IE60616B1 - Method and apparatus for identifying electrical circuits - Google Patents

Abstract

A method of finding the particular fuse 9 or circuit breaker that protects a remote outlet 6 comprises using the outlet to power a radio transmitter 4, opening or closing the circuits in turn by means of the fuses or circuit breakers, and monitoring events, by means of a radio receiver 3 which responds to signals from the transmitter, until a response is obtained indicating that the required fuse or circuit breaker has been found.

Description

This invention relates to a method for identifying electrical circuits. More especially it relates to a method for identifying a particular circuit accessed at a first location, from among a number of separate circuits accessible at another location or locations remote from said first location, one of which circuits is the circuit to be identified. Ά conventional lighting or power circuit comprises a pair of conductors insulated from each other and from their environment, said conductors being connected to separate bus bars on a fuse board and extending to one or more lighting or power points at which they may be optionally bridged by a current consuming device. One of these conductors is the live line, connected to a live bus bar on the fuse board through a circuit breaker or a removable fuse, and usually having a respective switch interposed in the bridging on the way to each lighting or power point.

The other conductor is the neutral line, connected to a neutral bus bar on the fuse board and to the unswitched side of each lighting or power point. 0 616 The invention seeks to permit identification of a given circuit by making or breaking the power connection to the live line at one point (normally by inserting or removing a sound fuse at the fuse board) and detecting the resultant change of state in the line at a second point, normally a remote lighting or power point.

The invention can be applied, in particular, to the electrician's well-known task of electrically isolating one circuit in a wiring system by removing the correct protective fuse, in order to carry out further work on that circuit in safety. It can also be applied to the converse task of ascertaining whether a fuse newly inserted in a holder has in fact restored power to a particular circuit accessed at a location remote from the fuse board.

It is a commonplace that, in a building, one or more rooms and/or flights of stairs may intervene between a system fuse board and the power socket, lighting fitment, or other appliance where a malfunction needs to be corrected, a circuit extension needs to be made, an appliance needs to be connected to the circuit, or the results of an accident need attention.

An electrician working alone in such a situation must laboriously trek, as a rule, between said location and the fuse board, repeatedly inserting or removing one fuse, visiting the location, checking to ascertain whether the circuit at the location is live or neutral, and returning to the fuse board to repeat the procedure with another fuse holder. This is costly in terms of the electrician's time, fatigue and concentration on the work in hand.

Perhaps more commonly the electrician employs an assistant, and the two of them speak or (often) shout their queries and observations to one another, one from the said outlet location and the other from the place where the fuse board is, until the required circuit identification has been achieved. This again is costly in terms of manpower, except where the assistant is an unpaid volunteer; but that option is limited in practice, and not available in many instances, such as outdoor work where the circuit to be identified is that of a particular dwelling, block, street or even district.

It is an object of the invention to alleviate the aforesaid disadvantages. Another object is to facilitate speedy and efficient identification of a relevant electrical circuit among even a large number of candidate circuits on a fuseboard or similar circuit display where live lines can be interrupted. A further object is to improve the cost-effectiveness of electrical repair, inspection and maintenance, indoors and out. Still further objects are to provide a method for ascertaining whether an electrical conducting pathway exists between a pair of terminals.

According to a first and general aspect, therefore, the invention provides a method for ascertaining whether an electrical conducting pathway exists between a pair of spaced apart terminals A and B, each of which may take either one of two predetermined electrical states, which method comprises changing terminal A from one said state to the other, detecting the consequent altered state, if any, at terminal B, broadcasting the result in the form of a radio frequency signal, receiving the radio frequency signal in the neighbourhood of terminal A, using said signal to generate a perceptible signal, and interpreting the perceptible signal to establish whether said conducting pathway exists, wherein each of several adjacent fuse holders or circuit breakers is treated in succession as terminal A, with a view to discovering which of them, if any, is part of a mains circuit having a remote outlet treated each time as terminal B, and the two electrical states are the public power supply live and neutral states. Terminal as used herein includes junctions.

The radio frequency signal is preferably a digitally encoded signal. The perceptible signal is preferably an audible signal such as an alternating two-tone alerting bleep, which an electrician having a suitable receiver can immediately interpret. Preferably the strength of the perceptible signal is independent of the distance between transmitter and receiver.

