GB2093221A - Control Devices - Google Patents

Abstract

A device for controlling the supply of electrical power to a load (19), for example an a.c. electric motor, includes a control panel and keyboard connected to processor means (10) including a microprocessor. The processor means (10) provides an output signal for operating a load control means (18) regulating the supply of power to the load (19). <IMAGE>

Description

SPECIFICATION Control Devices The present invention relates to apparatus for controlling electrical power and in particular to a device for controlling power supplied to the load of an electrical machine or appliance.

The present invention will hereafter be described with particular reference to fan appliances although it will be appreciated that it is not thereby limited to such applications. The control device of the present invention may be adapted to control the supply of power to any electrical load, for example electrical motors, heating or lighting installations.

The device of the present invention is particularly useful in applications where electrical power is supplied to a load in pulsed form or where the power fluctuates periodically. The device may be adapted to control power to a load incrementally or in stepwise fashion from a minimum to a maximum level. Power and hence speed control for a load such as, for example, an alternating current electric motor may thus be provided.

Hitherto, speed control of appliances such as domestic fans has been achieved by a row of mechanical push button switches which regulate the amount of power being supplied to the fan motor. These switches need to be fairly sturdy and hence cumbersome to handle the relatively high voltages and/or currents to which they are subjected. It is often difficult to seal them against ingress of moisture, dust and other contaminants.

This often leads to damage to high voltage sections of the appliance as well as corrosion and pitting of the switches themselves resulting in reduced reliability and high maintenance costs.

It is an object of the present invention to alieviate the disadvantages of the prior art.

According to the present invention there is provided a device for controlling supply of electrical power to a load comprising: operator means; processor means to which said operator control means is operably connectable, said processor means providing an output signal; and load control means operated in response to said output signal to regulate the supply of electrical power to said load.

The present invention accordingly provides a device which allows incremental control of power to a load. The device preferably incorporates a switching arrangement which is compact, light in construction and is easy to operate. Such switching arrangement may include a plurality of press or touch activatable keys which are generally of a low current type. The keys may comprise conductive rubber touch pads or touch control electrodes suitable for use with Integrated Circuit elements.

The control device of the present invention may incorporate a timer facility adapted to switch off power to the load automatically after a preset time has elapsed. Where a timer facility is provided the device preferably includes a manual overide facility.

The operator means of the present invention may comprise a control panel including a keyboard. The keyboard may include a plurality of switch elements. Switch elements may be provided to select speed, (in the case the load is an electric motor) duration of operation and manual/auto operation. A speed cancel switch element and an on/off switch for the appliance also may be provided on the control panel.

The switch elements preferably comprise conductive rubber (mylar) technology as above referred to. In one form six speed switch elements and four timer switch elements may be provided.

A manual operation switch element preferably is included to cancel an actuated timer switch element The speed cancel switch element may be adapted to reset the motor speed to 0 RPM at any time. The speed switch elements may be arranged adjacent one another to form a graphic speed control band. The graphic control band may provide slide finger speed control which may be used to simulate a conventional slide potentiometer.

To minimize the number of connections to the keyboard the switch elements of the keyboard may be arranged in matrix array form. In one form the keyboard may comprise a 4x4 matrix array. A suitable decoder may be provided to decode the matrix array. The operator means may additionally include a variable element such as a potentiometer to enable continuous adjustment of speeds selected by the switch elements. Where the highest speed selectable by a switch element corresponds to the maximum speed of the motor it is preferable that the variable element is not effective to adjust the speed corresponding to that switch element.

The present device may include overtemperature sensing means. In one form the overtemperature sensing means is adapted to interrupt power to the load whenever the temperature of the load exceeds a preset upper limit. The overtemperature sensing means may reconnect power once the load has cooled to a preset lower limit. All previous speed and timer settings are preferably cancelled once an overtemperature condition is sensed by the control apparatus. The control apparatus thus must be restarted once the temperature falls to the preset lower limit. The overtemperature sensing means may include a sensor in the form of a temperature responsive element. The sensor preferably comprises a thermister which may be placed in heat conducting relationship with the load.

The overtemperature sensing means may include a hysterysis circuit to provide an upper cut-out limit and a lower cut-in limit. The hysterysis circuit preferably comprises a schmidt trigger. The hysterysis circuit may be adapted to generate a logical "1" output whenever the load temperature exceeds the upper limit and a logical "0" output when the load temperature drops below the lower limit. In one form the upper limit (cut-out) temperature may be 1 00C and the lower limit (cut-in) temperature may be 800 C.

The device of the present invention may include display means. The display means preferably comprises an arrangement of display elements such as a plurality of light emitting diodes (LEDs) to indicate the state of the control apparatus.

