CA2254280A1 - Electrical power draw monitoring device - Google Patents
Electrical power draw monitoring device Download PDFInfo
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- CA2254280A1 CA2254280A1 CA 2254280 CA2254280A CA2254280A1 CA 2254280 A1 CA2254280 A1 CA 2254280A1 CA 2254280 CA2254280 CA 2254280 CA 2254280 A CA2254280 A CA 2254280A CA 2254280 A1 CA2254280 A1 CA 2254280A1
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Abstract
This invention relates to a novel electrical power draw monitoring device. More particularly, the power draw monitoring device provides information about the status of an electrical device by monitoring and indicating the amount of electrical power being drawn by the electrical device. An electrical power draw monitoring device installable in an electrical circuit for indicating availability of electrical power and electrical power being drawn through said monitoring device, said monitoring device comprising: (a) an electrical indicating circuit; (b) a first electrical terminal for connecting said indicating circuit to a socket for an electrical power source; and (c) a second electrical terminal for connecting said indicating circuit to an electrical power consuming device.
Description
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ELECTRICAL POWER DRAW MONITORING DEVICE
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TECHNICAL FIELD
This invention relates to a novel electrical power draw monitoring device. More particularly, the power draw monitoring device provides information about the status of an electrical device by monitoring and indicating the amount of electrical power being drawn by the electrical device.
BACKGROUND
Known electricity monitoring devices provide information relating to the status of an electrical power source or an electrical device using the electrical power. For example, devices which indicate the presence of voltage in the device or which indicate that power is available are well known.
U.S. Patent No. 3,942,859 illustrates an electrical cable, with two or more conductors, which is constructed so that its entire length is illuminated when voltage is present. It does not indicate power draw.
U.S. Patent No. 4,101,190 discloses a module, containing a neon bulb, constructed for insertion, at the connection points ) of a series of modular heating cables. The neon bulb, in each module, illuminates to confirm continuity of the circuit, as is evid~t by the presence of voltage at the heating cables' connection points. As is explained in the write-up, column 3, lines 60-62, the indicating capability of this module is that of "providing an effective means for determining whether the various modules are operable" . It does not indicate power draw.
. ~ _. y U.S. Patent No. 4,671,597 discloses an extension cord receptacle containing an indicator lamp to confirm the presence of voltage. It does not indicate power draw.
U.S. Patent No. S,003,249 discloses a device for penetrating the insulation of an electrical cord's conductors for the purpose of sensing the presence of voltage. It does not indicate power draw.
U.S. Patent No. 5,207,594 discloses translucent or transparent extension cord ends containing a bulb to indicate the presence of voltage between the "hot" and the "neutral", or to verify the continuity of the ground connection by responding to a voltage between "hot" and "ground" . It does not indicate power draw.
U.S. Patent No. 5,470,252 is very similar to U.S. Patent No.
5,207,594. It differs in that the connectors are molded to the cord and have greater mechanical integrity. It does not indicate power draw.
U.S. Patent No. 5,567,175, from an electrical perspective, appears to be identical to U.S. Patent No. 5,470,2S2. It does not indicate power draw.
U.S. Patent No. 5,062,807 (Guss, III) issued 5 November, l991, discloses a device which illuminates a red light when power is available and a green light when power is being applied; i. e. when the control device or switch is turned "on" . However Guss, III does not disclose a means for indicating the amount of power being applied to the load, or that power is actually being drawn by the load.
That is, the green light taught by Guss, III only indicates that the switch has been turned on. There could be a problem with the load and yet the green light will still be illuminated even though no power is being drawn.
_ CA 02254280 1998-11-20 The known devices do not indicate when power is presently being drawn by a load, and if so, how much. Accordingly, the known devices do not provide any warning in the situation where power is applied to a load, by turning on a switch, and no power is being drawn. A warning indication of this situation is useful for many applications where it is not readily apparent that there might be a problem with an electrical device and it is not drawing any power. Many electrical devices are located in remote locations such as a building's mechanical room or on the rooftop. Accordingly, there is a need for a device for monitoring power draw from a convenient location, particularly when the electrical device is located in remote locations. Detecting changes in power draw can be indicative of problems which, if addressed early, can avoid more extensive and more costly repairs to equipment which may otherwise operate in a poor condition for a more prolonged period.
Some specific examples help to illustrate the problem. A furnace fan uses more power when the blower bearings are in poor condition or when the filter is plugged. A device which simply indicates that power is available or that the switch is turned on will not indicate that power is being drawn or that there has been a change in the amount of power being drawn. By monitoring power draw, an increase in power draw may be an indication that maintenance is required, or that an inspection of the electrical device is warranted.
Another specific example of a situation where knowing the amount of power being drawn is useful, is monitoring power drawn by an electrical engine block heater. Block heaters are used to prevent cold weather from freezing fluids inside an engine. Without some indication that power is being drawn, it is difficult to determine that the block heater is functioning properly.
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ELECTRICAL POWER DRAW MONITORING DEVICE
S
TECHNICAL FIELD
This invention relates to a novel electrical power draw monitoring device. More particularly, the power draw monitoring device provides information about the status of an electrical device by monitoring and indicating the amount of electrical power being drawn by the electrical device.
BACKGROUND
Known electricity monitoring devices provide information relating to the status of an electrical power source or an electrical device using the electrical power. For example, devices which indicate the presence of voltage in the device or which indicate that power is available are well known.
U.S. Patent No. 3,942,859 illustrates an electrical cable, with two or more conductors, which is constructed so that its entire length is illuminated when voltage is present. It does not indicate power draw.
U.S. Patent No. 4,101,190 discloses a module, containing a neon bulb, constructed for insertion, at the connection points ) of a series of modular heating cables. The neon bulb, in each module, illuminates to confirm continuity of the circuit, as is evid~t by the presence of voltage at the heating cables' connection points. As is explained in the write-up, column 3, lines 60-62, the indicating capability of this module is that of "providing an effective means for determining whether the various modules are operable" . It does not indicate power draw.
. ~ _. y U.S. Patent No. 4,671,597 discloses an extension cord receptacle containing an indicator lamp to confirm the presence of voltage. It does not indicate power draw.
U.S. Patent No. S,003,249 discloses a device for penetrating the insulation of an electrical cord's conductors for the purpose of sensing the presence of voltage. It does not indicate power draw.
U.S. Patent No. 5,207,594 discloses translucent or transparent extension cord ends containing a bulb to indicate the presence of voltage between the "hot" and the "neutral", or to verify the continuity of the ground connection by responding to a voltage between "hot" and "ground" . It does not indicate power draw.
U.S. Patent No. 5,470,252 is very similar to U.S. Patent No.
5,207,594. It differs in that the connectors are molded to the cord and have greater mechanical integrity. It does not indicate power draw.
U.S. Patent No. 5,567,175, from an electrical perspective, appears to be identical to U.S. Patent No. 5,470,2S2. It does not indicate power draw.
