Abstract:
A signal generating circuit coupled to an AC supply, the circuit comprising at least one first switch device coupled to the AC supply, at least one triggerable switch device coupled to the first switch device, operation of the first switch device causing said triggerable switch device to trigger in response to the AC supply at a predetermined voltage, thereby providing at least a portion of a waveform of the AC supply as a control signal and wherein the control signal terminates within a predetermined period of time after operation of the first switch device terminates. A circuit for detecting and responding to the signals generated by the signal generator is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a divisional of U.S. patent application Ser. No. 09/400,928, filed Sep. 22, 1999 in the names of Donald R. Mosebrook and Lawrence R. Carmen, Jr. and entitled “Signal Generator and Control Unit For Sensing Signals of Signal Generator.” 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a signal generator capable of producing a plurality of control signals and a sensing circuit for detecting the control signals produced by the signal generator. Even more particularly, the invention relates to signal generators that can be produced at low cost. 
     BACKGROUND OF THE INVENTION 
     Remote signal generators capable of sending command signals are known. FIG. 1 shows an electric lamp wall box dimmer  12  coupled to a remote signal generator  10  through two conductors  14  and  16 . A wallbox dimmer and remote signal generator are available from the assignee of the present application and known as the Maestro dimmer and accessory dimmer. The wall box dimmer comprises a signal detector  32  capable of receiving and decoding three discrete signals generated by the signal generator  10 . The signals are generated when a user actuates momentary contact switches “T”, “R” or “L”. The “R” switch generates the signal shown in FIG. 2A when actuated which causes the dimmer to increase the light intensity of the coupled load  20 . The “L” switch generates the signal shown in FIG. 2B when actuated which causes the dimmer to decrease the light intensity of the coupled load  20 . The “T” switch generates the signal shown in FIG. 2C when actuated which causes the wall box dimmer  12  to turn on to a preset light intensity, go to full light intensity, fade off slowly or fade off quickly. Each time the switch “T” is actuated, the signal generated and sent to the signal decoder  32  is always the same. To cause the dimmer to react differently to the closure of switch “T”, the user must actuate the “T” switch differently. When a user actuates switches “R”, “L” or “T” the signal detector  32  actually receives a string of signals because the user is usually not capable of actuating and releasing the switches in less than one line cycle (16 mSec on a 60 Hz line). The signal is only generated as long as the switch is closed. 
     A microcomputer  28  in the wall box dimmer  12  is capable of determining the length of time the switch “T” has been actuated and if the switch “T” has been actuated and released a plurality of times in quick succession. The microcomputer is programmed to look for the presence or absence of an AC half cycle signal from the signal detector  32  a fixed period of time after each zero cross of the AC line, preferably 2 mSec. The microcomputer only looks once during each half cycle. The advantage of the signal generator of the prior art is its low cost. The drawback to this type of signal generator is that there are a limited number of signals that can be generated without requiring the user to actuate the same actuator repeatedly or actuate the actuator for an extended period of time in order to perform additional functions. Details of a signal generator according to the prior art are disclosed in issued U.S. Pat. No. 5,248,919, the entire disclosure of which is hereby incorporated by reference. There is a need for a low cost signal generator that does not require the user to actuate the same actuator in different ways to initiate multiple functions. 
     Also known are phase control lamp dimmers which use a semiconductor device to control the phase of an AC waveform provided to an electric lamp thereby to control the intensity of the lamp. These phase control dimmers are not ordinarily considered to be signal generators of the type contemplated herein. Further, such phase control dimmers, until turned off, produce a phase shaped AC waveform continuously unlike the signal generator described above in connection with FIG.  1 . 
     Other signal generators of the prior art can generate a plurality of control signals, but require a microprocessor in the signal generator which converts the actuator actuations into digital signals for processing by another microprocessor. The drawback to this type of signal generator is the added cost of the microprocessor and its associated power supply. 
     Accordingly, there is a need for a low cost signal generator that overcomes the drawbacks of the prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a signal generator which is capable of producing a plurality of different control signals. 
     Yet still a further object of the present invention is to provide a signal generator which can be manufactured at low cost. 
     It is yet still a further object of the present invention is to provide a signal generator which produces unique control signals based upon portions of alternating current waveforms. 
     Yet still a further object of the present invention is to provide a sensing circuit for detecting the control signals produced by the signal generator circuit according to the present invention. 
