BACKGROUND ART An ideal application of this device is for use by the disabled where a person frequently desires to select for operation an electrical appliance, or facility, from several available to him. For example there may be such facilities available as an electric lamp, radiator, radio, television, and even a "nurse call" alarm. If individual controls or switches, are provided for his use confusion can arise, especially for a mentally retarded patient. It is the principal object of the invention to provide a power control device responsive to operator-touch and which is simple to operate and functions reliably.

DISCLOSURE OF INVENTION According to a general form of this invention there is provided a selective power control device for the connection of electric power from a source to a selected one of a plurality of power lines associated with individual electrical functions or appliances, comprising a presentation to the operator of the functions or applicances available to him, operator-controlled sensor means, means responsive to a first signal from said sensor means to initiate a successive identification to said operator of individual ones of said functions or appliances, means responsive to a second signal from said sensor means to halt said successive identification at a selected one of said functions or appliances, and means to switch on power from said source to said power line associated with said selected one of said functions or appliances.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which:

Figures 1A and IB show respectively a front perspective, and a rear perspective on a smaller scale, of

OMPI

the cabinet of a power control device according to this invention;

Figure 2 is a block diagram of the circuit of the power control device; Figures 3A and 3B together depict a detailed schematic drawing of the circuit of said device;

Figure 4 shows schematically the construction of the power supply circuit;

Figures 5A and 5B depict the circuit of the touch sensor and wave forms occurring therein;

Figure 6 is a schematic drawing of the clock oscillator; and.

Figures 7A, 7B and 7C show wave forms associated with the clock oscillator. BEST MODE OF CARRYING OUT THE INVENTION

The selective power control device of the invention is housed within a cabinet 10 such as shown in Figures 1 and 2. A power cable 11 for connection to a power source (not shown) is connected to electronic circuitry within the cabinet 10 and an operator's touch sensor device 12 is plugged into the rear 18 of the cabinet 10. A row of power sockets 13 are arranged at the rear 18 of the cabinet 10 into which may be inserted the power plugs of respective electrical applicances (not shown) . A row of function panels 14 with corresponding overhead neon indicators 15 are arranged along the front 19 of the cabinet 10. The functions as shown, which may be varied, are in order "nurse call", light, fan, radio and television. Each of the panels 14 includes an interior lamp for illumination in turn during cycling of the individual functions as will become clear from the following description. An ON-OFF power button 16 and a selector-speed slide control 17 are also accessible to the operator at the front 19 of the cabinet 10.

The electronic circuit within cabinet 10 is shown generally by the block diagrammatic representation of the power control device shown in Figure 2. A touch interface 20 controls a divide-by-two flip-flop circuit Bl in such a manner that at successive touches of the sensor 12, the

output 1 of Bl goes alternately high (+12v) and low (ov) . These two states at the output of Bl correspond to two distinct phases of the circuit operation as follows: phase 1 serves for channel cycling where output 1 of Bl is high, and output 2 of Bl is low, while phase 2 is for channel on-off switching control when the output 1 of Bl is low and the output 2 of Bl is high. Therefore, at the initial touch by the operator and all succeeding odd-numbered touches, the state of the circuit is as follows: output 1 of circuit Bl is high which activates the clock oscillator 21. Pulses from the clock output are counted by a channel selector stage 22 whose 5 outputs correspond to 5 individual channels by which power to individual appliances is controlled. Other decade counters with longer counts may be used if more than 5 switching functions is required. Only one of the channel selector outputs is high at any one time, and when it is high that channel is selected to energize the corresponding display by lamps in the function panel 14 (see Figure 1A) , i.e. if say output 2 is high then lamp L2 becomes illuminated which would in Figure 1 correspond to say the room light function panel 14. Under these conditions output 2 of circuit Bl is low whereby input 1 of all of the and gates E6 to E10 are placed low. The channels, therefore, are cycled by the recurring count in channel selector 22 and the lamps behind panels 14 are lit ^• successively to indicate to the operator the channel choice available to him at that instant. If no further touch is recorded on the sensor 12, the channel selector 22 will continue to cycle through until its output 6 goes high for the fourth time at which point an auto-reset stage, via its 4-cycle counter 23, becomes effective. When an auto-reset signal is received at the end of the fourth selection cycle a signal is produced via the switch pulse discriminator 24 to reset circuit Bl to the stand-by mode, i.e. with its output 1 high and output 2 low. The switch pulse discriminator 24 prevents this auto-reset signal being transmitted over the ON-OFF control bus 25. Output 2 of circuit Bl is normally low, however during phase 2, which

