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United States Patent 3,720,939
Polanek ,   et al. March 13, 1973



A high sensitivity audio modulated switching circuit operates a plurality of lamps to create various and original lighting effects. The energization of the lamps is controlled by a thyristor circuit which is responsive to both the a.c. line voltage and varying amplified signals from an audio transducer.

Inventors: Polanek; Edward L. (Glendale Heights, IL), Micek; Daniel W. (Chicago, IL)
Assignee: Universal Research Laboratories, Incorporated (Elk Grove Village, IL)
Appl. No.: 05/124,284
Filed: March 15, 1971

Current U.S. Class: 340/815.46 ; 340/815.73; 367/197
Current International Class: H02M 1/088 (20060101); A63J 17/00 (20060101); H02M 1/096 (20060101); G08b 005/36 ()
Field of Search: 340/148R,366R

References Cited

U.S. Patent Documents
3579187 May 1971 Knott
3582671 June 1971 Ott
3586919 June 1971 Harris
3440489 April 1969 Davidson
3463936 August 1969 Adem
3530501 September 1970 Benschoten
3553528 January 1971 Somlyody
Primary Examiner: Pitts; Harold I.


What is claimed is:

1. An audio modulated switching circuit adapted to operate from an a.c. voltage source, comprising a plurality of lamps, a thyristor lamp-switching control circuit connected to said lamps and to said voltage source, transducing means responsive to an audio input to provide an electrical signal systematically related to the amplitude of the audio input, and means responsive to said electrical signal for providing triggering signals to said thyristor lamp-switching control circuit for producing lamp operation in a manner determined by the instantaneous variation in said triggering signals and said a.c. voltage, said thyristor control circuit comprising means for energizing one of said lamps during a.c. source half-cycles of like polarity only on the occurrence of an audio input and means for energizing another of said lamps during a.c. source half-cycles of said like polarity only when said one lamp is de-energized.

2. The circuit of claim 1 comprising means for adjustably setting a predetermined amplitude threshold for said audio input to permit energization of said one lamp only when the amplitude of the audio input is at least said threshold value.

3. The circuit of claim 1 wherein said thyristor control circuit comprises a pair of controlled rectifiers, each having anode, cathode and gate electrodes, each of said plurality of lamps being serially connected respectively in the anode-cathode circuit of each controlled rectifier and across the a.c. source, means coupling the gate of one controlled rectifier to the output of said amplifying means, and means coupling the anode-cathode circuit of said one controlled rectifier to the gate of the other controlled rectifier.

4. The circuit of claim 3 wherein said coupling means to the gate of said other controlled rectifier is connected to the anode of said one controlled rectifier.

5. The circuit of claim 4 wherein said coupling means is resistive.

6. The circuit of claim 1 wherein said amplifying means comprises two transistor stages connected in cascade and said transducing means comprises a loudspeaker connected to the first of said stages.

7. The circuit of claim 3 comprising a gain control for permitting lamp operation only for audio inputs above a set predetermined level.

8. The circuit of claim 7 wherein said control is automatic and responsive to said other controlled rectifier for varying the gain of said amplifying means.

The present invention relates to audio modulated switching circuits, and particularly to such circuits for the energization and illumination of a plurality of lamps for providing various and original lighting effects.

It is an object of the present invention to provide an improved circuit for creating original and asthetic light patterns from a plurality of lamps, which may be economically employed in the construction of novelty lighting devices and fixtures.

It is another object of the invention to provide such lighting devices which may employ, as desired, various size lamps from miniature to those of considerable power rating, and thus provide versatility in their use and application.

It is a further object of the invention to provide a circuit of the aforementioned type having a high degree of sensitivity to sounds, or other accoustical waves, to produce original and curious lighting effects in response thereto for entertainment, advertising, or other purposes.

These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings, of which:

FIG. 1 is a schematic diagram of a circuit in accordance with an embodiment of the present invention; and

FIG. 2 is a graphical illustration showing the voltage waveforms at various points in the circuit of FIG. 1, under various conditions, to aid in the understanding of its operation.

Referring now to FIG. 1, there is generally shown an audio modulated switching circuit in accordance with the present embodiment of the invention adapted to operate from an a.c. voltage source, typically being the standard 117 volt line, through a conventional plug 10 and leads 12 and 14. The circuit generally comprises a plurality of lamps 16 and 18; a thyristor lamp-switching control circuit, generally indicated as 20, connected to the lamps and to the a.c. voltage source; a transducer 22 responsive to an audio input to provide an electrical signal systematically related to the amplitude of the audio input; and amplifying means 24 responsive to the electrical signal for providing triggering signals to the thyristor control circuit for producing lamp operation in a manner determined by the instantaneous variation in the triggering signals and the a.c. voltage. The circuit further comprises means for providing a regulated and reduced d.c. voltage for the amplifier 24, such means being indicated in FIG. 1 generally as 26.

