Electronic Circuit

Flash slaves are used when you need to supplement one flash unit with one or several more. This slave trigger simply triggers those other units. It does this by “seeing” the first flash (using a phototransistor) and triggering the other flashes a few microseconds later. The sensitivity of the circuit is adjustable to compensate for ambient light or dimmer than usual master flashes.

1-Q1 should be aimed at the master flash. R1 should be adjusted for maximum sensitivity but no false triggering.

2-Keep your fingers away from SCR1 when the circuit is operating. It is at 50V-300V and will give you a nasty shock.

The UJT transistor Q1 can be replaced with a NTE6409 or ECG6409.
At the press of S1 the oscillator starts and runs the clock on pin 14 of the CD4017 decade counter at a time determined by R1 and C1. During that time both LED’s will flash back and forth until the oscillator stops and either the red or green led will be lit. The values shown are for working with 9 volts and none of the parts are critical.

coin tosser

This circuit is not my own, I copied it from Popular Electronics Magazine (Gernsback Publishing out of business) but still a good learning circuit.
Credits and © copyright goes to the author.