GB2517897A

GB2517897A - A control system for operating in an absence mode

Info

Publication number: GB2517897A
Application number: GB1311640.5A
Authority: GB
Inventors: Simon Bunting; Robert Townsend
Original assignee: Novar ED&S Ltd
Current assignee: Novar ED&S Ltd
Priority date: 2013-06-28
Filing date: 2013-06-28
Publication date: 2015-03-11
Anticipated expiration: 2033-06-28
Also published as: GB201311640D0; GB2517897B

Abstract

A lighting control system 1 for operating in an absence mode or semi-automatic mode comprises a lighting load 3, a presence detector 5 for detecting a person, the detector having a control module 17 arranged to switch off the lighting load in response to the output of a detector element 15 and a switch 9 actuatable from a closed state to an open state. The switch is in series with the detector such that when the switch is in the open state, the power to the detector is interrupted. The switch is biased into the closed state (for example it is a normally-closed push-button (NCPB) switch). The lighting control system is configured such that when the switch has returned to the closed state after actuation, the status of the lighting load is toggled to the opposite of its status prior to actuation of the switch.

Description

A control system for operating in an absenoe mode

Technical Field

The present invention relates to a control system incorpcrating a presence detector, and especially, but not exclusively, to a lighting control system incorporating a presence detector.

Background of the Invention

Lighting control systems incorporating a presence detector can often be classified into two modes of operation: "presence mode" (also known as fully automatic mode), and "absence mode" (also known as semi-automatic mode) . Tn presence mode, the control of the lighting load is wholly dependent on the output of the presence detector; when the detector detects a person has entered a room, the control system turns lights in that room on, and when the detector detects that the person has left the room, the control system turns the lights OFF. In absence mode, the control system still turns OFF the lights when the detector detects that the person has left the room, but the user must actuate the light switch in order for the lights to come on. The user may also switch off the lights manually if wanted. Absence mode enables the user to feel more in control and, for example, enables the user to briefly enter the room without all the lights automatically being switched. Lighting control systems that are able to operate in an absence mode are becoming increasingly popular.

Many lighting systems include a single-pole-single-throw (SPST) switch in the power feed such that the user can switch the lighting load ON/OFF. If these lighting systems include a control system that operates in absence mode, the user can become confused because in some circumstances actuating the switch will not change the status of the lights. For example, if the lights were switched on by the user, but were automatically switched OFF by the control system, the SPST switch will still be in the "ON" position when the user next re-enters the room. The user will therefore need to actuate the switch twice to switch the lights back on.

Summary of the Invention

The present invention seeks to reduce or mitigate at least some of the above-mentioned disadvantages.

According to a first aspect of the invention there is provided: a lighting control system comprising: (i) a lighting load (ii) a detector, the detector having a detector element and a control module, the detector element being arranged to generate an output dependent on its detecting the presence/absence of a person, and the control module being arranged to switch off the lighting load in response to the output of the detector element; and (iii) a switch actuatable from a closed state to an open state, the switch being in series with the detector such that when the switch is in the open state, the power to the detector is interrupted; characterised in that the switch is biased into the closed state, and the lighting control system is configured such that when the switch has returned to the closed state after actuation to the open state, the status of the lighting load is switched to the opposite of its status prior to actuation of the switch.

Such an arrangement ensures that the user is always able to alter the status of the lighting load with a single actuation of the switch, regardless of how the lighting load was previously switched. For example, if the lighting load is OFF (either as a result of the detector recognising no one is in the vicinity of the lighting load, or due to a manual switch by the user), then following actuation of the switch the lighting load is switched to the opposite status (i.e. ON) . Egually, if the lighting load is ON (for example the user has switched the lighting load on as described above), then following another actuation of the switch the lighting load is switched to its opposite status (i.e. OFF) The switch is biased to its closed state. This type of switch may be referred to as a normally-closed switch, or push-to-open switch. The switch is preferably a normally-closed push-button (NCPB) switch. The invention recognises that by using a switch biased to the closed state, power can always be made available to the detector following actuation of the switch. The detector can therefore control the status of the light to the reguired state. In principle, the switch need not be in series with the lighting load, but in preferred embodiments of the invention the switch is in series with the lighting load, such that when the switch is in the open state the power to the lighting load is interrupted. Such an arrangement is beneficial because power is made available to the lighting load following actuation of the switch (the switch being biased to the closed state), even if in some cases, for example if the lights were previously ON, the power is prevented from reaching the lighting load by the control system. The detector is preferably in series with the lighting load.

