GB2190803A - Light-dependent timer switching system - Google Patents

Abstract

When a low ambient light level (dusk) is detected by a sensor 30, a flip-flop 32 is caused to send a high signal to a switch 41 and a low signal to an inverter 33. A load 42 is thereby turned on and an inverter 36 supplying a low signal to an oscillator/timer 37 which is thus started and has its output set low whereby, via a flip-flop reset circuit 39, the flip-flop 32 is latched to prevent an erroneous turn off of the load 42 caused by light therefrom possibly being received, after reflection, by sensor 30. When timer 37 times out, the load 42 is turned off, flip-flop 32 is reset, and the circuit operates to prevent load 42 being erroneously turned on again should the light received by sensor 30 fall as the load was switched off. The system is reset at dawn in readiness for the next switch-on cycle. The load may be an incandescent or fluorescent lamp, a radio or T.V. set, or hi-fi equipment, and the circuitry may be incorporated into an adaptor (47) to fit a lampholder, or into a fluorescent lamp (46), (Fig. 4). <IMAGE>

Description

SPECIFICATION Light intensity dependent timer switching system This invention relates to a light intensity dependent timer switching system for general AC appliances control.

Automatic switching 'on' the lamp at dusk and 'off' at dawn can be controlled by electric motor driven timer. This is an electro-mechanical device and it consumes approximately 2 to 5 watts to power it. Moreover, in event of a power failure, it will not reset its timing cycle and this caused the timing periods to be wrong after the power outage. Such occurrences are not encouraging as a burglar deterrent as well as uneconomical to use as it consumes 2-5 watts of electricity.

The standard night lamp can also be used to automatic switching 'on' the lamp at dusk and 'off' at dawn. There is no timer switch off facility incorporated and will not handle inductive load such as fluorescent lamp, television set, radio and hi-fi equpment.

The standard nigh lamp is recommended to use on resistive load (incandescent lamp) up to a maximum rating of 60 watts due to the constraint of erratic function as a result of its selfreflected light from surrounding area/environment when it switches on the incandescent lamp.

This caused manufacturers to incorporate an adjustable light sensor on the device so that the light sensor can be adjusted such that the incandescent lamp light when reflected from surrounding area/environment will not be sensed by the light sensor, thus eliminating the erratic effect of light being switched on and off in response to its light sensor detecting the reflected light from the incandescent lamp.

Inspite the incorporation of an adjustable light sensor unit, the design still have difficulties to cope with incandescent lamp with rating more than 60 watts due to the high lumens generated from the incandescent lamp which increases the reflected light from the surrounding area/environment.

The purpose of this invention is to improve on the standard night lamp and to extend its features and its applications. The light intensity dependent timer switching system is a fully electronic design which incorporates a timing device to switch off the load at the end of the duration. In this design the selected switch off time period is set between 4 and 5 hours after the system switches on the load. The system is capable of switching 'on' and 'off' resistive (incandescent lamp) and inductive (fluorescent lamp, television sets, radio, hi-fi equipment) load with no erratic effect of the load being switched on and off in response to its light sensor detecting the reflected light from the load.

A specific embodiment of the invention will now be described by way of the example with reference to the accompanying drawing in which: Figure 1 shows the block diagram of the light intensity dependent timer switching system; Figure 2 shows the schematic diagram of the system; Figure 3 shows the components list of the system; and Figure 4 shows the applications of the system.

Referring to the block diagram in Fig. 1, the sensor 30 lowers its internal resistance when it detects light and its internal resistance varies proportionally to the level of light intensity. At dusk, the sensor 30 internal resistance increases, causing delay 1 31 to be active. When delay 1 31 reaches its timing duration, flip-flop 32 to inverter 1 33 changes to low state. Inverter 1 33 input being low state, the output becomes high state. Delay-bypass 34 is active towards high state condition. Since inverter 1 33 output is high state, delay-bypass 34 becomes active causing inverter 2 36 output to be low state.

