Strobe alarm circuit

Abstract

A strobe light circuit for flashing a flashtube at a desired frequency includes a transformer the primary of which is repetitively connected and disconnected across a D.C. power source by a switch so that energy stored in the primary winding during closed periods of the switch is transferred to the secondary winding of the transformer, with a step-up in voltage, during open periods of the switch, and through a diode to an energy-storing capacitor connected in parallel with the flashtube. The closed period of each switch cycle is initiated at regular intervals by a timing signal and the open period is initiated in response to the attainment of a predetermined voltage across a capacitor connected across the power source indicating that sufficient energy is being stored in the primary winding during each cycle such that the energy transferred to the energy-storing capacitor during the open period of all cycles occurring during one flash period will be sufficient to enable the flashtube to produce a flash when triggered. A flash unit associated with the flashtube includes a trigger circuit that responds to two closely following trigger pulses to produce a double flash during each flash period. The flash rate is constant over a range of input voltages and the light intensity of each flash is independent of variations in capacitance of the energy-storing capacitor.