WO1982002608A1

WO1982002608A1 - Control system for energy consuming installation

Info

Publication number: WO1982002608A1
Application number: PCT/GB1982/000013
Authority: WO
Inventors: Ltd Riftberry
Original assignee: Miles Terrance Allen
Priority date: 1981-01-20
Filing date: 1982-01-19
Publication date: 1982-08-05
Also published as: EP0069745A1

Abstract

A sensor (15) detects when a room or other area is occupied. Whenever the room has been unoccupied for say two minutes a controlling CPU (11) and ROM (12) turn off the lights by way of a relay (21). The lights are turned on manually by operation of a switch (13), which will also turn off the lights when they are already on. Alternatively the on/off state of the lights when the room is occupied is determined by the light level sensed by another sensor (23). At the end of a two minute period the CPU also selects a low set point for temperature control by way of a temperature sensor and heat control device (19). Thus, when the room is occupied it is maintained at a comfort temperature; when unoccupied it is maintained only at a reduced temperature from which recovery to comfort can be achieved reasonably quickly. The system saves substantial energy. The components are contained in a unit (10) occupying the place of a conventional wall switch just inside the door of the room. The unit (10) also provides for fire detection by way of a smoke detector (20) and signalling to a central fire control station (17) which is informed also of the precise room in which the fire has been detected. The unit can also be switched to an intuder alarm mode, warning of an intruder when a person is sensed by the sensor (15).

Description

CONTROL SYSTEM FOR ENERGY CONSUMING INSTALLATION The present invention relates to a control system for an energy consuming installation which may be a lighting and/or heating installation in an office or other building, or in some external area, or a limited area of a room. The invention is concerned in particular with a control system capable of reducing significantly the consumption of energy. There is currently great awareness of the need to save energy, bath for economic reasons and in order to preserve natural resources. Particularly in office buildings with many individual offices, but also in houses, hotels and other buildings, a substantial amount of energy is wasted because of lights left on in unoccupied rooms and because such rooms are constantly heated during working hours. Similarly outdoor lighting may be left on wastefully in floodlit yards, illuminated walkways and so on. The broad object of the present invention is to enable such waste of energy to be very much reduced by the provision of an inexpensive system, i.e. a system which is cheap enough for the cost, thereof to be recovered over say two or three years energy saving. It has been proposed in European Published Application 0002650 to reduce energy consumption in a preprogrammed manner but this is not different in principle from a boiler time switch and is not sufficiently flexible to cater for varying patterns of use. GB PS 1548 524 discloses a system which cuts down the consumption of a heating or cooling system when a room is unoccupied but relies upon operation of a switch by the occupant, e.g. by inserting his room key in a slot in a desk unit when occupying a hotel room. Such a system is not suited to general application, e.g. in domestic and office environments. A more specific object of the invention is to provide an improved system which does not require deliberate action on the part of the occupant.

According to the present invention there is provided a control system in an area with an energy consuming installation, comprising switching means operative when the area is unoccupied to reduce the power fed to the energy consuming installation , characterised by a sensor responsive to the presence of a human body to signal when the area is occupied, timing means arranged to time out a predetermined delay period, whenever the area ceases to be occupied and stays unoccupied till the end of the delay period, and in that the switching means are responsive to the timing means to reduce the power fed to the energy consuming installation when the delay period times out. As will be explained further below, the timing means can be a suitably programmed microprocessor which also performs various additional functions.

