METHOD AND APPARATUS FOR DRIVING NEON TUBE TO FORM LUMINOUS BUBBLES AND CONTROLLING THE MOVEMENT THEREOF

Abstract: More discernable luminous bubbles, or light and dark regions, in a neon tube are attained with the instant invention by providing a separately-driven oscillator including FET's (25, 26) with charging capacitors (27, 28) coupled to a luminous tube (NET) driven by a pulse width modulated supply (14) through a signal transformer (T1). The pulse width modulated supply (14) is controlled by a microprocessor circuit with memory capability such that various sequences of bubble movement can be preprogrammed. Ground fault sensing circuit is provided for operator hazard protection.

Description: METHOD AND APPARATUS FOR DRIVING NEON TUBE TO FORM LUMINOUS BUBBLES AND CONTROLLING THE MOVEMENT THEREOF Background and Brief Description of the Invention ∑n Kayser patent 1,939,903 and Becquemont patent 2,091,953, neon tubes are driven in such a way that the luminous discharge has the appearance of brilliant luminoua balla or bubbles separated by dark spaces and appearing to move in the interior of the tube from one electrode to the other. In Kayser, an oscillating current is applied to each end of the neon tube with one of the tube ends being grounded and the direction of travel of the luminous span iaauing from the non-grounded end of the tube ia varied by varying the characteristics of the oscillating current.. In the Kayser patent, a high frequency current has- the* voltage; level thereof varied in a slow and progressive manner according to the apparent movement and development of the bubbles and then the high frequency current is shut-off and a low frequency industrial current is applied in a slow and progressive manner so that the main voltage of the oscillating current is varied. In Becquemont, a high frequency alternating current is applied to the electrodes at a sufficient frequency to produce the luminous bubbles separated by dark regions and a portion of the alternating current is rectified and superimposed on the applied alternating current. In yet another prior art system, a frequency of between 1500 and 4000 Hz ia produced and the aymmetry of the current applied to the tube ia adjusted either by adjusting the clipping one of the peaks of a driving sinusoidal wave or by producing a substantially square wave voltage and adjusting the duty cycle thereof. Such a system la. disclosed in Kennan C. Herrick PCT application PCT/US86/00851, Iήterirafci-onal Publication No. 086/06572, incorporated herein by reference, entitled "Apparatus and Method for Forming Segmented Luminosity in Gas Discharge Tubes". The Herrick PCT application discloses regulation of the aymmetry of the resultant tube current, i.e., regulation of the net current flow between the electrodes. The resultant or net current flow through the tube is regulated so as to control the movement of these alternating light and dark regions lengthwise along the tube. Regulation of net current flow may be accompliahed either by imposition of a DC current acroaa the electrodes in addition to; the AC aignal, or- by use of an AC signal having an asymmetric wave form. Asymmetry of the wave form may be measured by determining the DC voltage across a capacitor connected in series with the gaβ diacharge tube, and thia eaaurement may be applied in a feedback loop to control the degree of asymmetry and hence control the rate of movement of the illuminated regions lengthwise along the tube. In a further variant, the tube may be provided with a midpoint electrode to provide net current flows either from the end electrodes towards the midpoint or from the midpoint towards the end, with corresponding movement of the light and dark regions towards or away from the midpoint. THE PRESENT INVENTION According to the present invention, a portion of an applied commercial AC supply (60 Hz) ia rectified, filtered and applied to a commercially available ae i-conductor chip element which haa a controllable oscillator serving aa a aignal generator and which haa both duty cycle and frequency control adjustments. The logical output signal is coupled via an impedance matching circuit to the input primary winding of a signal transformer. The signal transformer haa a pair of secondary windings which are used to drive a pair of tandem connected FET switches which, in turn, are connected acroaβ a second DC aupply which has a high direct current voltage derived from the input AC line voltage 110-120V AC 60Hz;). A pair- of tandem connected capacitors is connected acroaa the DC aupply and an intermediate point between the tandem connected FET switches ia connected to one end of the primary winding of a high voltage output transformer and a second intermediate point between the two tandem connected capacitors is connected to the opposite end of the primary winding of the high voltage output transformer ao that on alternate half-cyclea of th input aignal coupled to the aignal tranaformer from the impedance matching transistor switches is used to alternately drive the gate electrodeβ σ * the FET switches. * A series of control sequences for the FET switches is stored in a memory, such as a ROM or PROM, magnetic disk or tape or an optical memory, or a combination