GB2412870A - Electronic drive system for a droplet spray generation device - Google Patents

Electronic drive system for a droplet spray generation device Download PDF

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Publication number
GB2412870A
GB2412870A GB0407909A GB0407909A GB2412870A GB 2412870 A GB2412870 A GB 2412870A GB 0407909 A GB0407909 A GB 0407909A GB 0407909 A GB0407909 A GB 0407909A GB 2412870 A GB2412870 A GB 2412870A
Authority
GB
United Kingdom
Prior art keywords
drive system
power
generation device
power supply
electronic drive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0407909A
Other versions
GB0407909D0 (en
Inventor
Oliver Burstall
Andrew Sant
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Reckitt Benckiser UK Ltd
Original Assignee
Reckitt Benckiser UK Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Reckitt Benckiser UK Ltd filed Critical Reckitt Benckiser UK Ltd
Priority to GB0407909A priority Critical patent/GB2412870A/en
Publication of GB0407909D0 publication Critical patent/GB0407909D0/en
Priority to PCT/GB2005/001324 priority patent/WO2005098982A1/en
Publication of GB2412870A publication Critical patent/GB2412870A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
    • B05B17/0653—Details
    • B05B17/0669—Excitation frequencies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207—Driving circuits
    • B06B1/0215—Driving circuits for generating pulses, e.g. bursts of oscillations, envelopes
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K9/00—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers
    • G10K9/12—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated
    • G10K9/122—Devices in which sound is produced by vibrating a diaphragm or analogous element, e.g. fog horns, vehicle hooters or buzzers electrically operated using piezoelectric driving means
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/802—Circuitry or processes for operating piezoelectric or electrostrictive devices not otherwise provided for, e.g. drive circuits
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
    • B05B17/0638—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers spray being produced by discharging the liquid or other fluent material through a plate comprising a plurality of orifices
    • B05B17/0646—Vibrating plates, i.e. plates being directly subjected to the vibrations, e.g. having a piezoelectric transducer attached thereto
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/50—Application to a particular transducer type
    • B06B2201/55—Piezoelectric transducer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
    • B06B2201/70—Specific application
    • B06B2201/77—Atomizers

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Mechanical Engineering (AREA)
  • Spray Control Apparatus (AREA)

Abstract

An electronic drive system for a droplet generation device of the type having a droplet generator including a perforate membrane driven by a piezoelectric transducer. The electronic drive system comprising a programmable micro-controller 20 comprising a power supply unit 21 for converting in use a battery supply voltage 12 to power the device, a power amplifier 23 to receive electric power from the power supply unit 21 and supply a drive signal to the piezoelectric generator at regular intervals, and a mono-stable switch connected to a timer to generate a drive signal as a plurality of pulses of fixed interval over a predetermined period when the switch is operated. The power supply unit includes a DC-to-DC converter integrated circuit and supplies 5 volts at up to 200 mA from the cells 12. An air freshener having such a spray generation device is also claimed.

