We show in Figure 1 an optical power switch using a common optical isolator as a phototransistor. The type of drive depends on the application, and may come from TTL or CMOS logic circuits or other configurations, such as voltage comparators and operational amplifiers.
The circuit uses a common Triac whose current and voltage capacity depends on the controlled load. Likewise, the 51 k resistor was designed for the 110 V (120 V) grid and could be changed for operation on the 220 V grid.
The trigger element is a SBS (Silicon Bilateral Switch) and may be replaced by a DIAC, in which case the trigger characteristics must be considered in order to obtain the drive by the optical coupler, with possible changes of the resistor.
Note that the drive is made in full wave thanks to the presence of the diode bridge.
