GB2255166A - Light device - Google Patents

Abstract

A light device comprises a light unit 21 and circuitry in a casing 20. The circuitry includes a piezo-electric transducer 20 which detects impact to or in the region of the device to turn on the light unit 21. <IMAGE>

Description

LIGHT DEVICE The invention relates to a light device.

According to one aspect of the invention there is provided an impact triggered light device.

Thus, no button, toggle switch or the like need be operated to turn on the light which is triggered by simple impact.

The light device is preferably arranged to extinguish the light automatically. Preferably, the device is arranged such that the magnitude of the impact determines the period for which the light is on.

Thus, the period of light can be controlled by the impact applied.

The device may comprise an impact detector and a light source. The impact detector may take any suitable form and preferably comprises a piezo-electric transducer. The threshold of the impact detector may conveniently be adjustable to provide variable sensitivities to impact.

The period for which the light is on may be determined by any suitable means and may be determined by a delay circuit. The delay circuit may conveniently be adjustable to provide control over the period for which the light is on.

The power source for the light may comprise at least one battery, but alternative sources, such as a mains supply may be used instead.

Preferably, when the light is extinguished, the luminance therefrom progressively decays. Preferably, the decay period exceeds 1 second. In this way a person in the vicinity of the light is warned that the light is switching off and has a chance to reactivate it while there is sufficient light to see.

According to another aspect of the invention, there is provided an impact triggered automatic lighting device comprising an impact detector, a delay circuit coupled to the detector and a light source coupled to receive a signal from the delay circuit, the device being arranged to turn the light on when an impact is detected and to remain on for a period determined by the delay circuit.

The device may conveniently include attachment means to enable the device to be attached to a body and the attachment means may suitable enable the device to be attached to a flat surface of a body. The attachment means may take any suitable form.

According to a further aspect of the invention, there is provided a body including a device according to either of the previous aspects of the invention and including any or none of the sub-features mentioned in relation thereto.

In this way, and also in the case where a device has been attached to a body by attachment means, the device may be arranged to be activated by an impact at a location spaced from the device. Thus, unlike a conventional switch or button which has to be located before it can be operated, an impact in the general area of the device will be sufficient to trigger it and provide light. The body may for example be a door so that a knock on the door will trigger the light which may for example illuminate a keyhole.

Similarly, the body may be a wall or in an alternative embodiment may be a cot, for example. Clearly, the devices of wide application and suitable bodies of different types will be apparent to the reader.

One embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a circuit diagram of the light device of the embodiment; and, Fig. 2 is a perspective view of the light device of the embodiment.

in accordance with the present invention.

The automatic light is designed to be impact sensitive. An impact to the body of the lamp, or to the structure on which the lamp is mounted, is detected by the internal circuitry of the lamp. When an impact of sufficient size is detected, the lamp illuminates for a predetermined period of time which is proportional to the magnitude of the impact.

Referring to Fig. 1, power is supplied to the circuit by a battery 1. The battery could be replaced by a mains power supply. Impact detection is effected using a piezo-electric transducer 2 and an attenuation network comprising resistors 3 and 4. When the transducer is vibrated an alternating voltage is generated across its two terminals. This voltage is fed, via the attenuation network to the base of a transistor 5. The alternating voltage applied to the transistor base causes it to alternate between a conducting and non-conducting state allowing an electrolytic capacitor 6 to charge rapidly, during the transistor's conducting periods, from the positive supply rail.

The capacitor, a discharge path comprising two resistors 7 and 8 and a buffer transistor 9 form a delay circuit. The capacitance and resistance values are chosen to provide a time-constant that will maintain the light in its illuminated state for the desired time period.

When the voltage on the capacitor 6 is suffIciently high, transistor 9 will start to conduct thereby causing a transistor 10 to conduct also and thus causing a bulb 11 to illuminate.

