GB2391120A

GB2391120A - Pull-cord operated dimmer switch

Info

Publication number: GB2391120A
Application number: GB0211364A
Authority: GB
Inventors: Andrew Ekins
Original assignee: TRAYPOINT Ltd
Current assignee: TRAYPOINT Ltd
Priority date: 2002-05-17
Filing date: 2002-05-17
Publication date: 2004-01-28
Anticipated expiration: 2022-05-17
Also published as: GB2391120B; GB0211364D0

Abstract

A pull-cord operated mains-connected dimmer switch assembly for an electric lamp, the assembly comprising an ON/OFF switch 10 operated through a pull-cord, a microprocessor 11 connected electrically to the switch and programmed to generate a first pulse of limited duration on each initial operation of the pull-cord and a sequence of electrical pulses of varying timing on continuous operation of the pull-cord, the timing of the latter pulses being related to the duration of continuous operation of the pull-cord, and a triac 12 connected to receive these electrical pulses from the microprocessor, the switching intervals of the triac being determined by the timing of the received electrical pulses.

Description

23911 20

PULL-CORD OPERATED DIMMER SWITCH ASSEMBLES

This invention relates to pull-cord operated dimmer switch assemblies and more especially to ceiling mounted pull-cord operated switch assemblies for varying the brightness of electrically powered lamps.

Conventional dimmer switches including rotary or push operated switches are generally not suitable for use in bathrooms and other environments where safety regulations require a ceiling-mounted switch. Presently available ceiling mounted switches are operated conventionally through pull-cords and generally do not include a dimmer function. Proposals have been made to provide ceiling mounted light fittings with a dinuner facility operated through a conventional pull-cord but have generally been unsuccessful.

Examples of such proposals are disclosed in GB 23379855A and GB 2236025A. In the former, the dimmer function is achieved by rotating a control shaft associated with a pull-

cord, and in the latter a sustained pull on the cord causes a dedicated dimmer chip to enter a setting mode to vary the lamp brightness. This setting mode is retained by the dedicated chip until varied by a subsequent sustained pull on the cord.

One object of the present invention Is to provide a dimmer switch which can be operated through a pull-cord and which overcomes, or at least alleviates, disadvantages present in the proposals discussed above.

In one aspect, the invention provides a pull-cord operated mainsconnected dimmer switch assembly for an electric lamp, the assembly comprising an ON/OFF switch operated through a pull-cord, a microprocessor connected electrically to the switch and programmed to generate a first pulse of limited duration on each initial operation of the pull-cord and a sequence of electrical pulses of varying timing on continuous operation of the pull-cord, the timing of the latter pulses being related to the duration of continuous operation of the pull-cord, and a triac connected to receive these electrical pulses from the microprocessor,

the switching intervals of the triac being determined by the timing of the received electrical pulses. The triac is typically a 12C508 microprocessor chip.

The invention will now be described by way of example only with reference to the accompanying diagrarornatic drawings, in which the sole Figure is a circuit diagram of a pull-cord operated mains connected dimmer switch assembly in accordance with the invention. Pull-cord operated dimmer switch assemblies in accordance with the invention generally comprise a housing formed with apertures through which electrical cabling can pass for connection to the electric lamp which is to be controlled by the dimmer switch assembly The housing has a base which supports a printed circut-board which carries the control circuitry illustrated in the drawing. The housing includes a cap through which the pull-cord of a toggle-operated switch extends.

The mams connections of the illustrated circuit are indicated by reference numerals l, 2. The lamp whose brightness is to be controlled is indicated by reference numeral 3.

The circuit conventionally includes various capacitors (all bearing the prefix C) and resistors (prefix R).

The novel features of the dimmer switch assembly centre around a switch to operable through the pull-cord' microprocessor 11 and triac switch 1 2. The microprocessor is typically a 12C508 microprocessing chip. The pullcord is connected to the switch via toggle 14.

Electrical contacts of the switch 10 are connected through the mains electrical supply so that when the pull-cord is pulled and released, the switch lO toggles to provide a momentary short circuit. This action either turns on the lamp if previously off, or turns the lamp off if previously on. If the pull-cord is operated continuously for a period of time a short circuit condition exists and the duration of the short circuit lasts as long as the pull-cord is being operated.

f When closed, the switch 10 supplies an electrical signal to one pin 15 of the microprocessor l l.

