GB2071888A - A bedroom light control device - Google Patents

Abstract

A bedroom light control device for a mains operated bedroom light (4) comprises a microphone (6), a solid state switching circuit (18) for switching the light on and off in response to a non-continuous sound and a sensitivity control member (VR1) for controlling the sensitivity of the device to the sound. The power supply for the device comprises a transformer (T1) rectifier means (BR1) and capacitor means (C1, C2). Timing means (14) produces an output signal consequent upon the microphone detecting the sound, first switch means (16) switches between first and second states consequent upon receiving the signal from the timing means, and second switch means (BR2, 18) is responsive to signals from the first switch means and makes or breaks a mains circuit for the bedroom light to cause the bedroom light to switch on and off. <IMAGE>

Description

SPECIFICATION A bedroom light control device This invention relates to a bedroom light control device for a mains operated bedroom light. This invention also relates to a mains operated bedroom light when provided with the control device.

It often happens that persons in bed wake up during the night and they wish to turn on the bedroom light. This often necessitates the person getting out of bed which is inconvenient. Also, light switches can be difficult to find in the dark, even light switches for bedside table Imps.

It is an aim of the present invention to overcome the above mentioned problem by providing a bedroom light control device for a mains operated bedroom light that will enable the bedroom light to be turned on and off in response to a noncontinuous sound such for example as the clapping of a person's hands.

Accordingly, this invention provides a bedroom light control device for a mains operated bedroom light, which bedroom light control device comprises a microphone, a solid state switching circuit for switching the bedroom light on and off in response to a non-continuous sound detected by the microphone, and an audio sensitive control member for controlling the sensitivity of the bedroom light control device to the sound, the solid state switching circuit comprising a transformer for reducing the mains voltage, rectifier means for rectifying an A.C.

output from the transformer and for producing a DC output, capacitor means for smoothing the DC output from the rectifier means, timing means for producing an output signal consequent upon the microphone detecting the sound, first switch means for switching between first and second states consequent upon receiving the signal from the timing means, and second switch means which is responsive to signals from the first switch means and which makes or breaks a mains circuitforthe bedroom light to cause the bedroom light to switch on and off.

The present invention also provides a mains operated bedroom light when provided with the bedroom light control device.

It is envisaged that the control device may be simply and cheaply produced. It can then be sold, for example as a box, for fitting into the leads of the mains operated bedroom light. The bedroom light may be a table lamp, a standard lamp, a wall mounted lamp or a light hanging from the ceiling. By appropriately controlling the audio sensitivity control member, the bedroom light control device can be arranged to operate in response to a sound of any desired volume. This sound may be the clapping of a person's hands but it could also be a person's voice.

The bedroom light control device should obviously not be so sensitive that it will randomly turn on and off in response to extraneous sounds such for example as that of persons walking up and down stairs or shutting doors. With the control device of the present invention, a bedroom light can simply be turned on and off by a person making an appropriate noise such as the clapping of their hands and there will be no need for the person to get out of bed and/or fumble in the dark for light switches. The bedroom light control device may be especially useful for infirm or aged persons who find difficulty in getting out of bed.

Preferably, the audio sensitivity control member is constituted by a variable resistance which forms part of a feedback circuit for an amplifier, the amplifier being adapted to amplify output signals from the microphone. The amplifier will usually be an operational amplifier.

The rectifier means may be a bridge rectifier. The timing means may be a frequency divider whereby a multiple analogue input is converted to a digital output. The timing means is preferably a 555 timer.

The first switch means may be a J-K master slave flip-flop, an S-R master slave flip-flop or a counter device.

The second switch means is preferably a thyristor connected across a bridge rectifier. The second switch means may also be a triac.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows a first circuit for a bedroom light control device; Figures 2, 3 and 4 show the connections for three integrated circuits employed in the circuit shown in Figure 1; Figure 5 shows a second circuit for a bedroom light control device; and Figure 6shows a mains operated bedside lamp.

Referring to Figure 1, there is shown a first circuit 2 of a bedroom light control device for a mains operated bedroom light 4. The circuit 2 comprises a micophone 6 which is connected to an integrated circuit in the form of a 741 operational amplifier 8.