Terminal A is normally located on a fuse board along with an array of other similar terminals, thus presenting the problem of identification which the invention seeks to solve. The two electrical states are usually live and neutral, live toeing the public supply voltage such as 220 Volt AC. Terminal A can toe changed from one state to the other toy removing or replacing a sound fuse. This will usually toe done in the course of methodically removing and replacing the fuses on the board, a procedure now terminated toy the successful identification of terminal A which was the object aimed at.

Apparatus suitable for performing the method described above comprises a portable radio frequency transmitter adapted to respond to a terminal (B) in a selected one of said states by broadcasting a radio frequency signal, and comprises a portable radio receiver responsive to said radio frequency signal to generate a perceptible alerting signal the strength of which is preferably independent of the distance between transmitter and receiver.

The transmitter may be directly powered by a conventional mains current obtained from terminal B. Alternatively, and preferably, the transmitter is battery-powered, the power circuit having a relay-operated normally closed switch, as well as a manual on/off switch. The relay is operable by connection to terminal B in the live state, to open the relay-operated switch and thus close down the transmitter. If the terminal then becomes neutral, the relay ceases to operate, the associated switch closes (tha manual switch is of course already closed), the transmitter is energized and the radio frequency signal is broadcast.

The transmitter is preferably a short-range one, ranges up to 250 meters being sufficient for most practical purposes. It is preferably equipped with a standard power plug and a bayonet plug, or a multiple adaptor plug, for convenient connection to a range of different designs of electric power and lighting outlets.

The receiver, like the transmitter, preferably has a manual on/off switch to be closed whenever it is desired to use it. The receiver is preferably battery-powered. It generates its own perceptible signal, which may be continuous or discontinuous. The signal may be produced by a lamp or a light-emitting diode, but is preferably a sound signal of the familiar bleep type. The signal is preferably one of constant strength independent of the distance between the transmitter and the receiver. It is generated by the receiver on actuation by the received radio frequency signal from the transmitter. The radio frequency signal is preferably digitally encoded, as mentioned above, and can be identified and validated by the receiver.

The broadcast frequency should be remote from other frequencies commonly used, including public broadcast or service frequencies. The receiver is conveniently designed for wearing on the user's person. It may have a pocket clip or a wrist strap, for example.

The invention will be appreciated in greater detail from the following desciption of a particular and preferred embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which Fig 1 is a schematic illustration of the performance of the method of the invention; Fig 2 is a perspective view of apparatus for performing said method in a preferred embodiment of the invention; Fig 2(a) shows a radio transmitter and Fig 2(b) a receiver/alarm; Fig 3 is a circuit diagram of (a) a transmitter, and (b) a receiver of an earlier design than that of Fig 2, Referring now to the drawings, Fig 1 illustrates the performance of the method of the invention. Fig 1(a) shows an electrician 1 working at a domestic fuse board 2, while Fig 1(b) shows a transmitter 4 at a remote location in the same building, separated from the location of Fig 1(a) by one or two rooms and a flight of stairs 5. r The electrician 1, wishing to work on a circuit which includes a power socket 6, has plugged the transmitter 4 into that socket, closed the transmitter manual switch 7, and returned to the fuse board 2. It is to be assumed that the fuses are unlabelled. The electrician, who carries a radio receiver/alarm 3, closes its manual on/off switch 8.

It is also to be assumed that the live” terminal of power socket 6 is in fact for the time being live.

The live terminal of socket 6, having been thus connected to the relay-operated switch in the transmitter 4, opens the battery power circuit therein and thus disables the transmitter. The electrician 1 now removes and replaces the fuses 9 on the fuse board 2, one by one, until the fuse currently removed is that belonging to the circuit which includes the socket 6. The live terminal in said socket has been converted to neutral as a result, whereupon the relay-operated switch closes and the transmitter 4 commences to emit its digitally encoded signal. The signal is received by the receiver 3 which responds by producing an audible alarm tone, informing the electrician 1 that the fuse currently removed belongs to the circuit under investigation.

Referring now to Fig 2. the transmitter 4 incorporates, in addition to the manual switch 7, indicator lights 10, 11 of the LED type. Indicator light 10 corresponds to a so-called phase tester, and indicates that the transmitter is connected, through its connector plug 12, to a live circuit. Indicator lamp 11 lights to show that the transmitter 4 is transmitting. A connector lead 13, having (d a household plug 12 on one end thereof, has a covered-terminal plug (not shown) at its other end, which •J plugs into a corresponding exposed pin socket (not shown) in the transmitter case.