U.S. Patent No. 5,062,807 (Guss, III) issued 5 November, l991, discloses a device which illuminates a red light when power is available and a green light when power is being applied; i. e. when the control device or switch is turned "on" . However Guss, III does not disclose a means for indicating the amount of power being applied to the load, or that power is actually being drawn by the load.
That is, the green light taught by Guss, III only indicates that the switch has been turned on. There could be a problem with the load and yet the green light will still be illuminated even though no power is being drawn.
_ CA 02254280 1998-11-20 The known devices do not indicate when power is presently being drawn by a load, and if so, how much. Accordingly, the known devices do not provide any warning in the situation where power is applied to a load, by turning on a switch, and no power is being drawn. A warning indication of this situation is useful for many applications where it is not readily apparent that there might be a problem with an electrical device and it is not drawing any power. Many electrical devices are located in remote locations such as a building's mechanical room or on the rooftop. Accordingly, there is a need for a device for monitoring power draw from a convenient location, particularly when the electrical device is located in remote locations. Detecting changes in power draw can be indicative of problems which, if addressed early, can avoid more extensive and more costly repairs to equipment which may otherwise operate in a poor condition for a more prolonged period.
Some specific examples help to illustrate the problem. A furnace fan uses more power when the blower bearings are in poor condition or when the filter is plugged. A device which simply indicates that power is available or that the switch is turned on will not indicate that power is being drawn or that there has been a change in the amount of power being drawn. By monitoring power draw, an increase in power draw may be an indication that maintenance is required, or that an inspection of the electrical device is warranted.
Another specific example of a situation where knowing the amount of power being drawn is useful, is monitoring power drawn by an electrical engine block heater. Block heaters are used to prevent cold weather from freezing fluids inside an engine. Without some indication that power is being drawn, it is difficult to determine that the block heater is functioning properly.
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SUMMARY OF INVENTION
The present invention provides an electrical power draw monitoring device which can be installed in an electrical circuit between a power source and an electrical device. The monitoring device indicates when electrical power being drawn through the monitoring device exceeds a pre-determined power level.
This device requires no batteries or external source of power.
The monitoring device has an indicating circuit which includes a first electrical terminal for connecting to a power source and a second electrical terminal for connecting to an electrical device. In between the first and second terminals, the indicating circuit has a power indicator which is energized to indicate when power drawn through the monitoring device is greater than a pre-determined power value.
The power indicator can be a light which illuminates when energized or an audible alarm which sounds when energized. The power indicator can also include a terminal for connection to a secondary indicator. The second power indicator, when energized, indicates when power is being drawn through the monitoring device at a second pre-determined power value which is greater than the first predetermined power level.
In one embodiment of the invention, the monitoring device can be an extension cord with an electrical plug-in at one end and an electrical outlet at the other end. The power indicator can be located on the plug-in or the electrical outlet of the extension cord.
In an embodiment of the invention, the monitoring device also includes a voltage indicator which is energized when the monitoring device detects voltage at the first electrical terminal. The voltage indicator can be a light which illuminates when energized or an audible alarm which sounds when energized.
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- $ -In another embodiment of the invention, there is provided an adjustable control for varying the pre-determined power value within a pre-determined power range. The adjustable control can be a potentiometer. The potentiometer can be used to set to a pre-determined threshold power value for energizing the power indicator $ according to the particular situation where the monitoring device is installed. By adjusting the potentiometer, it is also possible to determine the power being drawn by determining the minimum power setting where the power indicator is energized.
The invention is also directed to an electrical power draw monitoring extension cord installable in an electrical circuit for indicating availability of electrical power and electrical power being drawn through said monitoring extension cord, said monitoring extension cord comprising: (a) an electrical indicating circuit;
(b) electricity conveying wires; (c) a first electrical plug-in at a first end of the electricity conveying wires for connecting said indicating circuit to an outlet socket of an 1$ electrical power source; (d) a second electrical plug outlet at a second end of the electricity conveying wires for connecting said indicating circuit to the inlet of an electrical power consuming device; and (e) a first power indicator which is energized to indicate when power drawn through said monitoring extension cord is greater than a first pre-determined power value.
The monitoring extension cord can further comprise a second power indicator which can be energized to indicate when power drawn through said monitoring extension cord is greater than a second pre-determined power value which is greater than said first pre-determined power value.
The monitoring extension cord can further comprise a voltage indicator which can be energized when said monitoring extension cord detects voltage at said first electrical terminal.
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. . . ~ ~ ,..,-., '3 The monitoring extension cord can include an adjustable control for varying said first pre-determined power value within a pre-determined power range.
The adjustable control can comprise a potentiometer.
The first power indicator can comprise a light emitting diode which can illuminate when energized. The second power indicator can comprise a light emitting diode which can illuminate when the second power value is reached.
The monitoring extension cord for 12 volt D.C. use can include a green light emitting diode which can illuminate when a source of power is detected, an amber light emitting diode which can illuminate when a functioning electrical load of about 0.5 amperes is reached, and a red light emitting diode which can illuminate when a functioning electrical load of about 5.0 amperes is reached.
The monitoring extension cord for 120 volt A.C. use can include a green light emitting diode which can illuminate when a source of power is detected, an amber light emitting diode which can illuminate when a functioning electrical load of about 35 watts is reached, and a red light emitting diode which can illuminate when a functioning electrical load of about 440 watts is reached.
The monitoring device can include a spring return switch to shunt out, or momentarily open, a portion of load sensing circuitry fox enabling use of the monitoring device for low range and high range electrical load detection.
BRIEF DESCRIPTION OF DRAWINGS
The present invention will be further understood from the following description with references to the drawings in which:
Figure 1 illustrates an isometric view of the electrical power draw monitoring device.
.r .r , _7_ Figure 2 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention for an alternating current power source.
Figure 3 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention for a direct current power supply.
Figure 4 is a circuit diagram for a potentiometer adjustable threshold control.
Figure 5 is a circuit diagram fox an external alarm.
DESCRIPTION
The invention is an electrical power draw monitoring device. The power draw monitoring device, unlike prior devices, provides information about an electrical device connected to it by indicating that electrical power is being drawn by such electrical device. In one specific embodiment of the invention, the device can be in the form of a flexible extension cord with power draw indicators on the plug-in end or the plug outlet end of the extension cord. The device can be used with a direct current (D.C.) or alternating current (A.C.) power source. The monitoring device uses an indicating circuit which is installed between the power source and the electrical device.
As an extension cord, the device is designed to provide information about the status of electrical equipment plugged into it. It is especially useful for remotely located electrical devices, and those for which proper operation is not readily apparent. Potential uses include supplying power to vehicle block heaters, car warmers, heat tapes, battery chargers, stock water heaters, sump pumps or remotely located fans or heat lamps.