The sensor may take various forms and advantage can be taken of the considerable knowledge available in relation to burglar alarms to achieve a sensor which will reliably detect the presence of a person in the area without being sensitive to non-human influences. The sensor may be a passive device sensing sound or heat (infra-red rays) emanating from a person in the room Alternatively and preferably an active sensor may be employed, e.g a senor which establishes an ultra-sonic wave pattern in a room and detects disturbances of the wave pattern when someone enters the room, or a sensor which sends out ultra-sonic or infra-red pulses and detects returns. The switching means reduce the power fed to the energy consuming installation when the area has been unoccupied continuously for the duration of the predetermined delay period. This may be set at a value of a few minutes , say two to five minutes , to prevent the power being reduced every time a room is left briefly by its occupant. The nature of the power reduction will depend upon the installation controlled. In the case of lights the power is preferably reduced to zero , i .e . the lights are simply switched off, although in some situations it may be preferred to switch off only the main lighting and leave some small background lighting on. In this case it may be arranged that the lights switch on again automatically when the occupant re-enters the room, unconditionally if the room always requires artificial light or conditionally ipon the level of ambient light, sensed by another sensor, if the lights do not always have to be on during the day . On the other hand, regulations or user preference may dictate the provision of a manual switch for switching the lights on, only the switch off being automatic.

The preferred construction of the control system is accordingly a unit which can take the place or be fitted to a conventional wall switch just inside the door to a room, (although such a unit can obviously be fitted elsewhere if required) . The unit can contain the timing means and the switching means , the nature of which will be discussed further below. For some applications it may be possible also to incorporate the sensor in the unit but in general, in order to "aim" the sensor optionally, the sensor will be remote from the unit and there may be a plurality of sensors distributed round the area in question of which one or none may be in the unit. For an open-plan office , restricted areas may be provided with their own lighting control units incorporating a directional sensor. For control of a local heater, e .g . an electrical heater, a unit can be constructed to plug into a 3-pin socket between the socket and the heater. In general the construction of the unit can be adapted to the most varying locations and types of use . In the case of a heating installation the power is preferably reduced only to a level which maintains the room at a reasonable stand-by temperature from which recovery to normal comfort temperature, is possible quite rapidly. The nature of the control will depend upon the nature of the heating system. In the case of a hot water radiator system, control can be by way of a motorised valve to mention one of many possibilities. Basically the system will operate to a normal set point (e.g. 20ºC) when the room is occupied and a lower set point when the room is unoccupied. Seducing the set point by even a few degrees will save large amounts of energy if the room is unoccupied on average by some hours every week. The system can incorporate various refinements, e.g. the additional of an external thermostat to provide frost protection, advance response when the outdoor temperature is changing rapidly, and so on.

For control of a central heating installation the control system must communicate with some controlled device of the installation, e.g. the above mentioned, motorised valve, and must almost certainly communicate with at least one temperature sensing device. The latter could perhaps be incorporated in the control system itself but, assuming this to be in a unit immediately inside the door, the location for temperature sensing is not ideal and at least one separate device mounted elsewhere will be preferred.

Communication with these devices (the controlled device and a separate temperature sensing device) can be effected in various ways including the provision of dedicated wiring. In order to reduce the expense associated with yet more wiring in a building, it. is preferred to utilise one of the various techniques available for communication by way of existing wiring. For example it is known to superimpose digital signals on the electrical power circuitry of a building and it is known to provide a building with an information highway which can be utilised to carry very many information signals in time multiplexed manner.

Although the system can be constructed from components individually performing the sensing, timing and switching functions it is preferred, for cheapness, to make use of a microprocessor and a ROM programmed to provide the necessary control functions. As already mentioned the microprocessor then acts, inter alia, as the timing means . The processor can be programmed to cater for a wide variety of functions, only those required being utilised in a given application. Thus the same or similar units will serve for heating control or lighting control or both. Furthermore the unit can advantageously additionally provide for fire detection if it incorporates a suitable sensor, e .g. an ionization detector for detecting smoke or gas fumes or a sensor detecting excessive heat. The unit then preferably transmits a coded signal to a central station for raising the alarm and what is more indicating precisely the room from which the alarm emanates . Another optional feature is an intruder alarm relying upon the sensor which signals when the area is occupied in conjunction with some means for selecting when the intruder alarm facility is activated. This may be a switch, e. g. a key switch, for a single room or group of rooms , or a central station may be capable of selecting which rooms of a building are protected at any given time . Thus , each individual unit can have its own address and the central station can send commands to the units individually to select their modes of operation (energy control mode or intruder alarm mode) and to poll the units for fire alarm messages and, if required, to send commands establishing the currently applicable set points for temperature control, and so on. Polling the units avoids problems arising from simultaneous interrupts . It is also possible to poll for fault messages , and so on. One embodiment of the invention will now be described in more detail by way of example and with reference to the accompanying drawings . This embodiment provides full facilities for controlling lighting and heating and fire detection but, as note already, any unwanted facility can simply be omitted. In the drawings :