The display means preferably is arranged with the operator control panel for convenience. A display element may be associated with each switch element of the control panel. The display elements preferably are arranged so that actuation of a switch element causes illumination of an associated display element to indicate that the switch element has been actuated. In the preferred form six LED elements may be associated with the six speed switch element respectively. A further four LED elements may be associated with the four timer switch elements respectively.

The display means preferably includes overtemperature indication. Overtemperature indication may be provided by means of at least one further display element. Preferably however, overtemperature indication is achieved by means of the LED elements referred to above. In one form this may be achieved by arranging the LED elements to flash at a convenient rate whilst an overtemperature condition persists. In one form the LED elements may be arranged to flash at a 1 Hz rate. Preferably the LED elements associated with the timer switch elements are arranged to provide overtemperature indication.

The processor means of the present invention may comprise discrete LSI circuit elements or may include a single chip microprocessor. The microprocessor preferably incorporates a control unit and a data memory. The processor means may include a read only memory (ROM). In one preferred form the microprocessor and ROM may be provided on a single chip microcomputer. The microcomputer may comprise a four bit single chip device such as a Hitachi circuit type HMCS 42.

The load control means of the present device is operably connectable to the processor means.

The load control means may be adapted to regulate electrical power to the load. In one form the load may comprise an alternating current type induction motor. The processor means preferably makes adjustments to the load control means to regulate supply of power to the load.

The load control means preferably includes a solid state switch such as a silicon controlled rectifier or a triac to switch the supply of power to the load. As will be appreciated when a triac or an SCR is used, timing of trigger pulses to the gate of the triac or SCR with respect to the zero crossing of the power supply determines the conduction period of the triac or SCR. The conduction period in turn determines the amount of power supplied to the load. Generally speaking the longer the delay of the trigger pulses with respect to the zero crossing the less power is supplied to the load.

The processor means may be operably connectable to the load control means via an interface means. In one form the interface means may include a driver element such as a transistor.

The processor means of the present invention preferably includes trigger generator means. The trigger generator means is adapted to generate trigger pulses having a delay time which is variable with respect to the zero crossing of the power supply. A reference signal may be derived from the power supply. The reference signal preferably is applied to the processor means to provide a zero crossing reference for the trigger generator means. The reference signal may be derived via a clamping circuit connected to the mains power supply. In one form the processor means may be adapted to detect waveform transitions (from high to low or from low to high) and to interpret each "transition" as a crossover point.

The delay time may be controlled by the processor means which is responsive to information received from the operator control means and overtemperature sensing means. In one form the trigger generator means may be adapted to generate trigger pulses having approximately .5mS duration every half cycle of the mains power supply. In the case of a 50 Hz mains power supply one trigger pulse may be generated every 1 Om S. Preferably the trigger pulses pass to the load control means via an interface. The interface may include a facility whereby the width of each trigger pulse may be expanded if required.

In one form the operator means may communicate to the processor means information concerning desired speed, whether manual or auto operation is required and duration of operation selected (auto mode only).

As previously described it is preferable to arrange the switch elements of the operator means in a matrix array. Such an arrangement has advantages in that the number of separate lines with connect the processor means to the operator control means be reduced. A suitable decoder means for the matrix may be provided by the processor means. The decoder means and/or processor means preferably are arranged to provide exclusivity of speed selection so that, if multiple switch elements of the keyboard are actuated simultaneously, only that switch element corresponding to the highest speed is actually selected. Multiple selection may thus be avoided whilst allowing synthesis of "slider" graphic speed control selection.

The present device may include a clock means to supply timing pulses to the processor means.

The clock means may be provided by any suitable means. In one form the clock means may comprise a stable high frequency generator. In the preferred form the clock means may be provided on a single chip microcomputer as previously described.

The device further includes a program store connectable to the processor means to store the program for running of the control apparatus. The program store may be provided by any suitable means. The program store conveniently comprises a read only (ROM) such as a cross bar matrix ROM or a semiconductor ROM. In the preferred form the program store may be conveniently provided on a single chip microcomputer.

The processor means may be arranged to provide a timer facility as previously described.

The timer facility preferably is adapted to shut down the load control means after a predetermined time has elapsed. In one form the timer facility may be adapted to disable the trigger generator means after a predetermined time. The timer facility may be engageable by actuating timer switch elements on the operator control means. Preferably the timer facility is engageable after a speed switch element has been actuated. Each timer switch element preferably is adapted to select a different time duration. The effect of actuating multiple timer switch elements may be cumulative.

In one preferred form time switch elements may be adapted to select runs of T HR, + HR, 1 HR and 2 HRS respectively. Actuation of all four switch elements thus will result in a total run of 3i HRS.

The display elements of the display means preferably are adapted to display the duration of time remaining before the timer facility automatically shuts down the load control means.

In one form the LED elements may be arranged to change state to indicate the time remaining before auto shut off. The manual operation switch element or speed cancel switch element may be actuated at any time to deactivate the timer facility.