will be referred to later, output 2 of circuit Bl goes from low to high and a positive-going edge is detected by the edge detector unit 26 and transmitted over the ON-OFF bus. During phase 1 when output 2 of circuit Bl goes from high to low the negative-going edge is detected by the unit 26 and no signal is allowed to pass through the switch pulse discriminator 24 to the ON-OFF control bus 25.

Concerning phase 2 of the circuit operation, upon the second touch of the sensor 12 the circuit Bl reverses its outputs so that output 1 goes low to stop the clock oscillator 21 thereby causing the channel selector 22 to halt its count and de-energises the display lamps Ll to L5 via and gates El to E5. Simultaneously, output 2 of the circuit Bl goes high sending all of the inputs 1 of and gates E6 to E10 also high. Now as both inputs 1 and 2 of gate E7 are both high, its output also goes high. The rising edge of this transition clocks the flip-flop B3 and as can be seen the remaining flip-flops B2 and B4 to B6 are not clocked in this condition as their inputs 2 are all low. As output 2 of circuit B3 changes from low to high it causes power switch S2 to close and apply power to outlet 02, while neon N2 (indicator 15 of Figure 1A) becomes illuminated to indicate that channel 2 is energized. If, however, output 2 of flip-flop B3 had changed from high to low then the reverse would have happened, i.e. switch S2 would have gone open to interrupt power to the outlet 02 and indicator neon N2, with channel 2 then being de-energized. Hence, due to the transitionary action of the edge detector 26, described in more detail hereafter, switching from power on to power off, and vice-versa, occurs alternately with each even-numbered touch providing that the same channel is selected. If, of course, different channels are selected, with each even-numbered touch ultimately all of the functions available would be switched on. The reason for the de-energisation of the display lamps Ll to L5 should now become clear. If, for instance, power output on channel 2 had been turned off and the display was not de-energised, the corresponding lamp L2

would have been illuminated to mislead the operator. De-energisation of the display also serves as an indication that the circuit is in a stand-by mode ready to pass back into phase 1. If, for example, channel 2 had been turned off, and channel 1 is required to be energized, the procedure would be to touch the sensor 12 once and wait until lamp Ll is illuminated, then touch again so that channel 1 becomes energized. It will become clear from the following description of the clock oscillator that a delay occurs in the oscillator before pulses are produced and this delay can be found to enable the operator to touch again to switch off power on the selected channel before cycling re-commences.

As an accessory to the control device a feature incorporating control of intensity of power supplied at the respective outlet 01 to 05 may be included. For instance, upon even-numbered touches if the operator's contact with the sensor 20 is maintained the output voltage may be varied incrementally, or even continuously, by the response in known fashion of an integrated circuit such as presently available chip S576 marketed by Siemens Ag of West Germany. DETAILED DESCRIPTION OF CIRCUITRY Reference is now made to Figures 3A and 3B for a more detailed description of the circuitry of this invention. In the "untouched" condition of sensor 12, points Al and A2 are high while A3 is low. When the sensor 12 has been touched the wave forms at Al and A2 are as shown in Figure 5B of the drawings. Resistor R2 and capacitor C2 form a low pass filter for the Schmitt Trigger inverter 27 which squares-up the wave form from points A2 to A3. Thus a fast rise-time positive transition is obtained when the sensor 12 is touched.

The divide-by-two circuit Bl is a flip-flop connected in the toggle mode, where the Q output leads the D output. At successive pulses from the touch interface circuit 20 the Q output alternately goes high and low. These two states correspond to two distinct phases of the circuit operation, viz. high in the case of channel cycling

and low in the case of channel on-off switch control.

