Lights and Display Board CircuitsPower Supplies

Slave flash trigger

The circuit in the diagram is intended for synchronous, wireless triggering of one or more slave flash units when the mother flash is triggered, so as to obtain better lighting of the photographic object.

Phototransistor T1 is switched on upon the receipt of the light of the mother flash unit. The potential at the inverting input of comparator IC1a rises, the comparator toggles and for a brief instant, determined by the value of C1, the voltage level at the inverting input of IC1b is lower than that at the non-inverting input. This causes 1Cib to toggle momentarily, which results in the thyristor being triggered and the flash contacts to be closed.

Slave flash trigger Schematic diagram

The circuit may be used in dark as well as brightly lit places. The operating range depends on the mother flash and will formally be 5-15 m (15-50 ft). The sensitivity depends primarily on the base resistance of the phototransistor and this rna• be modified according to circumstances. Any tendency to instability may be cured by shunting R2 with a 100 pF capacitor.

Power is supplied by a 9-V (PP3) battery.

A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a capacitor is known as capacitance. capacitor, a device for storing electrical energy, consists of two conductors in close proximity and insulated from each other. A simple example of such a storage device is the parallel-plate capacitor. The capacitor is a device and it does not have a unit.

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