The timing facility preferably is engageable only after a speed switch element has been actuated.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein: Figure 1 shows a functional diagram of a load control device incorporating the principles of the present invention.

Figure 2 shows a functional diagram of a speed control device for an electric fan or similar appliance incorporating a preferred embodiment of the present invention.

Figure 3 shows a schematic diagram of one form of speed control device in accordance with the principles of the present invention.

Referring to Figure 1 a load control device is shown incorporating a processor means 10, an overtemperature sensing means 11, operator means 13, clock means 14, program store 15, display means 16 and load control means 18. The control apparatus is arranged to regulate the supply of power from power supply 17 to load 19.

Referring to Figure 2, the preferred speed control arrangement according to the present invention includes a microcomputer 20 and a thermister 21 connected to the microcomputer 20 via a schmidt trigger 22.

An operator control panel 23 and an LED display 24 are also connected to the microcomputer 20. The microcomputer 20 is connected to a triac switch element 25 via an interface 26. The triac switch 25 is connected between the mains supply 27 and the electric motor 28 of the appliance.

Interface element 26 preferably comprises a suitable driver circuit which may include a transistor.

Referring to Figure 3, the preferred form of fan control apparatus includes a single chip four bit microcomputer 30. The microcomputer is connected to a suitable power supply via pins 11 and 14. The power supply comprises a half wave rectifier including diode D1, resistor Dl 1 and capacitors C1 and C2, clamped via zener diode Z1 to -1 0V.

The operator control panel includes a plurlity of switch elements shown generally at 32. The switch elements are arranged in a 4x4 matrix and are used to program information regarding time and speed selected. Four lines of the matrix act as outputs delivering a scan pulse, the other four are inputs which receive this scan when a switch element is actuated. All exclusivity and priorities of actuation are performed by the software program stored in the ROM of the microcomputer 30.

íMe control panel includes six speed switch elements S1--S6 and speed cancel element SC.

Switch elements S1--S6 are arranged adjacent one another to form a slide graphic control band.

Four timer switch elements S7-810 provide timed runs of T HR, T HR, 1 HR and 2 HRS respectively. Cumulative runs may be provided by actuating multiple switch elements. A selected run may be cancelled at any time by actuating manual switch element SM.

The display means includes ten logical outputs (pins 1-5 and 23-28 of microcomputer 30) which supply current to display LEDs L1--L10 via associated resistors R1--R10. Display LEDs L1- L6 are associated with speed switch elements S1--S6. Display LEDs L7--L10 correspond to timer switch elements S7--S10.

Phase control is referenced to a zero-crossover input DO (pin 8) to the microcomputer. The input reference is derived through a clamping circuit comprising diodes D2, D3 and resistor R12.

Pin D9 of microcomputer 30 applies trigger pulses to the load control means comprising triac TR 1 and driver transistor T3. Trigger pulses approximately .5mS in duration are applied to the base of transistor T3 via resistor RI 3. The phase delay of the trigger pulses is adjusted by the processor means according to the speed selected by speed switch elements S1--S6. The microcomputer may be programmed to provide the following trigger phase angles.

Mains Frequence 50Hz 60 Hz Speed 1 108 degrees 100 degrees Speed 2 100 degrees 90 degrees Speed 3 95 degrees 82 degrees Speed 4 88 degrees 74 degrees Speed 5 78 degrees 65 degrees Speed 6 50 degrees 50 degrees The microcomputer includes a 50/60 Hz turnover switch SF enabling choice of operating mains frequency.

Triac switch element TR 1 connects power to electric motor M1 when it is triggered into conduction by the trigger pulses.

The microcomputer is wired to reset at power up.

The overtemperature sensing means is shown generally at 31 and comprises thermister TH 1 firing a schmidt trigger circuit including transistor T1 and T2. The schmidt trigger circuit operates in the well known manner to provide a HIGH output at D2 whenever the sensed temperature exceeds 1 1 OOC. This has the effect of isolating trigger pulses from pin D9 of microcomputer 30.

An overtemperature state is accompanied by display LEDs L7--L10 flashing at a 1 Hz rate. The unit cannot be restarted and no time or speed selection can be made until flashing stops indicating temperature has fallen below the acceptable lower limit of 800 C.

Two methods may be used for selecting speed.

1. A finger may be placed about the center of the slide graphics and pressed at the position that indicates the desired speed.

2. The finger may slide along center of slide graphics and LED indication should follow finger.

Programmed time may be entered by pressing the appropriate timer switch elements S7--S10.

Programmed time may be altered in two ways: First, set time may be cancelled by pressing manual switch element SM and a new time entered by pressing the appropriate timer switch element or elements.

Second, after approximately 30 seconds of setting initial time, pressing any timer switch element will automatically cancel all previous time and the desired time will be entered.

