Condition indicator for appliance

3,480,940

Nov. 25, 1969

Z.· LIESER

CONDITION INDICATOR FOR APPLIANCE

Filed Dec. 14, 1966

CENTRALLY located ZESPOUDER

<img file="US3480940A_D0001.tif" />

United States Patent Office

3,480,940

Patented Nov. 25, 1969

3,480,940

CONDITION INDICATOR FOR APPLIANCE Zeev Lieser, New York, N.Y., assignor to RCA

Corporation, a corporation of Delaware Filed Dec. 14, 1966, Ser. No. 601,766

Int. CI. G08b 21/00,1/08

U.S. CI. 340—253 9 Claims

This invention relates to an apparatus for indicating, locally or remotely, the operativeness of an appliance which when properly operative draws power periodically from an electrical supply. Such appliances include refrigerators and freezers.

If the power supply of an appliance such as a freezer or refrigerator is interrupted for too long a period of time, or if the appliance is disabled in such a manner that it can draw no power from the power supply for an excessive period of time, the food stored in the appliance, if it is a freezer or refrigerator, will spoil. An indicator that merely shows that the appliance is drawing power is insufficient to show cessation of the operation of the appliance, since in its normal operation, such an appliance does not draw current continuously. Therefore, an indication that the appliance is not drawing current is a false indication of inoperativeness during periods of time when the appliance would not normally draw current.

It is an object of this invention to provide an improved indicator of improper operation of an appliance which only draws current periodically from a power supply.

Another object of this invention is to provide an indicator of improper operation of an appliance which will not indicate improper operation during normally occurring periods when the appliance is not drawing power.

Another object of this invention is to provide an indicator of improper operation of an appliance when the power supply therefor fails for an excessive period of time.

According to this invention, a remote indicator comprises an oscillator of the type whose oscillations can be prevented by applying a stop or blocking voltage to an oscillation blocking input of the oscillator. Means responsive to the power supply is provided to produce this blocking voltage and to apply it to the blocking input of the oscillator to prevent the oscillator from oscillating whereby if the power supply ceases, the blocking voltage also ceases. A stand-by battery is provided to energize the oscillator when the power supply fails, means being provided to charge the stand-by battery while the power supply continues. Further means are provided to charge a delay storage battery only when current is flowing to the appliance. Circuit means are provided whereby when the voltage of the delay storage battery falls below a predetermined minimum due to failure of current to flow to the appliance, the blocking voltage (that is produced from the power supply) is prevented from blocking the oscillations of the oscillator. Therefore, upon failure of the supply voltage, the oscillator, powered by the standby battery, operates to provide an output wave of its predetermined frequency. Furthermore, if the appliance fails to draw sufficient power for proper operation thereof, even though the power supply has not failed, the voltage of the delay storage battery will fall below a predetermined minimum value whereupon the blocking voltage is prevented from blocking the oscillator and the oscillator, powered by the power supply, will provide an output wave. The output wave, when produced is applied back to the power lines and picked up by a centrally located responder. Since the oscillator at any one appliance can be tuned to a frequency different from that at any other appliance, the waves of different frequencies transmitted back to the centrally located responder are characteristic of respective appliances whereby the responder can show which appliance is inoperative. Furthermore, since the power lines carry the oscillations back to the central location, no extra wiring is necessary for proper operation of the system. Where a local indication of operativeness of an electrical appliance that does not draw power continually is desired, a local indicator, such as an alarm, bell or light is substituted for the oscillator and the local indicator is caused to provide a local indication upon failure of the power supply or upon failure of the appliance to draw enough current from an operative power supply to cause the delay battery to be charged above a predetermined minimum.

The invention will be better understood upon reading the following description in connection with the accompanying drawing in which the sole figure is a circuit diagram, partly in block form of one embodiment of the herein described appliance condition indicator.

