US2717336A - Flasher circuit - Google Patents

Description

Sept. 6, 1955 c. L. CRADDOCK FLASHER CIRCUIT 2 Sheets-Sheet 1 Filed May 8, 1955 INVENTOR CHnnLes L. cknnnoaK BY W,% 75Q W illir fitter/Le J Sept. 6, 1955 c. L. CRADDOCK FLASHER CIRCUIT 2 Sheets-Sheet 2 Filed May 8, 1953 G l. m I}. 7 3 3 [w M 5 I a a w w x2 my.

INVENTOR. Cmmss L. 632.400 acz United States Patent- O FLASHER CIRCUIT Charles L. Craddock, North Hollywood, Calif., assignor to Michael Research Company, Inc., a corporation of California Application May 8, 1953, Serial No. 353,736

6 Claims. (Cl. 315-183) My invention relates generally to flashers intended to control the flashing of an electric light, and more particularly to such flashers that are electronically operated, as opposed to those that are mechanically operated.

It is often desirable to have a flashing light, and such lights are frequently used for warning devices or signals, for decorative purposes, and for a multitude of other uses. However, the flashing mechanisms heretofore employed have usually relied upon mechanical devices, such as magnetically operated vibrators, motor-driven means, or thermally actuated mechanisms. Such prior devices have been open to the objection that many of them will not operate in all positions, and a number of them are adversely afiected by the surrounding temperature. These objections have seriously limited the fields to which the flasher mechanisms have been applied, and in many instances, their cost has been such as to prevent their use where otherwise they would be acceptable.

Electric or electronic circuits are known that provide a periodic pulse, but in general, the circuits have not been suificiently stable, particularly at low frequencies, to warrant their use where reliability is an important factor. Furthermore, because of the particular voltage limitations of such circuits, their use as means for controlling lights has been neglected. However, I have found that it is possible to use the characteristics and peculiarities of these circuits to advantage, and have produced flashing lights that have a very long period of usefulness, and operate at a very low cost per hour.

It is therefore a major object of my invention to provide an electronic flasher intended primarily to operate a light source.

Another object of my invention is to provide such a flasher that may have its rate of flashing controlled, either being adjusted to some predetermined value at the time the flasher is manufactured, or made continuously adjustable for control in the field.

It is a further object of my invention to provide an ornamental device making use of such an electronic flasher, and producing a novel and pleasing effect.

Still another object of my invention is to provide an electronic flasher adapted to operate a warning signal light, the flasher having a controllable rate of flashing, and requiring a very small current drain.

It is a still further object of my invention to provide flasher circuits of the above described characteristics that can be easily and inexpensively formed from readily available components, and compactly installed in a very small space.

An additional object is to provide a flasher means which relies upon electronic and electrical characteristics of its components, and has no moving parts that may become inoperative by reason of dirt, corrosion, or theposition they occupy.

These and other objects and advantages of my invention will become apparent from the following description of two forms thereof, and from the drawings illustrating those forms in which:

iii

2,717,336 Patented Sept. 6, 1955 Figure 1 is a perspective view of an ornamental device, here shown as a simulated Christmas tree, in which my electronic flasher controls the operation of the various lights thereon;

Figure 2 is a schematic wiring diagram showing the circuit used in connection with the lights on the tree shown in Figure 1;

Figure 3 is a perspective view of a stop sign similar to that used on highways, and in which a flashing light is normally incorporated; and

Figure 4 is a schematic wiring diagram of the flasher control used in warning signal lights of the type shown in Figure 3.

Description of illuminated decorative article Referring now to the drawings, in Figure 1, I have illustrated one form of a decorative article, such as a simulated Christmas tree on which a series of lights are 10- catedthat flash off and on at varying times and rates. Such a device is very attractive and the constant flashing of the lights, without any sound, quickly secures the interest of both children and adults. It will be appreciated that the use of the flashing lights hereinafter described is not restricted to such articles, but may be incorporated in many other devices.