The clock oscillator circuit 21 consists of an ICM7555 low power timer chip 28 which is connected as an astable multivibrator. The frequency and mark/space ratio are provided by resistors R3, R4 and VRl (corresponding to the control 17 of Figure 1A) and capacitor C3. Capacitor C4 decouples pin 5 to ground. The equivalent circuit of the chip 28 is shown in Fig. 4 and it contains a 3-resistor potential divider R20, R21 and R22, two voltage comparators 29 and 30, a flip-flop 31, a transistor T10 and an output buffer 32. The divider ratios are such that 1/3 of the supply voltage (i.e. 4v) is set on the lower comparator 30 and 2/3 of the supply voltage (i.e. 8v) is set on the upper comparator 29. The circuit action is such that, in each operating cycle, capacitor C3 first charges up to 8v through resistors R3, R4 and VRl, at which point the upper comparator 29 activates the flip-flop 31 and turns the internal transistor T10 on. The transistor T10 then discharges capacitor C3 through resistor R4 until the capacitor C3 voltage falls to 4v, at which point the lower comparator 30 activates the flip-flop 31 and turns the internal transistor T10 off to cause capacitor C3 to recharge through resistors R3, R4 and VRl. The operating cycle is then complete and repeats ad infinitum. A ramp waveform with an amplitude that swings between 4v and 8v is generated across capacitor C3 and a rectangular wave form is generated at the output pin 3. The clock oscillator wave forms are shown in Figures 7A, B and C. Figure 7A shows the gating voltage VI from circuit Bl, Figure 7B shows voltage V2 at capacitor C3 and Figure 7C shows the output voltage V3. The oscillator is gated on or off by diode Dl. When the circuit is gated on, diode Dl is back-biased and the astable operates in the normal way, but when the circuit is gated off, diode Dl shorts out capacitor C3 and pulls voltage V2 to ground. It should be noted that when the astable is gated on, the first half cycle is again considerably longer than the succeeding half cycles, but that the capacitor C3 voltage falls abruptly to zero at

gate-off. Furthermore, the output is high in the off state.

The channel selector 22 consists basically of a 4017

CMOS counter chip. Only one of its outputs is high at any time. When power is applied, the circuit is reset across the network of resistor R7, capacitor C7, and Dual Input

Nand Schmitt Trigger 33. The output Q then goes high when a negative transition is applied to the clock enable input CE, Q, goes high and Q low. This sequence continues until Q ₅ goes high and a second reset circuit is initiated. This includes resistor R6, capacitor C6 and

Schmitt Trigger Inverter 34. Consequently Q then goes high again and the cycle is repeated while resistor R5 and capacitor C5 prevent spurious clocking. The auto-reset circuit 23 (Figure 2) is "clocked" at the end of each selection cycle, i.e. the transition of Q5 from low to high is detected at the output of gate 35 which feeds the 4-cycle counter 23 composed of two flip-flops 36 and 37. The

4-cycle counter is energised by the clock-start signal from the Q output of circuit Bl. At the end of the fourth cycle

Q2 of circuit 37 goes high which, via the switching signal discriminator 24, is able to reset circuit Bl. Hence, the clock oscillator is disabled and the system reverts to the stand-by mode. If phase 2 is initiated before the fourth cycle is reached, the auto-reset counter 23 is stopped until phase 1 is re-activated and the clock oscillator 21 is re-started. The auto-reset counter 23 is initialised again by the "clock-start" signal from the Q output of circuit Bl, and the above procedure is repeated. During operation of the device a visual indication of the channels selected is required and this is achieved by the channel display units (Figure 33) , each composed of an

AND gate such as any one of gates El to E5, cascaded transistors Tl and T2 and one of lamps Ll to L5. For simplicity only one of these circuits and associated channels is shown and each circuit functions in a similar manner, such as gate El has its input 1 connected to terminal Q of the channel selector 22, and its input 2

