AU592135B2 - Vapour sensor - Google Patents

Description

-1, 4U11WWA 6 592,135 P/0/01 Form PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: 635/99~ Lodged: 0 o s~Craiplete Specification-Lodged: 00 Accepted: o Lapsed: o o Published: o c lirity: 00.0 -13,,;Ntee. Art: o 00 o 0 o c This documn cnas th amendbnerts 4 CUai&a t Section 49, d ud and la correct 4W TO BE COMPLETED BY APPLICANT Namne of Applicant: MORRIS CLIFFORD HINCH 00 I 2Ater tet Address of Applicant: Actual Inventor: Bankstown, N.S.W. 2200 Morris Clifford Hinch Address for Service: -HAL-FERl)D--MA-WEff 2Tct-f) r* wL c-u- OSz' Paten ~~T-ade ark Attorneys, 1- piW'4 Level 20, National-Mlitual Centre, h S -2000 Complete Specification for the Invention entitled: VAPOUR SENSOR The following statement Is a full description of this invention. including the bes mesthod of peirtoqving it knowni to me:- 146"/70-L 1460/76- I nnted by C I I wwou,.o, Commoeweahh Gowtum.at Priew. Casbewy.

-2- This invention relates to automatic sensing devices and more particularly to a device for automatic switching of electric power in response to the presence of a vapour.

For the sake of brevity, the invention will be described in relation to the switching of electrical appliances upon the presence of excessive water vapour in an enclosed area such as an exhaust fan for a i bathroom or shower recess. However, it is to be understood that the invention is not limited thereto as J a sensor device according to the invention could be used A for other purposes including the control of an alarm in the vicinity of a steam boiler.

Hitherto, bathroom exhaust fans have, in the main, been switched under manual control. It frequently occurs, however, that a person showering forgets to switch on the fan before commencing to shower, or omits i to switch the fan off after showering.

i i 20 automatic switching of an electrical appliance, such as i an exhaust fan or an alarm, by the provision of a 4 liquid-vapour sensor device.

;r i According to the invention there is provided a device for controlling the supply of electrical energy to an electrical load in response to the presence or otherwise of liquid-vapour, said device comprising input means for connection to a power supply and output means for connection to the load, a vapour sensor adapted to detect the presence of liquid-vapour, first circuit r I -3means actuated by the sensor upon the presence of liquid vapour operative to connect the input power means to the output power means so as to provide electrical energy to the load when a predetermined amount of liquid vapour is present, and second circuit means operative to provide power to the load for a predetermined time after the sensor no longer detects the presence of the vapour, said first circuit means including a first circuit unit which is normally gated low that is connected to the sensor, a second circuit unit which is normally gated off that is connected to the first circuit unit and an oscillator controlled by the second circuit 'c t unit,the arrangement being such that when the sensor detects I e 'the presence of a liquid vapour, the first circuit unit is Ij gated high, the second circuit unit is gated high and the oscillator made operative to switch the power to the load.

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawing which is a schematic t tc diagram of an electrical circuit embodying a sensor according to one embodiment of the invention.

The sensor circuit shown in the drawing includes a fan I 10 connected between the active A and neutral N of a convenient power supply through a triac 11. A resistor 12 and capacitor 13 are connected across the triac 11.

Resistor 14, diodes 15 and 16 and capacitor 17 provide a regulated 12 volt DC supply between the lines 18 and 19.

r i

'I

i aa r i i -3a- Vapour sensor 20 is connected between the lines 18 and 19 through resistors 21 and 22 which have capacitor 23 connected across them.

Integrated circuit 24, which is normally gated low, is connected between the sensor 20 and resistor 21 and is coupled to integrated circuit 25 which is normally gated high and to integrated circuit 26 which is normally gated off.

Programmable unit 27 is connected to the output of integrated circuit 25 and its output is connected through line 28 to the integrated circuit 26.

t t C 4 t r t t t t t 4 «G~ t s.l; U

I

I IL; i: (Ct C C C C

SCC

C C C t C C C Cr C cL rc I C tet A first oscillator 29 is coupled to the programmable unit 27 which acts as an oscillator, counter, and reset unit. Integrated circuit 25 inhibits the counter and reset functions of the programmable unit whenever it is gated high.