The control system may be configurable, or configured, in an absence mode. In absence mode the lighting load may be switched ON and OFF by actuation of the switch, but the detector is arranged to only switch the lighting load off in response to the output of the detector element. In absence mode the lighting load is preferably not switched on in dependence on the output of the detector element. The present invention is especially advantageous for arrangements in which the control system is in absence mode because in absence mode the lighting load may have been switched off automatically but need to be switched on manually.

In principle, there may be a number of different ways of configuring the control system such that when the switch has returned to the closed state after actuation to the open state, the status of the lighting load is the opposite to its status prior to actuation of the switch. The control system may comprise a specific module for ensuring the status of the lighting load is switched to the opposite of its status prior to actuation of the switch. More preferably, the control module of the detector is configured to ensure the status of the lighting load is switched to the opposite of its status prior to actuation of the switch. In such embodiments the functionality of the control system may therefore be contained in a single piece of equipment (the detector) . It will be appreciated that the control module of the detector may also be configured to provide any or all of the other functionality described herein with reference to the lighting control ys tern.

In preferred embodiments of the invention, the control system may comprise a memory module, the memory module being configured to store the status of the lighting load prior to the switch being actuated to the open state, as its pre-actuation status. The control system is preferably configured to access the memory module to ascertain the pre-actuation status of the lighting load, such that when the switch returns to the closed state after actuation to the open state, the control system switches the status of the lighting load to the opposite of its pre-actuation status. The memory module may comprise non-volatile memory for storing the pre-actuation status. The control system may comprise a processing module for interrogating the lighting load to ascertain its status.

The processing module may be arranged to write the status to the memory module following the interrogation. The processing module may execute a computer program to store the pre-actuation status in the memory module.

The switch is in series with the detector. More specifically, the switch is more preferably in series with the control module of the detector. rhen the switch is in the open state, the interruption of power to the detector may cause the detector to turn OFF. When the switch returns to the closed state the detector may be turned back on. The detector may be configured such that upon turning back on, the detector switches the status of the lighting load to the opposite of its status prior to actuation of the switch.

Having the switch in series with the detector may be especially advantageous if the switch has been retrofitted into an existing lighting control system (for example having a SPST switch in series with the load and detector) . The detector may be mains powered. In embodiments of the invention having a memory module, the memory module may be located in the detector, and more preferably the control module of the detector. The memory module may be configured to store the pre-actuation status of the lighting load prior to the detector turning OFF.

According to another aspect of the invention there is provided a method of controlling a lighting load in a lighting control system, the method comprising the steps of: actuating a switch from a closed state to an open state, the switch being in series with a detector such that when the switch is in the cpen state, the power to the detectcr is removed and the detector is switched off, allowing the switch to return to the closed state under the action of a biasing force, thereby switching the detector back on, and switching the status of the lighting load to the opposite of its status prior to actuation of the switch.

According to yet another aspect of the invention there is provided a method of installing a lighting control system, comprising the steps of: installing a switch actuatable from a closed state to an open state but biased into the closed state, the switch being installed in series with a detector such that when the switch is in the open state, the power to the detector is removed, and configuring the lighting control system such that when the switch has returned to the closed state after actuation to the open state, the lighting load is switched to the status that is the opposite to its status prior to actuation of the switch. The method may be a method of retro-fitting a pre- existing lighting control system having a single-pole single-throw (SPST) switch. The method may comprise the step of replacing the SPST switch with the switch biased into the closed state.

The invention may also be applied to a Heating Ventilation and Air-conditioning (HVAC) control system for controlling an Ft/AC apparatus rather than a lighting load. Accordingly, according to another aspect of the invention, there is provided a control system comprising: a load a detector the detector having a detector element and a control module, the detector element being arranged to generate an output dependent on its detecting the presence/absence of a person, and the control module being arranged to switch off the load in response to the output of the detector element; and a switch actuatable from a closed state to an open state, the switch being in series with the detector such that when the switch is in the open state, the power to the detector is interrupted; characterised in that the switch is biased into the closed state, and the control system is configured such that when the switch has returned to the closed state after actuation to the open state, the status of the load is switched to the opposite of its status prior to actuation of the switch. The load may be an PP/AC load and the control system may be an HVAC control system.

Any features described with reference to one aspect of the invention are equally applicable to any other aspect of the invention, and vice versa.

Description of the Drawings

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing of which: Figure 1 is a schematic of a lighting control system according to a first embodiment of the invention.