The thyristor lamp-switching circuit 20 controls the energization of the two lamps 16 and 18, each being connected in the respective load circuits of thyristors 30 and 32, which are each illustrated in the present instance as a silicon controlled rectifier (SCR) having respective anode, cathode and gate electrodes. A trigger circuit for the first SCR 30 is formed by resistor 34 across which the trigger signal from amplifier 24 is applied to the gate electrode, after passing through a variable resistor or potentiometer 36. A trigger circuit for the second SCR 32 is formed by series resistors 38 and 40 which are connected across the line voltage leads 12 and 14 through the lamp 16 to provide a trigger voltage across resistor 40 and gate drive to the SCR 32 when the SCR 30 is nonconductive.

Consequently, SCR 32 is normally conductive and lamp 18 is normally on, while the SCR 30 is normally nonconductive and lamp 16 is normally off. The transducer 22, in response to sound waves incident thereto, however, provides electrical signals to the amplifier 24 which are thereby amplified to a sufficient magnitude to trigger the first SCR 30, both SCR's being preferably of the so-called sensitive gate type. The SCR 30 becomes conductive in response to trigger signals of sufficient magnitude when the line voltage thereacross is of the proper polarity, i.e., when lead 12 is positive relative to lead 14. When the SCR 30 conducts, lamp 16 will be energized to full brilliance, while lamp 18 which is normally illuminated will be extinguished by the action of the SCR 30 shorting out the gate current of SCR 32. As a result, the two lamps 16 and 18 provide a flickering on and off action in opposite phase relation in response to the audio input to the circuit, and in a particular manner described in greater detail hereinafter.

The thyristor lamp control circuit 20 is operative for lamp energization only on the positive alternation of the line voltage (relative to the polarity of the SCR's) so that the positive alternations are used to light the lamps. The negative alternations are used to cut off the thyristors and turn off the lamps. Thus, lamp 18 is normally on only when no audio actuated trigger signal is present and the line voltage is on a positive alternation. However, since lamp 18 switches on and off at 60 times a second, it appears to the eye to be uniformly or constantly on. This situation prevails until an audio actuated trigger signal turns on lamp 16, which extinguishes lamp 18, as previously indicated. Lamp 16 will therefore light at varying times or phases during positive alternations of the line voltage depending on when an audio signal of sufficient magnitude is received by the circuit, and at all other times during the positive alternations the lamp 18 will be lighted.

More particularly, the line voltage across the leads 12 and 14, which powers the thyristor control circuit 20 to provide energization of the lamps, is also rectified by a diode 42 to supply a half-wave rectified voltage across a voltage dropping resistor 44 and a series connected filter capacitor 46. Lead 14 is taken as common and is consequently shown as being grounded. The filtered d.c. voltage across the capacitor 46 is coupled via resistor 48 across a Zener diode 50 which provides a constant low voltage of, for example, 10 volts, on the amplifier supply lead 52 relative to the common lead 14.

Amplifier 24 comprises a pair of cascaded transistor amplifier stages, each having an NPN transistor, 54 and 56, respectively connected in a common emitter configuration. Each of the transistor stages may be biased for Class A operation or for operation as a switch from nonconduction to saturation. Accordingly, suitable base bias resistors 58 and 60 and suitable collector bias resistors 62 and 64 are provided for each transistor stage, respectively, and the emitter of each transistor is connected directly to ground. The transducer 22 provides the input signal to the first transistor 54, and is preferably a conventional loudspeaker (having, e.g., an 8 to 40 ohm coil impedance) which is used as a microphone. The speaker 22 is a.c. coupled across the base and emitter electrodes of the first stage transistor 54 through a coupling capacitor 66.

The transistor 54 is biased at approximately the middle of its characteristic so that the low amplitude signals from the speaker 22 cause its collector voltage to swing abruptly from one extreme to the other, and these voltage swings are a.c. coupled to the base of the second transistor 56 via coupling capacitor 68. Likewise, the second transistor 56 is also biased at about the middle of its characteristic so that its collector voltage provides large amplitude swings in response to the signal from the first transistor 54, and thus provides the amplifier output trigger signal on lead 69 through the output coupling capacitor 70.

The potentiometer 36 which is serially connected between the output lead 69 and the gate of the first SCR 30 provides an adjustable trigger level control for setting the desired threshold for triggering or actuation of the SCR 30. Thus, for a given setting of the potentiometer 36, only sound amplitudes above some predetermined value will result in triggering the first SCR of the thyristor lamp control circuit 20, and the consequent illumination of lamp 16. The optimum setting of the potentiometer 36 may be found empirically, and will generally depend on the particular application and general environment in which the circuit is to be used.

Referring now to FIG. 2, the voltage waveforms at various points in the circuit of FIG. 1 are illustrated under a "no sound trigger signal condition" and under a "sound trigger signal condition" wherein the sound signal amplitude is sufficient to produce a sufficiently large trigger signal to fire the first thyristor of the lamp control circuit 20. The circuit operation under the "no trigger signal condition" is illustrated during the time period from t.sub.1 through t.sub.6, and the circuit operation during the "trigger signal condition" is illustrated during the time period from t.sub.6 through t.sub.11, each period being taken relative to two full cycles of the a.c. line voltage applied to leads 12 and 14. This line voltage, taken, for example, at 117 volts rms, is illustrated in FIG. 2 (a) as varying between -168 volts and +168 volts, peak-to-peak. Taking t.sub.1 arbitrarily as a zero line-voltage crossing point, as shown, FIG. 2(b) shows the voltage waveform across the anode and cathode of the first SCR 30, FIG. 2(c) shows the voltage waveform across the anode and cathode of the second SCR 32, and FIGS. 2(d) and (e) respectively show the voltage waveform across the first and second lamps 16 and 18.

