Alarm circuit for monitoring the amplitude of a-c voltages

Claim 2

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, a circuit output, switching means having an input and an output, said switching means serving as means for establishing a first voltage at the output thereof when the voltage at the a-c input varies outside of predetermined input voltage limits and for establishing a second voltage at the output thereof when the voltage at the a-c input does not vary outside of said input voltage limits, means for connecting the a-c input to the input of the switching means, resetting means for forcing the switching means to establish said first voltage for a preset period following the establishment of said second voltage, means for connecting the Resetting means in voltage responsive relationship to the output of the switching means, means for connecting the resetting means to the switching means to control the reset of the switching means, and output control means connected to the switching means and the resetting means for establishing at the circuit output a voltage which indicates that the voltage at the a-c input has a satisfactory magnitude when the switching means continues to establish said first voltage after the resetting means stops resetting the switching means and for establishing at the circuit output a voltage which indicates that the voltage at the a-c input does not have a satisfactory magnitude when the switching means reestablishes said second voltage within a relatively short time after the resetting means stops resetting the switching means.

Claim 3

A circuit as set forth in claim 1 in which said preset period has a duration greater than the time required for an a-c voltage which has a satisfactory magnitude to vary between said input voltage limits.

Claim 4

A circuit as set forth in claim 1 in which the switching means comprises an operational amplifier having a first input connected to a source of reference voltage and having a second input connected to the a-c input.

Claim 5

A circuit as set forth in claim 1 in which the resetting means comprises a one-shot multivibrator responsive to the voltage at the output of the switching means.

Claim 6

A circuit as set forth in claim 1 in which the output control means comprises a flip-flop and a capacitor and which includes means for charging the capacitor when the resetting means is resetting the switching means, and means for connecting the flip-flop to the switching means and to the capacitor.

Claim 7

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, a circuit output, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the a-c input varies outside of predetermined input voltage limits and for establishing a second voltage at the output thereof when the voltage at the a-c input does not vary outside of said input voltage limits, means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a pulse of predetermined duration at the output thereof each time that said second voltage appears at the output of the comparing means, means for connecting the comparing means to the input of the timing means, means for connecting the timing means to the comparing means to cause the comparing means to establish said first voltage while a pulse appears at the output of the timing means, output control means for establishing at the circuit output a voltage which indicates that the voltage at the a-c input does not have a satisfactory magnitude when the comparing means establishes said second voltage within a relatively short time after the end of a pulse from the timing means, and means for connecting the output control means to the circuit output, to the comparing means and to the timing means.

Claim 8

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, a circuit output, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the a-c input varies outside of predetermined input voltage limits and for establishing a second voltage at the output thereof when the voltage at the a-c input does not vary outside of said input voltage limits, means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a pulse of predetermined duration at the output thereof each time that said second voltage appears at the output of the comparing means, means for connecting the comparing means to the input of the timing means, means for connecting the timing means to the comparing means to cause the comparing means to establish said first voltage while a pulse appears at the output of the timing means, output control means for establishing at the circuit output a voltage which indicates that the voltage at the a-c input does not have a satisfactory magnitude when the comparing means establishes said second voltage within a relatively short time after the end of a pulse from the timing means, and means for connecting the output control means to the circuit output, to the comparing means and to the timing means.

Claim 9

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, a circuit output, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the a-c input exceeds predetermined input voltage limits and for establishing a second voltage at the output thereof when the voltage at the a-c input does not exceed said input voltage limits, means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a timing pulse of preset duration at the output thereof after said second voltage appears at the output of the comparing means, means for connecting the output of the comparing means to the input of the timing means, switching means for forcing the comparing means to establish said first voltage during the time that a pulse appears at the output of the timing means, means for connecting the switching means to the comparing means and to the output of the timing means, storage means for establishing a voltage indicative of the occurrence of each of the timing pulses for a predetermined time after the termination of each of the timing pulses, means for connecting the storage means to the output of the timing means, output control means for applying to the circuit output a voltage which varies in accordance with the voltage across the storage means and the voltage at the output of the comparing means, the output control means being adapted to apply to the circuit output a voltage which indicates that the voltage at the a-c input does not have a satisfactory magnitude when the comparing means energizes the timing means at a time when a substantial voltage remains across the storage means.

Claim 10

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, a circuit output, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the a-c input exceeds predetermined input voltage limits and for establishing a second voltage at the output thereof when the voltage at the a-c input does not exceed said input voltage limits, means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a timing pulse of preset duration at the output thereof after said second voltage appears at the output of the comparing means, means for connecting the output of the comparing means to the input of the timing means, switching means for forcing the comparing means to establish said first voltage during the time that a pulse appears at the output of the timing means, means for connecting the switching means to the comparing means and to the output of the timing means, storage means for establishing a voltage indicative of the occurrence of each of the timing pulses for a predetermined time after the termination of each of the timing pulses, means for connecting the storage means to the output of the timing means, output control means for applying to the circuit output a voltage which varies in accordance with the voltage across the storage means and the voltage at the output of the comparing means, the output control means being adapted to apply to the circuit output a voltage which indicates that the voltage at the a-c input does not have a satisfactory magnitude when the comparing means energizes the timing means at a time when a substantial voltage remains across the storage means.