Detailed Description

Lighting control systems being operable in an absenoe mode are known. The control system turns off the lights when the detector detects that the person has left the room, but the user must actuate the light switch in order for the lights to come on. The user may also switch off the lights manually if wanted. Absence mode enables the user to feel more in control and, for example, enables the user to briefly enter the room without all the lights automatically being switched.

Lighting control systems that are able to operate in an absence mode are becoming increasingly popular.

Many lighting systems include a single-pole-single-throw (SPST) switch in the power feed such that the user can switch the lighting load ON/OFF. If these lighting systems include a control system that operates in absence mode, the user can become confused because in some circumstances actuating the switch will not change the status of the lights. For example, if the lights were switched ON by the user, but were automatically switched OFF by the control system, the SPOT switch will still be in the ON" position when the user next re-enters the room. The user will therefore need to actuate the switch twice to switch the lights back on.

The embodiment of the invention shown in Figure 1 seeks to overcome this problem. The lighting control system 1 (denoted by the dotted line) comprises a lighting load 3 (formed of several ceiling lights in a room (not shown) ) and a passive infra-red (PIR) presence detector 5. The presence detector 5 is in series with the lighting load 3 and is connected to a mains power source 7. Tn accordance with known control systems having presence detectors, the detector 5 comprises a detector element 15 which is arranged to generate an output dependent on its detecting the presence/absence of a person in the room, and a control module 17. The control system 1, and more specifically the detector 5 is configured in an absence mode. Thus, the control module 17 switches off the lighting load 3 in response to an output of the detector element in the detector 5 which indicates the room is vacant.

The control module 17 does not, however, switch the lights ON in response to the output of the detector element. The lighting load 3 is instead switched ON (and optionally OFF) using a manual switch 9 in series with the lighting load.

Unlike existing lighting control systems, the switch 9 in the control system of the present invention is an NCPB switch (i.e. a push button switch that is biased into the closed position) . The control module 17 of the detector 5 also comprises a memory module 11 and processor 13. such a detector, in series with the NOPB switch 9, has been found to be especially advantageous for control systems operating in absence mode, as will now be described.

If the lighting load 3 is ON, a user may actuate the switch 9 to switch it OFF, or he may simply leave the room and allow the control system to switch off the lights once the detector 5 outputs a signal to indicate that no one is detected in the room. The latter of these functions is known per se and is not described in further detail. The former (i.e. the manual actuation of the switch) may take two forms: If the user makes only a short press to open the switch (but of sufficient time that the detector does not power down), the detector 5 experiences a sharp trough in power; the control module 17 of the detector 5 is arranged to interpret this trough as an instruction to toggle the lighting load 3 to its opposite state (i.e. OFF in this case) . If the user makes a longer press on the switch 9, the detector and lighting load are turned off because the user has his finger on the switch for sufficient time to starve these devices of power. Once -10 -the user releases his finger, the switch is returned to a closed state thereby re-establishing the power supply to the detector 5 and the detector 5 is switched back on. In many known detectors the lights would be automatically switched on when the detector switches back on. This is undesirable however, as the user may have been actuating the switch in an attempt to turn the lights off. 7&ccordingly, the detector 5 includes the memory module 11 and the processor unit 13. Just before the detector 5 powers down, the processor unit 13 assesses the status of the lights 3 and stores that status in the memory store (as a so-called pre-actuation status) . Upon powering back up, the control module 17 of the detector 5 accesses the memory store 11 to establish the pre-actuation status. The control module 17 of the detector 5 is configured so as to control the lights 3 to ensure their status is the opposite to the pre-actuation status stored in the memory module 11. Therefore, if the lights were ON prior to the detector turning off and back on, the detector unit control system ensures the light is OFF after actuation of the switch.

If the lights are OFF when a user enters the room, the first embodiment of the invention allows the user to also turn those lights ON. More specifically, the invention allows the user to turn the lights back ON with only a single manual actuation of the switch: If the user makes only a short press (of sufficient time that the detector does not power down), the detector 5 experiences a sharp trough in power and, as above, the detector 5 is arranged to toggle the light 3 to the opposite status (i.e. ON) in response to such a signal. If the user makes a longer press, the detector 5 is turned OFF because the user has his finger on the switch for sufficient time to starve the device of power. Just before the detector powers down, the processor unit 13 assesses the status of the lights 3 and stores that status in the memory store 11 as -11 -the pre-actuation status (overwriting any previously stored pre-actuation status) . Once the user releases the switch 9, it is returned to a closed state thereby re-establishing the power supply to the detector 5 and the detector is switched back on. As above, as the detector 5 powers back up, it accesses the memory store 11 to establish the pre-actuation status. The detector 5 controls the lights 3 to ensure their status is the opposite to the stored pre-actuation status.

