WO2010041085A1

WO2010041085A1 - Automatic switching apparatus.

Info

Publication number: WO2010041085A1
Application number: PCT/GB2009/051355
Authority: WO
Inventors: Timothy Paul Jarvis; Darren Craig Wilkinson
Original assignee: Timothy Paul Jarvis; Darren Craig Wilkinson
Priority date: 2008-10-09
Filing date: 2009-10-09
Publication date: 2010-04-15
Also published as: GB0818497D0; GB2464293A

Abstract

An automatic switching apparatus (10) comprising: switch means (54) for selectively connecting or disconnecting an electrical load (58) from a mains power supply (56); trigger means (76, 86, 88) for detection of a first predetermined event; reset means (84, 36) for detection of a second predetermined event; and programmable control means (72) for actuating the switch means (54).

Description

Title: Automatic switching apparatus

Description:

This invention relates to an automatic switching apparatus.

It is often desirable to control the connection of an electrical device to an electrical power source. In particular, landlords or property owners might wish to limit the amount of electricity used to minimise expenditure and/or to safeguard the electrical safety of premises. Additionally or alternatively, the landlord or property owner might wish to ensure that conditions, e.g. the temperature, humidity etc. within the property are maintained within predetermined parameters. Moreover, it is common for electrical devices in temporarily vacated premises not to be switched off, which can be wasteful and/or uneconomic.

Automatic controllers for electrical devices are known, such as on/off switches, timer switches, (un)switched fuse units (FSUs), residual current devices (RCDs), thermostats, Passive Infrared detectors (PIRs) etc., but these known devices are generally "dumb", i.e. they lack logic, and/or are not tamperproof.

This invention aims to provide an improved automatic switching means and/or to provide a solution to one or more of the above problems.

According to the invention there is provided an automatic switching apparatus comprising: switch means for selectively connecting or disconnecting an electrical load from a mains power supply; trigger means for detection of a first predetermined event; reset means for detection of a second predetermined event; and a programmable control means for actuating the switch means.

The switch means may comprise a relay or a triac. The automatic switching means may be electrically connectable to the mains power supply and the electrical load via screw terminals arranged to receive and clamp onto the ends of the conductors of electrical cables.

The programmable control means may comprise a microcontroller. A communications port may be provided to enable the microcontroller to be programmed and/or re-programmed. The communications port may utilise an RS232 serial communications protocol, and may be connectable to physically, for example, using a stereo plug & jack or a USB plug and socket etc., or wirelessly, for example using infrared, WiFi or Bluetooth®.

The first predetermined event can be any one or more of the group comprising: an electrical current exceeding a predetermined threshold, a temperature falling outside a specified range, inactivity for a predetermined period and "normally off' periods of a programmable seven day timer.

The second predetermined event can be any one or more of the group comprising: a soft reset, a button press, an electrical current falling below a predetermined threshold, a temperature falling within a specified range, a detected activity, "normally on" periods of a programmable seven day timer.

The trigger and/or the reset means may comprise a current detection means for detecting the electrical current flowing into the electrical load. The current detection means may comprise a differential current detection means for detecting a step change in the electrical current flowing into the electrical load. Either or both of the trigger and/or the reset means may comprise a temperature detection means, e.g. a thermocouple, a bimetallic strip or a thermistor.

Either or both of the trigger and/or the reset means may comprise an infrared detector, for example, a passive infra red motion detector. The trigger means may comprise a circuit for actuating the switch means upon non-detection of a signal from the infrared detector after a predetermined interval. The reset means may comprises a timer for resetting the switch means after a predetermined interval.

The reset means may comprise a reset switch, which could be operable using a push switch, a touch pad, or using a computer interface. The reset means may comprise a lock to prevent/inhibit unauthorised resetting of the switch means. The lock, where provided, may comprise a key-operated lock, a combination lock and/or a password protection device/circuit and/or PIN protected computer interface.

