referring to fig1 a through 1f , there is shown in schematic form a drawing of the monitoring module of a first preferred embodiment of the present invention . in normal operation , the monitoring module is either physically connected to a bed pad through its legacy monitoring connection , or physically connected to an improved pad that contains an embedded data generator module of the present invention , or connected wirelessly to a transmitter module of the present invention ( which is , in turn , connected physically to the pad and continuously monitoring its physical connection with the pad ). in fig1 b it can be seen that microcontroller u 4 is the heart of the monitoring module , providing all system control . the software operating on microcontroller u 4 dictates the actions of the system based on the inputs to microcontroller u 4 . the microcontroller input signals include the following : pin 7 ( ra 1 ) of microcontroller u 4 is an input that detects low battery conditions , wherein an the alarm triggers at approximately 7 vdc . pin 12 ( rb 2 ) of microcontroller u 4 is an input that detects loss of ac power through the well - known technique shown in the circuit diagram . pin 9 ( ra 3 ) of microcontroller u 4 is an input that detects the condition of switch sw 3 ( reset button ) to reset the monitoring module after an alarm has been triggered . it should be noted that a magnetic switch connected at connector j 8 ( con 2 ) can be used to reset the monitoring module when the manual reset switch has been disabled via switch sw 1 . the magnetic reed switch can only be closed by a ‘ caregiver key ’ since only a caregiver has the magnetic key necessary to reset the monitoring module when switch sw 1 is set to disable the manual reset button sw 3 . switch sw 4 allows the selection of one of three tone signal types available on the monitoring module ( one , two or three - pulse sounds ). the output sounds and indicators provided by the monitoring module are driven by the software operating on microcontroller u 4 , and include the following : relay k 1 is available to trigger external ‘ dry contact ’ detection alarm systems . a buzzer or speaker connected at jack j 7 sounds when an alarm is triggered . the volume level of the alarm sound is adjustable using variable resistor vr 1 . the software operating on microprocessor u 4 determines the number of alarm sound ‘ pulses ’ emitted for each type of alarm condition . led d 1 (‘ check pad ’) is illuminated to indicate to a local observer ( i . e ., a caregiver ) that there is a problem with the connection to the pad , or with the pad itself . pursuant to the program logic of the software operating on microcontroller u 4 , whenever microcontroller u 4 illuminates led d 1 , the buzzer or speaker connected to jack j 7 also sounds once to alert a local observer ( i . e ., a caregiver ). led d 2 (‘ status / in use ’) is illuminated to indicate to a local observer ( i . e ., a caregiver ) that the patient is on the pad and that the system is working correctly . led d 3 (‘ alarm led / low battery ’) is illuminated to indicate to a local observer ( i . e ., a caregiver ) that an alarm is active or that the battery needs to be changed . note that led d 3 illuminates in this condition even if the monitoring module sound is turned off . power is provided to the circuits of the monitoring module through the power regulation and filtering section comprised of capacitors c 13 , c 14 , c 15 , c 16 and c 17 , diodes d 9 and d 10 and voltage regulator u 7 . the output of voltage regulator u 7 is a regulated and filtered 9 vdc constant voltage source . a battery pack connected to jack j 6 provides emergency backup power when ac power fails or is disconnected . a commercial ac - to - 9 vdc ‘ wall wart ’ power adaptor is connected to dc power input connection jack j 5 to provide power to the monitoring module from the commercial ac power source . jack j 1 ( con 4 ) provides a wired connection between the monitored bed pad and the monitoring module circuit . unlike most units this connection is not a simple dc loop testing input connected to the pressure pad , but has the following additional features : the wired connection of jack j 1 includes two input - only pins ( pin 3 and 4 ), one output pin ( pin 2 ) and one vdd source ( pin 1 ). pin 3 of jack j 1 is connected through resistor r 16 to pin 8 ( ra 2 ) of microcontroller u 4 . microcontroller u 4 thus monitors the conditions present on pin 3 of jack j 1 . pin 3 of jack j 1 is also connected ( via the wired connection to the pad ) to one side of the pad &# 39 ; s internal alarm loop circuit , which , in prior art pads is always short - circuited ( or a non - open circuit ) to pin 2 of the pad &# 39 ; s connector when the pad is properly connected to the monitoring module . pin 2 of jack j 1 is