4 s ,~~, _g_ When the extension cord has been plugged into a properly functioning 120 V . A . C . outlet, the green light will illuminate-. This indicates the presence of voltage at the cord receptacle (the outlet plug).
When an electrical device that draws between approximately 35 and 400 watts is plugged into the outlet of the extension cord, and is operating properly, the amber light will also illuminate. A properly operating load in excess of 440 watts will turn on the red light as well. It should be noted that electrical loads of less than the 35 and 440 watt thresholds may, because of initial "inrush current" , give a higher than actual power draw status indication momentarily, when first plugged in or turned on. However, once stabilized, the lights will operate properly.
The invention will now be discussed with reference to the drawings.
Figure 1 illustrates a perspective view of a conventional three-prong AC plug inlet 2 with a three-wire cord 4 and a conventional three-hole AC plug outlet 6. The three wires 3, 5 and 7 are respectively coloured black (hot), white (neutral) and green (ground) as is conventional in the North American 120 volt AC power industry (Underwriters Laboratories (UL) or in Canada, the Canadian Standards Association (CSA)). In the embodiment shown in Figure 1, there are a green LED
(light emitting diode) 8, an amber LED 10 and a red LED 12, located on the outlet plug 6. The green LED 8 illuminates when AC power is available. The amber LED
10 illuminates when there is a low wattage AC load. The red LED 12 illuminates when there is a high wattage load. It will be understood that the three LEDs 8, 10 and 12 can be located on the plug inlet 2 if desired. It will also be understood that three LEDs can be installed in both the inlet plug 2 and the outlet plug 6, but four additional wires or two complete monitoring devices would be required.
The manner in which the LED's 8, 10 and 12 function is explained below in relatiow to Figure 2. Figure 2 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention, for an alternating ., current source. Figure 1 shows an indicating circuit for a power draw monitoring device with three light-emitting diodes (LED) 8, 10 and 12 for indicating the presence of available power, power draw in excess of a first pre-determined value, and power draw in excess of a second pre-determined value, higher than the first pre-determined value.
The indicating circuit has a first terlilfinal 2 (plug inlet) and a second terminal 6 (plug receptacle). First terminal 2 is for connecting the indicating circuit to an AC power source. Second terminal 6 is for connecting the indicating circuit to a load provided by an AC electrical device, such as an AC electrical motor or some other AC electrical power drawing implement. A mufti-conductor cable (see cord in Figure 1) can be used to connect each of the first and second terminals 2, 6 to the AC power source and electrical device respectively.
As shown in Figure 2, an A.C. signal is supplied to diodes D1 through D4. Diodes D1 through D4 are arranged in bridge configuration to provide full-wave rectification. Resistor R2 limits current flow through diodes DS through D 11.
Diodes DS through D 11 produce an equal amount of positive or negative volts D
. C .
( +/- V as shown), which is filtered by capacitors C 1 and C2. This D. C.
voltage is used by the quad operational amplifier U1 and the reference voltage circuits.
Resistor Rl is in series with the 120 AC load and has a very low voltage drop across it. Resistor Rl typically is a coil formed from an electrically conductive material. To enable precise detection of changes in electrical load under varying temperature conditions, resistor R1 is made from a conductive material which has a low temperature coefficient. The voltage drop across Rl is proportional to the wattage of the load and there is no voltage when a malfunctioning load is connected.
The effect of the voltage drop across R1 on the connected load is negligible.
For example, with a 100 watt load and a 120 volt supply, the voltage drop across resistor Rl is 0.007 volts, leaving 119.993 volts for the load. It is the magnitude of the very low voltage drop across R1 that is used to quantify the status of the load.
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..,..., A brief description of the U 1, the quad operational amplifier, fol lows .
An op-amp is a high input impedance, high gain precision amplifier. A basic op-amp has two inputs, an output, and terminals for D.C. voltage supply connection.
The device used in the prototype is a 14 pin integrated circuit containing four separate op-amps. It is conventional to use the triangle symbol for each portion of the op-amp circuitry, including the power supply connection (pins 4 and 11, in the present case) .
Three of the op-amps in U1 are used. The word "quadrant" has been chosen to identify the individual op-amps within U 1 and the first, third and fourth "quadrants"
have been used. Leaving the fourth quadrant (pins 11-13) unused, instead of the second (pins 5-7), would make the circuit diagram easier to understand, but this choice was made to simplify wiring between components on the circuit board.
Transformer T1 amplifies the voltage across R1 to approximately ten times its initial value. The first quadrant (pins 1, 2, and 3) of operational amplifier U 1, with resistors R3 through RS sized for a gain of 3 S , further amplifies the A. C.
signal from Rl, now 350 times its initial value. Diode D 12, resistor R6 and capacitor C3, respectively rectify, limit current and filter the output from pin 1 of operational amplifier U 1 to a D . C . voltage proportional to the load connected to the second terminal 6 (up to 4S0 watts). It is possible to change the power range which can be detected and indicated by the monitoring device by selecting a transformer T 1 with a different turns ratio. For example) by selecting a transformer T1 with a higher turns ratio, the monitoring device will be able to detect lower wattage loads, but the value of the upper power level will be reduced.
Diode D13 is a green light emitting diode (8). Current supplied to diode D 13 is limited by resistor R7 . Diode D 13 (8) illuminates whenever power is available at the first terminal 2, that is, plug-in 2. Thus illumination of diode D 13 indicates that voltage is present (the power supply is not dead).
The third quadrant (pins 8, 9 and 10) of operational amp U1 compares the output from pin 1 with the low load reference voltage. If this reference voltage ' . ~ ,-...,.
is exceeded, pin 8 goes "high" and amber diode D14 (LED 10) illuminates. This indicates that AC power draw by the electrical device is occurring and has exceeded a first pre-determined value.
S The fourth quadrant (pins 12, 13 and 14) of operational amp U1 compares the output from pin 1 with the high load reference. If the reference voltage is exceeded, output 14 goes "high" and red diode D15 (LED 12) illuminates.
This indicates that AC power draw by the electrical device is occurring and has exceeded a second pre-determined value, higher than the first pre-determined value.
Resistor R10, diodes D16 and D17 produce a low load reference of approximately 0.6 volts, while resistors Rll and R12 provide a high load reference of approximately l1.6 volts.
In the preferred embodiment, when each of diodes D 13 , D 14, and D 15 is energized, each one illuminates a uniquely coloured light. For example, when voltage is present (the power supply is not dead). Diode D13 is a green light-emitting diode (LED 8) which then illuminates, when power draw exceeds the first pre-determined power value, diode D 14 is a yellow light emitting diode (LED 10) which then illuminates, and when power draw exceeds the second pre-determined power value, light emitting diode D15 is red (LED 12) which then illuminates.
To allow for user adjustments of the lower and upper thresholds, R10/D16/D17 and R12 could be replaced with resistor/potentiometer combinations.