Fig 1 is a block diagram of the control system embodying the invention ,

Figs 2 to 4 are flow charts illustrating the operation thereof, a Fig 5 is a circuit diagram of a person sensor. In Fig 1, all of the blocks within the broken line box 10 can be contained within a small wall moun ted unit whi ch can take the place of a conventional wall switch just inside the door of a room. The four blocks outside the box 10 are separate units as described below. Within the unit 10 a CPU (microprocessor) 11 is controlled by the programme in a ROM 12 to sample various inputs and effect various control operations in dependence upon the nature of the inputs. One input is an interrupt input from a pushbutton switch 13 which, whenever it is pressed, causes a lights relay 21 to change state. This relay may be an electromechanical relay but is preferably a solid state device such as a thyristor and controls the lighting in the room by way of an external connection 22. The occupant of the room can thus control the lights in the normal way, switching them on and off as desired by pressing the switch 13. This may be the only way in which the lights can be switched on. The lights relay 21 is one of various devices connected to an interface chip 14 which is in turn connected to the input/ output bus of the CPU 11. The other devices connected to the interface 14 are firstly, within the unit 10, a person sensor 15 for sensing the presence of a person in the room, e.g. by detecting movement; upsetting the pattern of sound waves within the room. As noted above, this sensor may not be in the unit 10 but may be remotely mounted. Also within the unit 10 is a communications interface 16 by way of which signals are sent to a remote fire control station over some form of transmission facility 23 which may take any convenient fortt, pulse signalling over mains wiring in the building, for example.

Four external devices are connected to the interface 14. As input devices there are a temperature sensor 18 an ionization type smoke detector 20 (or other form of fire detector), and a light sensor 23 which senses the light level in the room. As an output device there is a heat, control device 19 which is assumed simply to be some form of on/off device, e.g. a relay for electrical heating or a motorised valve for hot watex heating.

The main supervisory programme for the microprocessor 11 is illustrated in the block diagram of Fig 2. This is self-explanatory and will not therefore be described in detail. However, it is noted that the implication of the diagram is that the person-sensor 15 is always fitted whereas the smoke detector 20, the light sensor 23 and the temperature sensor 18 are optional. If any of these three devices is not fitted, the corresponding level is set at zero. The fire level and person level may be signals varying over a range and effectively indicating the probability of there being fire or a person present, respectively, but these signals may equally be binary signals having only the values 1(fire or person present) and 0 (no fire, no person present). If a light sensor or heat sensor is fitted, it is assumed that the resulting signal will vary over a range to represent the actual light level and temperature respectively. Fig 3 illustrates how the person level signal is utilised to select between the person absent and person present states, ie the room unoccupied and room occupied states. When a person is detected in the room the person present state is unconditionally selected and the count cycle of the microprocessor which times out the predetermined delay period is reset. This count cycle is only operative to time out the delay when no person is detected and the person absent state has not already been selected. Once the count cycle is completed to time out the delay, the person absent state is selected. Fig 4 shows how the person present or absent state is utilised to control the lights in the room. Control depends upon threshold levels designated "HIGH" and "LOW" and an upper pair of these values is selected when a person is present while a lower pair of these values is.selected when a person is absent. Operation then depends upon whether the light level determined in accordance with Fig 2 exceeds "HIGH" or is less than "LOW". It will be seen that corresponding provision is made for reducing and increasing the light level and for indicating a fault when it is not possible to increase the light level as required. The provision of "HIGH" and "LOW" thresholds establishes normal hysteresis action preventing the lights turning on and off repeatedly when the light level is near a threshold value. It also provides a simple way of introducing manual control by way of the switch 13 of Fig 1. The microprocessor can select yet further "HIGH" and "LOW" thresholds to determine the mode of operation in response to interrupts from the switch 13. In particular, even if the level is permanently set to zero (because no light sensor is fitted) it is still possible to force a turn off of the lights by selecting "HIGH" and "LOW" thresholds such that the latter is actually above the former.