In the sole figure, the reference character 10 indicates the usual power lines normally found in houses and places of business. Receptacles 12 for the power line are provided at spaced positions along line 10, one of the receptacles 12 being at a central or convenient location for a responder 14 which is plugged into the receptacle 12 in a known manner. Since the responder 14 in itself is not a part of this invention, it is not described in detail. However, the responder 14 includes circuit means to show which one or ones of several frequencies is being received. A plurality of remote indication operation indicators 16, 16α are plugged into respective receptacles 12 by means of leads 18 and 18α and a plurality of appliances 20, 20α are plugged into respective remote indicators 16, 16α, respectively, by means of respective leads 21, 21α. Also a plurality of identical local indicators 16' (only one of which is shown) are plugged into respective receptacles 12. While there may be as many remote indicators 16, 16α and local indicators 16' and appliances 20, 20α and 206 as is desired, only two remote indicators 16, 16α and one local indicator 16' are shown. Since all the remote indicators 16 are identical, except that each indicator 16, 16α applies its own characteristic frequency to the line 10, only one of the remote indicators 16 is further described.

An indicator 16 is plugged into a receptacle 12 by means of leads 18. An appliance 20, which is plugged into the indicator 16 by means of leads 21, draws current periodically from the power line 10 by way of a primary winding of a current transformer 22 forming part of the indicator 16 and connected in series with one of the wires supplying current to the appliance 20. Since the appliance 20 is a conventional one, it is shown merely as a rectangle. Since the primary winding of the transformer 22 exhibits a drop of only about one and one-half volts, its presence has no effect on the operation of the appliance 20. The secondary winding of the transformer 22 is connected between a pair of diode junction points across one diagonal of a rectifier bridge 26 comprising part of the indicator 16. An adjustable battery charge resistor 28 is connected in series with a long life delay storage battery 30 between the other pair of diode junction points across a second diagonal of the bridge 26. Therefore, as long as the appliance 20 is drawing current via leads 21, the battery 30 is being charged. An adjustable battery discharge resistor 34 may be connected across the battery 30. The charging rate of the delay battery 30 may be varied by the adjustment of the resistor 28, and a discharge rate thereof may be varied by adjustment of the discharge resistor 34 to keep the battery voltage above a predetermined minimum value while the appliance 20 is operating in a normal manner. The positive terminal of the battery 30 is connected

3,480,940 through a biasing resistor 36 ot the base of a PNP transistor 38. The emitter of the transistor 38 is connected to a point of reference potential such as ground 52 and to the negative terminal of the delay battery 30. When the battery 30 is charged above a predetermined minimum value, the transistor 38 is biased to cut-off for a purpose to be described.

A conductor of the leads 18 is connected through a ballast resistor 40 and a non-dissipative voltage dropping capacitor 42 to one diagonal terminal of a second rectifier bridge 44. The other conductor of the leads 18 is directly connected to the opposite diagonal terminal of the bridge 44. A resistor 45 is connected across the leads 18 to permit discharge of the capacitor 42 when the leads 18 are disconnected from the receptacle 12. The ballast resistor 40 may be in the form of an incandescent lamp, whereby it acts as an indicator that current is flowing to the bridge 44. The power supply input terminals of an oscillator 46 are connected directly to the remaining or output terminals of the bridge 44. A Zener diode 48 and a power storage stand-by battery 50 are individually connected between the input terminals of the oscillator 46. The battery 50 acts as a large filter capacitor for the rectifier bridge 44 while being trickle charged thereby. The Zener diode 48 acts to protect the battery 50 and the oscillator 46 from overvoltages. The battery 50 is center tapped, and the center tap is connected to ground 52. A switch 54 is shown connected at the positive terminal of the battery 50, and a second switch 54 is shown connected at the negative terminal of the battery 50. These switches 54, 54 are opened when it is desired to store or ship the disclosed indicator 16. A ground terminal 55 of the oscillator 46 is connected to ground 52. The output terminals of the oscillator 46 are connected to the primary winding of a transformer 56 and the terminals of the secondary winding of the transformer 56 are connected through respective blocking capacitors 58, 58 to the leads 18 connected to the receptacle 12. If desired, the terminals of the secondary winding of the transformer 56 may be connected through the respective capacitors 58, 58 directly to the power line 10 rather than by way of the receptacle 12. Therefore, the oscillator will be supplied with power from the power lines 10 when these lines have power applied thereto, at which time the battery 50 is charged, the switches 54 being closed when the indicator 16 is in operation. If power fails in the power lines 10, the battery 50 will supply the oscillator 46. Also, as long as the oscillator 46 oscillates, its output will be applied to the line 10 and to the responder 14 which is plugged into a receptacle 12.