As indicated in Figure 1, a simulated Christmas tree 10 is mounted upon a base 11 that preferably comprises a box-like member within which I mount the power supply and various control members for the device. The tree 10 should preferably be of a type having a number of thin, thread-like or wire-like projecting members that simulate the appearance of branches and foliage of an actual tree. Mounted on the tree, and positioned in the general manner of the usual Christmas tree decorations are, a plurality of bulbs 12 that flash olf and on, each bulb having its own rate of flashing, independent of the remainder. The wires connecting the bulbs to the power supply and control mechanism in the base 11 may be conveniently run down the trunk of the tree 10, preferably within that trunk, but arranged otherwise if so desired. A switch 13 may be mounted on the base 11 to control the operation of the lamp 12, but as will hereinafter become more apparent, in most instances this switch is not needed. p

In Figure 2, I have indicated the schematic wiring diagram of the control unit, power supply, and lamps 12, the control unit or units and the battery being located within the base 11. As indicated in that figure, I provide a battery 14, preferably of dry cell type, and connect its" output terminals, through switch 13 to a pair of power leads 15 and 16. t

Branching off from the power'lead 15 are conductors 17, each of which leads to an individual lamp 12, and as indicated'by the dotted continuation of lead 15, the circuit may be continued to provide as many lamps 12 as are desired.

Branching off from the other power lead 16 are a series of conductors 20, and individually connected to each of these conductors is an RC circuit 21 comprising a capacitor 22 and a resistor 23 connected in parallel. The other terminal of each RC circuit 21 is connected by a conductor 24 to a corresponding lamp 12, and thus each lamp is connected by two conductors, 17 and 24, to' its associated control unit and the power supply. In general, the capacitors 22 and the resistors 23 have approximately the same value, but the individual components vary between the'different RC circuits. Consequently, each individual circuit is slightly different, and thus produces a slightly different rate. of flashing. By

way of example, I have found that if the following components are used, very satisfactory results are obtained:

Voltage of battery 14 135 volts (lOO-lSO volts). Lamps 12 NE-2 neon or equivalent. Capacitor 22 .25Q.05 mfd..

Resistor 23 2.0-0.5 megohms.

The circuit comprising the battery 14, thelamp 12, and the RC circuit 21'. produces the same general' result as that of a relaxation oscillator. However, an inspection of this circuit will clearly indicate the differences, and the operation of the deviceis believed to occur in the manner now to be described. When the switch 13 is closed, a voltage surge appears across the conductors 17 and 24, this voltage exceeding the breakdown voltage of the lamp 12, and consequently the latter is lit. However, assoon as the discharge occurs, current flows through resistor 23 producing a voltage drop thereacross that reduces the voltage between the conductors 17 and 24 to a point below that necessary to maintain the discharge within the lamp. The discharge is immediately extinguished, and at this instant, because of the voltage drop between the terminals of the resistor 23', the capacitor 22 which is connected to these terminals, has received a charge corresponding to this voltage drop. Until this charge is removed, the voltage appearing on the conductor 24, with respect to the conductor 17, is insufiicient to again ignite the lamp or cause the discharge therein, and the lamp thus remains unlit. However, the charge upon the capacitor 22 is quickly dissipated through. the resistor 23 until the voltage between the conductors 17 and 24 once again reaches the striking voltage of the lamp 12.

When the switch 13 is first closed, all of the lamps 12 flash on, substantially in unison, but thereafter the individual diiferences in the various RC circuits 21 cause the lamps 12 to flash at different rates. As a result, there is a random pattern of flashing of the lights 12 throughout the tree 10.