Integrated circuit 26 which is fed by either integrated circuit 24 or the programmable unit 27 is coupled to the integrated circuit 30 which is also fed by a second oscillator consisting of capacitor 31 and 10 resistor 32. Resistor 33 and diode 34 which are in parallel with each other are connected across the resistor 32 and integrated circuit 30. The output of integrated circuit is connected to the triac 11 through amplifying transistor 35 that is biased by resistor 36.

The sensor 20 may consist of a printed circuit board containing two electrically conductive tracks in close proximity to each other and yet normally electrically isolated. The resistance between the two tracks of the sensor 20 under normal atmospheric 20 conditions is high, ie. open circuit.

The sensor 20 extends through an opening in the bottom wall of a casing for the device so that it may be exposed to the interior of a bathroom (or other such enclosure) such as by projecting through the ceiling.

When water vapour generated within the enclosure contacts or condenses upon the face of the printed circuit board of the sensor 20, the resistance between the conductive tracks reduces considerably and when the water vapour is exhausted from the enclosure the vapour

,I:

i ~"1 "1 or condensed moisture has evaporated the sensor reverts to its high resistive condition.

Thus, it will be appreciated that the voltage between the integrated circuit 24 and the sensor varies with changing resistance of the sensor When there is no vapour at the sensor 20, there is no voltage supplied to the integrated circuit 24 which is gated low and retains integrated circuit 26 in the gated off state. At the same time, integrated circuit

C

25 inhibits the counter and reset function of the r cc r programmable unit 27. When water vapour is present at C 9 rC r the sensor 20 its resistance reduces and thus the C C C c C voltage applied to the integrated circuit 24 rises to turn that circuit element high. Integrated circuit 24 then gates integrated circuit 26 high which, when on, allows the second oscillator to control the triac 11 which turns on the fan When the water vapour has evaporated from the sensor 20, its resistance rises. Integrated circuit S 20 then releases the counter function of programmable unit 27 so that the output of the unit 27 at line 28 retains the integrated circuit 26 at its gated high disposition so that the fan continues to run for a predetermined time set by the counter. In one form of the invention, the counter is set so that the "run-on" time of the fan after the sensor has failed to detect water vapour is 200 seconds. At the end of that time, the programmable unit returns the integrated circuit element 26 to its gated off disposition.

iv i tu i; r

B

1 I

I

-6- Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

t C C f V C C V iii 4

Claims (6)

1. A device for controlling the supply of electrical energy to an electrical load in response to the presence or otherwise of liquid vapour, said device comprising input means for connection to a power supply and output means for connection to the load, an electrically operated vapour sensor adapted to detect the presence of liquid vapour, first circuit means actuated by the sensor upon the presence of liquid vapour operative to connect the input power means to the output power means so as to provide electrical energy to the load when a predetermined amount of liquid vapour is present, and second circuit means operative to provide power to the load for a predetermined time after the sensor no longer detects the presence of the vapour, said first circuit means including a first circuit unit which is normally gated low that is connected to the sensor, a second circuit unit which is normally gated off that is connected to the first circuit unit and an oscillator controlled by the second circuit unit,the arrangement being such that when the sensor detects the presence of a liquid vapour, the first circuit unit is gated high, the second circuit unit is gated high and the oscillator made operative to switch the power to the load.

2. A device according to claim 1 wherein the oscillator controls a triac which in turn switches on the power to the fan. IA t IA. -8-

3. A device according to claim 1 wherein the second circuit means includes a programmable unit controlled by a counter which is adapted to retain the second circuit unit in its gated high mode after the sensor has detected the absence of liquid vapour for a period of time controlled by the counter.

4. A device according to claim 3 wherein the counter is an oscillator.

A device according to claim 3 or claim 4 and further including a third circuit unit connected between the first Scircuit unit and the programmable unit which is operative to inhibit the counter and reset functions of the second circuit e means whenever the sensor detects the presence of liquid ,t vapour.

6. A device for controlling the supply of electrical energy to an electrical load substantially as hereinbefore described with reference to the accompanying drawing. t Dated this llth day of October 1989. MORRIS CLIFFORD HINCH, Patent Attorneys for the Applicant: PETER MAXWELL ASSOCIATES r_:a i