This circuit was taken from a Popular Electronics from the 90's. The power step can be changed to operate with the most powerful LEDs available today.
This version of the circuit is from 2000, using a source of negative voltage that allows to obtain...
This somewhat complex circuit was found in the May 1984 issue of Radio Electronics magazine. The...
This basic circuit is from an old documentation. The relay must be 50 mA maximum and must have a...