It will be appreciated that each of the lights 12 requires a very small amount of electrical power, and the RC circuit 21 likewise absorbs a very small amount of power. As a result, the lights 12 and their associated control circuits 21 draw a negligible amount of power, and it has been found in practice that if the switch 13 is kept closed,

the lights will continue to flash for a period of time approximately equal to that of the shelf life of the battery 14. This, it will be appreciated, amounts to several months, depending upon the construction of the particular battery. Consequently, in order to reduce the cost of the complete assembly, the switch 13 may be omitted, and the device placed in operation by inserting a battery within the base 11, and allowing the device to operate until the shelf life of the battery has been expended.

As previously indicated, the circuit indicated in Figure 2 may be extended to include more lamps 12 with their corresponding control circuit 21, though it will be appreciated that if too great a number of lamps are operated by a single battery 14, the operating life of this battery will become somewhat less than its shelf life.

Description of warning signal all) In Figures 3 and 4, I have indicated a warning flasher In some locations, as where traific signals are installed, a source of power together with mechanical flashing means are readily available. However, in many other locations, these facilities are not provided, and an independently powered light is of great value in such cases. For example, as indicated in Figure 3, a stop sign 3%) may be mounted upon a post or column 31, the sign having a case or housing of considerable depth in which a source of light and its lens 32, are mounted. The control circuit and the power supply are mounted within the housing of the sign 20, and since the sign may be located a considerable distance from any regular maintenance route, it is important that the control circuit and the power supply be of great reliability.

In Figure 4, I have indicated the schematic wiring di agram of such a circuit that meets the aforementioned requirements as well as others. It will be appreciated, of course, that the use of this Warning signal light is not restricted to permanent locations, but instead the device may be used on temporary installations, such as barricades during construction work, and in many other places. One of the major advantages of this particular circuit is that it does not make use of any mechanically separated electrical contacts through which current is passing, so that there is no arcing or sparking that might cause an explosion in the event that the surrounding atmosphere is explosive.

Briefly, my preferred circuit, as illustrated in Figure 4, includes a source of power such as a battery a timing and control circuit designated generally by the numeral 36, an electronic switch 37, a transformer 38, and a gaseous conduction tube, preferably mounted behind the lens 32 of the sign 30, and designated by the numeral 40. The battery 35 provides the power that operates the control circuit 36, and this circuit acts to operate or trigger the electronic switch 37 so that a pulse or current is delivered to the transformer 38 which raises the volt-' age of that pulse to a value sutlicient to energize and light the discharge tube 40.

Considering the circuit in greater detail, it will be noted that one terminal of the battery 35 is connected through a switch 41 to a resistor 42 that in turn is connected through a conductor 43 to one terminal of a capacitor 44. The other terminal of the capacitor 44 is connected through a conductor 45 to a conductor 46 that leads to one terminal of a resistor 47, the other terminal of that resistor being'connected' to the remaining terminal of the battery 35.

Connected to the conductor 43 is one terminal of a variable resistor 50, the other terminal of which is connected to one terminal of a fixed resistor 51, and the other terminal of this fixed resistor is connected to a junction point 52. A conductor 53 connects junction point 52 to another junction point 54, and a capacitor 55 is connected between junction point 54 and conductor '43.

Thus, resistors and 51 are connected in series, and capacitor 55 is connected in parallel with the resistor circuit, thereby providing an RC circuit not unlike the circuit 21 shown in Figure 2.

A capacitor 56 is connected between junction point 54 and conductor 46, and junction point 52 is connected by conductor 57 to anode 60 of the electron discharge tube or electronic switch 37. The grid or control electrode 61 of the tube 37 is connected through a resistor 62 to the conductor 57, and may also be connected through a capacitor 63 to the conductor 46. Finally, the cathode 64 of the tube 37 is connected to a junction point 65, and a capacitor 66 is connected between this junction point and the conductor 46.

7 As will hereinafter be described, high voltage pulses marked by a sign, and in many instances, a flashing red light is used in conjunction with that sign to call attenappear between junction and conductor 46. and conductor 67 connectsjunction 65 to one terminal of the primaryot the transformer 38. The other terminal of the primary of transformer 38 is connected to conductor 46, and the secondary terminals of the transformer are connected to the two terminals of the gaseous conduction tube 40, one of these conductors, if so desired, being in turn connected to conductor 46.