Specific electrical devices could be monitored for changes in load with an adjustable threshold version of this device; for example, it could be wired in series with a furnace fan power source, and the upper threshold adjusted so that the red light just went off when fan and blower bearings were in good condition and the furnace filter clean. Increased load due to a plugged filter or the need for bearing lubrication would be indicated by the illumination of the red light. The op-amp output that turns ,. ,, on the red light could also operate a relay. The relay could be wired for operating an audible alarm, flashing light or magnetic starter to shut off an overloaded device.
To enable very precise detection of changes in electrical load under varying temperature conditions, Rl would need to be made from a material having less resistance change due to temperature change than copper wire has.
Variations in the 120 V . A. C. supply voltage would also affect the precision of load-change detection. For the applicant's prototype, #19 AWG copper wire was used in Rl.
To meet CSA and UL requirements, Rl might have to be replaced with a proportionately longer piece of #16 or #14 wire for a cord rated for 15 amperes.
Design Variations and Other Uses This prototype has been constructed to verify the operation of electrical loads in excess of 35 watts. Replacing transformer T1 with one having a higher turns ratio would enable the detection of lower wattage loads, but the "high load"
indication threshold would need to be decreased.
The replacement of Rl with a coil wound from a longer piece of wire would also enable the detection of lower wattage loads but, beyond a certain point, would result in excessive heating of Rl when high wattage loads were connected.
This problem could be solved by reducing the cord's capacity rating or installing, for example, a 5 amp circuit breaker in the cord.
Both lower and higher wattage thresholds could be detected with the same cord if Rl was replaced with two coils wired in series. A spring-return switch could shunt out the higher resistance coil for normal operation and then be momentarily opened for the detection of very low wattage loads. Higher than watt loads could be differentiated by decreasing the length of wire in Rl and sacrificing the capability of detecting loads down to 35 watts. Another option is the use of an op-amp designed for a higher supply voltage, enabling a greater range between thresholds.
If multiple devices are powered from this cord, the failure or improper operation of just one could also be indicated; for example, two 250 watt heat lamps should turn on all three indicator lights. If one of the heat lamps burned out, only the green and amber lights would illuminate.
Figure 3 illustrates a circuit diagram for a power draw monitoring device for a 12 volt D.C. system. The monitoring device for a D.C. system can take the form of an extension cord or can be directly wired into a power supply. In respect of the extension cord model, there are a number of devices that can be plugged into a vehicle cigarette lighter receptacle, and there are also many D.C.
devices that use A. C. adaptors (a transformer/rectifier/regulator that plugs into a 120 volt A.C. receptacle with a cord that plugs into the D.C. device). For either of these applications, a monitoring device according to the present invention could be part of an extension cord.
There could also be automobile, truck, heavy equipment and RV
applications for the D.C. version of the power draw monitoring device. It could, for example, confirm that the lights on a log truck trailer are working. It could verify that power is available, that control devices are operating properly, and that the solenoid portion of the hydraulic valve for an attachment on a heavy equipment unit is functionally normally, thus facilitating troubleshooting. For applications such as these, the power draw monitoring device would preferably be located in the instrument panel or control console, directly wired into the power supply.
In the circuit diagram illustrated, the components are listed as follows:
Components R1 - 12" #19 AWG
copper wire wound into a 4 turn coil = .00852.
D 1 - Green LED D4 - 1 N914 D2 - Amber LED DS - 1N914 D3 - Red LED
U 1 - LM324N Op-Amp Terminal A - Wire to positive connection point of load Terminal B - Wire to positive connection point of D.C. source Terminal C - Wire to negative (ground) connection point For the extension cord embodiment, a11 components (LED's, resistors, diodes, and Op-Amp) other than the cord itself and the cord plug end would be located within the receptacle end. For the wired-in embodiment, the extension cord, plug end, and receptacle end shown in Figure 3 would be omitted and connections instead be made directly to terminals A, B, and C.
The green LED will illuminate when power is available. The amber LED will illuminate when a properly functioning load of 0.5 amperes, or more, is connected. The red LED confirms a properly functioning load of 5.0 amperes or more.
If it is desired that loads less than 0.5 amperes be monitored, the value of Rl can be changed. With a11 other components unchanged, increasing the value (~.. , of R1 by a factor of 10 (to .0851) would cause the amber LED to illuminate in response to a .OS ampere load. The value of R1 can be decreased to achieve the opposite effect.
Although the circuit diagram in Figure 3 is for a 12 volt D.C. system, components can be changed to enable monitoring systems of different voltages.
It may be practical, in some cases, to use a switch/relay combination or a multi-pole switch to set the unit for different D.C. voltages. A switch for selecting A.C. or D.C. could be incorporated but would probably not be practical.
A potentiometer adjustable threshold control can easily be added. For the basic extension cord model illustrated in Figure 1, the best potentiometer would be a conventional miniature screwdriver adjustable unit accessed through a small hole in the cord end via a tiny threaded plug. Other models of the applicant's device could have an external knob with actual wattage calibration marks. Figure 4 illustrates a circuit diagram for a typical potentiometer adjustable threshold modification that can be made to the circuit illustrated in Figure 2. This modification would enable adjusting the "high load" threshold from a low of approximately watts to a high of approximately 440 watts.
Audible alarms or lights and terminals for external indication can be included, if desired. Figure 5 illustrates a circuit diagram which shows a typical external alarm. The components in Figure 5 are:
CR 1 is a miniature mechanical relay with a high impedance 12 V . D . C . coil ( >_ 1,0005Z) with a normally open contact rated for a 120 V.A.C. load.
L1 is a beacon light.
RS is a 390SZ current limiting resistor.
When a "high wattage" load is sensed, D 15 (the red LED) illuminates and the coil of the control relay is energized. The normally open relay contact closes and the remote beacon light illuminates.
Table 1 Power-Draw Monitoring Extension Cord Components Rl - 12" #19 AWG
copper wire wound into a 4 turn coil = .008S1.
D 1 - W4007 D 10 - 15v 1 watt zener D2 - IN4007 D11 - 15v 1 watt zener D4 - IN4007 D 13 - Green LED
D5 - 20V 1 W ZenerD 14 - Amber LED
D6 - 20V 1 W ZenerD 15 - Red LED
D7 - 20V 1W Zener D16 - IN34 D8 - 20V 1W Zener D17 - IN914 D9 - 20V 1W Zener TRl - 1KCT to 8SZ miniature audio transformer U1 - LM324N Quad Operational Amplifier C1 - 100,F 25V C3 - 0.68.F 50V
C2 - 100~cF 25 V
The electrical power draw monitoring device according to the invention has the following advantages:
1. It confirms that the load is actually drawing power.
2. It indicates the wattage range of the connected load.
3. It has adjustable wattage range thresholds.
4. It triggers external alarms, based on power draw.
The present invention provides an electrical power draw monitoring device which can be installed in an electrical circuit between a power source and an electrical device. The monitoring device indicates when electrical power being drawn through the monitoring device exceeds a pre-determined power level.
