GB2428339A

GB2428339A - Power supply monitoring apparatus

Info

Publication number: GB2428339A
Application number: GB0613696A
Authority: GB
Inventors: Julian Bowyer
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-12
Filing date: 2006-07-10
Publication date: 2007-01-24
Also published as: GB0613696D0; GB0514252D0

Abstract

A power supply monitoring apparatus comprises: monitoring means 28-30 for monitoring a supply voltage: a memory that is set to a first state when a power interruption occurs and an output device 26 that indicates a power failure until it is reset by a user. The apparatus may either be a plug-in device (fig 3) having pins (fig 1, 2,3) and socket (fig 1, 4) for connection to an appliance or be incorporated into an appliance. The device may indicate the duration of a power cut and, may also monitor current drawn to warn when an abnormal pattern of current usage is detected. Where the appliance is refrigerator or freezer it may also use temperature data to assess degradation of food stored therein. The apparatus may comprise processor 24 with non-volatile memory; rechargeable battery 22; current monitoring means 30, 32: audio or visual display 26, remote communication device 28 for connection to the internet, and an optical docking sensor 34 to detect incomplete insertion of plug and socket pins. The display 26 may use a pattern of symbols (fig 2) from LEDs (fig 4, 56) to indicate the power supply status and the alarm may be reset using a light detector such as a phototransistor.

Description

P1078816B/SAB

POWER SUPPLY MONITORING APPARATUS

FIELD OF THE INVENTION

The present invention relates to an apparatus for monitoring a power supply and providing an alert if the supply falls outside an acceptable range or if the supply is interrupted.

BACKGROUND OF THE INVENTION

A problem that arises with appliances such as freezers and refrigerators, although it applies equally to other units, appliances and components is that it is not always easy to determine whether the appliance, unit or component is connected to a power supply and turned on. Similarly it, it can be difficult to detennine if normal operation of such a device, appliance, unit or component has been temporarily inhibited, either by design or accident.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a power supply monitoring apparatus comprising monitoring means for monitoring a supply voltage and indicating a status of the supply voltage, a memory, and an output device, wherein interruption of the power supply causes the memory to be set to a first state that the output device gives on indication of a power failure until such time as a user resets the monitoring apparatus.

It is thus possible to provide a device that can warn users that the power to a device has been interrupted or has fallen outside an acceptable operating range such that proper operation of the device cannot be guaranteed.

Preferably the device has an audible and/or visual user interface for givuig an indication that an interruption has occurred. However, embodiments of the device.- may provide outputs detectable by other senses, such as touch or smell, or even taste, in order to facilitate use of the device by people whose normal range of senses areS, impaired. Thus a vibration motor might be actuated to give a vibratory output, a heater may be activated to warm a pad containing a scent such that the scent is discharged, or a flavour or liquid may be dispensed into a delivery tube.

Advantageously the device also includes remote connectivity. This may, for example, be by radio connection to messaging services within mobile telephone networks, or interconnection to the internet, for example by interfacing with a wireless LAN or by sending encoded messages along the power supply cables to the device.

The power supply monitoring apparatus may further include a sensor responsive to a signal for indicating when a load connected to the power supply monitoring apparatus should be operating. The device may then compare the current drawn by the load with the signal indicating that the load should be operating and, based on a knowledge of the properties of the load, which properties may either adaptively learnt or be preprogrammed, may give an alert if the load appears to be non-functional.

Advantageously the monitoring device includes a data processor adapted to monitor the voltage of the power supply and, optionally, the current drawn by the load.

Advantageously the device further includes a counter or timer for recording the duration of a power supply interruption or, alternatively, the times at which changes of status in the power supply occur, such that times of interruption of a supply and the time of restoration of supply is known. The counter/timer and data processor are advantageously associated with a non-volatile memory such that this data can be recorded. The power supply monitoring apparatus advantageously further includes an internal power storage device, such as a battery or a capacitor, to provide operation for a period of time following interruption of the power supply. Advantageously the internal power store is replenished from the power supply.

As well as power failure, the device may be adapted to monitor for overvoltage or under-voltage conditions, transients and the like and to issue an appropriate warning.

