NZ525073A - Testing an electrical device using an apparatus having magnetic switch, the state of the switch showing the state of the device - Google Patents

Abstract

An emergency lighting unit 1 that includes a test circuit activated by a magnetic switch 2 is described. To test the circuit a member 5 with a magnet 6 at the tip is used, with the magnet being brought into close proximity to the switch 2. If the lighting system is working correctly an indicator light 3 is illuminated.

Description

525 WO 02/27339 PCT/NZO1/00208 AN APPARATUS FOR TESTING AN ELECTRICAL DEVICE TECHNICAL FIELD The present invention relates to a method and apparatus for testing an 5 electrical device. More particularly, although not exclusively, the present invention relates to an electrical device having a test circuit incorporating a magnetic switch wherein the test circuit generates a signal indicating the status of the device when the state of the magnetic switch is changed.

BACKGROUND ART A number of electrical devices, such as emergency lighting systems, require regular testing to ensure that components of the system are functioning correctly (eg battery, light source etc). Many emergency lighting systems incorporate test buttons which, when actuated, indicate 15 whether the components of the emergency lighting system are functioning as desired.

Where emergency lighting systems are located in inaccessible positions it is time consuming and difficult for a serviceman to test them. Typically, 20 this requires a serviceman to transport a ladder to the various emergency lighting systems and actuate each test button manually.

A smoke detector has been proposed in which a light detector is incorporated within a test circuit which, when light falls on the detector, 25 conducts a test and indicates the status of the unit. Such a system suffers from the disadvantage that the test circuit may be activated by stray light and requires a serviceman to carry a light source with them. As well as the cost involved in providing batteries for the light source there is the additional annoyance in that a test cannot be conducted should the 30 batteries of the light source fail. 1 PCT/NZ01/OO2O8 It is an object of the invention to provide a simple and convenient means of testing electrical devices located in remote positions that overcomes these drawbacks or at least provides the public with a useful choice.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided an electrical device including a test circuit having a magnetic switch and a signal generator electrically connected to the test circuit, the circuit being responsive to the state of the magnetic switch to generate a signal indicative of the state of the device.

The signal generator may generate a visible or audible signal indicative of the state of the electrical device. A signal may be generated when the test circuit determines that the electrical device is in an operational state. The magnetic switch may be a reed switch, Hall effect sensor or other magnetically actuated switch.

There is further provide a system comprising an electrical device as hereinbefore described and an elongate member having a magnet connected to a distal end thereof.

According to a further aspect of the invention there is provided a method of testing an electrical device having a magnetic switch connected to an electrical test circuit of the device which generates a signal perceivable by a user to indicate the status of the device when the state of the magnetic switch is changed, the method comprising bringing a magnet into sufficiently close proximity to the magnetic switch to change the state of the magnetic switch and observing the signal generated by the device to determine the status of the device.

PCT/NZO1/00208 BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of examples referenced to the accompanying drawing in which: Figure 1: is a pictorial representation of an electrical device and test actuating means according to the invention.

Figure 2: is a circuit diagram of part of the circuit of an emergency lighting system incorporating a test circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to figure 1 an emergency lighting system 1 has a reed switch 2 which is electrically connected to a test circuit within emergency lighting system 1. A light source 3 generates visible radiation 4 when driven by the test circuit. Elongate member 5 has a magnet 6 provided at one end thereof.

When magnet 6 is brought into sufficiently close proximity to reed switch 2 it changes the state of reed switch 2, The change in state of reed switch 2 causes the test circuit to generate visible radiation 4 from light source 3 if the components of the emergency lighting system are operating correctly. In particular, the test circuit may test the state of a backup battery within the emergency lighting system.

If magnet 6 is brought into close proximity to reed switch 2 and light source 3 is not activated this is indicative of failure of a component of the emergency lighting system and that servicing is required.

It will be appreciated that another form of signal generator may be substituted for light source 3, such as an audible signal.

Further, it will be appreciated that the test signal may be either a transition from an on-state to an off-state or from an off-state to an on-state or some other user identifiable sequence.

Likewise, reed switch 2 may be of a normally closed or normally open type and it is simply the transition of state that causes the test circuit to generate a signal or not in dependence upon the state of the components within the emergency lighting system.

Referring now to figure 2 a circuit diagram of part of an emergency lighting system incorporating a test circuit is shown. The circuit to the left of battery 7 is a power supply circuit for maintaining battery 7 in a charged state. The circuit to the right of battery 7 is a test circuit for testing the status of battery 7. Power is supplied to the power supply section via lines 8 and 9. Power passing through LED 10 causes it to emit radiation. LED 10 is optically coupled to opto-transistor 11. In normal use power flows through LED 10 and the radiation it generates causes opto-transistor 11 to switch on. This provides a low resistance path in parallel with transistor 12 which pulls the voltage at point 13 high.

A reference voltage is generated at point 15 (by virtue of zener diode 18 and diodes 17) which lies between the Voltages at point 13 when opto-transistor 11 is on and off (and battery 7 is charged).

If there is a power failure LED 10 turns off, causing opto-transistor 11 to turn off, and the voltage at point 13 to drop below the reference voltage at point 15. This causes a change in state of the output of comparator 16 which causes the emergency lighting 3 to be activated.

Reed switch 2 and resistor 14 are provided in parallel with LED 10. 4 When reed switch 2 is closed, resistor 14 provides a low conduction path in parallel with LED 10 which turns off LED 10. This causes opto-transistor 11 to turn off. Opto-transistor 11 thus becomes a higher resistance path in parallel with resistor 12. This causes the voltage at point 13 to drop.

Accordingly, when opto-transistor 11 is turned off there is a change in state of comparator 16. The change in state of comparator 16 causes a drive circuit (not shown) to drive light source 3 (figure 1). A serviceman may thus visually observe whether the emergency lighting system is operating correctly.

There is thus provided a system which enables easy testing of a remotely positioned electrical device without requiring a serviceman to ascend a ladder to test the device. In furtherance of that objective the magnet 6 is mounted at the end of the member 5, which member 5 is desirably in the form of a telescopic rod, which rod may be extended as necessary to bring the magnet 6 into proximate range of the reed switch 2.

Magnetic activation is cheap and simple and minimises the risk of erroneous activation. A magnetic switch may be placed within a housing and so requires no modification of the housing and does not compromise the aesthetics of the housing.

Where in the foregoing description reference has been made to integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the invention as claimed.

Claims (1)

1. An emergency lighting unit including a test circuit having a magnetic switch and a signal generator electrically connected to the test circuit, the circuit being responsive to the state of the magnetic 5 switch to generate a signal indicative of the state of the device, characterised in that the signal generator generates a visible or audible signal when the test circuit determines that the electrical device is in an operational state. 10 An emergency lighting unit according to claim 1 wherein the magnetic switch is a reed switch, a Hall effect sensor or any other form of magnetically actuated switch. 15 A system comprising an emergency lighting unit according to claim 1 or 2 and an elongate member having a magnet connected to a distal end thereof. 20 A method of testing the emergency lighting unit of claim 1 or 2, the method comprising bringing a magnet into sufficiently close proximity to the magnetic switch to change the state of the magnetic switch and observing the signal generated by the emergency lighting unit to determine the status of the emergency lighting unit. 25 An emergency lighting unit according to claim 1 substantially as herein described or exemplified with reference to the accompanying drawings. 30 A system according to claim 3 substantially as herein described or exemplified with reference to the accompanying drawings. A method according to claim 4 substantially as herein described or exemplified with reference to the accompanying drs_ intellectual property office! of n.z. 2 6 may 2005 Received