When switch 41 is first closed, the first action is the charging of capacitor 44 through resistors 42 and 47. The resistors 42 and 47 limit the current flowing into the capacitor 44, and produce a voltage drop so that the voltage appearing between conductors 43 and 45 is an exponentially increasing voltage that rises rapidly at first, and then increases at a gradually decreasing rate. The voltage appearing between conductors 43 and 45 is the same as the voltage appearing between conductors 43 and 46, and this voltage is appliedto the control circuit and electronic switch 37, connected in series. As this voltage increases, the voltage between the junction point 52 and the conductor 46 likewise increases, since tube 37 is initially non-conducting, and no large current is drawn through the resistors 50 and 51. However, capacitor 56, which is connected between junction point 52 and conductor 46 is being charged during this period, and when the voltage appearing between junction point 52 and conductor 46 reaches some critical value, the electron discharge tube 37 becomes conductive, and capacitors 44 and 56 discharge through it. The discharge continues until the voltage between junction 52 and conductor 46 decreases to a value insuificient to continue the discharge, whereupon the tube 37 becomes non-conducting.

At this point, capacitor 44 has discharged its charge through resistors 50 and 51, so that the voltage at junction 52 is less than the voltage appearing upon conductor 43, both related to conductor 46. As a result, capacitor is charged, and this charge will be dissipated by the flow of current from one terminal of that capacitor, through the resistors 50 and 51 through the other terminal. This flow of current through resistors 50 and 51 7 produces a voltage drop, and when the voltage drop occasioned by the flow of current from capacitor 44, as well as battery 35, is added to this, the potential appearing between junction point 52 and conductor 46, and hence the charge on capacitor 56, will be more slowly raised. Thus, the resistors 50 and 51 and the capacitor 55 are the fundamental elements of the timing circuit, corresponding to the resistor 23 and capacitor 22 of the RC circuit previously shown and described in connection with Figure 2. The function of capacitor 44 is to provide a supply of current that may be discharged relatively rapidly, and in an amount greater of that capable of being provided by battery 35. The function of capacitor 56 is similar, and its effect is to reinforce or increase the brilliance of the flash occurring in gaseous discharge tube 40 since capacitor 56 discharges directly through the electron discharge tube 37 while capacitor 44 discharges through resistors 50 and 51.

The operation of electron discharge tube 37 is somewhat similar to that of a thyratron. The control electrode or grid 61 of the tube 37 is connected through resistor 22 to conductor 57, and this conductor is likewise connected to the anode or plate of that tube. Consequently, when the tube 37 is not conducting, no current flows through the resistor 62, neglecting for the moment the presence of capacitor 63. Thus, grid 61 and anode 60 are at the same potential, and the grid acts as the trigger electrode for the tube 37. When junction 52 reaches a predetermined value, the same voltage, which appears upon the grid 61, triggers or starts the discharge in tube 37 and current flows between the anode 60 and the cathode 64, and also flows through the grid 61 and the resistor 62. However, the presence of the resistor 62 causes a voltage drop to appear across the terminals of the resistor, so that a lower voltage appears upon the grid 61 than the anode 60 when the tube is conducting. This, however, does not stop the discharge within the tube 37 once it has been initiated.

The effect of the capacitor 63 is to receive a charge while the tube 37 is not conducting, and to discharge a portion of this charge when conduction is first established. At the time that the discharge through the tube ceases, the capacitor 63 can again reach its discharge-initiating potential, the capacitor 63 must be recharged to this value. As a result, the presence of the capacitor 63 is to permit the obtaining of a lower flash rate for the timing and control circuit 36, without any change in the brilliance in the flash obtained.