The oscillator 46 is of a known type in which a negative voltage applied to an input terminal 60 causes the oscillator 46 to cease oscillating, while grounding of the input terminal 60 causes the oscillator to oscillate at its own frequency. Means are provided to apply an oscillation blocking potential to the terminal 60. This means comprises a pair of rectifiers 62, 62 whose anodes are connected through a current limiting resistor 64 to the terminal 60 and whose cathodes are connected to the respective terminals of the bridge 44 to which the power leads 18 are connected. Therefore, the rectifiers 62, 62 and the resistor 64 operate normally to apply a potential to the terminal 60 to bias the oscillator 46 into a nonoscillating state. The transistor 38 and its connections are provided to short circuit this blocking bias to ground when the transistor 38 is conductive.

The collector of the transistor 38 is connected to the terminal 60 and the base of the transistor 38 is connected through a current limiting resistor 66 and one of the switches 54 to the negative terminal of the battery 50. The resistor 36 and the resistor 66 comprise a biasing network for the transistor 38. Also, by means of this connection, the diode rectifiers 62, 62 which apply a blocking bias for the oscillator 46, also supply negative operating potential to the collector of the transistor 38. The re4 sistors 36 and 66 act like a voltage divider whereby a portion of the voltage across the delay battery 30 and of the lower half (as viewed in the figure) of the battery 50, that is applied between the base and emitter of the transistor 38, render it non-conductive as long as the voltage of the battery 30 is above the predetermined potential required to block the transistor 38.

When the transistor 38 is held non-conducting, the potential provided by the rectifiers 62, 62 is applied to the oscillator blocking lead 60 to block oscillations of the oscillator 46. When the potential of the delay battery 30 is reduced to the point where the transistor 38 is conductive, the voltage provided by the diodes 62, 62 is shunted through the transistor 38 to ground and the oscillator 46 is permitted to oscillate.

When leads 18 are plugged into the receptacle 12 and the leads 21 are plugged into the indicator 16, power is supplied to the appliance 20 and current flows through the primary winding of the transformer 22. The voltage appearing at the secondary winding of the transformer 22 is rectified in the bridge 26, and this current is applied through the resistor 28 to charge the delay battery 30. As the battery 30 charges, its voltage rises and soon a voltage is applied across the base and emitter of the transistor 38 to block it as noted above. Current is also supplied to the rectifier bridge 44 through the ballast resistor 40 and the capacitor 42. The rectified output of the bridge 44 is applied to charge the stand-by supply battery 50, and also energize the oscillator 46. Also, voltage is applied by the rectifier diodes 62, 62 to the blocking input terminal 60 of the oscillator 46 to block its oscillations, as long as the transistor 38 is held non-conducting. Since blocking bias is applied to the terminal 60 of the oscillator 46, the oscillator 46 provides no output oscillations.

As soon as the appliance 20 ceases to draw current in the natural operation thereof, the delay battery 30 is no longer being charged, and it continues to discharge through the resistor 34. As it discharges, its voltage decreases. If the appliance 20 does not call for more current (which causes charging of the delay battery 30), the voltage of the battery 30 drops to the point where it no longer is sufficient to block the transistor 38, whereby the blocking voltage provided by the rectifiers 62, 62 is shunted to ground 52 through the conducting transistor 38 and the blocking voltage is removed from the blocking terminal 60 of the oscillator 46. The oscillator 46 starts to oscillate at its own tuned frequency and these oscillations are applied over the leads 18 and the power line 10 to the remotely located responder 14. The responder 14 then shows that the oscillator 46 is sending out oscillations of a particular frequency and that therefore the appliance 20 associated therewith is not drawing enough current to keep the battery 30 charged and transistor 38 non-conducting. The charging resistor 28 and the discharging resistor 34 are adjusted so that as long as the appliance 20 associated therewith is drawing the current normally drawn by a properly operative appliance, the delay battery 30 remains charged to transistor blocking potential. The delay battery 30 therefore comprises a time measuring or delay element.

Since it may be desirable to test the system periodically, a normal open switch 64 is provided between the oscillator blocking terminal 60 and ground 52. When this switch 64 is closed, the blocking potential is removed from the oscillator 46 to permit it to send out oscillations of the frequency to which it is tuned. Reception of these oscillations at the responder 14 shows that the system is operating to produce oscillations.