A large impact will cause the transducer 2 to generate a higher amplitude alternating voltage of longer duration than a smaller impact. This will have the effect of turning transistor 5 on harder and for loner. This will allow capacitor 6 to receive a greater charge thereby extending the illumination period of the lamp. In this way a degree of proportionality is provided between the impact magnitude and the illumination period.

As capacitor 6 approaches a discharged state transistor 9, and consequently transistor 10, will leave the fully-on, saturated state and enter a partially conducting state. Subsequently the transistor will gradually enter a non-conducting state at a rate determined by the discharge rate of the capacitor 6 through the resistors 7 and 8. This will have the effect of causing the light output to gradually decay at the end of the illumination period.

It will be appreciated that the substitution of variable resistors for fixed resistors 3 and 4 and fixed resistors 7 and 8 would allow the impact sensitivity and illumination period to be adjusted respectively. It will also be appreciated that the delay circuit could be replaced by any known monostable circuit.

The values of resistors 4 and 8 are of the order of 1OMQ to minimize unnecessary battery current drain.

The values of the other components in the circuit are resistor 3: 470k.ohms, resistor 7: 4700k.ohms, resistor 12: 47k.ohms and resistor 13: 4700k.ohms.

Transistor 5 is a BC212L, transistor 9 is an MPSA14 and transistor 10 is a BC327. Capacitor 6 has a capacitance of 22uF and the piezo-electric transducer is an XTAL 20mm component. The battery 1 is a 9-volt battery.

Fig. 2 shows the entire device. The device comprises a long rectangular casing 20 at one end of which is provided a light unit 21 which consists of a concave silverd reflector 22 with the lamp 11 substantially at its centre. On the top surface of the casing 20 is provided a removable cover 23 behind which the battery 1 is located. The battery 1 is positioned at the opposite end of the casing 20 to the lamp 11 and the piezo-electric transducer 2 and the circuitry schematically illustrated in Fig. 1 are provided between the battery 1 and the lamp 11. On the underside of the casing 20 are provided two adhesive pads 24 which can be used to attach the device to a flat surface of a body such as a door.

Claims (20)

1. An impact triggered light device.

2. A light device as claimed in claim 1, wherein the light device is arranged to extinguish the light automatically.

3. A light device as claimed in claim 2, wherein the device is arranged such that the magnitude of the impact determines the period for which the light is on.

4. A light device as claimed in any preceding claim, wherein the device comprises an impact detector and a light source.

5. A light device as claimed in claim 4, wherein the impact detector comprises a piezo-electric transducer.

6. A light device as claimed in claim 4 or claim 5, wherein the threshold of the impact detector is adjustable to provide variable sensitivities to impact.

7. A light device as claimed in claim 2 or any claim when dependent thereon, wherein the period for which the light is on is determined by a delay circuit.

8. A light device as claimed in claim 7, wherein the delay circuit is adjustable to provide control over the period for which the light is on.

9. A light device as claimed in any preceding claim, wherein the power source for the light comprises at least one battery.

10. A light device as claimed in any preceding claim, wherein when the light is extinguished, the luminance therefrom progressively decays.

11. A light device as claimed in claim 10, wherein the decay period exceeds 1 second.

12. A light device as claimed in any preceding claim, wherein the device includes attachment means to enable the device to be attached to a body.

13. A light device as claimed in claim 12, wherein the attachment means enables the device to be attached to a flat surface of a body.

14. A light device as claimed in claim 12 or claim 13, wherein the device is arranged to be activated by an impact on a body to which it is attached at a location spaced from the device.

15. An impact triggered light device substantially as described herein with reference to the accompanying drawings.

16. A body including attached thereto a light device as claimed in any preceding claim.

17. A body as claimed in claim 16, wherein the body is a door.

18. A body as claimed in claim 17, wherein the light device is arranged to illuminate a keyhole of the door.

19. A body as claimed in claim 16, wherein the body is a wall.

20. A body as claimed in claim 16, wherein the body is a cot.