This circuit was obtained in a 1970 EEE and applies to almost any operational amplifier. The supply voltage depends on the operational amplifiers used.
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...