When power in the power line 10 fails, the blocking potential for the terminal 60 also fails and the oscillator is supplied by the stand-by battery 50. Since no blocking potential is produced when the power in the line 10 fails, the oscillator 46 sends its oscillations out over the line to indicate that the power supply has failed. If the

3,480,940

S failure of the appliance is such as to apply a short circuit to the leads 21, a circuit breaker normally comprising a part of the appliance 20 will open and charging potential for the battery 30 will cease whereby the described indicator will indicate inoperativeness of the appliance 20 whether the cause thereof is loss of power in line 10 or an open circuit or a short circuit in the appliance 20. If, as mentioned above, the output of the oscillator is connected permanently to the power line 10 and not through a receptacle 12 as shown, the indicator 16 will even indicate loss of power to the appliance 20 due to the leads 18 being disconnected from the line 10 or due to the leads 21 being disconnected from the indicator 16.

It may be desirable to provide a local indication that the appliance is not drawing the normal amount of current. Such an indication is provided by the indicator 16'. Similar elements having similar functions and that are similarly connected comprising parts of the remote indicator 16 and of the local indicator 16' have been given the same reference characters. The connections of these elements are mentioned hereinafter only as appears necessary.

Considering the local indicator 16', the negative potential provided by the rectifying diodes 62, 62 is applied through the current limiting resistor 64 to the collector of the transistor 38 as power supply therefor and to the base of an NPN transistor 70 to block it. A biasing resistor 72 is connected between the collector of the transistor 38 and the base of the transistor 70. A signalling device 74, which may be a light or bell or a relay is connected between the positive terminal of the battery 50 and the collector of the transistor 70. The base of the transistor 38 is connected to the junction 76 of two resistors 78 and 80 which are connected in series between the negative terminal at the battery 50 and the positive terminal of the delay battery 30. A normally closed (push to open) test switch 82 is connected between the resistor 80 and the positive terminal of the battery 30.

The local indicating appliance failure indicator 16' operates similarly to the remote indicator 16, except that, since no oscillator 46 is included in the indicator 16', the local signalling device 74 is energized in the indicator 16' to provide the local indication. Current is applied from the power line 10 by way of the receptacle 12 and the leads 18Z&gt; to the locally indicating indicator 16'. The elements of the indicator 16' supply power to operate the signalling device 74 as will be explained, and also to keep the battery 50 charged. The rectifiers 62, 62 provide blocking potential as long as there is power in the lines 10. When power in the lines 10 fails, the battery 50 takes over the function of providing operating current, and the blocking potential ceases.

Current for the appliance 20b is provided by the leads 21Z&gt;, and when the appliance 20Z&gt; is drawing; current, the delay battery 30 is charged from the rectifier bridge 26 at a rate determined by the setting of the charge resistor 28 and the discharge resistor 34. A portion of the voltage appearing across the battery 30 and the lower half as viewed in the figure of the battery 50 that appears at the terminal 76 is applied to the base of the transistor 38 in a direction to block it, and as long as the voltage of the battery 30 is above a predetermined minimum, the transistor 38 is blocked. The blocking potential provided by the rectifiers 62, 62 can then block the transistor 70, whereby no current flows through the transistor 70 or through the signalling means 74 in the collector circuit thereof, and no local signal is provided. However, as soon as the blocking potential ceases due to the failure of power in the line 10, the transistor 70 is no longer blocked and the transistor 70 becomes conductive and the signalling means 74 is energized to cause an indication. Also, if the appliance 20 b does not draw enough current to keep the battery 30 charged above the predetermined minimum, the potential at the point 76 is not sufficient to block the transistor 38, whereby blocking potential for the transis6 tor 38 fails and the transistor 38 short circuits the blocking potential produced by the rectifiers 62, 62 to ground and away from the transistor 70. The transistor 70 therefore becomes conductive to energize the signalling means 74 whenever the power supply represented by the line 10 fails or whenever the current drawn by the appliance 20b reduces below a predetermined minimum. If it be desired to test the equipment 16', the test switch 82 may be opened, lowering the voltage at the point 76 to the value where it will not block the transistor 38, whereby the relay coil 74 or other alarm means will be energized as long as the test switch 82 is kept opened.