The circuit below was suggested by the Motorola Linear Databook of 1990. The component used is uncommon and the power can be between 7.5 and 12 V.
With this circuit it is possible to fire an SCR from the light that falls on a phototransistor. The circuit...
This simple circuit can use any general-purpose transistor. The power supply must be isolated. The circuit...
Using a sensor from the time, this circuit was found in the 1992 Radio Electronics Handbook...