The automatic switching means may comprise a fascia affixable to a mains power outlet back box, for example using screws. The reset switch and/or communications port may located behind the fascia and only be accessible by partially or completely removing the fascia from the back box.

Preferred embodiments of the invention shall now be described, by way of example only, with reference to the accompanying drawings in which;

Figure 1 is a schematic perspective view of an automatic switching apparatus according to the invention;

Figure 2 is a schematic circuit diagram of a first automatic switching apparatus according to the invention. Figure 3 is a circuit diagram of a current sensor utilised by the invention;

Figure 4 is a schematic circuit diagram of a second automatic switching apparatus according to the invention; and

Figure 5 is a lookup table for a bolometer.

In Figure 1 , an automatic switching apparatus 10 comprises a housing 12 that encloses an internal circuit and a fascia 14 that is affixable to a conventional mains back box 16 using screws 18. The rear of the housing 12 has two sets of screw terminals (not shown) for connecting the switching apparatus 10 to a mains power supply cable 20 and a cable 22 connected to an electrical load. It will be apparent to the skilled person that the automatic switching apparatus 10 can be wired into a mains circuit in place of a conventional switch or FSU, or in place of a ring main circuit breaker. A wire 75 is also shown that provides an electrical connection between the switching apparatus 10 and a remote PlR sensor (not shown).

In the embodiment depicted in Figure 1 , the fascia 14 is generally square-shaped and comprises a lip 11 that conceals the back box 16 when installed.

The housing 12 comprises a pressed aluminium box that attaches to the rear face of the fascia 14, which is manufactured from stainless steel, using barbed clips or self-tapping screws (not shown). The design of the housing 12 is standardised so that different housings, for example comprising different sensor types, can be affixed to a common fascia 14.

In the centre of the fascia 14, a touchpad 26 is provided for resetting the apparatus in a manner that will be described below. The housing 12 additionally comprises a socket 36 into which a plug 38 of a communications cable 40 can be plugged. In Figure 1 , the socket is a mini USB socket, although any electrical socket, e.g. a stereo jack, may be used. In use, an operator can program the automatic switching apparatus 10 by unscrewing it from the back box 16, retracting it sufficiently to expose the socket 36 and by connecting a portable computer 42 loaded with appropriate software to the socket 36 using a data cable 40.

The software loaded onto the portable computer 42 comprises a menu- type Graphical User Interface that enables a user to program various different aspects of the operation of the switch 10. The software also comprises a communications protocol, e.g. RS232, that enables the computer 42 to communicate with, program, and re-program the automatic switching apparatus 10.

In Figure 2, it can be seen that the automatic switching apparatus 10 comprises a circuit 50 having a bank of screw terminals 52 for connecting it to the mains power supply 20 and to an electrical load 22. A triac 54 is wired in series between the "mains phase" terminal 56 and the load "live" terminal 58. Both mains phase (live) and neutral may be additionally isolated by a mechanical switch and thermal fuse. The automatic switching apparatus 10 is wired to earth 64 for safety reasons.

A transformer 66 is wired in parallel with the load live 58 and load neutral terminals 62 via a resettable fuse 68. The transformer 66 is wired to an AC/DC converter 70, which is used to provide low-voltage DC power a programmable microcontroller 72. As a power saving measure, the quiescent power drain of the automatic switching device is low - the transformer 66 being rated at 41 mA at 9VDC.

The microcontroller 72 is wired to receive input signals from a variety of sensing devices, which shall be described in greater detail below. The microcontroller 72 is also wired (via an opto-isolator) to the gate terminal of the triac 54 and can thus control the flow of electrical current from the mains phase terminal 56 to the load live terminal 58 of the terminal block 52.