The flow chart, for heating control is not illustrated as it is essentially the same as Fig 4 with the word "LIGHT" altered to "HEAT" wherever it occurs. Simple on/off control of the heating can be effected to achieve proportional control in accordance with the ruling "HIGH" and "LOW" temperature thresholds. Naturally the programme in the ROM 12 can be developed to incorporate refinements in the heating control such as rate action and reset action and to handle inputs from additional sensors such as an external wall thermostat.

The system can also be utilised to control air conditioning where cooling as well as heating is available. Other facilities can be incorporated to maintain the environment of a room comfort, e.g. by controlling an extractor fan for a kitchen in dependence upon the level of cooking fumes, the humidity of a room can be controlled and so on.

Fig 5 shows a suitable sensor for reliably sensing the presence of a person, in a room. An oscillator 30 operating in the ultrasonic frequency range drives a piezoelectric transmitting crystal 31 which radiates an ultrasonic beam into the area being monitored and also provides a reference signal to a phase detector 32. Ultrasonic radiation reflected from objects within the said area is picked up by a receiving crystal 33. The signal from the crystal 33 is amplified by amplifier stages 34 and applied to the phase detector 32. The output signal across the phase detector is applied to a differential amplifier 35 with integrating action such that an output signal is only provided on output 36 (and indicated by a LED 37) when the output from the phase detector is changing because of movement in the area being monitored, under steady state conditions, there is no useful output signal, even although the output from the phase detector is itself not zero.

The output signal on output 36 is located as a two-level person present/absent signal which is sampled by the CPU 11.

Claims

1. A control system in an area, with an energy consuming installation, comprising switching means operative when the area is unoccupied to reduce the power fed to the energy consuming installation, characterised, by a sensor (15) responsive, to the presence of a human body to signal when the area is occupied, timing means (11) arranged to time out a predetermined delay period whenever the area ceases to be occupied and stays unoccupied till the end of the delay period, and in that the switching means (21) are responsive to the timing means to reduce the power fed to the energy consuming installation when the delay period times out.

2. A control system according to claim 1, characterised in that the switching means (21) are arranged to switch off lights in the area.

3. A control system according to claim 2 , characterised by a manual switch (13) for switching on the lights.

4. A control system according to claim 3, characterised in that at least the timing means (11, 12) , switching means (21) and manual switch (13) are incorporated in a single wall mounting unit (10) .

5. A control system according to claim 2 , characterised by means (23) operative when the area is occupied automatically to switch on the lights when the light level is below a predetermined value.

6. A control system according to any of claims 1 to 5 , characterised in that the switching means (19) are arranged to establish a lower temperature to which the area is heated.

7. A control system according to claim 6, characterised in that the switching means (11, 12) select a lower temperature set point when the delay period times out and a higher set point when the area is occupied.

8. A control system according to claim 6 or 7, characterised in that the timing means comprise a microprocessor (11) programmed to time the delay period, to sample the said sensor (15) and a temperature sensor (18) and to control the switching means and control means (19) for the heating.

9. A control system according to claim 8, characterised in that the microprocessor (11) is further programmed to sample a fire detector (20) and to send an alarm signal when fire is detected.

10. A control system according to claim 9, characterised in that the alarm signal is coded to indicate the room from which it emanates.

11. A control system according to claim 8, 9 or 10, characterised in that the microprocessor (11) is further programmed to provide in a selected mode of operation an intruder warning signal when the sensor (15) signals that the area is occupied.