US 3297910 A
Description (OCR text may contain errors)
United States Patent M 3,297,910 PERIODIC LIGHT FLASHER Bernard J. Gershen, Edison, N.J., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Dec. 31, 1963, Ser. No. 334,760 2 Claims. (Cl. 315-155) This invention relates in general to signaling devices and more particularly to an improved flasher circuit.
Circuits for periodically connecting and disconnecting a load circuit to and from a source of electrical power are well known and find wide application. In particular the load circuit may consist of one or more electric lamps which are turned on and oil in sequence and is generally known as a flasher.
In flasher circuits and other periodic switching circuits known to the art heretofore, unilateral control devices have commonly been employed to effect controlled operation of switches, or the switches have been actuated by motors or other mechanical timing devices. Systems employing unilateral control devices such as vacuum tubes or transistors lack the requisite reliability where the system must operate without supervision over extremely long time periods. They are, moreover, relatively expensive and their timing cycles tend to vary with aging of the unilateral control device and other circuit components associated with the latter. Motor control devices on the other hand tend to be relatively expensive and are subject to wear and require maintainance so that their utilization in unattended or unsupervised installations designed for automatic operation over long periods of time is inadvisable.
The disadvantages associated with the prior art flasher circuit are obviated by the present invention which provides a flasher which has long life, is not subject to a high degree of maintenance and can be fabricated economically in a package of very small size.
In accordance with the present invention a high power cadmium sulfide photocell is mounted in close proximity with a neon tube in a light tight enclosure. The photocell is connected in series with an incandescent lamp across a source of A.C. voltage. A rectifier, a resistor, and a capacitor are connected across the source, the capacitor being connected in shunt with the neon tube. The capacitor is periodically charged to the ionizing potential of the neon tube causing the neon tube to periodically flash and lower the resistance of the photocell to energize the incandescent lamp.
A more complete understanding of the present invention may be had from the following detailed description which should 'be read in conjunction with the accompanying drawing in which:
FIGURE 1 is a schematic circuit diagram of the flasher circuit in accordance with the present invention;
FIGURE 2 is a schematic circuit diagram of a modification of the circuit of FIGURE 1.
Referring now to the drawing and initially to FIG- URE 1, there is shown one embodiment of the present invention in which the numeral designates a cadmium sulfide power photocell (Delco Radio type LDR-25) connected in series with a load which in this instance is a 6 watt incandescent lamp 12. The photocell 10 and the lamp 12 are connected across a 115 volt A.C. source of power. The photocell 10 is mounted within an enclosure 14 and in close proximity to a neon lamp 1-6. A charging circuit for the neon tube 16 comprises a low current rectifier 18 providing a pulsating DC. output to a resistor 20 and a capacitor 22.
3,297,910 Patented Jan. 10, 1967 The operation of the circuit shown in FIGURE 1 is as follows. It will be understood that when no light impinges the photocell 10, it presents a very high resistance in series with the incandescent lamp 12 causing the lamp 12 to be deenergized. With the flasher circuit connected to the A.C. source, the capacitor 22 will begin to charge at a rate determined by the value of resistor 20. When the capacitor 22 charges to the ionizing potential of the neon lamp 16, the lamp 16 will fire thereby illuminating the photocell 10 and drastically reducing its resistance. The reduced resistance of the photocell 10 causes the lamp 12 to be energized. When the neon lamp 16 fires, the capacitor 22 will discharge therethrough extinguishing the neon lamp 16 and the cycle will then be repeated.
Referring now to FIGURE 2, a modification of the present invention is shown. An additional incandescent lamp 24 is connected in series with a second cadmium sulfide power photocell 26 across the source of power. The lamp 12 and the photocell 26 are disposed in close proximity with each other within a light tight enclosure 28.
When a circuit is connected to the volt A.C. source, a pulsating DC. voltage appears across the parallel circuit consisting of capacitor 22 and a neon lamp 16. Because the ionizing potential of the neon lamp 16 is greater than 60 volts, it presents a higher resistance to the pulsating DC. voltage than capacitor 22 which consequently charges at a rate determined by the value of resistor 20.
When the potential across the capacitor 22 reaches the ionizing potential of the neon lamp 16, it fires and illuminates the photocell 10 until the potential across capacitor 22 dissipates through the neon lamp 16 to such a value that the neon lamp 16 can no longer maintain its ionized condition.
When the photocell 10 conducts, incandescent lamp 12 illuminates photocell 26 at a level much higher than that which falls on photocell 10. Consequently, photocell 26 passes far more current than photocell 10 and lamp 24 attains virtually full brilliance.
Upon the extinction of neon lamp 1 6, capacitor 22 again charges to the firing potential of the neon lamp 16 and the entire cycle continues repeatedly. The chain of lamps and cells provides a regenerative effect which for practical purposes constitutes light amplification.
Although the description of this invention has been given with respect to a particular embodiment, it is not to be construed in a limiting sense. Many variations and modifications within the spirit and scope of the invention will now occur to those skilled in the art. For a definition of the invention, reference is made to the appended claims.
1. A high voltage flasher operated from an A.C. source comprising a high power photocell connected in series with a lamp across said source, means for periodically illuminating said photocell to lower the resistance thereof and periodically energize said lamp, said means comprising a diode, a resistor, and a capacitor connected across said source and a neon lamp in shunt with said capacitor, said photocell and said neon tube being located in a light tight enclosure and in close proximity to each other, said neon lamp having a predetermined ionizing potential, said capacitor being periodically charged to said ionizing potential thereby energizing said neon lamp to illuminate said photocell and cause energization of said lamp.
2. An A.C. flasher circuit comprising a series circuit including a capacitor, a resistor, and a diode connected across a source of A.C. voltage, a neon lamp connected in shunt with said capacitor, a series circuit including a high power photocell and an incandescent lamp connected across said source, a series circuit including a second photocell and a second incandescent lamp connected across said source, said neon lamp and said first photocell being mounted in close proximity with each other within a light tight enclosure, said incandescent lamp and said second photocell being mounted in close proximity with each other Within a second light tight enclosure.
References Cited by the Examiner UNITED STATES PATENTS 2,838,719 6/1958 Chitty 315158 2,905,862 9/1959 Giuffrida 315156 3,062,961 11/1962 Kalns et a1. 250206 3,206,650 9/1965 Miller et al. 315-449 JAMES W. LAWRENCE, Primary Examiner. R. SEGAL, Assistant Examiner..