The microcontroller 72 is wired to receive input signals from an infrared sensor (not shown) that can be wired 75 to a separate terminal block 76. The infrared sensor is an off-the-shelf PIR sensor, and provides a small DC voltage to PIR terminal block 76 upon detection of the motion of a "hot body" within a predetermined zone. The provision of a PIR terminal 76 solves two problems, namely it allows segregation of mains (LNV) and low voltage (SELV) circuits, and it allows the wire to the PIR to optionally run up a wall on the surface. This is particularly advantageous as it enables the PIR to be optimally sited for the best "view" of the room, which is rarely where the switch will be.

The PIR sensor signal voltage is stepped-down by applying it to the gate terminal of a FET transistor 78, which stepped-down voltage is detected by the microcontroller as a "first event". Upon detection of a first event, i.e. movement, an internal clock within the microcontroller begins a pre-specified countdown. If no further "motion events" are detected within that period, then the microcontroller 72 removes the voltage from the gate of the triac 54 to isolate phase terminal 58 from the live load terminal 58, thereby shutting off the load. This functionality is particularly useful because if a room is left unoccupied, say for half an hour or more, then electrical appliances within that room can be automatically switched off to conserve electricity. When a user re-enters the room, they will be detected by the PIR sensor, but the power will not be restored until a reset event occurs. The user knows that the automatic switching apparatus 10 has isolated the power, rather than there being a general eiectrical fault, or a power outage, because the automatic switching apparatus 10 is programmed to indicate its status audibly, by way of a buzzer 80 and by way of a flashing LED 82.

Additionally or alternatively, the microcontroller can have an automatic time-delay reset feature, which automatically resets the switch after a predetermined period. Optionally, an automatic reset is indicated by the LED 82 flashing rapidly.

The automatic switching apparatus 10 can be reset by the user touching a touchpad 84 wired to an input of the microcontroller 72, or by a soft reset using a computer 42 connected to the communications port 36. The touchpad can be programmable to operate in one of three programmable modes:

(i) Non-retriggerable - the touchpad can only switch the load on and subsequent touches do not reset the associated timer,

(ii) Retriggerable - the touchpad can only switch the toad on but subsequent touches reset the associated timer and thereby extend the on time,

(iii) Toggle - the touchpad will toggle the load from on to off. When switching on the associated timer is started and will switch the load off when it expires if no other event has occurred within that period,

A remote touchpad, where provided, assumes the same function as the main touchpad.

A variant of the above automatic switching apparatus utilises an infrared detector for detecting infrared emissions from devices, e.g. television remote controls etc. within the predetermined zone. Thus, if a user remains still for long periods of time, but remains present in the room, for example when watching television, then every time he/she operates the TV's remote control, scattered infrared light from the remote control will be detected, thereby re-starting the countdown. This arrangement reduces the likelihood of the inconvenience of electrical appliances being switched off whilst the room is still occupied by a stationary person.

The invention has a built in PIR motion sensor and IR receiver. The invention can be designed to switch plugged in loads off when the room in which it is sited is not being used (inactivity being detected by the PIR) and on when any remote control is used within sight of the built in IR receiver. The device will learn' existing remote control signatures. If fitted with a wireless receiver can also optionally 'learn' wireless PIR signatures so that it can use existing installed wireless burglar alarm PIRs to determine inactivity.

The microcontroller 72 is also wired to receive signals from a temperature sensor 86 and can thus be used to control the operation of heating or cooling appliances. The automatic control apparatus 10 can be programmed to prevent a room from being overheated, for example by isolating the heating devices from the mains power supply 20 when a predetermined temperature has been reached, or to act as a frost guard, for example by turning on electrical heaters when the detected room temperature falls below a predetermined temperature, e.g. a temperature between O⁰C to 2O⁰C. A default minimum temperature may be 4⁰C.