OMPI

connected to receive control voltage CVl from the Q output of circuit Bl. During the channel cycling phase of the circuit output Q is high so that if output Q is also high then the output of gate El is also high. Thus current will flow through resistor R8 to saturate transistors Tl and T2 to cause lamp Ll to light thereby indicating that channel 1 is available in the cycle. If either output Q or Q is low then the output of gate El is also low and transistors Tl and T2 as well as lamp Ll are in an off condition. It is necessary for each channel to contain a circuit able to decide whether the power should be On or Off and this is achieved by the channel on-off control logic which for .each channel is composed of one of the AND gates E6 to E10 and an associated one of the divide-by-two circuits B2 to B6. Input 1 of gate 38 of the circuit 24,26 (Figure 3A) is normally low, except when an auto-reset signal is received. Gate 38 and resistor-capacitor R15-C13 form the negative edge trigger network 26. When Q of circuit Bl goes from high to low, the negative edge is produced at input 2 of gate 38. Since input 1 of gate 38 is normally low, the output thereof will remain high as will that of gate 39. Also as input 2 of gate 38 is normally low, no change is observed at the output of gate 39. Inputs 1 and 2 of gate 40 are high and hence its output is low. However, when Q of circuit Bl goes from low to high during phase 2, a positive-going edge is produced on input 2 of gate 39. Since input 1 of gate 39 is normally high, an output pulse is produced at the output as a result of the positive edge. This output pulse is transmitted as a control voltage CV2 along the on/off control bus 25 to the channel on/off control logic circuits and is shown for simplicity in Figure 3B as connected to gates E6 and E10. During auto-reset input 1 of gate 38 is normally low. hen an auto-reset signal is received at the end of the fourth selection cycle, a positive pulse is applied to input 1 of gate 38. Since input 2 is normally high, a negative edge pulse is generated at the output of gate 38 which is used to reset circuit Bl via gate 40. Since input

2 of gate 39 is normally low, the pulse signal at the output of gate 38 is blocked from being transmitted down the ON-OFF control bus 25. When circuit Bl is reset its Q output goes from high to low, which stops the clock oscillator 21 and the display is disabled.

The circuit from the 12V supply via resistor R30 and bypass capacitor C30 and inverter 44 supplies an initial . reset pulse, upon application of power to the device, to circuit Bl via inverter 45 and to circuits B2 to B6 via a filter represented by resistor R31 and capacitor C31.

Each of the first four channels has a solid state power switch Sl to S4, rated at 500 Watts, which is driven from the channel on-off control logic. These power switches Sl to S4 are identical. When the output from circuit B2 is high, current will flow through resistor R9 to saturate transistor T3 and permit gate current to flow through Triac TRl via resistor R10. Resistor Rll protects the gate junction of the sensitive gate TRl, which triggers TR2 via resistor R12 and hence power is supplied to the outlet 01. Under these conditions neon Nl lights up via the current limiting resistor R13. The Triacs TRl and TR2 are protected by a fuse Fl. When the input is low the reverse will occur so that no current flows into resistor R9 and hence transistor T3 and Triacs TRl and TR2 are in an off condition and the supply of power to outlet 01 is interrupted. The neon Nl indicates this condition by turning off. It will be noted that Triacs TRl and TR2 form an amplifying gate Triac system known as a "TRIWAG". Power is derived from the active, earth and neutral lines A, E, N. The fifth channel or switch S5, is utilized for driving heavy duty or inductive loads and switching is achieved by a 10 amp relay RLl. Input for the relay driver comes from the previous on-off control logic. When the input is high current flows through resistor R14 to saturate transistors T4 and T5 and their output current flows in relay coil RLl to close its contacts. Power is then applied to the outlet 05 and the neon N5 lights via the current li iter R13. Diodes D10 and Dll protect the transistor T5

OMPI

from voltage transients. When the input is low the reverse will occur, i.e. no current flows in resistor R14 so that transistors T4 and T5 are off and no excitation current flows in the relay RLl so that its contacts remain open. Power is therefore switched off and the neon is not illuminated. A spark quench circuit of resistor R20 and capacitor C20 is connected over contacts RL/, .

The power supply 41 is a full-wave rectified type using a bridge BRl and with a transformer TSl and a zener diode regulator ZNl. The two outputs are 15 volts unregulated at 200 A and 12 volts regulated at 10 A. The high current supply drives the lamps Ll to L5 and the relay coil RLl while the low current supply drives the low power CMOS circuitry. Diode D6 provides the power on-off indication for the power control device. Capacitors C21, C22 and C23 form a delta house suppression network.

The general form of the touch sensor unit is shown in more detail in Figure 5A. 50 Hz hum is received by the sensor plate 12 upon operator body contact and is applied through resistor R32 and capacitors C32 and C33, forming a low-pass high-pass filter, to the switching transistor T20 which is saturated during the presence of a signal and at cut-off when a signal is not present.

Whereas a preferred embodiment has been described in the foregoing passages it should be understood that other forms, embodiments and modifications are possible within the scope of this invention.