thereof, and a microprocessor is programmed to selectively retrieve one or more control, sequences so as to cause the neon tube to go through a predetermined program of movements. In thia regard, a plurality of neon tubea can be controlled in any predetermined pattern or sequence of luminoua bubble movements from the aa e or a aimilar memory. Thus, in one neon tube the luminoua bubbles can be controlled to move first in one direction at one speed, then in an opposite direction at the aame or a different speed and then be atationary (zero velocity) for a predetermined time while the luminoua bubblea in one or a plurality of other tubes of widely differing shape and curvatures are simultaneously controlled to go through their respective patterns of movements. A ground-fault sensing- shut-off circuit is connected to one? of the output terminals of the high voltage output transformer and includes; comparator circuitry which ia capable of βenβing when: a person, for example, touches one of the output terminals of the high voltage output electrode. Thia condition is sensed and used to operate a thyriator awitch which ahunta or by-passes the primary winding of the signal transformer to thereby terminate the operation of the FET switches and thereby terminate the generation of high voltages in the secondary windings of high voltage output transformer. As used herein, the term "neon tube" includes tubes filled with gases other than neon. The above and other objects, advantages and features of the invention will become more apparent when taken in conjunctio with the accompanying drawings wherein: Fig. 1 is a circuit diagram incorporating the invention. Fig. 2 is a modification of the circuit diagram shown in Fig. 1 illustrating the embodiment of the invention wherein a plurality of separate neon tubes are separately driven and controlled via a stored memory and a microproceaβor coupled to aame and to the separate driving circuita. Detailed Description of the Invention Referring now to the circuit diagram shown in Fig. 1, an AC supply 5 supplies alternating current through a choke filter and; fuse reaiβtor 7 to the- primary windin S of transformer T3. A variβter 9 stabilizes the input voltage. Transformer T3 is a step down transformer and applies a low AC voltage to a bridge rectifier 11 which has a pair of filter capacitors 12-1, 12-2 on the output thereof, and a zener diode 13 for stabilizing the output voltage, preferrably at about 30 volts DC. A switch mode pulse width modulation control circuit 14 <a Motorola MC34060 or MC35060) has an oscillator therein (not shown) connected to an external pulse width modulation control circuit constituted by resistors 16-1, 16-2 and potentiometer 16-3 and an external frequency control circuit constituted by capacitor 15C and potentiometer resistor 15R which permits the potentiometer to adjust the resistance leg and thereby adjust the frequency of the internal oscillator in chip 14. The output on terminal 9 has an internal transistor supplying output to the intermediate point between biaa control resistor 14-B and coupling resistor 17. The lower end of coupling resistor 17 is connected to the base inputs of a pair of tandem connected complementary emitter follower NPN-PNP transistors Ql and 02 which provide a low impedance driv circuit to the input of winding 20 of aignal tranaformer Tl via a coupling capacitor 19C and rββiβtor 19-R. Transformer Tl has a pair of secondary windinga 21 and 22 which have a back-to-back zener diodea 23 connected thereacroβa and with the aignalβ therefrom being used to drive the gate electrodes of FET transistors 25 and 26 respectively. A further bridge rectifier 24 rectifiea the AC line voltage from source 5 and has- a filter- capacitor 24-C connected thereacross for filtering purposes, (In this regard, the separate aupply conatituted by tranaformer T3 and bridge rectifier 11 can, if desired, be eliminated and a voltage divider used to supply the lower DC voltage to supply the pulse width modulator chip 14 with 30 volts) . The FET transiatora 25 and 26 have their drain-source electrodes connected in series or tandem relation across the high voltage supply (about 170 volts) and, a pair of capacitors 27, 28 are likewise connected in tandem across the high voltage supply. The intermediate point IP1 between the tandem connected FET transistors 26 and 27 ia connected to one end of the primary winding 29 of high voltage output tranaformer T4 and the intermediate point IP2 between capacitora 27 and 28 ia connected to the opposite end of primary winding 29 of transformer T2. Thus, when the input signal current flowing through tranaformer winding 20 ia in one direction, one of transistors 25 will be gated on to cause a current to flow through winding 29 in one direction and when the direction of current flow through tranaformer winding 20 is in the opposite direction, a further signal is generated in the secondary winding of one of transformer windings 21 and 22 to trigger the other FET transistor (and the opposite FET transistor ia biaaed off by oppoaite polarity aignala in the other aecondary winding of transformer Tl) on and thereby cause an opposite direction of current flow through transformer winding 29. Thus, by modulatin th widt of