Finally, it will also be noted that the automatic switching apparatus 10 comprises a current sensor 88 wired to monitor the current draw of the electrical load 12. The microcontroller 72 can be programmed to isolate the load live terminal 58 from the mains phase terminal 56 upon detection of a current exceeding a predetermined current. The predetermined current may be the upper limit that the building's wiring can withstand (e.g. 13A), or it might be much lower (e.g. 1A), for example, to discourage the use of multiple plug mains adapters etc, which can overload mains sockets. The predetermined current is programmable between 2A and 13A in 0.5A increments.

Alternatively the unit can be programmed to isolate the load if a step change in the load current exceeds a predetermined delta value. For example many low current devices may be plugged in without causing isolation, but a single high current device being plugged in will cause an alarm followed shortly by isolation of all plugged in devices if the high current device is not swiftly unplugged.

Inactivity timeout and over current conditions cause a disconnect alarm to sound for a programmable time (default 30 seconds). For inactivity only a touchpad touch can reset the disconnect alarm. For over current only reducing the load current can reset the disconnect alarm. On expiry of the alarm the unit disconnects the load. The disconnect alarm is programmable in 1 second units, but a setting of zero shall be used for immediate disconnect without warning. A normal disconnect condition can be reset by a touchpad touch and optionally by PIR activity or a remote touchpad . Nevertheless, disconnect shall not sound nor shall a disconnect take place when the heating is on for another valid reason, e.g. due to the frost stat or the timer.

A fault current of just over 13A should cause an immediate disconnect. To detect this condition the software needs to continuously monitor the bolometric ammeter. A fault current disconnect shall be immediate, without disconnect alarm and this function cannot be disabled by programming. This type of disconnect cannot be reset except by cycling the input AC power.

To extend the life of the relay and to prevent ambient temperature rises within the unit, a variant as shown in Figure 4 utilises a triac and a relay.

The triac is designed to connect cold loads and disconnect inductive loads. The relay is designed to short out the triac and thereby stop the product getting hot with high-current loads. The maximum continuous load current is 13A and the triac typical Vdrop is 1V. Therefore up to 13VV of heat needs to be dissipated. Tests show that the product will rise to 100+ ⁰C under these conditions, hence the inclusion of the relay. The relay will only switch 10A at 110 VAC (8A at 240 VAC) but can handle a 13A to 15A armature current. The triac and relay operate together by first engaging the triac and waiting 5 seconds. The current sense reading should now be stable and can be read and this timer allows the relay coil drive capacitor to recharge to 24V. Then the relay is engaged and a wait of more than approximately 100ms is required for full connection. The triac can then be disconnected for safety reasons. If the relay fails then the triac alone will operate.

To turn off, the triac is switched on and a wait of >20mS is required for connection. The relay is then switched off and a wait of >100mS is required for full disconnection. The triac is then switched off.

In Figure 3, a Bolometer is used to sense the current used by the load where the sensing resistor is very much smaller (15mΩ ). This allows it to pass large currents (up to 13A) without overheating and failing. Furthermore instead of sensing the voltage drop over the resistor, the temperature of the resistor is sensed using an NTC thermistor probe. The probe used is encapsulated in a glass bead that additionally acts as the mains supply safety barrier (a safety barrier between live circuits and safe control circuits being a legal requirement). This obviates the need for an opto-isolator as used in known devices. Furthermore to sense only the current into the load (and not a combination of the current into the load and the ambient temperature) the sensing thermistor is part of a potential divider where a second identical thermistor is used to sense the ambient temperature.

The bolometer senses the power dissipated in R10 (15mΩ). The bolometer comprises a potential divider R13=10K (TBPS0R103J410H5Q 10K 0402 thermistor) and bead sense thermistor (Semitec 103GT-1). Both devices have the same K factor and therefore the bolometer cancels out the ambient temperature giving analogue reading that's a function f() of the power dissipated in the current sense resistor. From this the current consumption can be determined:

VAI = f(I²) Λ I = f (VAI) Rather than determine f analytically it is best to interpolate I from the voltage on the A1 input using a linear interpolation between tabulated points from a look-up table, as shown in Figure 5.