This device requires no batteries or external source of power.
The monitoring device has an indicating circuit which includes a first electrical terminal for connecting to a power source and a second electrical terminal for connecting to an electrical device. In between the first and second terminals, the indicating circuit has a power indicator which is energized to indicate when power drawn through the monitoring device is greater than a pre-determined power value.
The power indicator can be a light which illuminates when energized or an audible alarm which sounds when energized. The power indicator can also include a terminal for connection to a secondary indicator. The second power indicator, when energized, indicates when power is being drawn through the monitoring device at a second pre-determined power value which is greater than the first predetermined power level.
In one embodiment of the invention, the monitoring device can be an extension cord with an electrical plug-in at one end and an electrical outlet at the other end. The power indicator can be located on the plug-in or the electrical outlet of the extension cord.
In an embodiment of the invention, the monitoring device also includes a voltage indicator which is energized when the monitoring device detects voltage at the first electrical terminal. The voltage indicator can be a light which illuminates when energized or an audible alarm which sounds when energized.
,.
- $ -In another embodiment of the invention, there is provided an adjustable control for varying the pre-determined power value within a pre-determined power range. The adjustable control can be a potentiometer. The potentiometer can be used to set to a pre-determined threshold power value for energizing the power indicator $ according to the particular situation where the monitoring device is installed. By adjusting the potentiometer, it is also possible to determine the power being drawn by determining the minimum power setting where the power indicator is energized.
The invention is also directed to an electrical power draw monitoring extension cord installable in an electrical circuit for indicating availability of electrical power and electrical power being drawn through said monitoring extension cord, said monitoring extension cord comprising: (a) an electrical indicating circuit;
(b) electricity conveying wires; (c) a first electrical plug-in at a first end of the electricity conveying wires for connecting said indicating circuit to an outlet socket of an 1$ electrical power source; (d) a second electrical plug outlet at a second end of the electricity conveying wires for connecting said indicating circuit to the inlet of an electrical power consuming device; and (e) a first power indicator which is energized to indicate when power drawn through said monitoring extension cord is greater than a first pre-determined power value.
The monitoring extension cord can further comprise a second power indicator which can be energized to indicate when power drawn through said monitoring extension cord is greater than a second pre-determined power value which is greater than said first pre-determined power value.
The monitoring extension cord can further comprise a voltage indicator which can be energized when said monitoring extension cord detects voltage at said first electrical terminal.
,...
. . . ~ ~ ,..,-., '3 The monitoring extension cord can include an adjustable control for varying said first pre-determined power value within a pre-determined power range.
The adjustable control can comprise a potentiometer.
The first power indicator can comprise a light emitting diode which can illuminate when energized. The second power indicator can comprise a light emitting diode which can illuminate when the second power value is reached.
The monitoring extension cord for 12 volt D.C. use can include a green light emitting diode which can illuminate when a source of power is detected, an amber light emitting diode which can illuminate when a functioning electrical load of about 0.5 amperes is reached, and a red light emitting diode which can illuminate when a functioning electrical load of about 5.0 amperes is reached.
The monitoring extension cord for 120 volt A.C. use can include a green light emitting diode which can illuminate when a source of power is detected, an amber light emitting diode which can illuminate when a functioning electrical load of about 35 watts is reached, and a red light emitting diode which can illuminate when a functioning electrical load of about 440 watts is reached.
The monitoring device can include a spring return switch to shunt out, or momentarily open, a portion of load sensing circuitry fox enabling use of the monitoring device for low range and high range electrical load detection.
BRIEF DESCRIPTION OF DRAWINGS
The present invention will be further understood from the following description with references to the drawings in which:
Figure 1 illustrates an isometric view of the electrical power draw monitoring device.
.r .r , _7_ Figure 2 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention for an alternating current power source.
Figure 3 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention for a direct current power supply.
Figure 4 is a circuit diagram for a potentiometer adjustable threshold control.
Figure 5 is a circuit diagram fox an external alarm.
DESCRIPTION
The invention is an electrical power draw monitoring device. The power draw monitoring device, unlike prior devices, provides information about an electrical device connected to it by indicating that electrical power is being drawn by such electrical device. In one specific embodiment of the invention, the device can be in the form of a flexible extension cord with power draw indicators on the plug-in end or the plug outlet end of the extension cord. The device can be used with a direct current (D.C.) or alternating current (A.C.) power source. The monitoring device uses an indicating circuit which is installed between the power source and the electrical device.
As an extension cord, the device is designed to provide information about the status of electrical equipment plugged into it. It is especially useful for remotely located electrical devices, and those for which proper operation is not readily apparent. Potential uses include supplying power to vehicle block heaters, car warmers, heat tapes, battery chargers, stock water heaters, sump pumps or remotely located fans or heat lamps.
4 s ,~~, _g_ When the extension cord has been plugged into a properly functioning 120 V . A . C . outlet, the green light will illuminate-. This indicates the presence of voltage at the cord receptacle (the outlet plug).
When an electrical device that draws between approximately 35 and 400 watts is plugged into the outlet of the extension cord, and is operating properly, the amber light will also illuminate. A properly operating load in excess of 440 watts will turn on the red light as well. It should be noted that electrical loads of less than the 35 and 440 watt thresholds may, because of initial "inrush current" , give a higher than actual power draw status indication momentarily, when first plugged in or turned on. However, once stabilized, the lights will operate properly.
The invention will now be discussed with reference to the drawings.
Figure 1 illustrates a perspective view of a conventional three-prong AC plug inlet 2 with a three-wire cord 4 and a conventional three-hole AC plug outlet 6. The three wires 3, 5 and 7 are respectively coloured black (hot), white (neutral) and green (ground) as is conventional in the North American 120 volt AC power industry (Underwriters Laboratories (UL) or in Canada, the Canadian Standards Association (CSA)). In the embodiment shown in Figure 1, there are a green LED
(light emitting diode) 8, an amber LED 10 and a red LED 12, located on the outlet plug 6. The green LED 8 illuminates when AC power is available. The amber LED
10 illuminates when there is a low wattage AC load. The red LED 12 illuminates when there is a high wattage load. It will be understood that the three LEDs 8, 10 and 12 can be located on the plug inlet 2 if desired. It will also be understood that three LEDs can be installed in both the inlet plug 2 and the outlet plug 6, but four additional wires or two complete monitoring devices would be required.
The manner in which the LED's 8, 10 and 12 function is explained below in relatiow to Figure 2. Figure 2 is a schematic circuit diagram of an embodiment of the indicating circuit of the present invention, for an alternating ., current source. Figure 1 shows an indicating circuit for a power draw monitoring device with three light-emitting diodes (LED) 8, 10 and 12 for indicating the presence of available power, power draw in excess of a first pre-determined value, and power draw in excess of a second pre-determined value, higher than the first pre-determined value.