The receiver 3 has a manual on/off switch 8, an LED-type indicator light 14 which lights up to show when the receiver is switched on and functioning, and a carrying strap 15.

Referring now to Fig 3(a), this transmitter circuit may be notionally analysed into a power supply Ps, a two-tone signal generator Sg, and a transmitter proper Tm. The values of the various components are given in the list at the end of this description.

Branched from the live and neutral lines of the mains power input L, N are respective indicating means Nl, N2 to act as a phase tester for the live line of the circuit under investigation, or for the neutral line if that happens to be live as a result of faulty wiring.

Xn the two-tone generator Sg (a CMOS 4001 unit) in use, the left-hand gate pair generates a tone, and the right-hand gate pair converts the tone into an alternating high/low frequency audio signal. A transistor Tl effects a modulation of the carrier wave (50 MHz) of the oscillator of the transmitter Tm corresponding to the two-tone signal produced by the generator Sg. The resulting radio frequency signal is broadcast from the antenna A. <1 Referring to Fig 3(b), this receiver circuit may be : analysed into a receiver proper or tuned circuit Tc, a demodulating circuit Dm, a driving transistor arrangement Ts, an audio transformer At, a speaker S, a power pack P Γ consisting of battery and switch, and an LED indicator D3 to show when the receiver is switched on. It also includes a flasher circuit R (CMOS 4001) to reduce the power consumption of the LED by converting it to flashing. Circuit R is powered from the power pack P.

Lists of components are given hereunder for the circuit diagrams of Fig 3.

Component Values Transmitter Rl 1 M R2 1 M R3 1 M 5 R4 1 M R5 10 M R6 470 R R7 10 M R8 220 K R9 22 K R10 10 K Rll 10 K R12 1 K R13 100 R R14 10 K R15 22 K Cl 470 P C2 0, . 1 p C3 1 C4 0. . 1 p C5 o. . 02 p C6 22 pF C7 10 I1 C8 5 pF C9 25 pF 05 TI 2N 3702 T2 2SC 945 DI IN 4001 D2 IN 4001 D3 IN 4148 10 D4 IN 4148 D5 (LED) D6 IN 4148 RECEIVER/ALARM Rl 470 R R2 22 K R3 10 K R4 470 R R5 470 K 20 R6 4 K 7 R7 22 K R8 470 K R9 100 R RIO 2 M 2 25 Rll 100 K R12 10 M Cl 5 : nP C2 25 : pF 30 C3 0. 02 H C4 10 H C5 0» 04 p C6 0. 04 f1 C7 0. 02 C8 0.02 p C9 10 μ CIO 0.02 μ Cll 0.04 p 05 C12 0.1 p C13 0.04 p TI 2SC945 T2, 3, 4 3 x ED 1403 E 10 DI IN 4148 10 D2 IN 4148 D3 (LED) 15 V 9 Volt

Claims (5)

Claims

1. A method for ascertaining whether an electrical conducting pathway exists between a pair of spaced apart terminals A and B, each of which may take either one of two predetermined electrical states, which method comprises changing terminal A from one said state to the other, detecting the consequent altered state, if any, at terminal B, broadcasting the result in the form of a radio frequency signal, receiving the radio frequency signal in the neighbourhood of terminal A, using said signal to generate a perceptible signal, and interpreting the perceptible signal to establish whether said conducting pathway exists wherein each of several adjacent fuse holders or circuit breakers is treated in succession as terminal A, with a view to discovering which of them, if any, is part of a mains circuit having a remote outlet treated each time as terminal B, and the two electrical states are the public power supply live and neutral states.

2. A method according to claim 1, wherein the strength of the perceptible signal is independent of the distance between transmitter and receiver.

3. A method according to claim 1 or 2 wherein the [ perceptible signal is an audible alternating two-tone alerting bleep.

4. A method according to any of claims 1-3 wherein the 05 radio frequency signal is digitally encoded.

5. A method for ascertaining whether an electrical conducting pathway exists between a pair of spaced apart terminals A and B, substantially as herein described with reference to or as illustrated in the accompanying 10 drawings.