When inverter 2 36 output is at low state, it enables timer 37 self-oscillator to functioning (clocking) while resetting all its output to low state. Since timer 37 outputs are all at low state, the reset-control 39 fflip-flop reset) is not active, thus flip-flop 32 to inverter 1 33 still remains at previous state, i.e. low state. With the inverter 1 33 input at low state, the output of flip-flop 32 connecting to the glitch-suppressor 40 becomes high state, turning on the zero-cross switch 41 which in turn switches on the load 42.

With the load 42 (in this case is a lamp) switched on, the sensor 30 internal resistance becomes low (on assumption that the light is reflected at the sensor which is at present the major problem encountered by standard night lamp) and causes delay 1 31 to be active. Even when delay 1 31 reaches its timing duration, the flip-flop 32 connecting to inverter 1 33 does not change state due to timer 37 output is still at low state.

When timer 37 reaches its determined duration, its output becomes high state and inhibits the self-oscillator through oscillator-inhibit 38 being activated. At the same time the flip-flop reset 39 is also activated and it resets the flip-flop 32 output connecting to the glitch suppressor 40 to low state and this turns off the zero-cross switch 41, switching off the load 42.

When the load 42 is switched off it also resets flip-flop 32 connecting to inverter 1 33 input to high state since delay 1 31 is not active. Inverter 1 33 input being high state, the output becomes low state. Delay-bypass 34 is not active but delay 2 35 becomes active. At this point inverter 2 36 input is still at high state and its output is low state. At the same time sensor 30 no longer picks up any reflected light and its internal resistance increases. This caused delay 1 31 to be active.

Delay 1 31 by virtual of design, reacts faster than the delay 2 35 action. Before inverter 2 36 input can be set at low state by delay 2 35, delay 1 31 now completes its duration which resets the flip-flop 32 connecting to inverter 1 33 input to low state. This caused inverter 1 33 output to be high state which interrupts delay 2 35 for further action through activating delaybypass 34. This action set inverter 2 36 input at high state and its output at low state. With the inverter 2 36 output at low state and the timer 37 self-oscillator still disabled, the timer 37 output is still held high state which causes the load 42 to be switched off.

When dawn approaches the sensor 30 begins to receives light and its internal resistance becomes low. Delay 1 31 becomes active and resets flip-flop 32 connecting to the inverter 1 33 to high state. Since inverter 1 33 input is at high state, the output becomes low state.

Delay-bypass 34 is not active but delay 2 35 becomes active. At this point inverter 2 36 input is still at high state and its output is low state. When delay 2 35 reaches its delay duration, it changes the inverter 2 36 output to high state. With the inverter 2 36 output now at high state, the timer 37 outputs are resetted to low state while its self-oscillator is disabled. This completes an entire cycle. The system is now ready to repeat its cycle when dusk approaches.

The purpose of delay 1 31 and delay 2 35 are also to prevent false triggering by lightning and/or any other short duration of light directed at the sensor 30 such as passing by vehicles.

The power supply system to power the light intensity dependent timer switching system is obtained directly from the mains electrical supply through a bleeder-dropper system 43 which consumes a very negligible amount of electricity that hardly activate the mains power kilowatt hour meter.

Referring to Fig. 4, the diagrams show the applications of the system in the lighting design. At the top of the diagram it shows the system installed inside a low energy lamp 46 (fluorescent) and at the bottom of the diagram it shows the system as a stand alone design 50 where it is used as an adaptor to the lamp holder. The light intensity sensor 44, it shown at the top of the low energy lamp while in the stand alone design 50 it is at the centre of the unit. The printed circuit board 45 is attached to the light intensity sensor and mounted as shown in the diagrams.

The stand alone design 50 has an adaptor 47, a lamp shade lock ring 48 and a lamp holder 49.