Power supply monitoring apparatus constituting embodiments of the present invention may be used both within the domestic and industrial environments. Indeed, the invention could be extended to monitoring other parameters other than power supply, and may be operated in conjunction with a suitable sensor, such as a pressure sensor or flow rate meter, to give an indication of a perturbation in a fluid supply, such as a drop in pressure in a gas supply, drop in pressure in a liquid supply or suspension of flow in the liquid supply.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will further be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows perspective views of the exterior of a warning device constituting a first embodiment of the present invention; Figure 2a, 2b and 2c show various graphical displays shown on a display portion of the embodiment shown in Figure 1; Figure 3 shows a placement of a sensor for detecting incomplete docking of a plug in a socket; Figure 4 is a circuit diagram of the first embodiment of the present invention; and Figure 5 is a schematic diagram of a further embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

As shown in Figure 1, a warning device constituting an embodiment of the present invention can be provided within a plug-in unit 1 adapted to be inserted into a wall socket. The plug shown conforms to the British Standard having live, neutral 2 and earth 3 pins although, it will be appreciated, that other jurisdictions have other plug configurations and the device can be adapted accordingly. It also has a display screen 4.

As shown in Figure 5, the device generally comprises a AC to DC converter 20, either in the form of a switching converter or a step down transformer with associated regulation and smoothing. An output of the AC to DC converter is provided to a power store 22, for example a battery, although it could be a capacitor, and to a processor 24. The voltage on the live conductor "L" may also be rectified by a diode 26, and attenuated and clamped by a resistor network 28 in combination with Zenner diode 30 so as to provide a signal which indicates the presence of the power supply and which is also provided to the data processor 24. The data processor 24 is in communication with a output device 26 which may be an audible or visual display, and optionally may be in communication with a remote communication device 28 in order to enable radio or internet communication, for example, with remote devices.

The device may also include a "docking" sensor 34 for confirming that the device is properly engaged with the electricity socket.

In embodiments of the invention where it is desired to monitor the current drawn by a load, a current sensor 30 may measure the current flowing to a live output pin L', and the current measurement may be digitised by an analogue to digital converter 32 and provided as a further input to the data processor 24. Thus the data processor can monitor, or indeed learn, expected patterns of current drawn by a device.

When the device is plugged into a power supply, it enters an initial mode to alert the user that it is functional. Simultaneously, the internal power store 22 starts charging.

In a first embodiment of the present invention, the user interface 26 comprises a plurality of light emitting diodes LEDs and an audible buzzer.

With the first embodiment the LEDs and sound alert the user it is working. Once the initial start procedure has completed the device LED's are illuminated in the form of a no-enter sign as shown in Figure 2a. The device has a sensor 34 that is sensitive to light, and which sits flush with the plug surface base casing located where the plug pins extend, as shown in Figure 3. As the plug is pulled out from the socket by just a few millimetres, for example 1 - 5 mm, the sensor triggers the circuit inside the plug and activates the audible alert and causes the display to change to flashing lights in a circle formation shown in Figure 2b. At this point the device can be replaced back into the socket and the lights display a further symbol, such as the cross formation Figure 2c and the sound alert stops. The device is now in operational mode. If however the device is taken away from the socket altogether the device will constantly flash lights in a cross formation Figure 2c and the sound alert will continue until the device has been turned off or reset, by a source of light. To turn off or reset the device it can be held up to a source of light, skylight, torch or flashlight or the like that is bright enough to trigger the senor to restart or reset the device.

Figure 4 shows a circuit diagram for a further embodiment of the invention. The embodiment shown in Figure 4 uses several methods to keep power consumption and internal heat generation as low as possible.

The circuit works from a single 5Vdc supply. This supply is obtained from one of two sources. The first is from the 220/240V mains supply. When the unit is plugged into the mains the circuit brings the 220/24OVAC down to 5. lVdc. This supply is closely regulated and filtered. A second supply is also generated from the mains, regulated and filtered for detection of the mains by the logic, (Power fail). This supply is extremely low power. The second source for power is from a 4.8V nickel metal hydride battery 40. The battery 40 supplies the circuit when the 220/240AC is not present. The battery supply 40 switches into the circuit power supply via a diode 42 with a very low forward volt drop. (0.2Vdc). A trickle charge resistor 44 bypasses this diode in normal operation to supply a charging current for the battery.

The control logic for the device is a microprocessor 50 having internal non-volatile memory. The flash based program storage for the device can be updated without removing it from the board. The device is clocked from a crystal. Programming the flash memory is achieved via a six-pin header socket 52 mounted on the board.

Thirteen light emitting diodes LEDI to LED13 are surface mounted to the topside of the circuit board. The LEDs are arranged in a circle with a cross in the centre at forty- five degrees. The LEDs are wired in groups of two with one LED on its own.

Each pair of LEDs connects to the microprocessor via current limiting resistors. A common rail resistor 54 is used for the paired LEDs, while the single led has its own resistor 56.

A docking sensor is connected to the board with wires is order to mount it on the case.

The sensor has two parts to it.

A transmitter emits light, for example infrared light, from a surface, such as the front surface via a LED. The circuit provides a steady current for the emitter via a resistor.