The indicating circuit has a first terlilfinal 2 (plug inlet) and a second terminal 6 (plug receptacle). First terminal 2 is for connecting the indicating circuit to an AC power source. Second terminal 6 is for connecting the indicating circuit to a load provided by an AC electrical device, such as an AC electrical motor or some other AC electrical power drawing implement. A mufti-conductor cable (see cord in Figure 1) can be used to connect each of the first and second terminals 2, 6 to the AC power source and electrical device respectively.
As shown in Figure 2, an A.C. signal is supplied to diodes D1 through D4. Diodes D1 through D4 are arranged in bridge configuration to provide full-wave rectification. Resistor R2 limits current flow through diodes DS through D 11.
Diodes DS through D 11 produce an equal amount of positive or negative volts D
. C .
( +/- V as shown), which is filtered by capacitors C 1 and C2. This D. C.
voltage is used by the quad operational amplifier U1 and the reference voltage circuits.
Resistor Rl is in series with the 120 AC load and has a very low voltage drop across it. Resistor Rl typically is a coil formed from an electrically conductive material. To enable precise detection of changes in electrical load under varying temperature conditions, resistor R1 is made from a conductive material which has a low temperature coefficient. The voltage drop across Rl is proportional to the wattage of the load and there is no voltage when a malfunctioning load is connected.
The effect of the voltage drop across R1 on the connected load is negligible.
For example, with a 100 watt load and a 120 volt supply, the voltage drop across resistor Rl is 0.007 volts, leaving 119.993 volts for the load. It is the magnitude of the very low voltage drop across R1 that is used to quantify the status of the load.
,, "
..,..., A brief description of the U 1, the quad operational amplifier, fol lows .
An op-amp is a high input impedance, high gain precision amplifier. A basic op-amp has two inputs, an output, and terminals for D.C. voltage supply connection.
The device used in the prototype is a 14 pin integrated circuit containing four separate op-amps. It is conventional to use the triangle symbol for each portion of the op-amp circuitry, including the power supply connection (pins 4 and 11, in the present case) .
Three of the op-amps in U1 are used. The word "quadrant" has been chosen to identify the individual op-amps within U 1 and the first, third and fourth "quadrants"
have been used. Leaving the fourth quadrant (pins 11-13) unused, instead of the second (pins 5-7), would make the circuit diagram easier to understand, but this choice was made to simplify wiring between components on the circuit board.
Transformer T1 amplifies the voltage across R1 to approximately ten times its initial value. The first quadrant (pins 1, 2, and 3) of operational amplifier U 1, with resistors R3 through RS sized for a gain of 3 S , further amplifies the A. C.
signal from Rl, now 350 times its initial value. Diode D 12, resistor R6 and capacitor C3, respectively rectify, limit current and filter the output from pin 1 of operational amplifier U 1 to a D . C . voltage proportional to the load connected to the second terminal 6 (up to 4S0 watts). It is possible to change the power range which can be detected and indicated by the monitoring device by selecting a transformer T 1 with a different turns ratio. For example) by selecting a transformer T1 with a higher turns ratio, the monitoring device will be able to detect lower wattage loads, but the value of the upper power level will be reduced.
Diode D13 is a green light emitting diode (8). Current supplied to diode D 13 is limited by resistor R7 . Diode D 13 (8) illuminates whenever power is available at the first terminal 2, that is, plug-in 2. Thus illumination of diode D 13 indicates that voltage is present (the power supply is not dead).
The third quadrant (pins 8, 9 and 10) of operational amp U1 compares the output from pin 1 with the low load reference voltage. If this reference voltage ' . ~ ,-...,.
is exceeded, pin 8 goes "high" and amber diode D14 (LED 10) illuminates. This indicates that AC power draw by the electrical device is occurring and has exceeded a first pre-determined value.
S The fourth quadrant (pins 12, 13 and 14) of operational amp U1 compares the output from pin 1 with the high load reference. If the reference voltage is exceeded, output 14 goes "high" and red diode D15 (LED 12) illuminates.
This indicates that AC power draw by the electrical device is occurring and has exceeded a second pre-determined value, higher than the first pre-determined value.
Resistor R10, diodes D16 and D17 produce a low load reference of approximately 0.6 volts, while resistors Rll and R12 provide a high load reference of approximately l1.6 volts.
In the preferred embodiment, when each of diodes D 13 , D 14, and D 15 is energized, each one illuminates a uniquely coloured light. For example, when voltage is present (the power supply is not dead). Diode D13 is a green light-emitting diode (LED 8) which then illuminates, when power draw exceeds the first pre-determined power value, diode D 14 is a yellow light emitting diode (LED 10) which then illuminates, and when power draw exceeds the second pre-determined power value, light emitting diode D15 is red (LED 12) which then illuminates.
To allow for user adjustments of the lower and upper thresholds, R10/D16/D17 and R12 could be replaced with resistor/potentiometer combinations.
Specific electrical devices could be monitored for changes in load with an adjustable threshold version of this device; for example, it could be wired in series with a furnace fan power source, and the upper threshold adjusted so that the red light just went off when fan and blower bearings were in good condition and the furnace filter clean. Increased load due to a plugged filter or the need for bearing lubrication would be indicated by the illumination of the red light. The op-amp output that turns ,. ,, on the red light could also operate a relay. The relay could be wired for operating an audible alarm, flashing light or magnetic starter to shut off an overloaded device.
To enable very precise detection of changes in electrical load under varying temperature conditions, Rl would need to be made from a material having less resistance change due to temperature change than copper wire has.
Variations in the 120 V . A. C. supply voltage would also affect the precision of load-change detection. For the applicant's prototype, #19 AWG copper wire was used in Rl.
To meet CSA and UL requirements, Rl might have to be replaced with a proportionately longer piece of #16 or #14 wire for a cord rated for 15 amperes.
Design Variations and Other Uses This prototype has been constructed to verify the operation of electrical loads in excess of 35 watts. Replacing transformer T1 with one having a higher turns ratio would enable the detection of lower wattage loads, but the "high load"
indication threshold would need to be decreased.
The replacement of Rl with a coil wound from a longer piece of wire would also enable the detection of lower wattage loads but, beyond a certain point, would result in excessive heating of Rl when high wattage loads were connected.
This problem could be solved by reducing the cord's capacity rating or installing, for example, a 5 amp circuit breaker in the cord.
Both lower and higher wattage thresholds could be detected with the same cord if Rl was replaced with two coils wired in series. A spring-return switch could shunt out the higher resistance coil for normal operation and then be momentarily opened for the detection of very low wattage loads. Higher than watt loads could be differentiated by decreasing the length of wire in Rl and sacrificing the capability of detecting loads down to 35 watts. Another option is the use of an op-amp designed for a higher supply voltage, enabling a greater range between thresholds.
If multiple devices are powered from this cord, the failure or improper operation of just one could also be indicated; for example, two 250 watt heat lamps should turn on all three indicator lights. If one of the heat lamps burned out, only the green and amber lights would illuminate.