Claim 11

A circuit as set forth in claim 7 in which said timing means is adapted to produce a pulse having a duration greater than the time required for an a-c voltage which has a satisfactory magnitude to vary between said input voltage limits.

Claim 12

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the input thereof exceeds a predetermined value and for establishing a second voltage at the output thereof when the voltage at the input thereof does not exceed said predetermined value, rectifying means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a pulse of preset duration at the output thereof after said second voltage is established by the comparing means, means for connecting the output of the comparing means to the input of the timing means, switching means for forcing the comparing means to establish said first voltage when a pulse is present at the output of the timing means, means for connecting the switching means to the comparing means and to the output of the timing means, storage means for establishing voltages indicative of the occurrences of each of said pulses for predetermined times after the terminations of each of said pulses, output control means having first and second inputs and an output, the control means serving as means for applying to the output thereof a voltage which indicates an input voltage fault when the storage means applies a substantial voltage to the first input thereof and the comparing means applies a predetermined voltage transition to the second input thereof, means for connecting the storage means to the first input of the output control means and means for connecting the comparing means to the second input of the output control means.

Claim 13

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, comparing means having an input and an output, the comparing means serving as means for establishing a first voltage at the output thereof when the voltage at the input thereof exceeds a predetermined value and for establishing a second voltage at the output thereof when the voltage at the input thereof does not exceed said predetermined value, rectifying means for connecting the a-c input to the input of the comparing means, timing means having an input and an output, the timing means serving as means for establishing a pulse of preset duration at the output thereof after said second voltage is established by the comparing means, means for connecting the output of the comparing means to the input of the timing means, switching means for forcing the comparing means to establish said first voltage when a pulse is present at the output of the timing means, means for connecting the switching means to the comparing means and to the output of the timing means, storage means for establishing voltages indicative of the occurrences of each of said pulses for predetermined times after the terminations of each of said pulses, output control means having first and second inputs and an output, the control means serving as means for applying to the output thereof a voltage which indicates an input voltage fault when the storage means applies a substantial voltage to the first input thereof and the comparing means applies a predetermined voltage transition to the second input thereof, means for connecting the storage means to the first input of the output control means and means for connecting the comparing means to the second input of the output control means.

Claim 14

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, an operational amplifier having an input and an output, the operational amplifier serving as means for establishing a first voltage at the output thereof when the voltage at the input thereof exceeds a predetermined reference voltage and for establishing a second voltage at the output thereof when the voltage at the input thereof does not exceed said predetermined reference voltage, rectifying means for connecting the a-c input to the operational amplifier, a timing network having an input and an output and serving as means for establishing a pulse at the output thereof each time that an energizing voltage is applied to the input thereof, means for connecting the output of the operational amplifier to the input of the timing network, a flip-flop having first and second inputs and an output, switching means for forcing the operational amplifier to establish said fiRst voltage while a pulse appears at the output of the timing network, means for connecting the switching means to the operational amplifier and to the output of the timing network, a capacitor adapted to charge during the times that pulses appear at the output of the timing network and adapted to discharge within preset times after the terminations of said pulses, means for connecting the capacitor to the first input of the flip-flop and means for connecting the operational amplifier to the second input of the flip-flop, the flip-flop serving to establish at the output thereof a voltage which indicates an input voltage fault when the capacitor applies a substantial voltage to the first input of the flip-flop and the output of the operational amplifier undergoes a transition from the first voltage to the second voltage.

Claim 15

In a circuit for detecting whether an a-c voltage has a satisfactory magnitude, in combination, an a-c input, an operational amplifier having an input and an output, the operational amplifier serving as means for establishing a first voltage at the output thereof when the voltage at the input thereof exceeds a predetermined reference voltage and for establishing a second voltage at the output thereof when the voltage at the input thereof does not exceed said predetermined reference voltage, rectifying means for connecting the a-c input to the operational amplifier, a timing network having an input and an output and serving as means for establishing a pulse at the output thereof each time that an energizing voltage is applied to the input thereof, means for connecting the output of the operational amplifier to the input of the timing network, a flip-flop having first and second inputs and an output, switching means for forcing the operational amplifier to establish said fiRst voltage while a pulse appears at the output of the timing network, means for connecting the switching means to the operational amplifier and to the output of the timing network, a capacitor adapted to charge during the times that pulses appear at the output of the timing network and adapted to discharge within preset times after the terminations of said pulses, means for connecting the capacitor to the first input of the flip-flop and means for connecting the operational amplifier to the second input of the flip-flop, the flip-flop serving to establish at the output thereof a voltage which indicates an input voltage fault when the capacitor applies a substantial voltage to the first input of the flip-flop and the output of the operational amplifier undergoes a transition from the first voltage to the second voltage.

Claim 16

A circuit as set forth in claim 10 in which the flip-flop is a D-type flip-flop, in which said first input of the flip-flop is the signal input thereof, and in which said second input of the flip-flop is the clock input thereof.

Claim 17

A circuit as set forth in claim 10 in which the operational amplifier has a strobe input and in which the switching means comprises a transistor connected to the strobe input and adapted to conduct during the times that pulses appear at the output of the timing network.

Claim 18

A circuit as set forth in claim 10 in which said timing network is adapted to produce an output pulse having a duration greater than the time required for an a-c voltage which has a satisfactory magnitude to vary between a positive value in excess of the reference voltage and a negative value in excess of the reference voltage.