When the timer progresses from zero time to program time, the motor speed selection will cancel if the motor is running. The speed will need to be reselected.

It will be appreciated that various alterations, modifications and/or additions may be introduced into the constructions and arrangemenfs of parts above described without departing from the spirit or ambit of the present invention.

Claims (38)

Claims

1. A device for controlling supply of electrical power to a load comprising: operator means; processor means to which said operator means is operably connectable, said processor means providing an output signal; and load control means operated in response to said output signal to regulate the supply of electrical power to said load.

2. A device according to claim 1 wherein said operator means comprises a control panel including a keyboard.

3. A device according to claim 2 wherein said keyboard includes a plurality of switch elements.

4. A device according to claim 3 wherein said switch elements comprise a 4x4 matrix array and said device includes a decoder for said matrix array.

5. A device according to claim 3 or 4 wherein said switch elements comprise conductive rubber touch pads.

6. A device according to claim 3 or 4 wherein said switch elements comprise touch control electrodes.

7. A device according to any one of claims 36 wherein said operator means includes at least one switch element adapted to select a predetermined electrical power level.

8. A device according to claim 7 wherein a plurality of switch elements are arranged adjacent one another to form a graphic control band.

9. A device according to any one of the preceding claims wherein said load control means comprises a solid state switch.

10. A device according to claim 9 wherein said solid state switch comprises a triac device connected in series circuit between said supply of electrical power and said load, the gate of said triac device being adapted to receive said output signal.

11. A device according to claim 9 or 10 wherein said output signal comprises trigger pulses adapted to operate said solid state switch.

12. A device according to claim 11 wherein said processor means is adapted to control supply of electrical power to said load by delaying said trigger pulses with respect to the zero crossing of the power supply.

1 3. A device according to any one of the preceding claims wherein said processor means includes a microprocessor.

14. A device according to any one of the preceding claims wherein said processor means comprises a microcomputer.

1 5. A device according to any one of claims 7-14 wherein said load comprises an alternating current electric motor and said predetermined power level corresponds to the speed of said motor.

1 6. A device according to claim 1 5 wherein a plurality of switch elements are adapted to select a corresponding speed of said motor.

1 7. A device according to claim 1 6 wherein said processor means is adapted to provide exclusivity of speed switch selection.

1 8. A device according to claim 16 or 1 7 wherein said operator means includes a switch element adapted to reset the motor speed to 0 RPM.

1 9. A device according to any one of claims 16--18 when appended to claim 12 wherein corresponding greater speeds of said motor are obtained by selecting respective switch elements which correspond respectively to smaller delays of said trigger pulses with respect to said zero crossing.

20. A device according to any one of the preceding claims further including overtemperature sensing means operatively connectable to said processor means and adapted to disable said output signal whenever the temperature of said load exceeds a preset upper limit.

21. A device according to claim 20 wherein said overtemperature sensing means comprises a temperature responsive element.

22. A device according to claim 21 wherein said temperature responsive element comprises a thermister placed in heat conducting relationship with said load.

23. A device according to any one of claims 20-22 further including a hysterysis circuit adapted to provide an upper cut-out limit temperature and a lower cut-in limit temperature.

24. A device according to claim 23 when appended to claim 21 wherein said hysterysis circuit comprises a schmidt trigger interposed between said temperature responsive element and said processor means.

25. A device according to any one of the preceding claims further including display means operatively connectable to said processor means.

26. A device according to claim 25 wherein said display means comprises a plurality of display elements.

27. A device according to claim 26 when appended to claim 3 wherein a display element is associated with each said switch element of said keyboard.

28. A device according to claim 27 wherein actuation of a switch element causes iliumination of the associated display element.

29. A device according to any one of claims 26-28 wherein each said display element comprises a light emitting diode.

30. A device according to any one of claims 25-29 wherein said display means is adapted to provide an intermittent output whilst an overtemperatu re condition persists.

31. A device according to any one of the preceding claims wherein said processor means includes timer means adapted to disable said output signal after a preset time duration.

32. A device according to claim 31 wherein said operator means includes at least one switch element adapted to preset said time duration.

33. A device according to claim 32 wherein said operator means includes a plurality of switch elements, each said element being adapted to select a different time duration.

34. A device according to claim 33 wherein the effect of actuation of multiple timer switch elements is cumulative.

35. A device according to any one of claims 32-34 wherein said operator means includes a switch element adapted to disable said timer means.

36. A device according to any one of claims 31-35 wherein said display means is adapted to display the duration of time remaining before said timer means disables said output signal.

37. A device according to any one of the preceding claims substantially as herein described with reference to the accompanying drawings.

38. An electrical appliance including a load comprising an alternating current electric motor and a device for controlling supply of electrical power to said motor according to any one of the preceding claims substantially as herein described with reference to the accompanying drawings.