In this 2001 circuit we have the way to trigger an SCR with a phototransistor. The circuit appears elsewhere in this section, obtained from publications from different eras.
Published in an old Popular Electronics, this circuit makes use of components that are still...
This stage can be used in power supplies to increase the current capability up to 10 A. The...
This circuit activates an LED, but it can be modified to activate a relay. The time is set in VR1,...