The amplifier 8 is provided with current along line 10 and this current is obtained by reducing mains voltage in a transformer T1 and then rectifying this mains voltage in a bridge rectifier BR1. The DC output from the bridge rectifier BR1 is smoothed by capacitors C1 and C2.

The amplifier 8 is operatively connected to fixed resistances R1 and R2 and a variable resistance VR1.

The resistances R1, R2 and VR1 form a negative feedback circuit for the amplifier 8. The variable resistance VR1 forms an audio sensitive control member which controls the amount of negative feedback and therefore the gain of the amplifier 8.

The resistance of the variable resistance VR1 is thus set at a desired noise level. The connections for the amplifier 8 are shown in Figure 2.

Current from the amplifier 8 passes along line 12 to a second integrated circuit in the form of a 555 timer 14. As will be explained in more detail hereinbelow, the timer 14 produces an output signal consequent upon the microphone 6 detecting a sound. The timer 14 is associated with a resistance R3 and a pair of capacitors C3, C4. The resistance R3 and the capacitor C4 form a resistance/capacitance network which controls the duration of the output signal from the timer 14. The connections for the timer 14 are shown in detail in Figure 3. The capacitor C3 is a small value capacitor which ties an unused integrated circuit terminal in the timer 14 to the negative rail but at the same time blocks the flow of DC current.

The output from the timer 14 is fed to a third integrated circuit in the form of a dual J-K master slave flip-flop 16. Whilst the J-K master slave flip-flop 16 is supplied by manufacturers as a dual package, only half of the dual package is in fact used.

The connections for the flip-flop 16 are shown in detail in Figure 4 and the flip-flop 16 acts as a first switch means.

The flip flop 16 operates between first and second states and activates second switch means in the form of a bridge rectifier BR2 having a thyristor 18.

The bridge rectifier BR2 and the thyristor 18 are effective to make or break a mains circuit including the lines 20, 22 to cause the light 4 to switch on and off.

The circuit 2 includes a second variable resistance VR2 which is adjusted after assembly of the components to give a null reading across the resistances Rl,R2andVR1.

The circuit 2 operates as follows. The tranformer Tithe bridge rectifier BR1 and the capacitors C1, C2 give a positive-zero-negative DC supply voltage to the amplifier 8 with the centre tap 24 of the secondary of the transformer T1 at zero volts.

When a short duration noise is made such as a clap of the hands, a chain of sound waves at, for example 1000 Hz impinge on the microphone 6, for example for one tenth of a second. The sound waves are converted into electrical waves by the microphone 6 and they are fed into the non-inverting input of the amplifier 8. The output from the amplifier 8 is fed onto the feedback network including the resistors R1, VR1 and R2 and back to the inverting input of the amplifier 8 thereby giving negative feedback. The gain of the amplifier 8 may be designed to vary between approximately unity and 25000.

The output from the amplifier 8 is sinusoidal and it is fed on to the trigger input of the timer 14. The timer 14 acts as a frequency divider. The first negative going half cycle fed on to the trigger input flips the timer 14 into the timing state giving an output voltage from the timer 14. Subsequent input negative half cycles in the duration of operation of the microphone 6, for example the above mentioned one tenth of a second, have no effect on the timer 14.

The resistance/capacitance network of the resistor R3 and the capacitor C4 is arraged to give an output of approximately one quarter of a second duration from the timer 14 before the output from the timer 14 flops back to its steady state condition. For stability of operation of the lamp 4, the duration of the sound pulse must be shorter than the time constant of the resistance/capacitance network.

The output from the timer 14 is fed on to the clock inputoftheflip-fiop 16. The inputJ1 and K1 ofthe flip-flop 16 are held at logic 1 by connection to the positive rail. When the timer 14 gives an output, the clock input of the flip-flop 16 goes to logic 1 and the output of the flip-flop 16 toggles over from Q1 to Q1 orfrom Q1 to Q1 depending upon whether Q1 orQ1 was giving an output before the arrival of the clock pulse. The clock pulse will usually be a square wave form clock pulse.

When Q1 gives an output is fed via the resistor R5 to the gate of the thyristor 18. The thyristor 18 thus switches on an allows a current to flow through the lamp 4, the bridge rectifier BR2 and the thyristor 18, thus turning the lamp 4 on.

When Q1 gives an output, Q1 gives no output.

There is then no direct current on the gate of the thyristor 18 and the lamp 4 turns off when the applied AC voltage passes through zero, and the lamp stays off.

