by depressing a power push-button switch. This switch may be used to reset the unit in the event of a fault condition. 
     A range push-button switch sets a range limit. Current range limit, in feet, and approximate direction are indicated by a Liquid Crystal Display (LCD). 
     When the range limit is exceeded, the device will alert the diver with either an audible tone or a vibration. The desired alarm indicator may be selected by a warning indicator push-button switch. An active alarm indicator is displayed on the LCD. 
     To communicate effectively, and prevent interference from other groups using the same device, the device can be set to operate on different channels. A Ch/D push-button switch facilitates this function. The current channel of operation is shown on the LCD. 
     To allow co-channel operation with multiple units, the user must identify which device in the group his/her unit is. This is accomplished by selecting a device number ( 1  through  8 ) with the Ch/D push-button switch. 
     The battery compartment is on the rear panel and houses two coin cell batteries. A belt clip is also located on the rear panel. It allows the diver to fasten the device to a belt or other suitable clothing. An optional Velcro strap may be used to attach the device to the diver. 
     On all sides of the device except the rear panel, a pair of piezoelectric transducers are provided. In each pair, one is the transmitter and the other is the receiver. These transmitter/receiver pairs allow the devices of the present invention to communicate with each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective external view of a first embodiment of the device of the present invention; 
     FIG. 2 is a back elevation view of the embodiment of the device as seen in FIG. 1; 
     FIG. 3 is a side view of the device as seen in FIG. 1; 
     FIG. 4 is a side external view of the device according to another embodiment of the present invention; 
     FIG. 5 is a schematic block diagram of operational components of the present invention; 
     FIG. 6 is a schematic circuit diagram of the microcontroller circuitry of the present invention; and 
     FIG. 7 is a schematic circuit diagram of transceiver circuitry of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An underwater location and communication device in accordance with the present invention is indicated in FIG. 1 by the reference numeral  10 . As will be noted in FIG. 1, the device  10  has a box-like external appearance and is broadly comprised of: a durable, water proof outer case or housing  11  that is made of high strength plastic or any other sound material; a group of push-button switches  12 ,  13 ,  15  and  17  that is located on a front panel of the device  10  and are used by a diver to operate the device  10 ; a liquid crystal display  14  that is also situated on a front panel of the device  10  and that provides informational data to the diver; a belt clip  20  that is fastened to a rear panel of the device  10  and serves as a means by which the device  10  is worn by the diver; and a plurality of ultrasonic transmitter/receiver pairs  22 . As is more clearly shown by reference to FIGS. 1 and 2, a transmitter/receiver pair  22  is provided on all panels (top, bottom, left, right and front) except for the rear panel of the device  10 . The device  10  is electrically powered by coin-like cell batteries (shown in FIG. 4) that are stored in a battery compartment (not shown) provided inside housing  11 . As shown in FIG. 4, which provides a view of the rear panel of the device  10 , a generally circular cover plate  19  is provided over a rear panel aperture that serves as a means of access to the battery compartment. The cover plate  19  is kept firmly in place over the rear panel aperture by a plurality of screws  24  or other suitable known fastening means. The rear panel of the housing  11  is made removable from the device by a bore provided at each corner of the rear panel and that receives a screw  26  for threadably engaging the housing  11 . 
     FIG. 1 shows that the push-buttons  12 ,  13 ,  15  and  17  are horizontally aligned in the bottom half of the front panel of the housing  11 . The power push-button switch  12 , which is marked with a letter “P”, serves to turn power to the device  10  on or off by depressing. The switch  12  also serves to reset the device  10  in the event of a fault condition. The range push-button switch  13 , which is designated with a letter “R”, operates to let a diver set a desired range or distance limit between the device  10  and other such devices being used by other members of the diver&#39;s diving group. The warning indicator push-button switch  15  allows the diver to select the warning or alert mode that the device  10  will employ in the event that the range set by use of the range push-button switch  13  is exceeded. Two warning modes, either an audible tone or a vibration, may be selected by the diver. Lastly, a Ch/D push-button switch  17  is provided to allow a channel of operation to be selected for the device  10 . Channel changing capability is provided so that interference may be prevented from any other nearby diving groups who may be using the same type of location and communication apparatus. 
     The liquid crystal display  14  provides the diver with informational readouts that relate not only to the above described push-button functions, but also to the positional status of any other device  10  in use by a diving partner. As also shown in FIG. 1, the display  14  has a range readout  14   a  and a direction readout  14   b.  When the device  10  is in operation, the range readout  14   a  registers the the current range limit selected with the range push-button switch  13 , and the direction readout  14   b  indicates approximate direction of other diving partners having a device  10  in operation. The display  14  also has an active alarm readout  14   c  that is displayed when warning push-button switch  15  has been used to select one of the two alarm modes. Operating channel selected with Ch/D push-button switch  17  is registered on Ch/D readout  14   d.  Display  14  is also provided with a low-battery readout  14   e  that becomes visible when the power level of the batteries diminishes below a predetermined level. 