In both designs, the light intensity sensor 44 is installed on the units with an exposed casing.

In both designs, the units are made such that the user need not have to install, change or rewire their existing house, office or factory electrical wiring.

Referring to the schematic diagram in Fig. 2 and with cross-reference to the block diagram in Fig. 1, the functions of the various elements are described by way in which: Sensor 30 is 3; Delay 1 31 is 1, 2 and 4; Flip-flop 32 is 26 and 27; Inverter 1 33 is 28; Delay-Bypass 34 is 8; Delay 2 35 is 6 and 9; Inverter 2 36 is 29; Timer 37 is 25; Oscillator Inhibit 38 is 16; Flip-flop Reset 39 is the output connection between Timer 37, 25 and Flip-flop 32, 27; Self-Oscillator is 12, 13 and 14; Glitch-Suppressor 40 is 10 and 11; Zero-Cross Switch 41 is 17, 18, 19, 20 and 21; Load 42 is 24 and Bleeder-Dropper 43 is 5, 7, 15, 22 and 23.

Detailed component part list with cross-reference to the schematic diagram in Fig. 2 is shown in Fig. 3.

Claims (5)

1. The light intensity dependent timer switching system is a device intended to automatically switch 'on' mains powered electrical appliances at dusk or when there is a change in environmental lighting equivalent to dusk and switch 'off' the appliances after four to five hours later through its internal electronic timer.

2. The light intensity dependent timer switching system does not have any erratic effect of the load (which is solely a mains electric lamp) being switched 'on' and 'off' in response to its light sensor detecting the reflected light from the load (a mains electric lamp).

3. The light intensity dependent timer switching system does not function from a transformer power supply design. Instead a bleeder-dropper approach is adopted as a means to reduce electrical energy consumption, heat generation and miniaturization of components so as to enabie the system to be fixed inside a low energy lamp.

4. The light intensity dependent timer switching system as claimed in claim 1, 2 and 3 is designed as a finished product ready to be installed directly to the electric mains power line equipped with a lamp holder whereby the user need not have to do any alteration, installation or rewiring to his/her electrical wiring.

5. The light intensity dependent timer switching system as claimed in claim 1 wherein the timer provided an energy conservation as the load needs to be powered to a duration of four to five hours rather than straight through the night.

FIG. 3 Item Number Component Description 1 4M7 Carbon Film 4W 5% Resistor 2 1MO Carbon Film -41W 5% Resistor 3 Photodiode 4 22 microfarad Electrolytic Capacitor 5 22 microfarad Electrolytic Capacitor 6 22 microfarad Electrolytic Capacitor 7 6V2 2W Zener Diode 8 IN4148 Diode 9 10MO Carbon Film 4W 5% Resistor 10 10MO Carbon Film 4W 5% Resistor 11 0.02 microfarad (22nF) Disc Ceramic 50V Capacitor 12 2M2 Carbon Film 4W 5% Resistor 13 10MO Carbon Film 4W 5% Resistor 14 0.10 microfarad (100nF) Mylar 100V Capacitor 15 IN4148 Diode 16 IN4148 Diode 17 2A 400V Silicon Controlled Rectifier 18 2A 400V Rectifier Diode 19 2A 400V Rectifier Diode 20 2A 400V Rectifier Diode 21 2A 400V Rectifier Diode 22 100KO Carbon Film W 4W 5% Resistor 23 1A Quickacting Fuse 24 LOAD-lnductive or Resistive up to maximum 250W rating unless item 17 to 21 are changed to support likewise for higher power ratings.

25 CD4060 14 stage binary counter/divider 2 osc CMOS Integrated Circuit 26-29 CD4001 Quad 2 input NOR Gate CMOS Integrated Circuit 14 0.15 microfarad (150nF) Mylar 100V Capacitor -this component value is used for a longer on duration e.g. a five hour on-time instead of four hour on-time with component value of 0.10 microfarad (100 nF).