GB2360147A - Mobile telephone with auxiliary lighting or alarm - Google Patents

Abstract

A mobile telephone includes a built-in torch 6 or siren. Control circuitry 16 integrated into the mobile telephone circuitry limits the power being supplied to the torch 6 or siren. The control circuitry acts to limit the duration of the supply of current and also inhibits the supply of power when a battery condition monitor determines that the battery charge has fallen below a minimum level. A floating circuit is provided to switch the light on and off at a predetermined rate.

Description

2360147 AUX[LIARY LIGHTING AND ALARM SYSTEMS The present invention relates

to auxiliary lighting and alarm systems.

Portable electric and electronic equipment uses battery power, which may be of the rechargeable or disposable type. Using such power sources to power auxiliary equipment, such as lighting or alarm systems, often constitutes an undesirable drain on the power, with the result that the primary purpose of the equipment may be compromised.

It is an object of the invention to provide an ftnproved system for controlling the power supplied to auxiliary equipment.

According to the present invention there is provided apparatus comprising primary piece of electrical equipment having its own power source, an auxiliary system arranged to share the said power source and control means for controlling the power from the power source to the auxiliary system, said control means including means limiting the quantity of power supplied to the system following a demand for power by the system.

Mobile telephones incorporating auxiliary equipment, will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of a mobile telephone incorporating a torch light; Figure 2 is a block diagram of the electric system for the torch light; Figure 3 is a block diagram of the control circuit of the system of Figure 2; Figure 4 is a waveform diagram; and Figure 5 is a block diagram of a modified embodiment.

As shown in Figure 1, a mobile telephone 2 has an antenna 4 extending from the roof thereof and illuminating means 6, in the form of a filament lamp and light focusing means (similar to that of a conventional torch or flashlight) also mounted on the roof A normally open switch 8, having a spring-loaded depressible control button, projects from 1 1 one side of the mobile telephone.

The electric system for the mobile telephone is shown in Figure 2. As shown, the mobile telephone circuitry 12 is connected to two output terminals 14 and 16 of a rechargeable mobile telephone battery 10. Also connected across the output terminals 14 and 16 is a series combination of the switch 8, the lamp 6 and a control circuit 15. The power supply for control circuit 15 is derived through separate connections to the terminals 14 and 16. A battery condition monitor 18 is connected across the tenninals 14 and 16 and acts to inhibit the control circuit from energising the lamp 6 when the battery has reached a 10 predetermined level of discharge.

The control circuit 15, which consists primarily of CMOS digital logic, is shown more clearly in Figure 3. This type of logic has a very low quiescent operating power drain on the battery, often less than the normal battery leakage current. As shown, a master clock 20 generates clock pulses at the rate of one pulse per second and these pulses are fed simultaneously to the clock input of a divide by 30 counter 22 and a debounce logic unit 24.

The debounce logic circuit 24 has two outputs, one connected to the "seC input of the counter 22 and the other connected to the "preseC input.

The output from the counter 22 is connected via a resistor 26 to the base of a switching transistor 28. The collector emitter path of the switching transistor is connected in series with the lamp across the terminals 14 and 16. The output of the battery condition monitor 18 is connected to the junction of the resistor 26 and the base of the switching 25 transistor 28.

The operation of the control circuit will now be described in conjunction with the timing diagram shown in Figure 5.

The master clock 20 produces a square wave signal (see waveform A). When the switch 8 is momentarily depressed during a period when the output of the master clock pulse waveform is at a low, the debounce logic circuit (using appropriate gating circuitry) will feed a pulse (see waveform B) to the set input of the divide by 30 counter. The counter will then respond to the clock pulses and start counting. At this point, the output of the counter will fall to a low level (see waveform C) which, in turn, will cause the transistor 28 to switch ON (see waveform D). Current will then flow through the lamp 6.

At the end of a count of 30, the output of the counter 22 will rise to a high level (see waveform C) and this, in turn, will cause the transistor 28 to switch OFF and so deenergise the lamp 6.

If during the counting period, the switch 8 is again momentarily closed (eg after the 27th pulse), the debounce logic circuit will respond by triggering the reset input of the count to 30 to reset the counter to zero. This will drive the output of the counter 22 to a high level and so switch OFF the transistor 28.

The battery energy monitor 18 detects the amount of charge remaining in the battery. When the charge capacity is reduced to 30% (say) of full charge, the signal at the output 'operation control' adopts a logical 0 (low). This low output from the monitor 18 prevents the base potential of transistor TR1 from rising to switching level (and hence lamp 6 cannot be turned ON). Thus, the circuit is inhibited from turning the lamp ON if the energy level of the battery falls below the selected value of 30%.

In a modification, the divide by 30 counter 22 may be replaced by a divide by 5 counter (not shown) so that the larnp 6 will be extinguished after five seconds.