Cathode 64 is connected in series with the primary of transformer 38, and when tube 37 is non-conducting, the potential of the cathode is substantially equal to that of conductor 46. However, the primary of the transformer 38, has a certain resistance, and when the first peak current from the .tube 37 flows through the primary, this produces a voltage drop that causes the capacitor 66 to be charged. As the tube 37 discharges, the first surge of current decreases or decays, and a lower voltage drop appears between the terminals of the primary of transformer 38. As this occurs, the capacitor 66 returns the energy stored in it, to the circuit and the charge on the capacitor 66 is then discharged through the primary of the transformer 38. This means that the lamp 40 is illuminated a slightly longer time. The etfect of the capacitor 66 is thus to decrease the initial surge of current through the primary of transformer 38, and to continue the passage of current through that primary for a longer period of time.

Flashing rate of the control circuit can be controlled by varyingthe resistor 50, so in this way the time to discharge capacitor 55 can be controlled. Each of the different capacitors and resistors has its own effect on the flash rate, some increasing and some decreasing the frequency of flashing. Very satisfactory results will be obtained if the following values of the various components are used:

Battery 35 360 volts.

Resistors 42 and 47 47,000 ohms.

Capacitor 44 2.0 mfd.

Resistor 50 500,000 ohms.

Resistor 41 47,000 ohms.

Capacitor 55' 2.0 mfd.

Capacitor 46 0.5 mfd.

Resistor 62 2.5 megohms.

Capacitor 63 0.5 mfd.

Tube 36 OA4G (cold cathode,

triode, gas-filled).

Capacitor 66 0.5 mfd.

Transformer 38 1 to ratio.

These values work very satisfactorily, and a wide range of flashing rates may be obtained. For convenience, it is sometimes desirable to combine the variable resistor 50 with the switch 21 so that as the control knob of the resistor is first turned, the first action is to close switch 41 and thereafter the value of the resistor in the circuit may be controlled.

As previously indicated, it is possible to omit capacitor 63 from the circuit, and this may be particularly desirable where simplification is in order. Under these circumstances, the circuit may be further simplified by reducing the value of resistor 47 to zero, but when this is done, capacitor 56 should be increased to a value of 4 mfd. In all important respects this simplified circuit operates in the same manner as does the more elaborate circuit, and where cost and reliability are of utmost importance, the simplified circuit produces very satisfactory results.

From the foregoing, it will be seen that the flasher circuit just described has many advantages over the mechanically operated flashing systems previously used. Important among these is the fact that all moving contacts are eliminated, and consequently there is no opportunity for corrosion, dust, or other high resistance material to interfere with the operation of the electrical components of the circuit. Additionally, since no moving mechanical elements are concerned, the device will operate equally well in any position, and vibration has a very minimum of effect upon it. Likewis with the elimination of open contacts and their sparking, the device may safely be used in an explosive or otherwise hazardous atmosphere, where heretofore previous devices were not practical.

All of the circuits shown and described herein have made use of conduction devices, such as the lamps 12 of the circuit shown in Figure 2, having particular electrical properties. In each circuit, the lamp 112 or theelectron discharge tube 37 has the characteristics of remaining substantially non-conductive until a relatively high breakdown voltage is applied to it, whereupon the device becomes conductive and has a comparatively low resistance. Once the conductive state is achieved, the voltage may be reduced and the device will remain conductive until a relatively low extinction voltage is reached, whereupon the device becomes non-conductive and remains so until the breakdown voltage is again applied. These characteristics are those of a glow discharge device, and

when I refer to such characteristics, these are the ones I means to include.

It will thus be seen that I have shown and described an electronic flashing circuit fully capable of achieving the objects and securing the advantages heretofore set forth.

Many modifications and variations will occur to those skilled in the art, but these are included within the broad scope of my invention. Consequently, I do not wish to be restricted to the particular forms described and shown except as limited by my claims.