Therefore, as the light was OFF prior to the detector turning off and back on, the detector unit control system ensures the light is ON after actuation of the switch 9.

The above-described arrangement is an improvement over known control systems in absence mode because the user only need actuate the switch once in order to toggle the status of the lights; the lights will always go to the opposite status to that prior to actuation of the switch. This overcomes the problem in existing systems in which the user must actuate a SPST switch twice to turn the lights on in the event that they had been automatically turned off previously.

The first embodiment of the invention was retrofitted into an existing lighting system that had comprised a lighting load in series with a SPOT switch. To install the system of the first embodiment of the invention, the NCPB switch 9 was installed in place of the SPST switch. The detector 5 (configured such that the lighting load could be turned OFF in dependence on the output of the detector and comprising the memory module and processor) was also installed in the system.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. For example, the invention may be allied to a Heating Ventilation and Air-conditioning -12 - (HVAC) control system for controlling an HVAC apparatus rather than a lighting load. By way of another example, in another embodiment, the processor unit stores the pre-actuation status of the lights straight after their previous switch, rather than just before shut-down of the detector caused by a future actuation. This ensures the memory of the pre-actuation status is written during a more stable part of the operating cycle, rather than just before the detector powers down.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. Tt will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

-13 -Claims 1. A lighting control system comprising: (1) a lighting load (ii) a detector, the detector having a detector element and a control module, the detector element being arranged to generate an output dependent on its detecting the presence/absence of a person, and the control module being arranged to switch off the lighting load in response to the output of the detector element; and (iii) a switch actuatable from a closed state to an open state, the switch being in series with the detector such that when the switch is in the open state, the power to the detector is interrupted; characterised in that the switch is biased into the closed state, and the lighting control system is configured such that when the switch has returned to the closed state after actuation to the open state, the status of the lighting load is switched to the opposite of its status prior to actuation of the switch.
2. A control system according to claim 1, wherein the control system is configured in an absence mode, in which absence mode the lighting load may be switched on and off by actuation of the switch, but the detector is arranged to only switch the lighting load off in response to the output of the detector element.
3. A control system according to claim 1 or claim 2, wherein the switch is also in series with the lighting load, such that when the switch is in the open state the power to the lighting load is interrupted.

-14 -
4. A control system according to any preceding claim, comprising a memory module, the memory module being configured to store the status of the lighting load prior to the switch being actuated to the open state, as its pre-actuation status.
5. A control system according to claim 4, wherein the control system is configured to access the memory module to ascertain the pre-actuation status of the lighting load, such that when the switch returns to the closed state after actuation to the open state, the status of the lighting load is the opposite of its pre-actuation status.
6. A control system according to any preceding claim, the control system being arranged such that when the switch is in the open state the interruption in power to the detector causes the detector to switch off, and when the switch returns to the closed state the detector switches back on.
7. A control system according to claim 6 when dependent on claim 4 or claim 5, wherein the memory module is configured to store the pre-actuation status of the lighting load prior to the detector switching off.
8. A control system according to any of claims 4 to 7, wherein the detector comprises the memory module.
9. A control system according to any preceding claim, wherein the switch is a normally-closed push-button (NCPB) switch.
10. A method of controlling a lighting load in a lighting control system, the method comprising the steps of: actuating a switch from a closed state to an open state, the switch being in series with a detector such that when the -15 -switch is in the open state, the power to the detector is removed and the detector is switched off, allowing the switch to return to the closed state under the action of a biasing force, thereby switching the detector back on, and switching the status of the lighting load to the opposite of its status prior to actuation of the switch.
11. A method of installing a lighting control system, comprising the steps of: installing a switch actuatable from a closed state to an open state but biased into the closed state, the switch being installed in series with a detector such that when the switch is in the open state, the power to the detector is removed, and configuring the lighting control system such that when the switch has returned to the closed state after actuation to the open state, the lighting load is switched to the status that is the opposite to its status prior to actuation of the switch.
12. A method according to claim 11, wherein the method is a method of retro-fitting a pre-existing lighting control system having a single-pole single-throw (SPST) switch, and the method comprises the step of replacing the SPST switch with the switch biased into the closed state.