Also, the debounce logic circuit 24 may be modified so that if the switch 8 is closed and held closed, a continuous signal will be sent to the set input of the counter 22 to change the output of the counter 30 to a low level and so turn the transistor 28 ON. The counter 22 will not start counting until the switch 8 is allowed to open whereupon after a count of 5, the output of the counter 22 will rise to turn the transistor 28 OFF.

In yet another modification, the debounce logic circuit can be made to respond to a double switching action (within the period of one second) to initiate a flashing mode of 5 operation for the lamp 28. This is done either to save power or to attract attention.

The necessary modifications are shown in Figure 5 in which parts similar to those of Figure 3 are similarly referenced.

As shown, the debounce and double pulse logic circuit 24A, which replaces the logic circuit 24 of Figure 3, contains additional circuitry to detect the rapid double depression of switch 8 (see waveform E). This circuit, called a flashing circuit 30, has a clock input connected to the master clock 20, an input connected to a double pulse detection output from the logic circuit 24A and an output connected to the base of the transistor 28. The flashing circuit 30 contains a bi-stable device which changes state every 2 seconds (say) as determined by the timing of the master clock 20. A low output from flashing circuit 30 prevents the base potential of transistor 28 from rising to switching level (and hence lamp 6 cannot be turned ON) as shown by lamp status of Figure 5. Thus, the lamp is flashing with a period 2 s ON and 2 s OFF for the period during which the counter 22 counts up to 30 (see waveform F). Other periods and frequencies are possible according to design requirements.

Preferably, the lamp control circuits would be fully integrated with the mobile telephone circuit design. The lamp switch 8 would be part of the telephone handset button arrangement, and the existing battery energy monitor of the telephone can have a duplicate role as a battery status display driver and a low charge lamp inhibitor. Additionally, the control circuits can be integrated widiin the existing chipset of the mobile telephone.

While the auxiliary equipment described herein is a lamp 6, it will be appreciated that other types of auxiliary equipment can be used instead. For example, where a personal alarm facility is required, the lamp 8 may be replaced by a siren (not shown). Such a siren device will need to be small, operate on low current and provide a high output volume. A piezo-electric sounder has these attributes and frequently has its own built-in drive circuits so that the simple supply of a DC potential (at sufficient current) is adequate for operation.

A high frequency horn speaker can also be designed to provide high intensity in a low volume profile and a rotating electro-mechanical system may also be suitable given miniaturisation. Such devices would require a different form of output drive, but otherwise will operate to the described circuits.

The mobile telephone may incorporate a change over switch to change over from a lamp to a siren as required or may include separate circuits for both lamp and siren.

It will be appreciated that other auxiliary equipment may replace the lamp 8 or the siren.

While the auxiliary equipment has been described as auxiliary to a mobile telephone, it can be controlled independently in its own right or be controlled from other apparatus such as a palm top computer or electronic organiser.

In a modification, instead of the battery condition monitor 18 inhibiting the lamp 16 or the siren, it can respond to an output of the debounce logic circuit 24 and the sensing of a low voltage signal from the battery to turn the transistor 28 ON for the duration that the control button 8 is pressed. This by-passes the divide by counter 22 and, assuming that the button 8 is released soon after being depressed, reduces the delay period of the lamp or siren. The net effect is to reduce the drain on the battery.

Claims (12)

1. Apparatus comprising primary piece of electrical equipment having its own power source, an auxiliary system arranged to share the said power source and control means for controlling the power from the power source to the auxiliary system, said control means including means limiting the quantity of power supplied to the system following a demand for power by the system.

2. Apparatus according to Claim 1, wherein said control means is responsive to the operation of a switch to limit the energisation of the system to a predetermined maximum period.

3. Apparatus according to Claim 2, wherein the control means is responsive to the operation of the switch during said predetermined period to discontinue the supply of power.

4. Apparatus according to Claim 2 or to Claim 3, wherein the control means is responsive to a double operation of the switch within a limited time frame to cause regular interruptions of the power supplied to the system.during said predetermined period.

5. Apparatus according to any preceding claim including means for monitoring the level of charge sustained by the power source and responding to the level of charge falling below a predetermined minimum value to inhibit the supply of power to the system.

6. Apparatus according to any preceding claim, wherein said primary piece of equipment comprises a mobile telephone.

7. Apparatus according to any preceding claim, wherein said auxiliary system comprises a torch lamp.

8. Apparatus according to any one of Claims 1 to 6, wherein said auxiliary equipment comprises a siren.

9. Apparatus according to any preceding claim, wherein said power source comprises 5 a rechargeable battery.

10. Apparatus according to any preceding claim, wherein the control means are integrated within the chipset contained in the primary piece of equipment.

11. Apparatus substantially as hereinbefore described, with reference to Figure 1 to 4 of the accompanying drawings.

12. Apparatus substantially as hereinbefore described, with reference to Figure 5 of the accompanying drawings.