I claim:

1. A flasher circuit of the class described which includes: a conductive device having the electrical characteristics of a glow discharge device; a control circuit comprising a resistor and a capacitor connected in parallel; a power utilization device connected in series with said conductive device; a reinforcing capacitor connected in parallel with the series circuit comprising said conductive device and said utilization device, forming a first series-parallel circuit; means connecting said control circuit in series with said first series-parallel circuit to form a second seriesparallel circuit; a power capacitor connected in parallel with said series-parallel circuit to form a network; and a resistor connected in series with said network and through which said network is adapted to be connected to a source of electrical energy.

2. A flasher circuit of the class described which includes: a conductive device having the electrical characteristics of a glow discharge device; a control circuit comprising a resistor and a capacitor connected in parallel; a reinforcing capacitor connected in parallel with said conductive device; means connecting said control circuit in series with said parallel circuit to form a seriesparallel circuit; a power capacitor connected in parallel with said second series-parallel circuit to form a network; and a resistor connected in series with said network and through which said network is adapted to be connected to a source or electrical energy.

3. A flasher circuit of the class described which includes: a conductive device having the electrical characteristics of a glow discharge device; a control circuit comprising a resistor and a capacitor connected in parallel; a transformer having its primary winding connected in series with said conductive device; a modifying capacitor connected in parallel with said primary winding and acting to modify the pulse of current through the latter; a reinforcing capacitor connected in parallel with the circuit comprising said conductive device, said primary winding, and said modifying capacitor to form a first seriesparallel circuit; and means connecting said control circuit in series with said first series-parallel circuit to form a second series-parallel circuit, said means being further adapted to connect said second series-parallel circuit to a source of electrical energy.

4. A flasher circuit of the class described which in- 8 cludes: a conductive device having the electrical characteristics of a glow discharge device; a control circuit comprising a resistor and a capacitor connected in parallel; a transformer having its primary winding connected in series with said conductive device; a modifying capacitor connected in parallel with said primary winding and acting to modify the pulse of current through the latter;

means connecting said control circuit in series with said conductive device and the parallel circuit formed by said primary winding and said modifying capacitor, to form a series parallel circuit; a power capacitor connected in parallel with said series-parallel circuit to form a network; and a resistor connected in series with said network and through which said network is adapted to be connected to a source of electrical energy.

5. A flasher circuit of the class described which includes: a conductive device having the electrical char acteristics of a glow discharge device; a control circuit comprising a resistor and a capacitor connected in parallel; a transformer having its primary winding connected in series with said conductive device; a modifying capacitor connected in parallel with said primary winding and acting to modify the pulse of current through the latter; a reinforcing capacitor connected in parallel with the circuit comprising said conductive device, said primary winding, and said modifying capacitor to form a first series-parallel circuit; means connecting said control circuit in series With said first series-parallel circuit to form a second series-parallel circuit; a power capacitor connected in parallel with said series-parallel circuit to form a network; and a resistor connected in series with said network and through which said network is adapted to be connected to a source of electrical energy.

6. A flasher circuit of the class described which includes: an electron discharge tube having the electrical characteristics of a glow discharge device, and including an anode, a cathode, and a control electrode; a gaseous conduction, electrical discharge tube providing light when energized; a common conductor; a transformer having its secondary winding connected to said gaseous conduction tube for operation thereof, and having one of its primary winding terminals connected to said cathode, and the other primary winding terminal connected to said common conductor; a modifying capacitor connected in parallel with said primary winding; a control resistor; a control capacitor connected in parallel with said control resistor to form a control circuit having a pair of terminals, the first of which is connected to said anode of said electron discharge tube; a limiting resistor connecting said control electrode to said first terminal of said control circuit; a retarding capacitor connected between said control electrode and said common conductor; a reinforcing capacitor connected between said first terminal of said control circuit and said common conductor; a power capacitor connected between the other terminal of said control circuit and said common conductor; a resistor having one terminal connected to said other terminal of said control circuit; and means for connecting the other terminal of said last-mentioned resistor and said common conductor to the terminals of a source of electrical energy.

References Cited in the file of this patent UNITED STATES PATENTS

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