Self-monitoring battery operated circuit

Abstract

Time pulse generator having biasing means therefor including a control device, which may be a transistor and means interconnecting the biasing means to the battery being monitored. The output of the time pulse generator is utilized to drive a signaling device to indicate a low level of battery energy and/or an alarm condition as detected by an external condition sensor.

What is claimed is: 
     
       1. Battery operated electronic detection apparatus, comprising: a set of electrical terminals for connection to the terminals of a battery power source;   battery powered means for sensing a selected condition .Iadd.external to said apparatus .Iaddend.and generating a first electrical signal representative of said condition, said sensing means being connected to receive power from said electrical terminals whereby to be powered by .[.a.]. .Iadd.said .Iaddend. battery power source connected thereto, .Iadd.a common portion of .Iaddend.said sensing means also being responsive to the output voltage of .[.the.]. .Iadd.said .Iaddend. battery power source connected to said electrical terminals to generate a second electrical signal whenever said output voltage falls below a predetermined level; and,   battery powered alarm means .Iadd.including only a single alarm giving device .Iaddend. connected to receiver power from said electrical terminals whereby to be also powered by .[.the.]. .Iadd.said .Iaddend.battery power source connected thereto, said alarm means being connected to said .Iadd.common portion of said .Iaddend.sensing means to be driven by either said first or second electrical signal and being operable to generate .[.an.]. .Iadd.a respective .Iaddend.alarm signal corresponding to .Iadd.and indicating .Iaddend.the .Iadd.particular .Iaddend.electrical signal by which it is driven.   
     
     
       2. The invention defined in claim 1 wherein: said selected condition sensed by said sensing means is the clarity of air; and,   said sensing means includes ion chamber means for sensing air clarity, said ion chamber means being operable to control current flow therethrough as a function of the clarity of the air being monitored therein.   
     
     
       3. The invention defined in claim 2, wherein said sensing means includes a field effect transistor, said sensing means being operable to generate said first and second electrical signals by controlling the current flow through the drain-source current path of said field effect transistor as a function of, respectively, the intensity of said selected condition being sensed and the level of the output voltage of the battery power source connected to said electrical terminals. 
     
     
       4. The invention defined in claim 3, wherein said sensing means includes: sensor means for sensing said selected condition and generating an electrical control signal corresponding thereto, the gate electrode of said field effect transistor being connected to receive said control signal whereby the electrical resistance of the drain-source current path of said field effect transistor varies as a function of the magnitude of said control signal; and,   a first transistor having its emitter-collector current path connected as current control device in series with said drain-source current path, the base electrode of said first transistor being connected to monitor the output voltage of the battery power source connected to said electrical terminals whereby to control the current flow through said series connected emitter-collector and drain-source current paths as a function of the level of said output voltage.   
     
     
       5. The invention defined in claim 4, wherein: said alarm means includes a horn connected in series with the anode-cathode current path of a silicon controlled rectifier; and including:   resistor means having a voltage pickoff connected in series with the drain-source current path of said field effect transistor whereby to generate a voltage signal on said voltage pickoff proportional to the current flow through said drain-source current path; and,   a second transistor connected as an amplifier between said voltage pickoff and the gate electrode of said silicon controlled rectifier said second transistor being operable to generate and apply said first and second electrical signals to said control electrode by amplifying the voltage signal appearing on said voltage pickoff.   
     
     
       6. The invention defined in claim 5, including a capacitor connected between the control electrode of said silicon controlled rectifier and the base electrode of said first transistor, said capacitor being discharged through said silicon controlled rectifier whenever the anode-cathode current path of said silicon controlled rectifier is triggered into conduction by the generation of either said first or second electrical signal on said control electrode, the discharge of said capacitor being operable to apply a feedback pulse to the base electrode of said first transistor which biases the emitter-collector current path of said first transistor into a substantially nonconductive state. 
     
     
       7. The invention defined in claim 1, wherein said first and second electrical signals generated by said sensing means are distinctly different so that the alarm signal generated by said alarm means in response to said first electrical signal is noticeably different from the alarm signal generated in response to said second electrical signal. 
     
     
       8. The invention defined in claim 7, wherein: said first electrical signal is a first pulse train having a pulse spacing inversely proportional to the intensity of said selected condition being sensed; and,   said second electrical signal is a second pulse train having a pulse spacing noticeably greater than the pulse spacing of said first pulse train and a pulse width noticeably shorter than the pulse width of said first pulse.   
     