Figure 3 illustrates a circuit diagram for a power draw monitoring device for a 12 volt D.C. system. The monitoring device for a D.C. system can take the form of an extension cord or can be directly wired into a power supply. In respect of the extension cord model, there are a number of devices that can be plugged into a vehicle cigarette lighter receptacle, and there are also many D.C.
devices that use A. C. adaptors (a transformer/rectifier/regulator that plugs into a 120 volt A.C. receptacle with a cord that plugs into the D.C. device). For either of these applications, a monitoring device according to the present invention could be part of an extension cord.
There could also be automobile, truck, heavy equipment and RV
applications for the D.C. version of the power draw monitoring device. It could, for example, confirm that the lights on a log truck trailer are working. It could verify that power is available, that control devices are operating properly, and that the solenoid portion of the hydraulic valve for an attachment on a heavy equipment unit is functionally normally, thus facilitating troubleshooting. For applications such as these, the power draw monitoring device would preferably be located in the instrument panel or control console, directly wired into the power supply.
In the circuit diagram illustrated, the components are listed as follows:
Components R1 - 12" #19 AWG
copper wire wound into a 4 turn coil = .00852.
D 1 - Green LED D4 - 1 N914 D2 - Amber LED DS - 1N914 D3 - Red LED
U 1 - LM324N Op-Amp Terminal A - Wire to positive connection point of load Terminal B - Wire to positive connection point of D.C. source Terminal C - Wire to negative (ground) connection point For the extension cord embodiment, a11 components (LED's, resistors, diodes, and Op-Amp) other than the cord itself and the cord plug end would be located within the receptacle end. For the wired-in embodiment, the extension cord, plug end, and receptacle end shown in Figure 3 would be omitted and connections instead be made directly to terminals A, B, and C.
The green LED will illuminate when power is available. The amber LED will illuminate when a properly functioning load of 0.5 amperes, or more, is connected. The red LED confirms a properly functioning load of 5.0 amperes or more.
If it is desired that loads less than 0.5 amperes be monitored, the value of Rl can be changed. With a11 other components unchanged, increasing the value (~.. , of R1 by a factor of 10 (to .0851) would cause the amber LED to illuminate in response to a .OS ampere load. The value of R1 can be decreased to achieve the opposite effect.
Although the circuit diagram in Figure 3 is for a 12 volt D.C. system, components can be changed to enable monitoring systems of different voltages.
It may be practical, in some cases, to use a switch/relay combination or a multi-pole switch to set the unit for different D.C. voltages. A switch for selecting A.C. or D.C. could be incorporated but would probably not be practical.
A potentiometer adjustable threshold control can easily be added. For the basic extension cord model illustrated in Figure 1, the best potentiometer would be a conventional miniature screwdriver adjustable unit accessed through a small hole in the cord end via a tiny threaded plug. Other models of the applicant's device could have an external knob with actual wattage calibration marks. Figure 4 illustrates a circuit diagram for a typical potentiometer adjustable threshold modification that can be made to the circuit illustrated in Figure 2. This modification would enable adjusting the "high load" threshold from a low of approximately watts to a high of approximately 440 watts.
Audible alarms or lights and terminals for external indication can be included, if desired. Figure 5 illustrates a circuit diagram which shows a typical external alarm. The components in Figure 5 are:
CR 1 is a miniature mechanical relay with a high impedance 12 V . D . C . coil ( >_ 1,0005Z) with a normally open contact rated for a 120 V.A.C. load.
L1 is a beacon light.
RS is a 390SZ current limiting resistor.
When a "high wattage" load is sensed, D 15 (the red LED) illuminates and the coil of the control relay is energized. The normally open relay contact closes and the remote beacon light illuminates.
Table 1 Power-Draw Monitoring Extension Cord Components Rl - 12" #19 AWG
copper wire wound into a 4 turn coil = .008S1.
D 1 - W4007 D 10 - 15v 1 watt zener D2 - IN4007 D11 - 15v 1 watt zener D4 - IN4007 D 13 - Green LED
D5 - 20V 1 W ZenerD 14 - Amber LED
D6 - 20V 1 W ZenerD 15 - Red LED
D7 - 20V 1W Zener D16 - IN34 D8 - 20V 1W Zener D17 - IN914 D9 - 20V 1W Zener TRl - 1KCT to 8SZ miniature audio transformer U1 - LM324N Quad Operational Amplifier C1 - 100,F 25V C3 - 0.68.F 50V
C2 - 100~cF 25 V
The electrical power draw monitoring device according to the invention has the following advantages:
1. It confirms that the load is actually drawing power.
2. It indicates the wattage range of the connected load.
3. It has adjustable wattage range thresholds.
4. It triggers external alarms, based on power draw.
5. It requires no batteries or external source of power.
Prototype Test Data (20 ~ Ambient Temperature) Load R1 U1 Pin3Ul Pin 1 Green Amber LED Red LED
LED
Voltage VoltageVoltage W .002 .018 0.58 On Off Off W .003 .024 0.80 On On Off W .004 .031 1.10 On On Off 20 SO W .00S .042 1.50 On On Off 100 W .009 .080 2.80 On On Off 250 W .020 0.20 7.20 On On Off 400 W .031 0.32 l1.5 On On Off 425 W .033 0.34 11.6 On On Unstable 25 450 .034 0.36 11.7(clipped)On On On W
1500 W 0.1151.30 11.7(clipped)On On On 1800 W 0.15 1.60 11.7(clipped)On On On Voltages shown are "peak" values measured with an oscilloscope.
30 "True" (RMS) voltages are 0.707 times these values. The output of the Op-Amp signal amplifier is limited by the supply voltage (pins 4 and 11) and, regardless of the . ... ,~>..
input voltage (pin 3), cannot exceed l1.7 volts. The AC sine wave peaks are "clipped" whenever the input voltage would result in an output greater than 11.6 volts. The loads tested were combinations of light bulbs and electric heaters.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof.
Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Prototype Test Data (20 ~ Ambient Temperature) Load R1 U1 Pin3Ul Pin 1 Green Amber LED Red LED
LED
Voltage VoltageVoltage W .002 .018 0.58 On Off Off W .003 .024 0.80 On On Off W .004 .031 1.10 On On Off 20 SO W .00S .042 1.50 On On Off 100 W .009 .080 2.80 On On Off 250 W .020 0.20 7.20 On On Off 400 W .031 0.32 l1.5 On On Off 425 W .033 0.34 11.6 On On Unstable 25 450 .034 0.36 11.7(clipped)On On On W
1500 W 0.1151.30 11.7(clipped)On On On 1800 W 0.15 1.60 11.7(clipped)On On On Voltages shown are "peak" values measured with an oscilloscope.
