GB2236642A

GB2236642A - Control of equipment at a remote site from another site via cellular phone

Info

Publication number: GB2236642A
Application number: GB9020565A
Authority: GB
Inventors: James Neil Deas; Robert Charles Ellett; Christopher John Morgan
Original assignee: National Grid Co PLC
Current assignee: National Grid Co PLC
Priority date: 1989-09-21
Filing date: 1990-09-20
Publication date: 1991-04-10
Also published as: GB8921330D0; GB9020565D0

Abstract

A data logger unit 4 installed at a remote site communicates its data to another site via cellular telephone 2 and modem 8. The telephone and modem are powered by a rechargeable battery 14 itself powered from a solar panel 16. The power to the telephone and modem is switched 12 by clock 10 so that the telecommunications link is only powered up for short periods so that data from the logger unit is downloaded rapidly in such periods. The arrangement reduces battery capacity substantially. <IMAGE>

Description

APPARATUS FOR THE CONTROL OF EOUIPMENT AT A REMOTE SITE FROM ANOTHER SITE This invention relates to apparatus for the control of equipment at a remote site from another site, and also to apparatus for the transfer of data from a remote site to another site, for example the storage of data at the remote site and the transmission of that data to another, possibly more central, site.

It is often necessary to sample and store data at remote locations where no source of mains power exists. Typical examples might be at sites in remote countryside where the utility companies (electricity, water, gas) may wish to sample data of use to them. Another example is the storage of meteorological data at remote locations. The data must be collected and stored at the site in a data logger unit; some means must be provided for enabling the data to be transferred to a data collection or processing centre, and the logger unit optionally reprogrammed with a new control sequence. Similarly, it is sometimes desirable to reprogram control equipment at the remote site from the central base site.

Two problems exist - firstly the provision of power for the apparatus at the remote site, and secondly the necessary means for transfer of data or control signals to or from the remote site. Insofar as power is concerned, as no mains electricity is likely to be available, the likely solution is a free-standing generator (which is noisy, and needs refuelling and servicing regularly) or batteries which can be recharged. As concerns the transfer of signals, direct cable connection is likely to be impossible and the likely solution might be a radio link, for example as provided by a cellular radio system. One combination which might solve these problems is a solar-rechargeable battery assembly linked to a modem and cellular telephone. Such a combination is relatively-maintenance free. One disadvantage of such a combination is the current drain on the battery from the communications side.A modem and a cellular telephone consume, when transmitting, relatively large amounts of power. This would dictate a large capacity battery and a large solar panel. This itself would add considerable weight to the equipment to be carried to the remote site, not to mention the cost.

It is known from United States Patent No. US-A-4788711 to transmit data at a set time each day rather than continuously. The equipment at the remote site is therefore not continuously connected to the communications link, but only at a certain set period each day. This can save dramatically on the necessary battery capacity. However, the apparatus disclosed in this patent still suffers from the drawback that it consumes a substantial amount of power.

Further reductions in power consumption would be advantageous.

According to the present invention there is provided apparatus for the control of equipment at a remote site from another site, comprising, at the remote site, a cellular telephone, power means for powering the cellular telephone, a clock, switch means controlled by the clock and connected between the power means and the cellular telephone to power the cellular telephone periodically so that it is receptive for a selected interval to signals transmitted from said another site, and control means connected to the cellular telephone for controlling the equipment in response to signals transmitted from said another site during said interval.

As used herein, the term "connected" is not limited to hard-wired connections, but includes reference to any arrangement across which signals can pass.

This invention is based on the fact that a cellular telephone operates at essentially three power consumption levels, namely a zero power consumption level when the telephone is switched off, a low power consumption level when the telephone is switched on and is thus open to receive calls but is not actually transmitting or receiving calls, and a high power consumption level when the telephone is transmitting or receiving calls. The apparatus powers the cellular telephone at periodic selected intervals ("windows") so that it is receptive to, but does not itself initiate, any transmissions. Rather, the other site (usually a base site) can successfully transmit to the remote site at any time during any of these windows at will.

Thus, for example, one 10 minute window per day may be created, but the base site may not transmit more than once every week. It can be seen that control of the remote site by the other site (the base site) during intervals or windows created by the apparatus at the remote site can allow significant power savings to be made.

A further advantage of allowing the other site to control the remote site is that the mode of operation of the equipment at the remote site can be changed as required without visiting the remote site.

The invention extends to an apparatus as aforesaid comprising the equipment. The equipment may, for example, be a valve or relay, but in the preferred embodiment includes data collection means (preferably forming part of a data logger unit), in which case the control means is preferably capable of initiating the transmission of data collected by the data collection means to said another site.

