Using an LDR, this Philips circuit directly activates a relay when light strikes the sensor. The relay is 45 V with 20k coil resistance. The 220 nF capacitor must be polyester for 400 V.
We found this circuit in a 1986 documentation. It causes 40 LEDs to flash sequentially. The big...
Exciting a sequential circuit with the output of a stereo we can make a set of lamps run at a...
This alarm from an old 1978 publication uses PNP transistors and driver and output transformers that are...