Reflected IR light is collected by a phototransistor mounted in the device. The circuit provides output current conversion for the sensor. This set up provides an analogue output from the sensor. A reference voltage is derived from the circuit to provide a switching level for the sensor. The analogue reference level and analogue sensor level are fed into the microprocessor which has an internal programmable comparator for analogue use. The light level viewed by the sensor can be taken as being indicative of whether the plug is removed from a socket, partially inserted or fully inserted.

When power is applied to the circuit, the microprocessor resets via a reset circuit on the board. This consists of a capacitor, connected to the reset pin of the device and zero volts.

The microprocessor executes the following actions. The sensor input is checked as is the mains failed input pin. The output to the LEDs depends on the state of these pins.

The LEDs are switched on in turn to display either a no entry sign, or a cross.

The circuit also has a sounder connected, driven by the microprocessor to alarm the user of a problem.

If the mains power supply fails a non-volatile code is written to the memory of the data processor. The next time the data processor wakes up on the power returning, all lights will be illuminated to show the power had failed previously. A reset button at the rear of the unit allows normal operation to continue.

A power interrupt switch is mounted on the underside of the enclosure. This disconnects the battery from the circuit when the device in not in use. Thus operation of the device is simple and automatic.

Plugging the device into a mains socket supplies the power to the circuit and switches the battery circuit out. This happens seamlessly due to the O.5V difference between the battery (4.8V-O.2V) and the 5.IV supply from the mains. The display is!it showing a flashing cross a power failure has been detected. Pulling the device away from the power source and pointing it to a light will reset the device once again.

To keep power dissipation down to a minimum and reduce internal heating of the unit, the L.E.D.S are multiplexed in groups of two. The total demand for current in the embodiment shown is just 4OmA maximum.

The required micro-processing functionality can be provided by an AT90523 13 which is a micro-controller from ATMEL Corp. The device may be stored alone as described here, or may be integrated with items of equipment, for example freezers to warn of supply interruptions.

The display may be modified to be capable of displaying nwneric or alphanumeric symbols such that indications of the duration of the failure can be given. This may enable a user to judge whether, for example, the contents of a freezer might have thawed and then refrozen. Where the device is integrated within a freezer, the display may also display the maximum temperature -as recorded upon resumption of power to the freezer.

Claims

I. A power supply monitoring apparatus comprising: monitoring means for monitoring a supply voltage and indicating a status of the supply voltage, a memory, and an output device, wherein interruption of the power supply causes the memory to be set to a first state that the output device gives on indication of a power failure until such time as a user resets the monitoring apparatus.
2. A power supply monitoring apparatus as claimed in claim 1, further including a timer such that an indication of the duration of the interruption can be provided to a user.
3. A power supply monitoring apparatus as claimed in claim I or 2, wherein the output device is a visual output device.
4. A power supply monitoring apparatus as claimed in claim 3, wherein the output device displays one of a plurality of symbols to indicate a power supply status.
5. A power supply monitoring apparatus as claimed in any one of the preceding claims further comprising current monitoring means for detecting that a load is drawing current.
6. A power supply monitoring apparatus as claimed in claim 5, wherein the apparatus further comprises a data processor adapted to monitor the current drawn by the load and to learn a pattern of use such that abnormal current use patters can be detected an a warning asserted.
7. A power supply monitoring apparatus as claimed in any one of the preceding claims wherein the apparatus comprises an internal power store replenished from the power supply.
8. A power supply monitoring apparatus as claimed in any one of the preceding claims further comprising at least one sensor for detecting incomplete docking of a plug into a socket of the power supply monitoring apparatus or incomplete docking of a plug of the power supply monitoring apparatus with a power supply socket.
9. A power supply monitoring apparatus as claimed in claim 8, in which the at least one sensor for detecting incomplete docking comprises an opto-detector.
10. A power supply monitoring apparatus as claimed in claim 9, wherein the apparatus can be reset by a sequence of disconnection from a power supply and exposure of the opto-detector to light.
11. A power supply monitoring apparatus as claimed in any one of the preceding claims, further including an audible warning device.
12. A power supply monitoring apparatus as claimed in any one of the preceding claims, further including connection means for establishing communication with the internet so as to send messages or to be remotely interrogated.
13. An appliance including a power supply monitoring device as claimed in any of the preceding claims.
14. A freezer or refrigerator including a power supply monitoring apparatus as claimed in any one of the preceding claims.
15. A freezer or refrigerator as claimed in claim 14, further including a temperature sensor to monitor temperature within a food storage region and a data processor adapted to examine the duration of the power supply interruption and temperature to assess degradation of food stored within the freezer or refrigerator and output its assessment.