30 "True" (RMS) voltages are 0.707 times these values. The output of the Op-Amp signal amplifier is limited by the supply voltage (pins 4 and 11) and, regardless of the . ... ,~>..
input voltage (pin 3), cannot exceed l1.7 volts. The AC sine wave peaks are "clipped" whenever the input voltage would result in an output greater than 11.6 volts. The loads tested were combinations of light bulbs and electric heaters.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof.
Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Claims (24)
1. An electrical power draw monitoring device installable in an electrical circuit for indicating availability of electrical power and electrical power being drawn through said monitoring device, said monitoring device comprising:
(a) an electrical indicating circuit;
(b) a first electrical terminal for connecting said indicating circuit to a socket for an electrical power source;
(c) a second electrical terminal for connecting said indicating circuit to an electrical power consuming device; and (d) a first power indicator which is energized to indicate when power drawn through said monitoring device is greater than a first pre-determined power value.
(a) an electrical indicating circuit;
(b) a first electrical terminal for connecting said indicating circuit to a socket for an electrical power source;
(c) a second electrical terminal for connecting said indicating circuit to an electrical power consuming device; and (d) a first power indicator which is energized to indicate when power drawn through said monitoring device is greater than a first pre-determined power value.
2. A monitoring device as defined by claim 1 further comprising a second power indicator which is energized to indicate when power drawn through said monitoring device is greater than a second pre-determined power value which is greater than said first pre-determined power value.
3. A monitoring device as defined by claim 1 further comprising a voltage indicator which is energized when said monitoring device detects voltage at said first electrical terminal.
4. A monitoring device as defined by claim 3 further including an adjustable control for varying said first pre-determined power value within a pre-determined power range.
5. A monitoring device as defined by claim 4 wherein said adjustable control comprises a potentiometer.
6. A monitoring device as defined by claim 1 wherein said first power indicator comprises a light which illuminates when energized.
7. A monitoring device as defined by claim 6 wherein said first power indicator comprises an audible alarm.
8. A monitoring device as defined by claim 3 wherein said voltage indicator and said first power indicator are lights which illuminate when energized.
9. A monitoring device as defined by claim 8 wherein said first power indicator has a terminal for connection to a secondary indicator.
10. A monitoring device as defined by claim 8 wherein said secondary indicator comprises an audible alarm.
11. A monitoring device as defined by claim 2 further comprising a voltage indicator which is energized when said monitoring device detects voltage at said first electrical terminal.
12. A monitoring device as defined by claim 11 further including:
(a) a first adjustable control for varying said first pre-determined power value within a first pre-determined power range;
(b) a second adjustable control for varying said second pre-determined power value within a second pre-determined power range.
(a) a first adjustable control for varying said first pre-determined power value within a first pre-determined power range;
(b) a second adjustable control for varying said second pre-determined power value within a second pre-determined power range.
13. A monitoring device as defined by claim 12 wherein said first and second adjustable controls are potentiometers.
14. A monitoring device as defined by claim 1 further including a circuit breaker which breaks said indicating circuit when power being drawn through said monitoring device is greater than a pre-determined upper power limit.
15. An electrical power draw monitoring extension cord installable in an electrical circuit for indicating availability of electrical power and electrical power being drawn through said monitoring extension cord, said monitoring extension cord comprising:
(a) an electrical indicating circuit;
(b) electricity conveying wires;
(c) a first electrical plug-in at a first end of the electricity conveying wires for connecting said indicating circuit to an outlet socket of an electrical power source;
(d) a second electrical plug outlet at a second end of the electricity conveying wires for connecting said indicating circuit to the inlet of an electrical power consuming device; and (e) a first power indicator which is energized to indicate when power drawn through said monitoring extension cord is greater than a first pre-determined power value.
(a) an electrical indicating circuit;
(b) electricity conveying wires;
(c) a first electrical plug-in at a first end of the electricity conveying wires for connecting said indicating circuit to an outlet socket of an electrical power source;
(d) a second electrical plug outlet at a second end of the electricity conveying wires for connecting said indicating circuit to the inlet of an electrical power consuming device; and (e) a first power indicator which is energized to indicate when power drawn through said monitoring extension cord is greater than a first pre-determined power value.
16. A monitoring extension cord as defined by claim 15 further comprising a second power indicator which is energized to indicate when power drawn through said monitoring extension cord is greater than a second pre-determined power value which is greater than said first pre-determined power value.
17. A monitoring extension cord as defined by claim 15 further comprising a voltage indicator which is energized when said monitoring extension cord detects voltage at said first electrical terminal.
18. A monitoring extension cord as defined by claim 17 further including an adjustable control for varying said first pre-determined power value within a pre-determined power range.
19. A monitoring extension cord as defined by claim 18 wherein said adjustable control comprises a potentiometer.
20. A monitoring extension cord as defined by claim 15 wherein said first power indicator comprises a light emitting diode which illuminates when energized.
21. A monitoring extension cord as defined by claim 16 wherein said second power indicator comprises a light emitting diode which illuminates when the second power value is reached.
22. A monitoring extension cord as claimed in claim 21 for 12 volt D.C.
use including a green light emitting diode which illuminates when a source of power is detected, an amber light emitting diode which illuminates when a functioning electrical load of about 0.5 amperes is reached, and a red light emitting diode which illuminates when a functioning electrical load of about 5.0 amperes is reached.
use including a green light emitting diode which illuminates when a source of power is detected, an amber light emitting diode which illuminates when a functioning electrical load of about 0.5 amperes is reached, and a red light emitting diode which illuminates when a functioning electrical load of about 5.0 amperes is reached.
23. A monitoring extension cord as claimed in claim 21 for 120 volt A.C.
use including a green light emitting diode which illuminates when a source of power is detected, an amber light emitting diode which illuminates when a functioning electrical load of about 35 watts is reached, and a red light emitting diode which illuminates when a functioning electrical load of about 440 watts is reached.
use including a green light emitting diode which illuminates when a source of power is detected, an amber light emitting diode which illuminates when a functioning electrical load of about 35 watts is reached, and a red light emitting diode which illuminates when a functioning electrical load of about 440 watts is reached.
24. A monitoring device as claimed in claim 1 including a spring return switch to shunt out, or momentarily open, a portion of load sensing circuitry for enabling use of the monitoring device for low range and high range electrical load detection.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US401198A | 1998-01-07 | 1998-01-07 | |
| US09/004,011 | 1998-01-07 | ||
| USUNKNOWN | 2002-08-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2254280A1 true CA2254280A1 (en) | 1999-07-07 |
Family
ID=29547622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2254280 Abandoned CA2254280A1 (en) | 1998-01-07 | 1998-11-20 | Electrical power draw monitoring device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2254280A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2447465A (en) * | 2007-03-13 | 2008-09-17 | Richard Pledger | Electrical power consumption monitor |
-
1998
- 1998-11-20 CA CA 2254280 patent/CA2254280A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2447465A (en) * | 2007-03-13 | 2008-09-17 | Richard Pledger | Electrical power consumption monitor |
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