The bolometer is slow at reacting to current changes. It takes about 5 seconds to get within 80% of the final temperature. At worst, the bolometer takes 4 minutes to return to ambient (zero) when cooling down after reading 12A.

Taking readings and nulling the bolometer is accomplished with the load disconnected and the system settled (V_Ai is not changing). The zero reading is taken and this should be ~1.65V. The exact reading is needed to set the zero point to account for bolometer component tolerances. When nulling make sure the bolometer is cold, e.g. at least 10 minutes after the load was last switched on or after reset.

If the current reads more than 13A at any point the load should be immediately disconnected using the turn-off algorithm above.

Any one or more of the above functions can be used simultaneously or in isolation. In one example, the automatic switching apparatus 10 can be programmed to control the temperature of a room and to guard against over currents with al! other functions disabled. In another example, the automatic switching apparatus 10 might be programmed to control the power to an electrical device based on activity/inactivity within a predetermined zone, and to monitor for over currents, but instead of shutting off the power in such a case, to alert users to over currents using the buzzer 80 and or LED 82. A continuous green LED indicates the load is switched on and a flashing green accompanies a disconnect alarm. Brief periodic red flashing indicates the load has been disconnected normally, whereas fast (urgent) flashing red light indicates load disconnection due to fault current. Other indication conditions (e.g. amber) can be used to indicate a connection to the programmer or other programming conditions.

It will be appreciated that the use of a microcontroller and a computer user interface enables the automatic switching apparatus to operate in a variety of modes.

Nevertheless, it is envisaged that the microcontroller will be pre-loaded with a menu of default operating modes, which can be used "out of the box", but which can also be customised using the computer 42/communications port 30.

One class of user (e.g. Landlords) can program the operation of the switch whereas another class of user (e.g. tenant) can only make minor changes to the operation of the switch, being prevented by various security devices built in to the switch.

The invention can be programmed by the Landlord to operate on any, one or combination, of the following parameters:

(i) If the ambient temperature falls below a programmable set point the load will be connected (frost-stat).

(ϋ) If the ambient temperature falls below a programmable set point and the time falls within a pre-programmed period the load will be connected (thermostat with timer controller).

(iii) If the load current exceeds a pre-programmed value the load will be disconnected (current limiter), (iv) If the energy used exceeds a pre-programmed value within a preset period the load will be disconnected (energy limiter). (v) If the room in which the unit is sited be unoccupied for a preprogrammed period the load will be disconnected (occupancy switch).

Importantly, since the microcontroller will need to be used continuously for extended periods of time (months or years) without user intervention, it is programmed to self-reset periodically and/or upon detection of a lock-up.

The microcontroller is protected using a PIN code device, which may comprise hardware buttons (not shown), or which may need to be input by a user when connecting thereto using the communications port 36. A default PIN is provided for first installation and setup, although the PIN can be changed for security purposes.

Programming can be via a USB connection or wireless connection) to a computer running special software incorporating the following security features:

(i) A dongle to prevent unauthorised users from re-programming switches.

(ii) A PIN code known only to the Landlord to prevent unauthorised users from re-programming switches.

Conversely the tenant (a user without the ability to program a switch) can only use the touch-pad to connect the load for a short period (period being programmed by the landlord), e.g. extra-hour feature, and set the time of day and week on the 7-day timer (tenant cannot change the programme on and off periods).

Thus, the invention uniquely provides: (i) a USB connection for programming a switch, (ii) a wireless connection for programming a switch, (iii) ability of one group of users to change settings that another group cannot thereafter alter (security), with (A) the security feature of a PIN code in a switch and (B) the security feature of requiring a dongle to program a switch.