Data can thus be downloaded from the apparatus during the selected intervals at the command of the other site.

The apparatus suitably comprises an interface between the cellular telephone and the control means, although this is by no means essential. For example, with the PAKNET (trade mark) cellular network (which transfers signals in digital form) a modem is not required. The control means may conveniently consist of circuitry, some of which may be associated with the equipment and some of which may be associated with the interface. In the preferred embodiment what is referred to as the data logger unit actually incorporates most of the control circuitry. This circuitry may be programmable, both before installation of the apparatus and also by control signals from the other site.

If the equipment includes data collection means, the apparatus advantageously further comprises means for permitting transmission of data to continue after said interval has terminated, to prevent loss of data.

Again, if the equipment includes data collection means, the control means may perform such functions as changing the data being logged or the frequency of logging, or selecting the length or time of occurrence of said interval.

The apparatus preferably includes fail-safe means whereby, on the occurrence of a predetermined event, the cellular telephone is continuously powered, so that the window can be overridden. The predetermined event may, for instance, be failure or disablement of the control means due, perhaps, to obliteration of any program instructions contained therein.

The power means preferably includes at least one rechargeable battery (although this is not essential), in which case the apparatus preferably further comprises at least one primary battery, and means for switching the or each primary battery into circuit when the voltage of the or each rechargeable battery falls below a preset level. The primary battery therefore acts as a backup power supply, which may be particularly useful for maintaining the data logger unit. The rechargeable battery may conveniently be recharged by a solar panel.

Preferably also, the apparatus further includes means for calling said another site when the voltage of the power means falls below a preset value. By warning the other site of a low battery state, remedial action, such as a reduction in the size or frequency of the interval, may be taken.

According to a related aspect of the present invention, there is provided apparatus for the transfer of data from a remote site to another site, comprising a data logger unit, a cellular telephone connected to said data logger unit for transmission of data collected and stored by the data logger unit to said another site, at least one battery for powering said cellular telephone, means for powering said data logger unit, a clock incorporated within the data logger unit, and switch means controlled by said clock and connected between the or each battery and the cellular telephone whereby the latter is towered on a periodic basis.

This aspect of the invention allows a simple and cheap circuit design for the apparatus to be adopted. If the clock were separate from the logger unit and it were required to control the clock from said another site (the base site), the apparatus would need to have at least two lines of communication, one to the logger unit and one to the clock. This in turn would probably require the use of a tristate driver to control whether communication was to be with the logger unit or the clock, which would render the circuitry of the apparatus more expensive.

Preferred features of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block circuit diagram of the apparatus; and Figure 2 is a schematic diagram showing the apparatus in more detail.

Referring to Figure 1, the apparatus comprises a cellular telephone and aerial 2, a data logger unit 4, and an interface 6 between the telephone and the data logger unit including a modem 8. The data logger unit 4 includes a clock 10 which, as well as performing its normal timing functions within the logger unit, controls the opening and closing of a switch 12 connected between a rechargeable battery 14 and the cellular telephone and its interface. A solar panel 16 is connected via a voltage regulator 18 to the battery for recharging purposes. The rechargeable battery 14 is connected to the data logger unit 4 via the voltage regulator 18 and a voltage comparator 20. A primary dry cell battery 22 to act as a standby is connected to a second input of the voltage comparator 20.

In more detail, referring to Figure 2, the cellular telephone and aerial 2 includes a transmitter/receiver 30 and a voice/data box 32. It is thus possible to communicate not only data from a remote site to a base site, but also voice information. This is useful if the operator is visiting the remote site and wishes to communicate directly with the other Cite. It will be understood that the cellular telephone may be capable of communicating over any cellular network, such as the VODAFONE, CELLNET or PAKNET (trade marks) networks, but that if the PAKNET (trade mark) network is used no voice communication would be possible.

In one preferred embodiment as tested successfully the cellular telephone was a transportable model commonly available for use in automobiles.

The data logger unit 4 is a commercially available model, designated as model CR10 available from Campbell Scientific Limited, College Road, Sutton Bonington, Loughborough, United Kingdom. Two main output ports are used on the data logger unit, and these are designated as ports CPl and CP2. Port CP1 feeds into an inverter 34 and thence into an OR gate 36. Port CP2 feeds straight into the OR gate 36. The logger unit 4 also has d data terminal ready (DTR) output, whose purpose will be described later.

The output from OR gate 36 and the DTR output are fed into a second OR gate 38, which ultimately outputs to the switch 12 which is a relay switch. A manual override switch 40 is provided for overriding the switch 12 to assist in the initial setting up of the apparatus and to enable fault diagnosis to be carried out.

