This simple circuit can work with either 4.5 V or 6 or 9 V if a 1k resistor is added in series with the set of LEDs. The circuit is from an old French publication.
This configuration (using a logic gate with TTL compatible output) uses an amplifier transistor to obtain...
In addition to the didactic purpose, the figure circuit can also be automated. In this case, the...
The maximum time interval of this circuit depends on C1. Larger values can be used to get closer to...