     Yet still a further object of the present invention is to provide a signal generator which requires only two wires for connection to a sensing circuit. 
     The above and other objects are achieved by a signal generator comprising a switch in series with at least one of a zener diode and a diac, the signal generator producing an output when the switch is actuated, the output having a region where the current is substantially constant. 
     The above and other objects are also achieved by a signal generator comprising at least one of a zener diode and a diac, the signal generator producing an output when a switch in series with the at least one of a zener diode and diac is actuated, the output having a region where the current is substantially constant. 
     The above and other objects are also achieved by a signal detector circuit coupleable to an AC source comprising a sense circuit, and a control circuit, the control circuit producing a signal when the sense circuit receives an AC signal having a region where the current is substantially constant. 
     The above and other objects are also achieved by a signal generating circuit coupled to an AC supply, the circuit comprising at least one first switch device coupled to the AC supply, at least one triggerable switch device coupled to the first switch device; operation of the first switch device causing said triggerable switch device to trigger in response to the AC supply at a predetermined voltage, thereby providing at least a portion of a waveform of the AC supply as a control signal and wherein the control signal terminates within a predetermined period of time after operation of the first switch device terminates. The triggerable switch device can be a zener diode, a diac or may be a semiconductor switching device having a control electrode, e.g., a triac, SCR or transistor, or an opto coupled version of such switching devices. 
     The above and other objects are also achieved by a circuit for sensing one of a voltage and current from a signal generator circuit producing a plurality of unique control signals based on an AC supply voltage, the sensing circuit comprising a detector detecting one of a voltage level and current level in a line coupling the sensing circuit and the signal generator and producing a sensed signal; a controller for causing said detector to detect one of the voltage level and current level at a plurality of times in a half cycle of the AC supply voltage; the controller providing a control signal based on the sensed signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed. In the drawings: 
     FIG.  1 . is a block diagram of a signal generator coupled to a wall box dimmer according to the prior art. 
     FIGS. 2A,  2 B, and  2 C are plots of the outputs of the signal generator of FIG.  1 . 
     FIG.  3 . is a simplified schematic diagram of a first embodiment of a signal generator and a block diagram of a signal decoder according to the present invention. 
     FIGS. 4A,  4 B,  4 C,  4 D and  4 E are plots of the outputs of the signal generator of FIG.  3 . 
     FIG. 5 is a simplified schematic diagram of a second embodiment of a signal generator according to the present invention. 
     FIGS. 6A,  6 B,  6 C,  6 D and  6 E show further embodiments of signal generators according to the present invention. 
     FIGS. 7A,  7 B,  7 C,  7 D and  7 E show waveforms of the circuits of FIGS. 6A,  6 B,  6 C,  6 D and  6 E, respectively. 
     FIGS. 8A and 8B show how the control unit decodes the control signals produced by the signal generator for two examples. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference again to the drawings, FIG. 3 shows a remote signal generator  100  coupled to a control unit  200  with conductors  112  and  114 . The control unit  200  may be, as shown, a motorized window shade motor unit that controls a coupled window shade. However, the control unit  200  may be a control unit controlling other electrical devices, as desired. The control unit  200  is provided AC power (24 V AC) from a transformer  400 . 
     The remote signal generator  100  comprises a plurality of momentary switches  102 A- 102 H. A signal is provided to the control unit  200  only when one or more of the switches  102 A- 102 H has been actuated. Each switch can be a momentary contact mechanical switch, touch switch, or any another suitable switch. For example, the switches may be tactile feedback or capacitance touch switches. The switches could also be semiconductor switches, e.g., transistors, themselves controlled by a control signal. In series with switch  102 A is a diode  104 A with the anode coupled to the sense circuit  202  and the cathode coupled to the switch. In series with switch  102 B is a diode  104 B with the cathode coupled to the sense circuit  202  and the anode coupled to the switch. There are no diodes in series with switch  102 C. In series with switch  102 D is a diode  104 D with the anode coupled to the switch and a zener diode  106 D with the anode coupled to the sense circuit  202 . In series with switch  102 E is a diode  104 E with the cathode coupled to the switch and a zener diode  106 E with the cathode coupled to the sense circuit  202 . In series with switch  102 F is a zener diode  106 F with the anode coupled to the sense circuit  202  and the cathode coupled to the switch. In series with switch  102 G is a zener diode  106 G with the cathode coupled to the sense circuit  202  and the anode coupled to the switch. In series with switch  102 H are two zener diodes  106 H 1  and  106 H 2  with the anode of zener diode  106 H 1  coupled to the sense circuit  202  and the anode of zener diode  106 H 2  coupled to the switch. In the preferred embodiment, diodes  104 A,  104 B,  104 D, and  104 E are type IN 914  and zener diodes  106 D,  106 E,  106 F,  106 G, and  106 H 1  and  106 H 2  are type MLL 961 B with a break over voltage of 10 V. 