the- pulse& and/or- the frequency of the pulses from pulse width modulation control circuit 14, one is able to contro both the direction and speed of the luminous bubbles flowing in the neon tube NET. A coupling capacitor 31 in the lower lead from aecondary winding 30 has a pair of back-to-back diodes connected thereacross and adjacent the neon tube NET ia coupled through a zener diode capacitor circuit 32 to the input of a ground-fault βenaing circuit which includes a pair of comparison resistors 36-1, 36-2 which receive, via a further fixed resistor, a selected reference voltage. The voltage on the output of winding 30 is sensed across resistor 37 and comparator 33 compares thia against the reference voltage to detect a change in that voltage. Upon detecting a change in that voltage, a signal is applied through the resistor capacitor output thereof to a further cQ-rrparator circuit 34 which likewise receives via resistor 37 at the 1 - intermediate point between resistors 30 and 39 the aignal voltage which forms a second comparison. Thus, a person touching one of the electrodes on the tube NET causes a change in the voltage such that that change is detected in the ground-fault detection circuitry to produce an output signal via resistor 40 and onto the gate electrode of switching thyrlstor pair 41. This provides a shunt bypass to signal input on the primary winding 20 of transformer Tl thereby avoiding or preventing the application of control signals to the gate- electrodes of the FET'a 25 and 26 and thereby preventing the further generation of a high voltage until the ground-fault ia removed. Referring now to Fig. 2, a plurality of neon tubea NET-1, NET-2...NET-N, aupplied by a. high voltage transformers T3-1, T3-2... T3-N, eacti of which are separately driven from a pair of tandem connected switches 25-1, 25-2...25-N, 26-1, 26-2...26-N and paralleled by a pair of tandem connected capacitors 27-1, 27-2...27-N, 28-1, 28-2...28-N with the intermediate points IP1-1, IP1-2, IP2-1, IP2-2...IPN-1, IPN-2 between the tandem connected switches and the tandem connected capacitors being connected to the ends of the primary windings P-l, P-2...P-N of the high voltage output transformers T3-1, T3-2...T3-N. Each of the switches ia an electronic awitch correβponding to the FET switches 25 and 26 shown in Fig. 1. The drive circuitry 18-20-1, 18-20-2...18-20-N for the switches is schematically shown as operating and opening and closing of the switches 25, 26, it being, understood that these are representations of the electronic FET' switches 25 and 26 shown in Fig 1 and the transformer circuitry related thereto. Each of the switches is driven from a pulse width modulator circuit 14-1, 14-2, 14-N each of which in turn receives duty cycles (pulse width) and frequency adjust input signals DS and E from a microprocessor 50 which, in turn, receives a sequence of control aignala representing a pattern correβponding to a predetermined direction, speed (including stationary) of movement of the different luminoua bubblea in each of the tubea NET-1, NET-2, NET-N, reapectively. The apeed can, of courae, be ao fast that the luminous bubbles are no longer diβcernable and. a conventional neon light display results. Thus, the.-- programmable read-only memory 51 is accessed by the microprocessor 50 which, in turn, supplies the different patterns (luminous bubble flow direction, speed, etc.) to the pulse width odualtor circuits 14-1, 14-2...14-N to thereby simultaneously control the direction of movement rate of movement and/or stationary positions of the luminous bubbles in each of the individual tubes. The individual tubes NET-1, NET-2, NET-N can be either stacked-up in vertical order for viewing simultaneously, or serially in any sequence desired so that many combined luminous effect can be achieved through the combination of the tube either in serial, parallel or atacked vertical order for viewing purpoaea. While there has been shown and described a preferred embodiment of the invention, it will be appreciated that numerous other embodiments will be readily apparent to those skilled in the art and it is intended that the accompanying claims embody within their scope those obvioua modifications that would be readily apparent to one skilled in the art. WHAT IS CLAIMED IS:

Claims: CLAIMS 1. A system for driving a neon tube to form luminous bubbles or beads and controlling the motion thereof in said neon tube comprising, a high voltage transformer having primary and aecondary windingβ, said secondary winding being electrically connected to said neon tube, a high voltage DC supply having a pair of terminals, a pair of electronic switches connected in tandem across said pair of terminals, there being a first common point between said tande connected electronic switches, a pair of capacitors connected in tandem across said pair of terminals, there being a second common point between said tandem capacitors, means connecting one end of said primary windingβ to said first common point and the other end of said primary winding to said second common point,. means connecting the ends- of said -secondary winding to said neon tube, a control signal generator having means for adjusting at least one of the duty cycle and frequency thereof, a signal transformer having primary and secondary windingβ, an impedance matching circuit coupling said control signal generator to said primary winding, and conductor means, connecting said secondary windings to said electronic switches to alternately control the on/off conditions of said electronic switches and thereby the formation and movement of said luminous bubbles or beads. 