The microphone 6 in the input circuit of the amplifier 8 is a moving coil type of microphone to allow the minute bias current of the amplifier 8 to flow.

Referring now to Figure 5, there is shown a second circuit 2 of a bedroom light control device for a mains operated bedroom light 4. The circuit 2 shown in Figure 5 is very similar to the circuit 2 shown in Figure 1. Similar parts in both circuits have been given the same reference numeral and their precise operation will not again be given.

In Figure 5, the Figure 1 circuit has been modified to include additional smoothing means in the form of a pair of additional capacitors C5, C6 and a pair of additional resistors R6, R7.

In operation of the circuit shown in Figure 5, on each rectified half cycle, the capacitors C1 and C2 charge up to the peak value of each rectified half cycle and, since current flows through the resistors R6 and R7, the capacitors C5 and C6 charge up to a lower value. On each half cycle of the rectified voltage, after rising to its peak, the voltage falls away again to zero, and during this portion of the cycle and until the voltage again reaches near peak value, the current for the control circuit inciuding the variable resistance VR1 is supplied by the capacitors C5 and C6.As both of the capacitors C5, C6 supply current, both their voltages start to drop but since the capacitors C1 and C2 have been charged to a higher value, the capacitors C1 and C2 replace the current taken from the capacitors C5 and C6 and maintain the voltage on the capacitors C5 and C6 at an almost constant value, giving rise to a considerable reduction in the ripple on the output of the operational amplifier 8.

For good smoothing, typical values of the capaci torsC1, C2, C5 and C6 are 1,000 microfarads each and the resistors R6 and R7 are typically equal to 100 ohms.

Referring now to Figure 6, the lamps 4 shown in Figures 1 and 5 are shown as a bulb 4 in a bedside lamp 26. The lamp 26 has a base 28 and an upstanding body portion 30. The body portion 30 houses and supports a supply switch 32, the circuit 2, a sound level control knob which is in effect the variable resistor VR1 and the microphone 6. A lead 34 extends from the base 28 and the lead 34 is fitted with a piug 36.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modification may be effected.

Thus, for example, different types of amplifier 8, timer 14, and flip-flop 16 may be employed. Also, the specific design of the bedside lamp 26 may be varied. Further, the circuit 2 shown in Figures 1 and 5 may be employed in a standard lamp or in a wall-mounted or ceiling-hanging bedroom lights.

Claims (10)

1. A bedroom light control device for a mains operated bedroom light, which bedroom light control device comprises a microphone, a solid state switching circuit for switching the bedroom light on and off in response to a non-continuous sound detected by the microphone, and an audio senstivity control member for controlling the sensitivity of the bedroom light control device to the sound, the solid state switching circuit comprising a transformer for reducing the mains voltage, rectifier means for rectifying an AC output from the transformer and for producing a DC output, capacitor means for smoothing the DC output from the rectifier means, timing means for producing an output signal consequent upon the microphone detecting the sound, first switch means for switching between first and second states consequent upon receiving the signal from the timing means, and second switch means which is responsive to signals from the first switch means and which makes or breaks a mains circuit for the bedroom light to cause the bedroom light to switch on and off.

2. A bedroom light control device according to claim 1 in which the audio sensitivity control member is constituted by a variable resistance which forms part of a feedback circuit for an amplifier, the amplifier being adapted to amplify output signals from the microphone.

3. A bedroom light control device according to claim 2 in which the amplifier is an operational amplifier.

4. A bedroom light control device according to any one of the preceding claims in which the rectifier means is a bridge rectifier.

5. A bedroom light control device according to any one of the preceding claims in which the timing means is a frequency divider whereby a multiple analogue input is converted to a digital output.

6. A bedroom light control device according to any one of the preceding claims in which the timing means is a 555 timer.

7. A bedroom light control device according to any one of the preceding claims in which the first switch means is a J-K master slave flip-flop, an S-R master slave flip-flop or a counter device.

8. A bedroom light control device according to any one of the preceding claims in which the second switch means is a thyristor connected across a bridge rectifier.

9. A bedroom light control device substantially as herein described with reference to the accompanying drawings.

10. A mains operated bedroom lightwhen provided with a bedroom light control device as claimed in any one of the preceding claims.