Description

ELECTRONIC DRIVE SYSTEM FOR A DROPLET SPRAY GENERATION DEVICE
The present invention relates to an electronic drive system for droplet spray generation and, more particularly to an electronic drive system for use in a droplet spay generator for an air-freshening device.
An aim of the present invention is to provide a low cost electronic drive system for a droplet generator using a micro-controller to implement signal generation and timing elements of a circuit to drive the droplet generator.
Spray generators of the general type to which the present invention relates may, for example, be of the type described in EP-A-0615470.
According to the present invention, there is provided an electronic drive system for a droplet spray generation device of the type having a droplet generator including a perforate membrane driven by a piezoelectric transducer, the electronic drive system comprising: a programmable microcontroller providing a power supply for converting, in use, a battery supply voltage to power the device, a power amplifier connected to receive electric power from the power supply and supply a drive signal to the piezoelectric generator at regular intervals; a mono-stable switch connected to a timer to generate the drive signal as a plurality of pulses of fixed interval over a predetermined period when the switch is operated.
By using a micro-controller the components of the present invention cost less than the expected cost of a device using a custom application specific integrated circuit (ASIC) providing the same functionality.
The micro-controller may include a further timer to set an interval at which the drive signal is provided to the power amplifier thereby to control the interval at which the droplet generator is automatically operated.
The drive system may be used to power and control a droplet generator for an air freshening device By using a micro-controller device and using just a single pin to interrogate the multi position and mono-stable switches allows the use of a micro-controller with only six l/O pins.
The power provided by batteries is maximised by using the microcontroller's "sleep" mode, but waking it up under the control of a timed "watchdog" interrupt and whenever the mono-stable switch is pressed.
An example of the droplet spray generation device incorporating a drive system according to the invention will now be described with reference to the accompanying drawings in which: # . . # . . . . c . . Figure 1 illustrates a cross-sectional view of part of the droplet generator; and Figure 2 is a block diagram of the drive system for the device.
Figure 1 shows part of a spray head 11 for an air-freshening device 1 used for spraying air-freshening fluid into a room. The spray head 11 includes a perforate membrane 32 coupled to a transducer 30 formed by an annular piezoelectric element 31 mounted on a substrate 33. Such devices are well known in the art.
When the transducer is activated, air-freshening fluid is sprayed from a reservoir (not shown) through the perforate membrane 32 to the outside environment within the room.
The block diagram of Figure 2 shows an electronic drive system 10 connected to the spray head 11, the drive system incorporating a microcontroller 20 (described in more detail below) and the device being powered by two "M" alkaline batteries 12 providing in the range of 2 - 3.2 volts.
In an air-freshener of this type, there may be a requirement that the device 1 sprays fluid through the spray head 11 in two different modes. A background mode is provided wherein a preset quantity of fluid is emitted by the spray head 11 at intervals determined by a user. This is achieved by automatically actuating the piezoelectric transducer for a predetermined length of time, a slide switch 13 allowing the user to control how often the spray head 11 emits fluid. The slide switch 13 is a five-position slide switch that the user may adjust to set the time
interval between background sprays.
A boost mode is also provided; in this mode, when the user operates push switch 14 the spray head sprays a preset quantity of fluid. Typically, the background spray emits a maximum of 400mg of fluid per day and the boost mode emits 10mg of fluid in 10 seconds on activation of the push switch 14.
Micro-controller 20 is, for example, an Atmel "ATTINY13" or "ATTINY26L" device. These devices contain all of the functional blocks required to implement the features described herein. The micro-controller 20 has six l/O pins.
The air-freshening device 1 is constructed to be power efficient and the micro-controller 20 contains a number of features to achieve this. A power supply unit 21 is provided on the micro-controller to provide power for the components on the micro-controller 20 and to the spray head 11. This includes a DC-to-DC converter integrated circuit together with the inductor, diode and capacitors it requires to operate. It can supply 5 volts at up to 200 mA from the two "M" cells 12. It has very low quiescent power consumption when not under load, and its load current can be estimated by measuring its average switching frequency (as described below). The power supply circuit uses an integrated "pulse frequency l c 'c. r ë C mode" dc-to-dc converter integrated circuit to provide the stabilised 5-volt, 0.2 amp power rail. To minimise power consumption, the microprocessor is kept in "sleep" mode when not spraying.
A power amplifier circuit 23 provides a drive signal to the spray head 11. In this example, the amplifier circuit is configured as a resonant bridge circuit. It requires two digital drive signals in anti-phase at a desired frequency. Operating from the 5-volt power supply, it can generate a drive signal of the order of 32 volts peak-to-peak. A series capacitance of the spray head 11 forms part of the resonant bridge power amplifier circuit.
The background timer 24 is used to set the time interval between the "background" sprays as mentioned above. It also sets the time duration of each spray. The timer 24 is provided by software on the micro-controller 20. The slide switch 13 is connected to the background timer 24 to allow the user to set the
interval between each background spray.
A boost timer 25 is also provided as software on the micro-controller 20.
When the push switch 14 is pressed, the software executes the boost spray. It splits the fluid to be sprayed into a number of "quanta" of fixed length, with a fixed time interval between each. Each quanta is 1 second, which is repeated 10 times with a 200ms time gap between each pulse. The 200ms gap lowers the average flow rate and gives the spray head 11 time to recover between each spray.
The micro-controller 20 has a stable 9.6 MHz internal frequency source that is used to generate square wave drive signals at the frequencies required, and with the frequency resolution required to drive the spray head 11. By adjusting the number of CPU clock cycles between output transitions, frequency generator software 22 can generate square waves in the range of 75 - 90 KHz (which is required for the spry head 11), with a resolution of the order of 1 KHz. Since every other frequency step is an odd number of clock cycles, the duty cycle of the square wave generated is only approximately 50% in these cases. In addition, the micro controller 20 is programmed to generate dual signals in anti-phase, overlapping by one clock cycle. These overlapping drive signals are required for the resonant bridge circuit 23 that drives the spray head 11.
The spray head 11 operates best at its resonant frequency which is in the range of 75-90 KHz and requires a drive voltage in the order of 32 volts peak-to peak at this frequency. When driven at this frequency, the power consumption of the transducer is at a maximum. To determine this resonant frequency, the current supplied by the power supply 21 can be measured by counting the falling edges on its switching output. Comparator input and edge detector circuits in the micro controller 20 are used to monitor the occurrence of these edges. A measurement of c c c c c c I- e C ce.
c c c c c e c e c the power supply current is taken at each frequency step in the 75 - 90 KHz range, and the frequency at which the maximum current is consumed is recorded. It has been found that 6 millisecond test sprays with 6 millisecond gaps between them give an accurate measurement of the resonant frequency. The frequency generator 22 selects the operating frequency that places the highest load on the power supply 21 to be the resonant frequency, and this is then used in further operation to drive the spray head 11.
The system has two calibration modes: When the system is switched on, the resonant frequency is unknown. So, before spraying, all frequencies in the range are tested as described above to find the operating frequency of the spray head 11.
A full calibration measurement such as this makes an audible sound. When operating, the resonant frequency may appear to shift, due to variation of circuit parameters with temperature, etc. Therefore, each time the system sprays, a single frequency point is measured. When all frequencies in the range have been measured, the operating frequency value is updated, and the process restarts. The sound made by such a single point measurement is virtually inaudible due the calibration update being over many background sprays.
A problem solved by use of the boost function is the deleterious influence on device performance of a static layer of fluid which, in some circumstance may develop over time on the top surface of the spray head 11. On some devices it appears that the spray head 11 has difficulty producing droplets through this film of fluid. It was noticed that the initiation of spraying could move the fluid film away from the spraying area. Thus it was determined that a spray head 11 suffering from this problem could be cleared by subjecting it to successive initiation operations.
The boost function of the device of this example thus consists of 10 off 1s pulses with 200ms pauses between each, rather than a single 1 0s pulse.

