GB2114751A - A touch switch with delay means - Google Patents

Abstract

The touch switch includes a polarity eliminating circuit (Q1 R3 R4 R5 C6) and a mono-stable circuit (IC1a) for sensing and wave form shaping functions so that the touch induction (at TP1) is not affected by a neutral line or live line of an A.C. source, and for facilitating installation of the switch. The alternate Hi/Lo operation of a toggle-typed flip-flop (IC1b) and the use of an ON-OFF time delay and adjustment circuit (Q2 R8 C5 D3 Q3) permits control of the ON-OFF operation of the power source to an electric equipment. Such a switch provides a user with the facility of a short buffer period after turning off an electric device. In addition, the switch includes an overload protection and indicating circuit to prevent overload or short circuit and warns the user by the illuminating of a pilot light (LED1, NE). <IMAGE>

Description

SPECIFICATION A touch switch with delay means This invention relates to a touch switch having delay means. Switches are an indispensable part of any electrical equipment, and various kinds of switches for different electric equipment have been developed, such as, sliding switches, pushbutton switches, rotary switches, and microswitches. The life of a conventional switch is generally rather short, ranging for instance, from ten thousand to several hundred switching operations. Since the life of a switch affects the operation of an electric equipment a micro-switch has been proposed and usually, such switches have quite a useful life. However, use of the micro-switch is iimited by virtue of its amperage and size and, more recently, "a touch switch" has been proposed.Proposed touch switches have intrinsic drawbacks in that they are expensive, include no safety means, and possess polarity effects, that is, the neutral line and the live line are easily confused which leads to wiring problems.

Further, proposed touch switches cannot concurrently be used as time counters.

According to the present invention, a touch switch having delay means comprises a polarity eliminating circuit, a sensing and wave-form shaping circuit, a power-off automatic clear circuit, a flip-flop, an ON-OFF time delay and judgment circuit a D.C. power supply circuit, an overload protection and indicating circuit and a power control circuit, the polarity eliminating circuit serving to eliminate the influence of the neutral and the live lines of an A.C. source, the sensing circuit sensing a signal resulting from a touch on the touch switch, the power-off automatic clear circuit serving to restore equipment under the control of the touch switch into a power-off or power-on state, and the ON-OFF time delay and judgment circuit delaying the effect of a touch on the touch switch.

A touch switch having delay means according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of the switch, in which: Fig. 2 shows the switch circuit in more detail.

The switch of the present invention uses relatively simple circuitry, is relatively cheap to manufacture, is sensitive to touch, free from interference, has no polarity effect with respect to an A.C. source, is safe, uses less power than other switches, and eliminates or substantially reduces the drawbacks of known sliding switches, pushbutton switches and the conventional touch switches. Known touch switches possess, as previously indicated, polarity potential adverse effects, when connected to an A.C. source, in that the touch circuit would become inoperative or insensitive when connected to the wrong terminals of the A.C. source. The switch of the present invention includes a polarity elimination circuit.In order to maintain adequate sensitivity, and certainty of operation, the present invention includes a "power-off automatic clear circuit" for the purpose of restoring associated electric equipment into a power-on or power-off state in the event of A.C. source being cut off for about one to five minuteswhen, for example, an owner is not in his house or is sleeping. In other words, the circuit has a memory time for about three to five minutes, (the time selected being dependent on particular circumstances) but it will automatically cut off the power of load in event that the power is off for a considerable time. This feature of the switch of the present invention prevents wasting energy or giving rise to incidents during power off and the user having left his house without turning off the power supply switch.

As another example, before a person retires to bed, or leaves his house, it is usually necessary for certain preparations to be made, such as, putting on shoes, locking up the doors, etc. In such case, if the lights are switched off, it would put the user to considerable inconvenience, or danger.

Therefore the ON-OFF time delay and judgment circuit in this invention will overcome the aforesaid problems by, for example, after touching the switch OFF, the light will not be switched off until expiration of a delay time of up to sixty seconds. The time delay may be varied by changing the value of appropriate circuit components. A portion of circuit at the top of Fig. 1 shows the overload protection and indicating circuit, D.C power supply circuit, and the power-off automatic clear circuit.

Normally, the external A.C. source is connected through the overload protection circuit to a D.C.

power supply circuit so as to provide power to the sensing and control circuits. In case of electric equipment being overloaded or short circuited, the overload protection and indicating circuit will cut off the power in the electric equipment immediately so as to prevent the switch of the invention from damage, to protect the load and also any wiring system. At the same time, an overload pilot light is illuminated to warn a user that the electric equipment under control of the switch of the invention has been overloaded and that checks should be made.In the event that the A.C. source is cut-off for only a very short period, e.g. less than ten minutes, the circuit in this invention can be maintained in its original state with the D.C. power in the circuit because this invention uses CMOS IC (P-MOS, N-MOS, V MOS IC or the like may be used in the future), which consumes very little power. However, if the A.C. source is cut off for more than ten minutes, and is then turned on again, the power-off automatic clear circuit of the switch will generate a signal to control a flip-flop to turn off the equipment.