The software of the microprocessor 11 is programmed to generate electrical pulses whose timing is related to thetime during which the pull-cord is operated. Momentary operation of the pull-cord generates an initial electrical pulse of limited duration.

Continual operation of the pull-cord is recognised by the microprocessor and the timing of the generated electrical pulses varies accordingly.

Electrical pulses transmitted by the microprocessor 11 via output pin 16, capacitor C1 and resistor Rl are received by a triac 12. The circuit 17 including resistors R6 and R7 detect the sequential zero voltage points of the triac and ensure that the electrical pulses are timed from these points. The timing of the pulses generates a corresponding delay in the switching activity of the triac and, therefore, the average voltage at J1. A reduction in applied voltage will produce a reduction in the brightness of the electric lamp 3 connected to the dimmer switch assembly; and an increase in applied voltage will produce an increase in the brightness of the electric lamp.

In operation, pulling the cord down momentarily and then releasing it closes switch 10 to produce a momentary short circuit to cause an initial electrical pulse of limited duration to pass to the microprocessor. In turn, the microprocessor transmits to the triac pulses timed for full power and full lamp brightness or no pulses and no lamp brightness if the lamp was previously on. In other words, momentary operation of the pullcord causes the lamp to be switched on at full brightness or the lamp to be switched off if it was previously on.

If the lamp is initially off, a sustained pull will cause the light to start at maximum brightness and then to decrease to minimum brightness, the cycle repeating for as long as the pull-cord is held down. If the light is initially on, a sustained pull will start at the preset brightness level and will cycle to minimum as before. The complete cycle from maximum to minimum typically takes about ten seconds. On all occasions, when the lamp is first turned on, the triac setting is such as to ensure that the lamp is initially at full brightness.

( Thus, the microprocessor 11 is able to detect if the switch 10 is closed or open via pin 15 and resistor R3, detect the momentary mains voltage via pin 15 and resistors R6, R7 and to activate the triac 12 (the main power switch) via output pin 16, capacitor C I and resistor Rl.

It will be appreciated that the foregoing is merely exemplary of pull operated dimmer switches in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.

Claims

( CLAIMS

1. A pull-cord operated mains-connected dimmer switch assembly for an electric lamp, the assembly comprising an ON/OFF switch operated through a pull-cord, a microprocessor connected electrically to the switch and programmed to generate a first pulse of limited duration on each initial operation of the pull-cord and a sequence of electrical pulses of varying timing on continuous operation of the pull cord, the timing of the latter pulses being related to the duration of continuous operation of the pullcord, and a triac connected to receive these electrical pulses from the microprocessor, the switching intervals of the triac being determined by the timing of the received electrical pulses.

2. An assembly as claimed in claim I wherein the triac is a 12C508 microprocessor chip.

3. An assembly as claimed in claim 1 or claim 2 wherein the switch assembly comprises a housing formed with apertures through which electrical cabling can pass for connection to the electric lamp which is to be controlled by the dimmer switch assembly, the housing having a base which supports a printed circuit-board which carries the control circuitry illustrated in the drawing.

4. An assembly as claimed in claim 3 wherein the housing includes a cap through which the pull-cord of a toggle-operated switch extends.

5. An assembly as claimed in any one of the preceding claims wherein electrical contacts of the switch are connected through a mains electrical supply whereby when the pull-cord is pulled and released, the switch toggles to provide a momentary short circuit either to turn on the lamp if previously off, or to turn the lamp off if previously on.

6. An assembly as claimed in any one of claims 2 to 5 wherein the software for the microprocessor chip is programmed to generate electrical pulses whose timing is

! related to the time during which the pull-cord is operated whereby momentary operation of the pull-cord generates an initial electrical pulse of limited duration and continual operation of the pull-cord is recognised by the microprocessor and the timing of the generated electrical pulses varies accordingly.

A pull-cord operated mains-connected dimmer switch assembly substantially as herein described and as described with reference to the accompanying drawings.