(iv) that possibly also the combination of programmable frost-stat, thermostat, timer controller, current limiter, energy limiter and occupancy switch in a single device where any combination of these can be pre-selected and pre-programmed by a Landlord. The invention is not limited to details of the foregoing embodiments, for example:

Where the automatic switching device 10 comprises an infrared detector 26, the computer 42 can communicate with the internal circuit using IR communications protocol. Additionally or alternatively, the control circuit could comprise a radio transceiver, which could allow it to communicate with the computer using a radio communications protocol, e.g. VVLAN, Bluetooth® etc. An advantage of providing wireless programming capability is that the switching unit 10 does not necessarily need to be unscrewed from the back box 16 to enable it to be programmed, re-programmed or reset.

The PIR, where provided, may connect wirelessly to the switching apparatus obviating the need for additional wiring.

Claims

Claims;

1. An automatic switching apparatus comprising: switch means for selectively connecting or disconnecting an electrical load from a mains power supply; trigger means for detection of a first predetermined event; reset means for detection of a second predetermined event; and programmable control means for actuating the switch means.

2. An automatic switching apparatus as claimed in claim 1 , wherein the switch means comprises a triac and/or a relay.

3. An automatic switching apparatus as claimed in claim 1 or claim 2, wherein the automatic switching means is electrically connectable to the mains power supply and to the electrical load via screw terminals.

4. An automatic switching apparatus as claimed in any of claims 1 to 3, wherein the programmable control means comprises a microcontroller.

5. An automatic switching apparatus as claimed in claim 4, further comprising a communications port to enable the microcontroller to be programmed and/or re-programmed.

6. An automatic switching apparatus as claimed in claim 5, wherein the communications port comprises a USB port.

7. An automatic switching apparatus as claimed in any preceding claim, wherein the first predetermined event is any one or more of the group comprising: an electrical current exceeding a predetermined threshold, a temperature falling outside a specified range, inactivity for a predetermined period, and preset 'off period' of a seven day timer,

8. An automatic switching apparatus as claimed in any preceding claim, wherein the second predetermined event is any one or more of the group comprising: a soft reset, a button press, an electrical current falling below a predetermined threshold, a temperature falling within a specified range, a detected activity, and preset 'on period' of a seven day timer.

9. An automatic switching apparatus as claimed in any preceding claim, wherein the trigger and/or the reset means comprises a current detection means.

10,An automatic switching apparatus as claimed in claim 9, wherein the current detection means comprises a step-change or delta-current detection means,

11.An automatic switching apparatus as claimed in claim 9, wherein the current detection means comprises a bolometer.

12,An automatic switching apparatus as claimed in any preceding claim, wherein the trigger and/or the reset means comprises a temperature detection means.

13.An automatic switching apparatus as claimed in any preceding claim, wherein the trigger and/or the reset means comprises an infrared detector.

14.An automatic switching apparatus as claimed in claim 13, wherein the infrared detector is arranged to detect infrared transmissions from an infrared remote control.

15.An automatic switching apparatus as claimed in claim 13 or claim 14, wherein the infrared detector comprises a passive infra red motion detector.

16.An automatic switching apparatus as claimed in any preceding claim, wherein the trigger comprises a circuit for actuating the switch means upon non-detection of a first event after a predetermined interval.

17.An automatic switching apparatus as claimed in any preceding claim, wherein the reset means comprises any one or more of the group comprising: a timer for resetting the switch means after a predetermined interval; a reset switch; a push switch; a touch pad; and a computer interface.

18.An automatic switching apparatus as claimed in any preceding claim, wherein the reset means comprises a lock.

19.An automatic switching apparatus as claimed in claim 18, wherein the lock comprises any one or more of the group comprising: a dongle; a personal identification number locking device; and a key-operated lock.

20.An automatic switching apparatus as claimed in any preceding claim, further comprising a fascia affixable to a mains power outlet back box.

21.An automatic switching apparatus as claimed in claim 20, wherein the reset switch and/or communications port are located behind the fascia and are only be accessible by partially or completely removing the fascia from the back box.

22.An automatic switching apparatus substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.