This circuit, which is present in other points of this website, was found in a 90s Hands On Electronics. The circuit activates a buzzer with an oscillator.
With this circuit it is possible to use a common hair dryer as a hand dryer. The circuit is timed...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
This circuit was obtained in a 1975 magazine, but it can be easily assembled using BC548...