     In addition to the above described predominantly external features that comprise the device  10  of the present invention, certain internal electronic means also contribute to the unique capabilities of the present invention. Such means, which are shown schematically in FIG. 5, include a microcontroller circuit  30  and an ultrasonic transceiver circuit  40 . The microcontroller circuit  30  includes an Integrated Circuit (IC), U 1 , that is a microcontroller based upon the 8051 family of microcontrollers. The microcontroller U 1  serves as a low cost solution for handling all the complex operations of the present invention. The microcontroller U 1  sets up the operation parameters for a LCD driver U 2 , an analog MUX U 7  and an adaptive band pass filter U 8 . (U 7  and U 8  are shown in transceiver circuit  40 .) The microcontroller U 1  generates the carrier frequency of operation, provides a user interface, activates the warning indicators, and establishes the communication frame work of the present invention. 
     As previously stated, the present invention uses ultrasound to determine distance between the devices  10 . The microcontoller U 1  generates the desired carrier frequency by toggling pin  41  (shown in FIG. 6) on and off at the selected rate. Encoded on this carrier frequency are the device numbers of the querying device  10  and another device  10 . All the other co-channel devices  10  will receive this signal, but only the device  10  identified by this device number will respond. The distance between the querying device  10  and the responding device  10  is correlated by the amount of time it takes for the querying device  10  to receive a signal from the responding device  10 . Each co-channel device  10  queries all the other co-channel device&#39;s  10  on an individual basis for distance measurement. 
     The liquid crystal display  14 , is controlled by the LCD driver U 2 , and LCD driver IC. The liquid crystal display  14  indicates range limit  14   a,  device number  14   d  and approximate direction  14   b  of a communicating co-channel device  10 , low battery warning  14   e,  and warning indication type  14   c.  The liquid crystal display  14  has electro-luminescent back lighting to illuminate the display  14  in low ambient light. 
     The LCD driver U 2  is programmed by microcontroller U 1  to display the operating parameters of the device  10 . 
     The vibration indicator circuitry (FIG. 6) is comprised of a diode CR 1 , a DC motor M 1  and a resistor R 2 . The motor M 1  is activated when a pin  43  of the microcontoller U 1  outputs a logic 1. The pin  43  is set when the range limit set by the range push-button switch  13  is exceeded and vibration mode is selected by the warning indicator push-button switch  15 . A resistor R 1  limits the current through the motor M 1 , and a capacitor C 1  protects the microcontroller by shunting the reverse electromotive force generated when the motor M 1  is turned off. 
     A speaker SP 1  and resistor a R 3  make up the audible alarm. Speaker SP 1  is a piezoelectric speaker, and it generates a tone when a pin  42  of the microcontoller U 1  toggles between a logic 1 and a logic 0. The pin  42  will activate when the range limit is exceeded and audible alarm is selected. The speaker SP 1  will also generate a tone when the device  10  is first turned on to indicate that the device  10  is operational. 
     An Electronically Erasable Programmable Read Only Memory (EEPROM) is shown in FIGS. 5 and 7. The EEPROM U 3  stores all parameter settings of the device  10 , and retains them when the device  10  is turned off (non-volatile). 
     A four bit binary counter U 4  (FIGS. 5 and 6) divides the master clock frequency of 16 MHZ (established by capacitor C 1 , capacitor C 2 , crystal X 1 , and microcontroller U 1 ) to 2 MHz. This 2 MHz signal is used to set up the sampling rate of the adaptive, bandpass filter U 8 . 
     A DC to DC converter U 5 , with the help of the supporting microncontoller circuit  30 , boosts the +3 Vdc battery voltage to a regulated +12 Vdc. The +12 Vdc energizes the ultrasonic transceiver circuit  40 . 
     The circuit of the ultrasonic transceiver  40  shown in FIGS. 5 and 7 illustrates the transmitter and receiver sections of the device  10 . 
     The transmitter section is comprised of operational amplifier U 6 :A and a plurality of piezoelectric transducers TX 1  through TX 5 . Amplifier U 6 :A amplifies a carrier signal generated by the microcontroller U 1 . The plurality of piezoelectric transducers TX 1  through TX 5  convert the amplified carrier signal to a sound wave. This sound wave will propagate through the water to the other devices  10  units for detection by their receivers. 
     The receiver section is comprised of: a plurality of piezoelectric transducers, RX 1  through RX 5 ; an analog multiplexer U 7 ; a plurality of operational amplifiers, U 6 :B, U 6 :C and a U 6 :D; and switched capacitor, bandpass filter, U 8 . 