Claims (4)

rev.e C ce a r C C CLAIMS
1. An electronic drive system for a droplet spray generation device of the type having a droplet generator including a perforate membrane driven by a piezoelectric transducer, the electronic drive system comprising: a programmable micro-controller providing a power supply for converting, in use, a battery supply voltage to power the device, a power amplifier connected to receive electric power from the power supply and supply a drive signal to the piezoelectric generator at regular intervals; a monostable switch connected to a timer to generate the drive signal as a plurality of pulses of fixed interval over a predetermined period when the switch is operated.
2. A drive system according to claim 1, wherein the micro-controller includes a further timer to set an interval at which the drive signal is provided to the power amplifier to control an interval at which the droplet generator is automatically operated.
3. A spray generation device having an electronic drive system according to any of claims 1 to 2.
4. An air freshener having a spray generation device according to claim 3.
GB0407909A 2004-04-07 2004-04-07 Electronic drive system for a droplet spray generation device Withdrawn GB2412870A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB0407909A GB2412870A (en) 2004-04-07 2004-04-07 Electronic drive system for a droplet spray generation device
PCT/GB2005/001324 WO2005098982A1 (en) 2004-04-07 2005-04-06 Electronic drive system for a droplet spray generation device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0407909A GB2412870A (en) 2004-04-07 2004-04-07 Electronic drive system for a droplet spray generation device

Publications (2)

Publication Number Publication Date
GB0407909D0 GB0407909D0 (en) 2004-05-12
GB2412870A true GB2412870A (en) 2005-10-12

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB0407909A Withdrawn GB2412870A (en) 2004-04-07 2004-04-07 Electronic drive system for a droplet spray generation device

Country Status (2)

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GB (1) GB2412870A (en)
WO (1) WO2005098982A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009059373A1 (en) * 2007-11-07 2009-05-14 Air Aroma Research Pty. Limited Remote controlled aerosol dispensing system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0615470A1 (en) * 1991-12-04 1994-09-21 The Technology Partnership Plc Fluid droplet production apparatus and method.
JPH08202372A (en) * 1995-01-27 1996-08-09 Hitachi Koki Co Ltd Volume control system for piezoelectric buzzer
WO2000051747A1 (en) * 1999-03-05 2000-09-08 S. C. Johnson & Son, Inc. Control system for atomizing liquids with a piezoelectric vibrator

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2265845B (en) * 1991-11-12 1996-05-01 Medix Ltd A nebuliser and nebuliser control system
US5452711A (en) * 1992-12-24 1995-09-26 Exar Corporation Small form factor atomizer
NZ304285A (en) * 1995-03-14 1998-12-23 Siemens Ag Ultrasonic atomizer device with a removable precision dosing unit
AU2002230267A1 (en) * 2002-02-11 2003-09-04 Sara Lee/De N.V. Liquid spray-head, apparatus comprising a liquid spray-head and container therefore

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0615470A1 (en) * 1991-12-04 1994-09-21 The Technology Partnership Plc Fluid droplet production apparatus and method.
JPH08202372A (en) * 1995-01-27 1996-08-09 Hitachi Koki Co Ltd Volume control system for piezoelectric buzzer
WO2000051747A1 (en) * 1999-03-05 2000-09-08 S. C. Johnson & Son, Inc. Control system for atomizing liquids with a piezoelectric vibrator

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
WPI abstract accession no. 1996-416608 [42] & JP 08202372 A (HITACHI) 09.08.1996 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009059373A1 (en) * 2007-11-07 2009-05-14 Air Aroma Research Pty. Limited Remote controlled aerosol dispensing system

Also Published As

Publication number Publication date
GB0407909D0 (en) 2004-05-12
WO2005098982A1 (en) 2005-10-20

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)