2. The system for driving a neon tube to form luminous bubbles or beads and controlling the motion thereof in aaid neon tube as defined in claim 1, wherein said control signal generator includes a fixed frequency pulse width modulation control circuit for producing said control signal and means for modifying the pulse width of said control signal. 3. A system for driving a neon tube to form luminous bubbles or beads and controlling the motion thereof in said neon tube as defined in claim 1, including, a high voltage transformer,.having primary and secondary windings, said secondary windings being electrically connected to said neon tube, a DC voltage supply having a pair of terminals, a pair of electronic: switches connected in tandem across said pair of terminals, there being a firat common point between aaid tandem connected electronic awitches, a pair of capacitora connected in tandem across said pair of terminals, there being a second common point between said tandem capacitora, means connecting one end of said primary windings to said first common point and the other end of said primary winding to aaid second common point, means connecting the ends of said secondary winding to said neon tube, a source of control signals connected to control the operation of said electronic switches and thereby the formation and movement of said luminous bubbles or beads, and a memory means for storing a plurality of patterns of direction and speed of said luminous bubbles or beads and means for selectively coupling said patterns from said memory means to aaid switches. 4. In a ayatem for driving a neon tube to form luminoua bubblea and controlling the motion thereof in which a modulatable high AC voltage aource ia connected to electrodea of said neon tube, the improvement comprising, memory means for storing predetermined patterns of the direction and speed of said luminous bubbles and microprocessor means for controlling said modulatable AC voltage in accordance with said predetermined pattern by said memory means to cause said luminous bubbles to move in said predetermined patterns of direction and speed. 5. A system for driving a neon tube to form luminous bubbles and controlling the motion thereof as described in claim 4 wherein said memory means includes a plurality of predetermined patterns stored in said memory means, and means for selecting one of said patterns and driving said neon tube therewith. 6. The system as defined in claim 5 wherein there are a plurality of said neon tubes and a plurality of said modulatable high AC voltage AC sources connected to respective ones of said neon tubes and means for selecting one or more of said predetermined patterns for driving one or more of said neon tubes. 7. A system for driving a neon tube to form luminous bubbles or beads and controlling the motion thereof in said eαxr. tube-,, a high voltage transformer having primary and secondary windings, said secondary windings being electrically connected to said neon tube, a DC voltage aupply having a pair of terminala, a pair of electronic switches connected in tandem across said pair of terminals, there being a first common point between said tandem connected electronic switches, a pair of capacitors connected in tandem across said pair of terminals, there being a second common point between said tandem capacitors, means- connecting one end of said primary windings to aaid first common point and the other end of said primary winding to said second common point, means connecting the ends of said secondary winding to said neon tube, a source of control signals connected to control the operation of said electronic switches and thereby the formation and movement of said luminoua bubbles or beads, and a. ground fault sensor and shut-off circuit connected to said secondary winding to sense a touch thereof, and switch means controlled thereby for preventing operation of said electronic switches. 8. The system defined in claim 7 wherein source of control aignala includea a aignal tranaformer having a primary winding and a pair of secondary windings, a signal generator connected to the primary winding of said signal transformer, means connecting one of said secondary windings to one of said pair of electronic awitchea and the other of aaid aecondary windinga to the other of aaid pair of electronic awitchea to alternately control the operation thereof. 9. The system defined in claim 7 wherein aaid awitch eana ia connected in ahunt with the primary winding of aaid aignal tranaformer to prevent aignala from aaid aignal generator from operating aaid pair of electronic awitchea.

Inventors: ANDREASEN MARK S, ANDRESEN JACK S, ANDREASEN, MARK, S., ANDRESEN, JACK, S.
Applicants: ANDREASEN MARK S, ANDRESEN JACK S, ANDREASEN, MARK, S., ANDRESEN, JACK, S.
Application year: 1987
Main classification: H01J7
IPC codes: G09F13, G09G3, H05B41