Referring to Figure 2, an A.C. source is fed to the load of an electric equipment (or power socket), thence to the switch of the invention. If the load of an electric equipment is not connected to the power or the electric equipment is in open circuit state, an LED and an Ne tube will not be illuminated i.e: the switch is in an in-operative state, which may be heipful to a trouble shooter in checking the wiring system. As soon as the load of an electric equipment is connected with the switch, the A.C. source will normally go through the fuse, and is applied to R,3, Ne tube, Rut2, C7, TRIAC, R2 and D2. The overload protection and indicating circuit comprises R1, LED1, D1, and fuse.

Normally, the LEDa would not be illuminated as a result of no current passing through D1, LED1, and R, because the current is short-circuited with the fuse. As soon as the fuse is burned out by the overload current, the current will then pass through D1 to illuminate LED, to indicate an overload. Since the LED1 needs only about 8-20 mA to light up, in case of the load being shortcircuited, the circuit of this invention would not normally be damaged because resistor R1 limits the current to such an extent that a TRIAC would not conduct. The D.C. power supply circuit comprises R2, D2, ZD1 and C,, in circuit.The resistor R2 is a current-limiting resistor, D2 provides a half-wave rectification operation, ZD, is a Zener diode to provide about 5-10 Volts D.C. power supply for this circuit and C, is a filter capacitor. Irrespective of whether the TRIAC is in an "ON" or "OFF" state, it is necessary to have sufficient current to meet the requirement of the circuitry either in operative or in-operative state.

The value of R2 adopted (or the value of a capacitor connected in series) should meet the requirement of circuit during said TRIAC in "ON" or "OFF" state; especially when said TRIAC being in an "ON" state. Assuming that the A.C. source is 11 OV, the pulse voltage between T2and T, is approximately 1 + 1 8V (depending upon the trigger control phase), and the potential between point "a" and ground (i.e. +Vcc) is merely ranging from 3 to 8 volts.

As shown in said circuit, the polarity eliminating circuit comprises R3, R4, Q" R5 and C2 (said Q, is a PNP transistor); since the emitter of said Q, is connected to "+Vcc", the transistor Q, is in a "Ready" state. With R3 and R4, the polarity effect of power supply has been eliminated in said circuit. The value of resistor R3 should be large enough (for example over 500 KQ) so that no shock takes place during touching.The value of resistor R4 is specifically limited, but can be from 100 KQ TP, is a touch point and as soon as said TP, is touched, a signal will immediately cause C2R5 to be energised and will be applied to IC Moreover, the resistor R5 and capacitor C2 are connected in circuit to serve the purpose of preventing the next stage of said IC,a to continuously deliver pulses in case of the touch point TP, is touched for too long (exceeding the responding time constant of It18). The capacitor C2 is preferably a non-polarised capcitor so as to eliminate the polarity effect since even if a user touches the touch point TP, for a long time, the "CK" of IC18 receives only one input signal from the fully charged capacitor C2.Further the discharging time of C2R5 matches "CK" of IC,a changing from Hi to Lo within a range from 0.8 to one second so as to avoid careless re-touching after a user has touched the switch for about one second, or to avoid incorrect operation after a long touch. The value of resistor R5 may be over 100 K because of Q, is not used principally as an amplifier. IC,a is a non-stable circuit composed of D-type F/F and may also be used for shaping waveform so as to make sure that each touch signal is correctly coupled to next stage, It,,. IC,a and IC1b constitute one unit IC.The width "T" of said touch signal is determined by the value of CrR6)TD0.69R6C3) The "Q" point of IC,a is normally in "Lo" state, since "D" point is grounded (Lo), and when a touch signal is coupled to "CK" and "Q" point of IC,a will be changed to "Lo" and "Q" changed to "Hi". The "Hi" signal will be coupled to the "CK" of IC,b and simultaneously passes through R6 to cause C3 to be charged. As soon as the "SET" point of IC,a is actually changed to "Hi" (caused by charging said C3) the "Q" of IC,a becomes "Hi" and "Q" becomes "Lo".

i.e. ILaa restores to its normal stage. In the present invention, the "Q" of said IC,a may be connected to point "R" of IC,b through a resistor, or other means to change IC,a into a mon-stable circuit. Of course, the user may directly touch the said "CK" (TP2) of IC,a to generate touch sensing, but this way will not generate a better function of eliminating the polarity effect as mentioned above.

The toggle-typed flip-flop is formed by connecting the 'mQ" of IC1b to "D" point to modify the D-type flip-flop into a toggle function.