     Alternatively zener diodes  106 D,  106 E,  106 F,  106 G,  106 H 1  and  106 H 2  can be replaced with suitable value diacs in order to practice the present invention. 
     The control unit  200  comprises a sense circuit  202 , a control circuit  204  controlling, e.g., a motor  206 , a source voltage monitor circuit  208 , a power supply  210 , and optional local switches  212  provided for control functions, such as the same control functions controlled by the signal generator  100  and/or additional functions. The sense circuit  202  senses the current flowing between the AC source  400  and the signal generator  100 . 
     The sense circuit  202  senses the direction of this current, i.e., whether a forward current, reverse current or substantially zero current. When current flows through the sense circuit  202 , the sense circuit sends a signal to the control circuit  204  on line  250 . In one embodiment, the sense circuit  202  senses the current. Alternatively, the sense circuit  202  could sense the voltage. The source voltage monitor  208  signals the control circuit  204  when the control circuit  204  should read the sense circuit. In the preferred embodiment, the source voltage monitor signals the control circuit  204  on line  256  to read the sense circuit twice during each half cycle. The sense circuit is first read before the transformer  400  voltage is high enough to turn on a zener diode in the signal generator  100 . The sense circuit is then read after the transformer  400  voltage is high enough to turn on a zener diode in the signal generator  100 . In this way, a determination can be made of the shape of the waveform from the signal generator circuit  100 . In the preferred embodiment, the source voltage monitor signals the control circuit  204  to read the sense circuit at predefined times after each zero crossing, for example, two times after each zero crossing, when the AC supply is at 4.7 v and again when it reaches 18.0 v. 
     Based on this specification, circuits for implementing the techniques for detecting and processing the signals received from the signal generator  100  described herein can be readily constructed by those of skill in the art, and therefore, a detailed discussion of the circuitry of the control unit  200  is omitted. 
     In an embodiment controlling a motor, it is most preferred that the control circuit  204  includes a microprocessor operating under the control of a stored software program to produce output signals on line  252  to the motor  206  to cause it to rotate in a forward or reverse direction. In the preferred embodiment, the microprocessor is a Motorola MC68HC705C9A. 
     The control circuit  204  is powered from a suitable power supply  210  coupled to the AC source. The source voltage monitor circuit  208  provides a signal to the control circuit  204  concerning which half cycle (positive or negative) of the AC source is present at a particular time and a signal representative of the start of each half cycle. 
     The waveforms produced when switches  102 A,  102 B and  102 C are actuated are the same as those shown in FIGS. 2A,  2 B and  2 C respectively. The waveform produced when switch  102 A is actuated is a half sine wave only in the positive half cycle and the waveform produced when switch  102 B is actuated is a half sine wave only in the negative half cycle. The waveform produced when switch  102 C is actuated is a full sine wave. In the preferred embodiment of the present invention operating from a 60 Hz supply, a pulse 8.33 mSec in length during the positive half cycle can be produced when switch  102 A is actuated and a pulse 8.33 mSec in length during the negative half cycle can be produced when switch  102 B is actuated. Consecutive pulses 8.33 mSec in length can be produced when switch  102 C is actuated. The microcomputer  210  needs to look at the incoming signal over several line cycles in order to properly determine which switch or switches have been actuated. Although the drawing figures only show one half cycle or a full cycle, it is understood that the signal generator  100  will repeatedly produce the signals  2 A,  2 B or  2 C as long as the switch is actuated. 
     The waveforms produced when switches  102 D,  102 E,  102 F,  102 G and  102 H are actuated are shown in FIGS. 4A,  4 B,  4 C,  4 D, and  4 E, respectively. The waveform produced when switch  102 D is actuated is a half sine wave only in the negative half cycle delayed a time period after the zero crossing and ending a time period prior to the next zero crossing. See FIG.  4 A. The waveform produced when switch  102 E is actuated is a half sine wave only in the positive half cycle starting a delayed time period after the zero crossing and ending a time period prior to the next zero crossing. See FIG.  4 B. The peak current as illustrated is approximately 12.5 mA. 