connected via isolation resistor r 2 to pin 15 ( rb 5 ) of microcontroller u 4 . microcontroller u 4 can either transmit a digital signal to the pad on pin 2 of jack j 1 , or generate a dc voltage on the pin . in the event a digital signal is imposed onto pin 2 of jack j 1 , microcontroller u 4 is set to expect and detect the same signal looped to itself via the internal circuit of the pad and back through pin 3 of jack j 1 . if the signal is not seen looped back , microcontroller u 4 of the monitoring module causes an alarm to be emitted . when an analog dc voltage is imposed onto pin 2 of jack j 1 , microcontroller u 4 is set to expect and detect a voltage looped to itself via the pad internal circuit and back through pin 3 of jack j 1 . if the original voltage ( or some predetermined residual amount of that voltage ) is not seen looped back , microcontroller u 4 of the monitoring module causes an alarm to be emitted . another solution is simply detecting on pin 2 of jack j 1 the looped bad vcc signal from pin 1 . this is looped back by a connection on the pad and is not present if the pad is removed . when the monitoring module is connected to an improved pad having the embedded data generator module of this invention ( illustrated in fig3 ), pin 4 of jack j 1 on the monitoring module receives the data signal sent through the connections between the pad and the monitoring module by the embedded data generator module . pin 4 of jack j 1 is connected through resistor r 18 to pin 10 ( rb 0 ) of microcontroller u 4 . microcontroller u 4 is set to expect and detect the digital signal continuously through this path . if the signal is not seen for some predetermined amount of time , microcontroller u 4 of the monitoring module causes an alarm to be emitted . the circuit actually shows a memory chip ( but other chips such as processors can be used ). in this case pin 1 = vcc , pin 2 = 0v , pin 3 = clock to synchronize data , pin 4 = data ( in and out ). the bed monitor processor sends data to the memory chip and then reads back to make sure it is still in the circuit . it also updates the chip for the countdown timing function in the cpi bed monitor . when the monitoring module is monitoring the pad via the wireless transmitter module ( shown in fig2 a through 2d ) that is physically connected to the pad , the monitoring module expects to receive a wireless transmission regularly from the wireless transmitter module . if the wireless signal ( modulated with data containing the correct digital address ) is not detected within a predetermined amount of time , the monitoring module issues a ‘ check pad ’ alarm . in this arrangement , the monitoring module has a receiver module connected to jack j 2 . the baseband signal of the receiver is passed to programmable logic device u 3 , which acts as a decoder chip that retrieves the digital information from the received wireless signal and sends the results to microcontroller u 4 for interpretation . microcontroller u 4 is configured to stay in low current consumption mode until an interrupt is received from programmable logic device u 3 to reduce power consumption . at least one component of the digital content of the wireless signal is the digital address of the wireless transmitting module . in this manner , the wireless transmission received can be verified as coming from the transmitter module of interest . in order to avoid transmitted signal collisions when more than one system is used in close proximity ( within wireless signal range of each other ), the time between transmissions is different for each transmitter module , depending on the unique digital address programmed into the memory of each transmitter module . regardless of which of the possible operating configurations are chosen , the checks for proper connection between the pad and the monitoring module are made continuously from the time the monitoring module is powered up , so a caregiver can know the status of the monitoring system as a whole before a patient is even placed on a bed pad . referring next to fig2 a through 2d , there is shown a circuit diagram of the transmitter module used in the present invention . the transmitter module is controlled by software operating on microcontroller u 2 . as an alternative , a transceiver may be used on both the bed monitor and pad wireless pad unit . this would allow for two way communication and frequency channel hopping to overcome interference problems . in normal operation the transmitter module is physically connected ( via jack con 2 and jack j 1 ( con 6 )) to the bed pad being monitored . microcontroller u 2 of the transmitter module continuously checks the integrity of the physical connection between the bed pad and the transmitter module . as long as physical connection between the bed pad and the transmitter module is proper , microcontroller u 2 regularly causes the transmitter module connected to jack j 3 to emit wireless signals modulated with data that include the unique digital address of the transmitter module . in this condition , microcontroller u 2 also regularly illuminates led 1 to indicate that the connection is good . if the physical connection between the bed pad and the transmitter module is broken or fails , microcontroller u 2 stops causing the transmitter to emit wireless signals , and also stops illuminating led 1 , thus indicating the failure . still referring to fig2 b , it can be seen that microcontroller u 2 is able to detect the conditions of the connection between the transmitter module and the pad in a manner similar to that used by the monitoring module . pin 2 of jack j 1 is used by microcontroller u 2 to send a digital signal to the pad , which is looped back via the pad &# 39 ; s internal circuit to pin 3 of jack j 1 . pin 3 of jack j 1 is connected via isolation resistor r 4 to pin 17 ( ra 0 ) of microcontroller u 2 , so that microcontroller u 2 can monitor whether the digital signal sent out on pin 2 of jack j 1 arrives back intact at pin 3 of jack j 1 . if the digital signal is not seen at pin 3 of jack j 1 for more than a predetermined amount of time , the condition is interpreted by microcontroller u 2 as a failure of the connection or the pad itself . still referring to fig2 c , it can also be seen that power is provided to the transmitter module by two lithium button cell batteries through their connection with jack j 4 . these cells have sufficient power storage to last between two and three years under normal operating conditions . referring now to fig3 , there is shown a schematic circuit diagram of a data generator module that can be incorporated into a bed pad sensor . in normal operation , this module is connected to jack j 1 of the monitoring module via a wired connection . in this configuration , any digital signals generated by the monitoring module that are received on pin 2 of jack j 2 ( con 4 ) of the data generator module are shunted to ground . pin 1 of jack j 2 ( con 4 ) of the data generator module is used to receive the power source ( vcc ) for chip u 1 of the module . chip u 1 of the data generator module , when powered up by the presence of vcc , continuously generates a repeating data pattern at pin 4 of jack j 2 ( con 4 ), as well as continuously generating a clock signal at pin 3 of jack j 2 . in order to verify that the connection between the monitoring module and the pad is good , the monitoring module can continuously monitor these signals due to the pin - for - pin connection between jack j 2 ( con 4 ) of the data generator module and jack j 1 of the monitoring module . although the above is a possible solution in this diagram , the eeprom memory chip has data programmed into it and this is addressed serially by the clock ( 3 ) and data ( 4 ) pins . this can be to read out data from the memory chip or to program / update data on the memory chip . this is how the count down is done on the cpi monitor ; that is , the monitor reads in the number decreases by one and programs it back into the chip . however , it also means that if the monitor is not able to read the chip , then there is a fault and the pad has likely been removed . in the ways described above , the present invention provides a sensor connection integrity monitoring system that is significantly improved over the prior art , offering a substantial benefit to the user by preventing undetected system failures . the above disclosure is sufficient to enable one of ordinary skill in the art to practice the invention , and provides the best mode of practicing the invention presently contemplated by the inventor . while there is provided herein a full and complete disclosure of the preferred embodiments of this invention , it is not desired to limit the invention to the exact construction , dimensional relationships , and operation shown and described . various modifications , alternative constructions , changes and equivalents will readily occur to those skilled in the art and may be employed , as suitable , without departing from the true spirit and scope of the invention . such changes might involve alternative materials , components , structural arrangements , sizes , shapes , forms , functions , operational features or the like . therefore , the above description and illustrations should not be construed as limiting the scope of the invention , which is defined by the appended claims .
a circuit and method for providing an improved bed pad , seatbelt or floor mat sensor monitoring system with the ability to detect a connection failure between the monitoring module and the target sensor by monitoring the connection for loss of data being transmitted or returned by the sensor .