     
       9. Battery powered electronic detection apparatus, comprising: a set of electrical terminals for connection to the terminals of a battery power source;   battery powered first means for sensing a selected condition .Iadd.external to said apparatus .Iaddend.and generating a first electrical signal representative of said condition, said first means being connected to receiver power from said electrical terminals whereby to be powered by .[.a.]. .Iadd.said .Iaddend.battery power source connected thereto;   battery powered second means responsive to the output voltage of .[.the.]. .Iadd.said .Iaddend.battery power source connected to said electrical terminals for generating a second electrical signal whenever said output voltage falls below a predetermined level, said second means being connected to receive power from said electrical terminals whereby to be also powered by .[.the.]. .Iadd.said .Iaddend.battery power source connected thereto; and,   battery powered alarm means .Iadd.including only a single alarm giving device .Iaddend.connected to receive power from said electrical terminals whereby to be powered by .[.the.]. .Iadd.said .Iaddend.battery power source connected thereto, said alarm means .Iadd.device .Iaddend.being connected to .Iadd.a common portion of .Iaddend.said first and second means to be driven by either said first or second electrical signal and being operable to generate .[.an.]. .Iadd.a respective .Iaddend.alarm signal corresponding to .Iadd.and indicating .Iaddend.the .Iadd.particular .Iaddend.electrical signal by which it is driven. .Iadd. 10. Apparatus as defined in claim 1 which further includes means for effecting pulsation of said alarm means device when driven by said second electrical signal. .Iaddend..Iadd. 11. Apparatus as defined in claim 10 in which the frequency of pulsation of said alarm means device increases in proportion to the amount of fall of said output voltage below said predetermined level. .Iaddend. .Iadd. 12. An electronic detection apparatus adapted to be powered from the terminals of a single source of battery power, said electronic detection apparatus comprising:   a set of electrical terminals connected to the terminals of said source of battery power;   first means for sensing a selected condition external to said apparatus and generating a first electrical signal representative of said condition;   second means for generating a second electrical signal whenever the output voltage of said source of battery power falls below a predetermined level;   alarm means connected to said first and second means and responsive to either said first or said second electrical signal to generate an alarm signal indicating which of said first and second electrical signals it is responding to; and,   means connecting said first and said second means and said alarm means to said set of electrical terminals whereby said first and said second means and said alarm means are all powered only by said single source of battery power through said set of electrical terminals..Iaddend..Iadd. 13. An electronic detection apparatus as claimed in claim 12 wherein said first and said second means include common circuit means common to said first and said second means and through which said first and second electrical signals are generated, said alarm means being connected to said common circuit means. .Iaddend..Iadd. 14. An electronic detection apparatus comprising:   a set of electrical terminals adapted for connection to the terminals of a battery power source;   first means for sensing a selected condition external to said apparatus and generating a first electrical signal representative of said condition;   second means for generating a second electrical signal whenever the output voltage of said battery power source falls below a predetermined level;   alarm means connected to said first and second means and responsive to said first or said second electrical signal to generate an alarm signal indicating which of said first and second electrical signals it is responding to; and,   means connecting said first and said second means and said alarm means to said set of electrical terminals whereby said first and said second means and said alarm means are all powered by said battery power source;   said first and said second means including common circuit means common to said first and said second means and through which said first and said second electrical signals are generated, said alarm means being connected to said common circuit means. .Iaddend..Iadd. 15. An electronic detection apparatus as claimed in claim 14 wherein said common circuit means includes at least one active circuit element for generating said first and second electrical signals, said alarm means being connected to the output of said active circuit element. .Iaddend..Iadd. 16. An electronic detection apparatus as claimed in claim 15 wherein said active circuit element is a semiconductor device. .Iaddend..Iadd. 17. An electronic detection apparatus as claimed in claim 14 wherein said common circuit means includes first amd second active circuit elements connected to each other and through which said first and said second electrical signals are generated, said alarm means being connected to one of said active circuit elements. .Iaddend..Iadd. 18. An electronic detection apparatus as claimed in claim 17 wherein said first and second active circuit elements are semiconductor devices. .Iaddend..Iadd.19. An electronic detection apparatus as claimed in claim 14 wherein said common circuit means includes first, second, and third active circuit elements through which said first and said second electrical signals are generated, said first and said third active circuit elements being connected to said second active circuit element and said alarm means being connected to said first active circuit element. .Iaddend..Iadd. 20. An electronic detection apparatus as claimed in claim 19 where said first, second and third active circuit elements are all semiconductor devices. .Iaddend. .Iadd. 21. An electronic detection apparatus adapted to be powered from the terminals of a single source of battery power, said electronic detection apparatus comprising:   a set of electrical terminals connected to the terminals of said source of battery power;   first means for sensing a selected condition external to said apparatus and generating a first electrical signal representative of said condition;   second means for generating a second electrical signal whenever the output voltage of said source of battery power falls below a predetermined level;   alarm means connected to said first and second means and responsive to either said first or second electrical signal to generate an alarm signal indicating which of said first and second electrical signals it is responding to; and,   
     
     
       means connecting said first and said second means and said alarm means to said set of electrical terminals whereby said first and said second means and said alarm means are all powered only by said single source of battery power through said set of electrical terminals; said alarm means including a single alarm device, said single alarm device being responsive to said first electrical signal for generating a first alarm signal and said single alarm device being responsive to said second electrical signal for generating a second alarm signal that is distinct   
     
     
        from said first alarm signal. .Iaddend..Iadd. 22.  An electronic detection apparatus adapted to be powered from the terminals of a single source of battery power, said electronic detection apparatus comprising: a set of electrical terminals connected to the terminals of said source of battery power;   first means for sensing a selected condition external to said apparatus and generating a first electrical signal representative of said condition;   second means for generating a second electrical signal whenever the output voltage of said source of battery power falls below a predetermined level;   alarm means connected to said first and second means and responsive to either said first or said second electrical signal to generate an alarm signal indicating which of said first and second electrical signals it is responding to; and,   means connecting said first and said second means and said alarm means to said set of electrical terminals whereby said first and said second means and said alarm means are all powered only by said single source of battery power through said set of electrical terminals;   said alarm means comprising a single alarm device and a switch means connected together in series between the electrical terminals of said set of electrical terminals, said switch means being responsive to said first and said second electrical signals for controlling current flow through said single alarm device. .Iaddend. .Iadd. 23. An electronic detection apparatus as claimed in claim 22 wherein said single alarm device comprises: means emitting an audible sound; said first means comprises means producing, as said first electrical signal, a first sequence of electrical pulses at a first repetition rate; and said second means comprises means producing, as said second electrical signal, a second sequence of electrical pulses at a second repetition rate. .Iaddend..Iadd. 24. An electronic detection apparatus as claimed in claim 23 wherein said first repetition rate varies as the severity of said condition varies. .Iaddend.