     The waveform produced when switch  102 F is actuated is a half sine wave in the positive half cycle followed by a half sine wave in the negative half cycle delayed a time period after the zero crossing and ending a time period prior to the next zero crossing See FIG.  4 C. The peak current in the positive half cycle is approximately 20 mA and the peak current in the negative half cycle is approximately 12.5 mA. 
     The waveform produced when switch  102 G is actuated is a half sine wave in the positive half cycle delayed a time period after the zero crossing and ending a time period prior to the next zero crossing followed by a half sine wave in the negative half cycle. See FIG.  4 D. 
     The waveform produced when switch  102 H is actuated is a half sine wave in the positive half cycle delayed a time period after the zero crossing and ending a time period prior to the next zero crossing followed by negative half cycle delayed a time period after the zero crossing and ending a time period prior to the next zero crossing. See FIG.  4 E. 
     In the case of FIGS. 4A to  4 E, each waveform has a region of substantially constant current, and in particular, a region of zero current before the zener diode switching device switches on at its break-over voltage. Further, like FIGS. 2A to  2 C, the waveform shown or a portion thereof is repeated as long as the switch is actuated. 
     FIG. 5 shows a simplified schematic diagram of another low cost signal generator  300 . The signal generator  300  operates in a similar fashion to the signal generator shown in FIG.  3 . The difference is that the signal generator  300  does not have any switches. The signal generator receives switch closures or control signals from an external source as shown at  301 . The external source may be a plurality of remotely located switches or may be another controller sending control signals. For example, a fire detector or burglar alarm system could send a signal to the signal generator  300  to control a device. As an example, in the case of a fire, all motorized window shades could be raised. 
     FIGS. 6A-6E show further embodiments of signal generator circuits according to the present invention. These circuits use semiconductor switching devices having control electrodes controlled by a trigger circuit. FIG. 6A shows a signal generator circuit employing a triac  401  and a trigger circuit comprising diac  402 , a capacitor  404  and resistors R 1  and R 2  each coupled to a momentary contact switch  406  and  408 , respectively. In this circuit, triac  401  is fired at a given phase in the AC waveform to provide unique current waveforms. Changing of the values R 1  and R 2  varies the time at which triac  401  is latched on. Capacitor  404  and resistors R 1  and R 2  form time constant circuits. When either of momentary switches  406  or  408  are activated, the voltage at the junction of capacitor  404  and the resistors increases gradually according to the time constant determined by the resistance R 1  or R 2  and capacitance of capacitor  404 . Once the voltage reaches a value sufficient to trigger diac  402 , the diac conducts causing the triac  401  to conduct. Because the triac is bidirectional, the triac will conduct both for positive and negative half cycles. The waveforms generated by this circuit when switches  406  or  408  are actuated are shown in FIG. 7A for two different resistance values as illustrated in FIG.  7 A( a ) and FIG.  7 A( b ). The onset of conduction depends upon the value of the resistance. In contrast to the circuit of FIG. 3, the circuit of FIG. 6A produces a waveform having steep rising edges at the time the triac begins to conduct. Both however have a region where the current is substantially constant. 
     FIG. 6B shows another portion of a signal generator circuit according to the invention. In this signal generator circuit, a zener diode  502  triggers a triac  501  when a momentary contact switch  506  is actuated and a signal is generated. The waveform for the circuit of FIG. 6B is shown in FIG.  7 B. Once the zener break-over voltage is reached, the triac  501  conducts. The waveform of FIG. 7B shows that there is a sharp rising edge for the positive half cycle which occurs when the zener break-over voltage is reached. During the negative half cycle, zener diode conducts like a conventional diode, so triac  501  is turned on for the entire negative half cycle. The triac turn-on time can be changed and accordingly, the location of the steep rising edge of the waveform of FIG. 7B changed, thus producing different control signals, by changing the zener diode used, i.e., using a zener diode having a different break-over voltage. 
     FIG. 6C shows another embodiment using a triac  601  and a number of diodes and zener diodes. A zener diode  602  and a momentary contact  606  are connected in series to the gate of the triac  601 . Further connected to the gate of the triac  601  is a diode  610  and further zener diode  612  and a momentary contact  608  in series. The actuation of the switch  606  generates the signal of FIG.  7 C( a ). The time when the triac turns on can be delayed by using zener diodes having varying break-over voltage. 