The interface 6 includes, as well as the modem 8, a tensecond timer 42 and a level changer 44.

In one preferred embodiment as tested successfully, the rechargeable battery 14 was of 30Ah capacity, recharged from a 50W solar panel. The primary dry cell battery 22 was a series of 7.5 Ah alkaline dry D-cells which were capable of powering the data logger unit 4 for up to about a month.

The manner of operation of the apparatus will now be described.

Operational overview In brief, in normal operation, data, D, is received and stored continuously by the data logger unit 4 at whatever sampling rate is appropriate, the power for driving the logger unit being received from battery 14 which is recharged from the solar panel 16. The power consumption of the data logger unit is relatively low, but in the event of battery 14 failure (or lack of recharge) the drop in voltage is sensed by the voltage comparator 20 which, at a preset voltage, isolates the battery 14 and enables the dry cell battery 22 to continue powering the logger unit. Thus if the battery 14 is disconnected (for instance, during transit) the logger unit memory is retained.

For a major portion of periods of the day clock 10 maintains switch 12 open so that the telecommunications link of the apparatus (telephone 2 and interface 6) is switched off thus taking no power from the battery. At specific, programmable, preprogrammed times of the day (or perhaps week), switch 12 is closed by the clock 10 so as to create a "window" (time interval) during which the apparatus is receptive to in-coming calls (specifically from the base site). It should be noted that the switch only turns the telephone on, so that it is in a quiescent, receptive mode in which it would typically consume on the order of a few hundred mA of current. It does not initiate transmission of data (or any other signals) to or from the telephone. In "transmit" or "receive" mode the telephone would consume typically over an Amp of current.

During a window, a call can be transmitted from the base site and be successfully received by the apparatus at the remote site. Such a call could control the data logger unit 4 to download stored data, or might alternatively effect changes in the window timing or length or even completely re-program the logger unit. At a predetermined later period, the clock causes switch 12 to open, thus breaking the telecommunications link and depriving the latter of power once more. Should a call still be in progress, switch 12 is held closed until the logger unit is commanded to end the call. In this fashion, the power drain for the telephone 2 and interface 6 is kept to a minimum. It will be appreciated that, with the switch 12 open, basically only the logger unit 4, inverter 34 and two OR gates 36 and 38 are powered up.

Proaramming of the longer unit The logger unit 4 has l program for enabling measurements to be made from any connected input transducers, and also a core program which is written into the logger unit prior to installation on site. The core program controls communications with the base site by controlling the 5v output from the two ports CPl and CP2.

The core program also enables the monitoring of the voltage at comparator 20 by the data logger unit 4. During a transmission a signal is sent to the base site when this voltage falls below a critical pre-set level, so that the base site can take appropriate action in the event of excessive battery drain.

It will be understood that the logger unit program may be altered or even completely rewritten from the base site.

For example, the type of data being logged or its manner of processing and transmission may be varied. Also, as discussed later, the characteristics of the window may be changed.

Operation of port CPl Port CPl provides a fail-safe feature which is effective only when the core program has been destroyed by a remote re-set command from the base site to the logger unit 4 followed by call termination. Normally, with the core program written into the logger unit 4 memory, port CPl produces a 5v output. This output is set to the inverter 34, the output of which is thus 0v. A 0v output does not command the OR gate 36 and there is no further action.

However, if the core program is lost by a re-set command both ports CP1 and CP2 are set to 0v. The action of the inverter 34 ensures that the switch 12 (which supplies power to the interface 6 and telephone 2) is held closed so that a call can be re-established and the logger unit reprogrammed.

Operation of port CP2 Port CP2 controls the window described previously. In the core program in the logger unit 4 is a sector which defines the number of minutes that lapse before port CP2 goes from low (i.e. 0v) to high (i.e. 5v). Thus, if the number is 60, CP2 is commanded high every 60 minutes. The core program also specifies a number of minutes in the window before CP2 is set low again. Thus, if this number is 10, CP2 is switched low 10 minutes after it has been switched high. Both of the values (that is, in the example, 60 minutes and 10 minutes) can be altered when in communication. When the apparatus is first installed on site certain values will have been input for the window, so that communication can only be made in this window.

However, when in communication the values can be changed so that subsequent operations respond to the new values set.

It will be understood that if the logger unit program is destroyed the window command is lost and there is a danger of a permanent loss of communication when the call is terminated. The reason why the port CPl is required to carry out a fail-safe function can thus be appreciated.