As can then be seen, the second SCR 32 becomes conductive due to the presence of forward bias across its load terminals and sufficient gate drive which is established through the first lamp 16 and the resistors 38 and 40 in its gate trigger circuit. The first SCR 30 is nonconductive at this time and remains so until time t.sub.6 due to insufficient gate drive from the amplifier 24. The gate driving current for SCR 32 which flows through the lamp 16 is insufficient to produce any significant level of illumination from this lamp. Since SCR 32 becomes conductive at time t.sub.2, a voltage appears across the lamp 18, as shown in FIG. 2 (e), and this voltage varies through the remaining portion of its normal half-cycle period until the line voltage reverses its polarity and cuts off SCR 32 at time t.sub.3, at which time the voltage drops to a level which is insufficient to maintain its conduction. Lamps 16 and 18 are then off. During the period t.sub.3 - t.sub.4 both SCR's 30 and 32 are in the reverse blocking state and must be nonconductive, hence lamps 16 and 18 remain off during this period. The same sequence occurs in the interval t.sub.4 - t.sub.6 which was initiated at time t.sub.2. As previously mentioned, lamp 18 will appear to be continuously on under this condition.

At time t.sub.7 a varying amplitude signal of sufficient magnitude is developed across potentiometer 36 and resistor 34, and the first SCR 30 is triggered to conduction. The line voltage now appears across the first lamp 16 turning it on, and with SCR 30 conductive, SCR 32 must be nonconductive as shown in FIG. 2(c). During the period t.sub.7 - t.sub.8, SCR 30 and lamp 16 are on and SCR 32 and lamp 18 are off. At time t.sub.8 the line voltage drops to a level which is insufficient to maintain conduction of the SCR 30 and it becomes nonconductive, turning lamp 16 off. Lamp 18 is also off at this point. During the period t.sub.8 - t.sub.9 both of the SCR's 30 and 32 are in the reverse blocking state, and both lamps 26 and 28 are off. Again, during the period t.sub.9 - t.sub.11 the same sequence of events occurs as was initiated at time t.sub.7.

Because the varying output from the amplifier 24 is responsive to the sound of audio amplitudes received by the speaker 22, the lamps will be triggered at various times or phases of various positive alternations of the line voltage, successively or otherwise, and consequently the average energies that are supplied to the lamps will vary in accordance with variations in the sound energy input to the circuit relative to the a.c. line voltage phase. Accordingly, various original light patterns may be created by the flickering of the lamps to produce various artistic and asthetic effects.

A specific construction in accordance with the present embodiment of the invention has been found to perform satisfactorily with the component values and parameters shown in the drawings, wherein all resistance values are given in ohms and capacitance values are given in microfarads.

An example of an alternative construction which has also been found to be satisfactory employs an automatic gain control for the amplifier 24 and permits the substitution of a fixed resistor for the trigger level potentiometer and the elimination of the Zener diode. In particular, and if desired, an additional diode may be connected at its anode to the anode of the second SCR 32 with its cathode connected through a resistor to a multi-connection junction or node having a high resistance (e.g., 4.7M) coupled to the positive terminal of capacitor 46, another high resistance (e.g., 1M) coupled to the base of the second stage transistor 56, and a capacitor (e.g., 1 mfd.) coupled to ground. The base bias resistor 58 of the first amplifier stage may then be replaced by a self-biasing resistor (e.g., 1.5M) between the base and collector of transistor 54, and the base bias resistor 60 may be eliminated. In this alternative construction, the output capacitor 70 and the gate resistor 34 may also be eliminated, and the value of the coupling capacitor 66 may be substantially increased (e.g., to 1 mfd.). Also, amplifier supply resistor 48 may be chosen of appropriate value.

The automatic gain control (AGC) or the potentiometer 36, which is also a gain control, may be used to obtain desired operation of the lamps for any given average background or ambient sound level. That is, the circuit will not respond to audio inputs below some set predetermined level.

The illustrated circuit is relatively uncomplicated and can be employed economically in the manufacture of novelty lamps and the like having any desired type of lamp fixture to house the components, and the lamps may be of different colors or have different color filters applied. The lamps 16 and 18 in the illustrated embodiment, may be of any desired power, but should preferably not exceed 100 watts each for the component values given in FIG. 1. Other sizes may of course be employed with appropriate modifications, and lower voltage lamps may be operated with series connected resistors. Of course, other numbers of lamps may also be used.

Although a specific embodiment of the present invention has been illustrated and described herein, various modifications thereof will be apparent to those skilled in the art; accordingly, the scope of the present invention should be defined only by the appended claims and equivalents thereof.

Various features of the invention are set forth in the following claims.

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