     When the switch  608  is actuated, only the positive half cycle with a steep rising edge is produced because the diode  610  prevents any current flow when the negative half cycle of the AC waveform is present. See FIG.  7 C( b ). 
     FIG. 6D shows the use of a zener diode in a signal generating circuit to turn on an SCR. The circuit comprises an SCR  701  and a zener diode  702 . A momentary contact  704  is provided. When the momentary contact  704  is actuated, the SCR is triggered once the break over voltage of the zener diode  702  is exceeded during the positive half cycle. FIG. 7D shows the waveform generated by the signal generating circuit of FIG.  6 D. In contrast to the triac circuit, because the SCR is unidirectional, only the positive half cycle is generated. To generate the negative half cycle, the conductive direction of the SCR  701  would be reversed and the zener diode would be polarized oppositely to that shown in FIG.  6 D. 
     FIG. 6E shows another signal generating circuit according to the invention utilizing SCR  801  two zener diodes  802  and  804 , and momentary contacts  806  and  808 . The zener diodes  802  and  804  have break-over voltages of V and 2V, respectively. Accordingly, the SCR  801  conducts when the momentary switches  806  or  808  are actuated at times determined by the break-over voltage of the zener diodes. The waveforms generated are shown in FIGS.  7 E( a ) and ( b ). The waveform caused by actuation of switch  808  would have a delayed rising edge as compared to the waveform for the switch  806 . In order to generate a signal during the negative half cycle, the zener diodes and SCR would be polarized oppositely. 
     Zener diodes  502 ,  602 ,  604 ,  702 ,  802  and  804  can alternatively be replaced with suitable value diacs in order to practice the present invention. 
     FIGS. 8A and 8B show examples of operation of the sensing circuit  202  under control of the control circuit  204  and source voltage monitor circuit  208 . FIG. 8A shows an example of a control signal from the signal generating circuit of FIG.  6 A. The waveform shown has a period T. This circuit produces a control signal which has a steep rising edge once the triac  401  conducts. As discussed, the sensing circuit  202  can be controlled by the control circuit  204  to sense or sample the current or voltage in the line  112 , once prior to triggering of the triac  401 , at a time t1 and once after triggering of the triac at a time t2 in each half cycle. The timing may be controlled to be at predefined times after the zero crossings. Accordingly, at a time prior to triggering of the triac, the sensing circuit would sense that there is no voltage or current on line  112 . After the triac triggers at a time t2, the sensing circuit  202  would sense a voltage or current present on line  112 . Similarly, at time t3 and t4, the sensing circuit  202  would sense no signal present at t3 and a negative signal present at t4. The sensing circuit would thus be able to detect the presence of the unique signal provided by the signal generating circuit of FIG.  6 A. If the signal generating circuit of  6 A were used in conjunction with the other signal generating circuits of FIGS. 6B,  6 C,  6 D,  6 E or those of FIG. 3, in each case, the signal sensing circuit  202  would detect a unique signal which could be used to control a particular function. 
     Turning to FIG. 8B, for example, which shows the control signal like the signal of FIG. 4D generated by actuation of a switch  102 G coupled in series with a zener diode  106 G of FIG.  3 . At a time t1, before zener diode  106 G has triggered, no signal would be sensed. At a time t2, after zener diode  106 G has triggered, a signal would be sensed. At times t3 and t4, a negative signal would be sensed since the zener diode  106 G would be conducting for the negative half cycle. Accordingly, the unique signal provided by a control circuit having a zener diode  106 G and a momentary contact  102 G coupled in series as shown in FIG. 3 could be uniquely determined by the sensing circuit  202  and utilized by the control circuit  204  to control a specified function. 
     The source voltage monitor circuit  208  is used to inform the control circuit  204  of the appropriate times for sampling, i.e., the source voltage monitor circuit  208  can determine the zero crossings thus allowing the control circuit  204  to implement the samples at the times t1, t2, t3 and t4, as shown. 
     Similarly, for each of the unique control signals shown in FIGS. 7A-7E as well as  2 A- 2 C and  4 A- 4 E, the sensing circuit  202  is able to uniquely determine the presence of the uniquely coded signal and thus control the appropriate function as controlled by that control signal. 
     As fully described above, the present invention provides a novel circuit that can produce a plurality of control signal over only two wires and a circuit that can decode these control signals. The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.