     In operation, the sound wave is detected by the plurality of piezoelectric transducers, RX 1  through RX 5 . The transducers RX 1  through RX 5  convert the sound wave into an electrical signal. An analog multiplexer U 7  under the control of the microcontroller U 1 , connects one of the transducer signals to the amplifier section (U 6 :B and U 6 :C). The microcontroller U 1  tells multiplexer U 7  to use the transducer that provides the strongest signal to amplifier U 6 :D. Amplifier&#39;s U 6 :B and U 6 :C provide a 400 to 1 signal amplification (gain). Automotive Gain Control (AGC) is provided by the diodes CR 3  through CR 6  to prevent the amplifier from saturating. The band pass filter U 8  provides the adaptive filter function. It tunes the receiver to the proper channel and attenuates all other channel frequencies. Amplifier U 6 :D acts as a voltage comparator. It only detects carrier signals that exceed a trip level set by the resisters R 22  and R 23  and converts them into a digital signal for the microcontoller U 1  to interpret. The diode CR 7  clips this digital signal to an appropriate level for the microcontroller U 1 . 
     The microcontroller U 1  contains a computer software program that controls the device  10 . The software functions in accordance with the following description. Upon activation, the software of the device  10  activates both warning indicators (speaker SP 1  and motor M 1 ) and all elements  14   a - 14   e  of the liquid crystal display  14  to demonstrate that all portions of the device  10  are operational. Then the program reads the parameters stored in the EEPROM (U 3 ) and echoes them to the liquid crystal display  14 . During the first 15 seconds after power up, the program allows the diver to enter channel frequency, device number, range limit, and warning indication type. After the initial 15 seconds have expired, the program stores the new parameters in the EEPROM U 3 . Next the program determines how many co-channel devices  10  there are by querying each device  10 . Devices  10  that respond will have their device numbers stored. This operation will take about 10 seconds to complete. Once the initialization portion is complete, the program executes normal operation of the device  10 . 
     Each device  10  polls other co-channel Devices  10  by sending out a stream of ultrasonic pulses. Encoded in the ultrasonic pulse stream are the device numbers for the querying and responding devices  10 . The device numbers are three bit binary numbers. These two device numbers are encoded into the ultrasonic pulse stream. The encoded format is 16 pulses for a logic 0 and 20 pulses for a logic 1 with a “dead time” between pulse groups to identify individual bits. The microcontroller U 1  of the responding device  10  sends out a response in the same format. The amount of time it takes for the querying unit to receive a response is translated into a distance. If the distance exceeds the set range limit, a fault is registered and an alarm is activated. The software incorporates a delay which prevents the querying device  10  from responding to an echo of its own signal. 
     The microcontroller U 1  polls each receiving transducer RX 1  through RX 5  to see which transducer is receiving an adequate signal for communication and locks into that transducer. The direction indicator  14   b  on the liquid crystal display  14  shows which of the receiving transducers RX 1  through RX 5  is providing detection. The transducers RX 1  through RX 5  are only somewhat directional, so the direction indicator  14   b  is not precise. It is only an approximation. The microcontroller U 1  briefly polls the other receiving transducers to ensure tracking of the transmitting Device  10 . 
     The polling sequence of the co-channel device  10  starts with device  1  talking to the device recognized as device number  2 , then the device recognized as device number  3  etc. up to the device recognized as device number  8 . Device number  2  performs the same polling sequence, starting with device number  1  and ending with device number  8 . What effectively happens is each device  10  talks to the other devices  10  in a numerical sequence. This method of polling ensures no diver has exceeded the present range limit. If one has, all devices  10  will register a fault and activate an alarm. 
     The pulse stream format emitted from each device  10  will appear like the following: 
     &lt;Querying Device No.&gt;&lt;Responding Device No.&gt;Alarm 
     --XXXXXX---XXXXXX---XXXXXX---XXXXXX----XXXXXX---XXXXX---- 
     The X&#39;s indicate carrier present. As the device number is a three bit binary number defined by ones and zeroes, it is used to modulate, or control the carrier signal. There will be either 16 carrier oscillations for a logic 0 or 20 carrier oscillations for a logic 1. The ‘--’ indicates no carrier present. This allows the microcontroller U 1  to distinguish between each bit. The “Alarm” portion of the stream functions as a means of communicating to other devices  10  that a fault has been detected. The receiving devices  10  will activate their alarms to indicate a fault to all the other divers. 
     On the receiver side of the device  10 , the software tells the microcontroller U 1  to monitor the pin  16  of U 1 . The software counts the number of pulses in the stream to determine the code sent. As previously stated, the pauses between the bits will help the microcontroller U 1  distinguish them. After “demodulating” the carrier signal, the responding device  10  will send a similar pulse stream back to the querying device  10 . Once the querying device  10  receives this signal, it will determine the distance between it and the responding device  10  by analyzing the elapsed time from transmission to reception. Again, if the limit has been exceeded, an alarm will be activated. 
     While the preferred embodiment of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.