Capacitor C4 and resistor R7 are used for the power-off clear circuit. When the power is cut off for only about three to ten minutes, the sensing control means can still maintain in the original state because that C, still has some charges left to supply sensing control means which consumes very iittle power. Upon the power being cut off for over ten minutes, a "Reset" signal will through C4 R7, be coupled to "R" point of IC,b to set "Q" of IC,b in "Lo" state. As soon as a touch signal enters into the "CK" of IC,b, the "0" of IC,b will change its output state; the power supply of IC, is connected to +Vcc. The LED2 and the resistor R,4 are used for "OFF" touch operation. The ON-OFF time delay and judgment circuit simply comprises Q2, R8, C5, D3 and Q3.The delay time is determined by resistor R8 and capacitor C5 and C6 is merely an auxiliary capacitor (electrolyte) to C5 for temporary RF response so as to delay the "OFF" signal entering into D3 and Q3, Q4 connected as a Darlington pair. When the "0" of IC,b is in a "Hi" state, the TRIAC will be driven to an "ON" state, and the load of an electric equipment will be conductive. When "O" of said IC,b is in a "Lo" state, the TRIAC will be driven to "OFF", and the load of the electric equipment will also be turned off. In other words, upon the "Q" of IC,b being "Hi", Q2 is "ON", and Rs will have volt-drop (simultaneously, C5 and C5 will discharge) so as to cut off the conduction of D3, Q3 and Q4; as a result, a trigger signal is, through R,2, C7, DIAC, R" and Rro applied between "G--T,", causing TRIAC conducting as weil as the load.

As soon as the "Q" of IC,b changes to "Lo" Q2 will be cut off; the current will, through R8, charge into C5 and C6; upon the voltage across C5 and C6 exceeding the forward voltage (about 2.1 V) across B-E of 04 03, and the of D3, said 03 04 will become conductive to cause a short circuit between the G--T, of said TRIAC, and said TRIAC will be cut off; as result, the load of an electric equipment will be cut off as well. D3 is used for increasing the required voltage level to trigger the Darlington pair Q3 Q4. If more diodes or a Zener diode are/is fitted to the base of Q3, a longer "delay-OFF" time will result.Therefore, appropriate consideration should be given to practical design requirement together with the values of R5, C5, C5so as to limit the delay time within the range of 1-60 seconds. However, the circuit can still perform instant ON/OFF control without adding such delay circuit (i.e. the base of Q3 is directly connected to the output terminal of "O" of IC,b. Resistor R,, is the collector resistor for Q4. The power control circuit comprises R,2, Cv, DIAC, TRIAC, R1O, R, Q3 and Q4.

It will be understood that, during the later half "ON-OFF" delay period, the lamp load is preferred to be in a semi-illuminated state. By connecting a resistor in series with D3 the lamp will fully be illuminated during the first half delay period, and will be illuminated during the later half-delay period. In this way, the illuminating lamp system performs a two-step automatic "ON-OFF" delay functions thereby avoiding a suddenly cut-off state, which adversely affect a user's vision when adjusting from light to dark and vice versa. Where a semi-illuminated state is not required, it is simply necessary to increase the voltage across D3 of the Zener diode. The functions of a touch switch of the invention and delay time of touch may be fulfilled by just touching TP1, and, in case of using TP2 as a touching point, a high value resistor should be connected in series to prevent from shock.

Claims (7)

Claims

1. A touch switch having delay means and comprising a polarity eliminating circuit, a sensing and wave-form shaping circuit, a power-off automatic clear circuit, a flip-flop, and ON-OFF time delay and judgment circuit, a D.C, power supply circuit, an overload protection and indicating circuit and a power control circuit, the polarity eliminating circuit serving to eliminate the influence of the neutral and the live lines of an A.C. source, the sensing circuit sensing a signal resulting from a touch on the touch switch, the power-off automatic clear circuit serving to restore equipment under the control of the touch switch into a power-off or power-on state, and the ON-OFF time delay and judgment circuit delaying the effect of a touch on the touch switch.

2. A switch as claimed in claim 1 wherein said polarity eliminating circuit comprises a PNP transistor, 0,, resistors R3, R4, R5, and a capacitor C2

3. A switch according to claim 1 or claim 2 including two touch positions for initiating touch switch and delayed touch functions respectively.

4. A switch according to any preceding claim including a transistor (02) which when operated from On to Off, a time control circuit comprising capacitors C5 and C5 and resistor R5 serves to control transistors Q3, Q4 which, in turn, control operation of a TRIAC.

5. A switch according to any one of claims 1 to 4 including at least one lamp and an amplifier D3 connected in series with a resistor whereby the or each lamp can be piaced in a semi-illuminated state in the later half-delay period.

6. A switch as claimed in any preceding claim wherein said D3 is connected in series with diodes or be replaced by a Zener diode, so as to increase the full On state condition of the delay period for the lamp (or load).

7. A touch switch having delay means constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.