General communication With the switch 40 set in the auto position the relay switch 12 is closed when the window is opened by means of the logger unit 4 setting port CP2 high. Closing of the switch 12 powers up the telephone 2 and interface 6. In particular, the 10 second timer 42 in the interface 6 is powered, and thus immediately sets DTR (data terminal ready) high on the modem 8 via the level changer 44. The modem thus sets itself into auto answer mode. After 10 seconds DTR drops again to low, but this is of no consequence since the whole apparatus is awake (in its "quiescent" mode) awaiting a call. It will be understood that the closing of the switch 12 only turns the telephone 2 on so that it is receptive to in-coming calls, but that it does not itself initiate the transmission of data or other signals.If no in-coming call is received in the window the apparatus powers down by virtue of CP2 going low and the switch 12 disconnecting the 12v supply.

If an in-coming call is received in the window the modem 8 takes hold of the line and a ring call (RI) passes to the logger unit 4. The logger unit responds by setting a communication port high, which via the level changer 44 restores DTR on the modem so that data can be downloaded from the logger unit at a suitable command via the cellular network to the base site.

Since the DTR output from the logger unit communication port is also supplied to the second OR gate 38, if the window comes to an end whilst data is still being transferred from the logger unit 4 the switch 12 remains closed. The switch 12 then only opens when a call terminate instruction is sent from the base site, which is arranged to cause the logger unit communication port to drop DTR.

It will of course be understood that the present invention has been described purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

1. Apparatus for the control of equipment at a remote site from another site, comprising, at the remote site, a cellular telephone, power means for powering the cellular telephone, a clock, switch means controlled by the clock and connected between the power means and the cellular telephone to power the cellular telephone periodically so that it is receptive for a selected interval to signals transmitted from said another site, and control means connected to the cellular telephone for controlling the equipment in response to signals transmitted from said another site during said interval.

2. An apparatus according to Claim 1 further comprising data collection means and wherein the control means is capable of initiating the transmission of data collected by the data collection means to said another site.

3. An apparatus according to Claim 2 further comprising means for permitting transmission of data to continue after said interval has terminated.

4. An apparatus according to Claim 1, 2 or 3 wherein the control means is capable of selecting the length or time of occurrence of said interval.

5. An apparatus according to any of the preceding claims further including fail-safe means whereby, on the occurrence of a predetermined event, the cellular telephone is continuously powered.

6. An apparatus according to any of the preceding claims wherein the power means includes at least one rechargeable battery.

7. An apparatus according to Claim 6 further comprising at least one primary battery, and means for switching the or each primary battery into circuit when the voltage of the or each rechargeable battery falls below a preset level.

8. An apparatus according to any of the preceding claims further including means for calling said another site when the voltage of the power means falls below a preset value.

9. Apparatus for the transfer of data from a remote site to another site, comprising a data logger unit, a cellular telephone connected to said data logger unit for transmission of data collected and stored by the data logger unit to said another site, at least one battery for powering said cellular telephone, means for powering said data logger unit, a clock incorporated within the data logger unit, and switch means controlled by said clock and connected between the or each battery and the cellular telephone whereby the latter is powered on a periodic basis.

10. An apparatus according to Claim 9 wherein the or each battery is rechargeable, and further including means for recharging the or each battery.

11. An apparatus according to Claim 9 or 10 wherein the means for powering the data logger unit includes at least one primary battery.

12. An apparatus according to Claim 10 wherein the means for powering the data logger unit includes the or each rechargeable battery.

13. An apparatus according to Claim 10 wherein the means for powering the data logger unit includes at least one primary battery and the or each rechargeable battery, means being provided for switching between the or each primary battery and the or each rechargeable battery.

14. An apparatus according to Claim 13 wherein said switching means includes means for sensing the voltage of the or each rechargeable battery and switching the or each primary battery into circuit when the voltage sensed by the sensing means falls below a preset value.

15. An apparatus according to Claim 10, 12, 13 or 14 wherein the recharging means includes means for conversion of solar energy to electrical power.

16. Apparatus for the transfer of signals to or from a remote site to another site, comprising equipment at the remote site for the receipt of signals from, or the transfer of signals to, the said another site, a cellular telephone interfaced to said equipment for transmission of signals thereto or therefrom, one or more rechargeable batteries for powering said cellular telephone and interface, means for powering said equipment, a clock, switch means controlled by said clock and connected between the one or more batteries and the cellular telephone and its interface whereby the latter are powered and the transmission of signals is conducted on a periodic basis, and means for recharging the one or more batteries, said equipment comprising a data logger unit for collection and storage of data at the remote site and transfer of that data to said another site, the clock being incorporated within the data logger unit.

17. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.