GB1262623A - Circuit for sequentially flashing photoflash lamps - Google Patents

Abstract

1,262,623. Control systems for photoflash arrays. GENERAL ELECTRIC CO. 10 April, 1970 [29 April, 1969], No. 17259/70. Heading H2H. A circuit arrangement for flashing in sequence an array of replaceable photoflash lamps comprises a plurality of circuits connected across a pair of supply lines in parallel and sequencing control means coupled with the lamp circuits so as to flash the lamps in sequence from the first to the last together with means for inhibiting the flashing of each lamp until the preceding lamp has been flashed. An array of four flash lamps 11a-11d is connected across D.C. supply lines 13, 14 each time a camera shutter operated switch 17 is closed. Each lamp has a semiconductor device-such as thyristors 15a-15d -connected in series therewith and the lines 13, 14 are energized each time a switch 17, associated with the camera shutter release 19, is closed. The first closure of the switch 17 causes thyristor 15a to fire whereupon the lamp 11a is flashed. The current passing through the lamp 11a upon flashing creates a voltage drop across resistor 16, which turns on a thyristor 25 and thence a transistor 28 thus establishing a current path between the lines 13, 14 through resistor 24. No current thus flows through the Zener diode 23 and the bus-bar 21 remains de-energized. After a short time-8 milliseconds-the lamp 11a burns out and the thyristor 15a turns off. Upon the next operating of the switch 17 current flows through a circuit comprising resistors 16, 24, Zener diode 23, the emitter-base path of a transistor 20b, a resistor 22b and the gatecathode junction of thyristor 15a. Thyristor 15b is thus gated on to flash lamp 11b and the current flowing therethrough again develops a voltage drop across resistor 16 to turn on thyristor 25 and transistor 28 to de-energize bus-bar 21 thus turning off thyristor 15a. Thyristor 15b turns off when the lamp 11b burns out and the circuit remains quiescent until the switch 17 is again closed whereupon the operation repeats for the third lamp 11c and so on. Other embodiments are shown wherein open-circuited lamps are automatically by-passed, so called air lamps are burned out and flashed, short-circuited lamps may be visually indicated to enable the array to be replaced. In some embodiments current or light sensing operates the lockout transistor 28 or the lamp sequencing initiated by an externally generated pulse. Furthermore modifications may be made so that the sequencing of the lamp flashing may be interrupted at any selected time, the circuit may be de-energized after a predetermined interval or the start of the lamp flashing sequence delayed after the closing of the camera shutter.